Download - Module 08 Fixture I

Agilent 3070 User Fundamentals

Fixture I 8 - 1

Module 8: Fixture ITable of Contents

The Test Development Process ............................................................................................... 2The Test Fixture ...................................................................................................................... 3

The Test Probe................................................................................................................. 3The Personality Pin.......................................................................................................... 4The connection process.................................................................................................... 4Simplate Fixture (above left) ........................................................................................... 5Simplate Express Fixture (above right) ........................................................................... 5

Issues ....................................................................................................................................... 6Fixture Electronics........................................................................................................... 7

TestJet Probe ........................................................................................................................... 8Agilent IPG Test Consultant & the Fixture ........................................................................... 10

The Individual Parts of the Fixture Generation Software.............................................. 11Board Placement ............................................................................................................ 11Probe Select ................................................................................................................... 13Allocating Power Supply resources............................................................................... 15

Module Pin Assignment ........................................................................................................ 17Module Pin Assignment’s Inputs & Outputs ................................................................. 18

Fixture Tooling...................................................................................................................... 19Extra Personality Pins.................................................................................................... 20Fixture Tooling Outputs ................................................................................................ 21

The Files for the Fixture Builder ........................................................................................... 22Bank Row Column ................................................................................................................ 24Fixture Verification ............................................................................................................... 25Running Test Consultant Multiple times............................................................................... 28

Re-running Fixturing Software BEFORE a fixture is built ........................................... 28Rerunning Fixturing Software AFTER a fixture is built ............................................... 29Examine the “fixture/details” file .................................................................................. 30

Glossary................................................................................................................................. 31Appendix ............................................................................................................................... 32“fixture/fixture.o” details....................................................................................................... 32

“fixture/summary” - after Board Placement .................................................................. 33“fixture/details”.............................................................................................................. 33“fixture/summary” - after Probe Select ......................................................................... 33“fixture/fixture.o” output - after Module Pin Assignment ............................ 34

Agilent Technologies

Fixture I 8 - 2

The Test Development Process

During previous modules, you:

• Created the “config” file,• Translated the CAD into a board description,• Completed the board description using Agilent’s Board Consultant,

Part Description Editor, Digital Setup Editor,• Generated and evaluated the “testability.rpt”,• Generated the fixture and test files using Agilent IPG Test Consultant.• Regenerated and reevaluated the “testability.rpt”

Now, the development continues with an overview of fixture types, the fixture files, theparts of the fixture and fixture verification.

Later in the class, the Agilent Fixture Consultant will be examined. For now, it will beskipped so you can concentrate on a general overview of the entire fixture process.

13070 User FundamentalsModule 8: Fixturing sA

Test Development FlowchartProcess Files Tools

Generates Modify

board

testability.rpt

Fixture Files

Individual TestFiles

config

testplan

Translate CAD1

Generate Test & Fixture files3

Build & Verify test Fixture4

Turn-On / Debug all Tests5

Release to Production & Long Term Support

6

Describe board & system2

Custom libraries

board_xy

ECO

CAMCAD Translator

BT-BASIC

Board Consultant

Part Description Editor

Digital Setup Editor

IPG Test Consultant

PushButton Debug


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The Test Fixture

The goal of fixturing is to connect the testhead resources to the PC board with theminimum of impedance, reactance or inconvenience.There are two basic fixture types:

• Simplate• Simplate Express

During this class the focus is on the Simplate Express or “short wire” fixture.The Simplate or “long-wire” fixture is also described.

Two other fixture types are not described as they are only seldom used. The ExpressCassette fixture was used in the “EFS Board Handler.” The EFS is no longer inproduction, having been replaced by more modern automated board handling equipment.The XG-50 fixture was used to propagate higher frequency signals. As with the EFS,more modern test techniques have all but made this fixture obsolete.

The Test Probe

The test probe is a four part assembly.

• The socket is press-fit into the Probe Plate.− The height of the socket is carefully controlled. This ensures the probe

can compress more than the fixture, to make sure the probe is notdamaged during test.

− The “tail” of the socket is a wire wrap post.


The Fixtures

BoardSupport PlateProbe Plate

PersonalityPins

Alignment PlateSimplate Express

Simplate

Tooling Pin Vacuum Gasket

Pins


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− The test probe assembly is inserted into the socket during the fixturebuild process. This probe will last many months but can be replacedeasily.

• The probe assembly consists of three parts. A sleeve, a spring and the probeitself.

− The spring is mounted inside the sleeve. The probe inserts into thesleeve and attaches to the spring.

− The probe assembly is then inserted into the socket. Together these aregenerically referred to as the probe even though it is really the probeassembly and socket.

• During test, the probe tip lightly scratches the surface of the solder or copperwhen the fixture compresses. This scratch is usually sufficient to clear awayoxidation or surface contamination thus ensuring good electrical contactduring test. It is usually not enough to pit the surface.

• There are dozens of different point types for fixture probes. As with thedifferent probe point types, there are a number of different spring forces,probe lengths, probe diameters, etc. Most people try several variations andqualify one or two types of probes for their applications and environments.

NOTE: Caution should be used when cleaning the probes. Any solvent thatpenetrates between the probe and the spring/sleeve assembly will dry out thelubricants within the sleeve and the probe will fail prematurely.

The Personality Pin

The Personality Pin (or P-Pin for short) is used to connect to the testhead resource. It hasa plastic top that is press fit into the bottom of the Probe Plate at specific coordinates(defined by the fixture software). The post is simply a wire wrap pin that will hold at leastthree wires.

The connection process• The test Operator loads the board to test onto the fixture. Tooling Pins

mounted in the Probe Plate, but extend through the Support Plate ensure aquality alignment. The board rests on a combination of vacuum gasketsaround the parameter of the board and spacers or pads scattered evenlyaround the interior of the board.

• The system asserts vacuum to the fixture. This creates a vacuum chamberbetween the printed circuit board and the Probe Plate. Vacuum holds theprinted circuit board to the Support Plate. Springs holding the Support Plateto the Probe Plate compress pulling it and the board toward the Probe Plate.

• The test probes are also spring loaded and they compress as the board pushesthem toward the Probe Plate. The board travels to a physical stop. Theprobes, resisting that travel embed their points into the solder on the testpoints of the board.


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• The 3070 generates a signal. That signal is propagated from its source on aPin Card, to the fixture’s test Pin. Through the fixture wiring to the Probe.Through the probe to the test point on the printed circuit board.

• The signal travels through parts and traces on the printed circuit board.• The test circuit is completed when the signal is returned, via a separate

Probe, wire and Pin from the printed circuit board back to a Pin Card.• The returned signal is measured and evaluated with pass/fail criteria.

The final detail about this fixture is the use of spacers, pre-loaded board springs andgaskets to prevent warping of either the PC board or the Support Plate when vacuum isapplied or released.

Simplate Fixture (above left)

This older fixturing technique, the Simplate or long wire fixture has been used for aboutthe last 20 years. This test fixture features three plates.

• The printed circuit board rests on the “Support Plate.”• The “Probe Plate” has test probes mounted at specific coordinates. These

make contact to the printed circuit board during test. These test probes givethe fixture its “bed-of-nails” name.

• The third plate has test pins mounted in it. These pins connect to predefinedlocations in the testhead.

• The connection from the test probes to the test pins is made with wire wrapwire. You will notice that the fixture is hinged so it can open. The typicalfixture uses wires that range from 16 to 36 inches.

Issues

Long wire lengths can introduce excessive inductive and/or capacitive loading on theprinted circuit board. In high speed applications, the wire can act as a coil withpotentially damaging energy.Twisted pair, coaxial wire and/or Ferrite beads can minimize the impact of some of theseissues, but not all. The only real solution is to make the wires shorter.

Simplate Express Fixture (above right)

This style fixture offers typical wire lengths that range from 1.0 to 9 inches. It uses threeplates also, but in a very different manner.

• The Support Plate is the same as the long wire fixture’s.• The Probe Plate holds not only the test probes, but also the test pins, called

“Personality Pins.” By putting both probes and pins on the same plate, thewire length required to complete the connections are very short.

• The Alignment Plate is used to ensure proper alignment between the testheadand the personality pins. It consists of rows of funnels that help direct thepins into the proper locations.


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Issues

Because the probes and pins are on the same plate, conflicts became a concern. If a probehas to be at a particular location, and a pin needs to occupy that same space, whathappens?

• The answer, the probe wins! (Because they are assigned first.)• Why? Because there is a limited number of probe sites for a given node.• But that means one of the testhead resources is blocked.

Perhaps, but not necessarily. If a pin is blocked, it is usually not a seriousproblem because there are lots of testhead resources. But there are ways to“un-block” pin locations:

− Ideally, the personality pin is installed so it aligns straightthrough the Alignment Plate without interfering with aprobe.

• But what happens if a probe and a personality pin both need tooccupy the same space?

− There are three methods for overcoming this limitation of the ExpressFixture. All of these are done automatically by the fixturing software.

− The first is to simply use a different location for the personality pin.Few testhead resources truly require a personality pin be located at aspecific location.

− If a personality pin cannot be used it is considered“blocked”. The probe remains at its location; the testheadresource (BRC) below this Alignment Plate funnel isflagged as non-usable.

− The second method is to locate the personality pin as close as possible(without causing a short) to the probe. Then bend the pinso that when the Alignment Plate is installed it ensures thebent personality pin aligns properly to the testhead.Personality pins may be bent up to 0.1”. However, theymay only be bent in the “Y” direction (in parallel with thealignment plate funnels).

− The third method involves an “offset personality pin”. It allows apersonality pin to be located close to the blocking probe,then to transfer its signal to a very small plated printedcircuit board that is mounted to the Alignment Plate. Theeffect is to bypass the probe that is blocking thatparticular system resource. The use of offset personalitypins is not recommended for signals that are sensitive toadded impedance.

− A fourth, manual technique, uses Agilent’s Fixture Consultant. Thistool, detailed later in the class, allows you to manually reposition theprinted circuit board on the fixture. The software then evaluates blockedtesthead resources. By spending a few minutes with this interface, youcan frequently minimize the number of blocked testhead resources.


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Fixture Electronics

Fixture Electronics are sometimes needed to assist in testing your board. There are twotypical methods for including fixture electronics in a test fixture.

• One is to suspend those components within the fixture on nothing more thanthe wire-wrap wire. This will work if you are adding a resistor or othersimple component. Any exposed, conductive surfaces should be enclosed inheat-shrink or electrical tape to prevent shorting.

• For more complex fixture electronics, a printed circuit board (breadboard)should be assembled. This board may be mounted on the top of the ProbePlate where it should be enclosed with a housing or shield to prevent it frombeing shocked (ESD) or damaged in handling. The Fixture Electronics boardshould be connected to the rest of the fixture through a connector. In thisway, you can easily swap to a backup board if the primary board becomesfaulty.

• Agilent’s Fixture Consultant provides tools for describing fixture electronicsand even extending these parts into tests so you know the electronicscontinue to function normally.


Fixture Electronics

Add a printed circuit assembly to the top of the fixture.- Cover it with a protective housing. - Connect it to the Board Under Test using a cable and connector

Board UnderTest

Add a load inside the fixture Hang a pullup inside the fixture


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TestJet Probe

The TestJet probe consists of three parts:

• The Sensor Plate,• An Electronics board• The TestJet Pins

TestJet Test Theory

During the test, one lead of the device is driven. This signal is capacitively coupled to thesensor plate. The capacitively coupled signal is amplified by the electronics board. Theresulting signal is sent to the Multiplex card (not shown) and is relayed to the ASRU foranalysis.

Installation of the TestJet Probe

Because TestJet measures the capacitive coupling between the lead and the die of anintegrated circuit, the TestJet probe must be physically very close to the device under test.Touching is acceptable.

• Given: A device mounted on the bottom of the board to be tested withTestJet.

• When you enabled TestJet testing, you also described the outside radius ofthe device. The fixture software uses this radius to create a “keepout” region.This region defines an area where no probes or personality pins should beinstalled.

• Given: A device mounted on the top of the board to be tested with TestJet.


The TestJet Probe

Sensor PlateElectronics BoardTestJet Pins

PCB

Support& ProbePlates

Top Plate

Small TestJetor Polarity CheckProbe


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• When you enable the TestJet test, you must also enable the use of a TopPlate. This custom built plate holds the TestJet probes mounted above thedevice. To load and unload the printed circuit board, this Top Plate must behinged. It is opened to load the board, closed to test and reopened to removethis board and load the next.

The Small TestJet probe is used to test polarized capacitors (through-hole or surfacemount) or small surface mount integrated circuits. The pins are 100 mil probes with aspecial end that saddle-mounts onto the edge of the electronics board. These are solderedtogether using a special tool provided with the fixturing kit. The electronics board issimilar to the standard TestJet electronics board, but because of the mounting differences,they are not interchangeable.The Small TestJet sensor plate is very different. It is basically a folded metal plate withmounting pins that you solder to the electronics board (again using the special toolprovided in the fixture kits). The sensor plate is coated to prevent shorting.

The Foam-mounted TestJet Sensor is designed to test large devices including connectorsand integrated circuits. Because it is so long (up to 6”), the use of mounting pins is notpractical. Therefore, adhesive backed foam pads are used to mount the sensor above thedevice to be tested. It mounts on the top plate only, where vacuum is not required.


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Agilent IPG Test Consultant & the Fixture

Notice that there are two Fixturing Processes shown.

• The Initial Fixturing tasks are:− Board Placement, which defines where the board will be located on the

fixture.− Probe Select, which locates all possible probing locations for each node.

• After the initial fixturing process, the test software writes the individual testsfor each device. A part of this process defines the resources required to testeach device.

• The Final Fixturing tasks are:− Module Pin Assignment that chooses which testhead resource to

connect to which probe.− Fixture Tooling that determines the wire length, number of wires, color

and size of wires, etc. The fixture builder uses this information.Fixture Tooling also defines several additional wire connections neededwithin the fixture. These are discussed in greater detail later in thismodule.


Agilent IPG Test Consultant


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The Individual Parts of the Fixture Generation Software

The Fixturing Software associated with Test Consultant consists of five pieces of code:

• Board Placement• Probe Select• Module Pin Assignment• Fixture Tooling• Plot File generation

Board Placement

Board Placement operates on a set of assumptions, some of which may not be valid foryour application.

• It always places the longer edge of the board at the front edge of the fixture.• The board is placed just above the lower left vacuum port in Bank 2.• The board’s placement is based on the lowest and left most location on the

printed circuit board. This allows the software to define all coordinate valuesas positive values.(NOTE: This does not necessarily place the origin on the corner of the board,it is simply a point that is more left and lower than any other point on theboard.


The Parts of Fixture Generation

Board Placement

Probe Select

Module Pin Assignment

Fixture Tooling

Generation of Fixture Plots

Board Origin(0,0 point)

Board Placement:

Fixture Origin(0,0 point)


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The Fixture 0,0 point (not the board 0,0) is located on the left boundary about mid-waybetween top and bottom of the fixture. This provides an asymmetrical midline so thefixture plates can be aligned on the drilling machine.There are two mounting holes drilled on this mid-line. These are drilled into the ProbePlate while the plate is being shaped and is therefore under precise control.

Output of Board Placement

The board placement software creates three files.

• “fixture/fixture.o”Board Placement created the “fixture” directory and the “fixture.o” fileautomatically. This file currently contains only preliminary informationabout the PC board obtained from the “board_xy” file. The“fixture/fixture.o” file is an object file and is not user readable. Therefore ade-compiler has been created to allow you to see these files when desired. Toconvert the object into a text file:

list object “fixture/fixture.o” to “fixture/fixture”

• “fixture/details”• “fixture/summary”

These files contain warning and error messages generated during thedevelopment process.Other software will augment the “fixture/fixture.o”, “fixture/details” and“fixture/summary” files.

The BT-BASIC command list object “<file.o>” to “<file>”can be used to decompile five object files. Four files (board.o, board_xy.o,wirelist.o and fixture.o) are covered in this course. The fifth file (states.o) iscovered in an advanced class. No other object files can be regenerated to theiroriginal source file states.

“fixture/fixture.o”

The “fixture/fixture.o” file contains several elements.

• The board outline• Tooling pin locations• Keepout areas if any were specified• Global information including:

− Fixture type− Autofile code


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Probe Select

The basic function of Probe Select is to determine where each node will be probed.

When the probe locations have been defined, the software can “visualize” the Probe Plateand the numerous holes that have been placed in it both actual probe locations and the“blind hole” or partially drilled holes

Default Criteria

The default criteria takes over after allocating the “critical” and “mandatory” locations.

• Electrical considerations− Digital pins defined as “dynamic” for flash programming.− Digital output pins are preferred over inputs or non-digital devices.− Probe directly on small value resistors. (< 10ohms)− Probe directly on large value capacitors. (>1uf)− Probe directly on small value inductors (< 10mH)

• Fixture density considerations− If the probe density default maximum threshold for a specific area of the

board has been reached, no additional probes are assigned to that area.


Fixturing: Probe Select

U1

U2

R23.9 Ohms

R310K

R1500K


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• Board edge clearance− A probe that is within the gasket area or within 0.125 inches of the

board edge will be considered among the last choices. Only “unreliable”and “no_probe” nodes have lower evaluations.

• Collision Considerations− Probes that will be located too close together (physically) are not

allowed.− 100 and 75 mil probe locations are preferred.− 50 mil probe locations are second best.− Tooling pins are allocated with a keepout band also, this to prevent

shorts to the tooling pins.

• Testhead considerations− For scarce testhead resources, warnings are issued if these are blocked.− There are 12 ground pins on each Double Density Hybrid card. It is

possible to block all these grounds with probe locations. If this happens,Fixture Tooling software will output a warning that this card is notusable due to blocked resources.

• The last consideration for each node is that of access.− If a node has only one access point its priority is increased.− Topside probing is not used often, and will only be used if the Board

Consultant’s Global Options have the Top Electrical Probes enabled.This will require a fixture top probe plate.


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Allocating Power Supply resources

From “board.o”, the Probe Select software receives the user requirements for powersupplies. During the assignment of nodes, the power nodes received some of the wiresneeded for testing, but not the wires needed for carrying the current specified in thePower Options Menu of Board Consultant. These additional wiring requirements areadded after other nodes have been assigned.

A quick look at the Power Supply wiring scheme for the Ground node, (we are countingground wires):

• The current (I) value of each power supply in rounded up to the next higherinteger. One wire is required for each amp (2.1Amps requires 3 wires).

• The number of supplies needed for this PC board are added to this number.• Add one ground return for every 32 nodes (rounding up).


Probe SelectPower Wiring

There are 1203 nodes on this board.If: +5V draws 2.2 Amps +12V draws 0.8 AmpsHow many +5V, +12V and GND wires are required?

+5V +12V GND1 wire per amp: 3 1 41 per supply 1 1 21 for sense 1 1 2Node Count / 32 38Total: 5 3 46


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• The Fixturing Process is done in two disjointed steps• Board Placement places the board on the test fixture.• Probe Select identifies the best probing location.• Test Consultant writes the individual tests.

− For Node En:• Pins & Shorts test will require a G bus.• Analog Incircuit test of R1 will need an S or I bus.• Digital test for U1 will require a Digital Driver.• Digital test for U2 will require a Digital Driver to disable U1…

• The individual tests are compiled− This creates requirements or .r files.− These list the resources needed for this test to function properly

• Module Pin Assignment runs.− MPA gathers all the requirements for the node En and identifies a BRC

as close as possible to the probe location that provides all the resourcesneeded by the various .r files.

− If MPA cannot find one BRC, it assigns two.

• Fixture Tooling runs:− Given the probe location and the BRCs assigned, Fixture Tooling

defines the wiring scheme.


Fixturing:Requirements are generated and evaluated

En

Vcc

R1

U1

U2Large ASIC


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• Module Pin Assignment evaluates how each node will be used to determine:− Which testhead resource(s) needs to be paired with each node

• MPA selects the appropriate testhead resource− The goal, place the Personality Pin as close as possible to the test Probe.− This will ensure the shortest possible wire.− MPA knows that a personality pin can be bent up to 0.10 inches or the

Offset Kit can be used if necessary.− When selecting the “appropriate resource” MPA makes sure there are

no multiplexing conflicts

• Module Pin Assignment then writes the “wirelist.o” file that is used bysubsequent software. The “wirelist.o” file lists:

− Each test− The nodes used in that test− The node’s BRC number− Which internal multiplexed bus that node needs to contact.− To read the wirelist.o, de-compile it with the list object

command:list object “wirelist.o” to “wirelist”

• Module Pin Assignment follows a criterion similar to the one used by ProbeSelect when assigning Personality Pins:



Board Placement

Probe Select


Fixture Tooling



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− Some testhead resources were identified as being blocked as probeswere assigned; therefore, MPA no longer has access to these resources.

− Assign “critical” nodes first. Scan all the nodes, looking for those thatthe user marked “critical”.

• Assign those resources that are limited− Clocks: There are several clock resources on the Control Card. These

are important, but not covered in the User Fundamentals class. They aredescribed in detail in the Advanced Digital class.

− External Instrumentation: Typically external instruments can connect tothe board under test, but in a limited number of locations. Therefore,these personality pins are assigned early in the sequence.

• The powered test resources are assigned next.− Resources that involve clusters rather than the individual parts.− Large pin-out devices, these need to be assigned early before channels

are loaded with potential multiplexing conflicts with smaller devices.(The smaller pin count devices can be assigned more easily.)

• Next, nodes that are involved with both powered and unpowered tests. Thesenodes are allocated after the digital resources but before purely analog nodes.

• The purely analog nodes are assigned next. The analog multiplexing schemeis rather complex, but completely different from the digital assignmentsmade so far. While these nodes are assigned late in the process, earlier stepsdo consider the analog multiplexing and assign their resources “breath first”using as many test cards as possible, filling as few channels on any one cardas possible. This means that analog distribution is more easily implemented.

• The final allocation goes to nodes that are only tested in the shorts test. Thesemight include nodes on the output of a digital gate that is not used on theboard, or devices marked “no-test” in the “board” file.

Module Pin Assignment’s Inputs & Outputs

MPA uses the test.r files, “testorder”, “config.o” and “fixture/fixture.o” files as input.These provide the software with the information needed about each test.Notice that Module Pin Assignment deals with the fixture based on tests, not on devices.

• Module Pin Assignment does not augment the “fixture” file. Instead itcreates a new file, “wirelist.o”. This lists each of the tests and the specificresources used for that test.

• Module Pin Assignment adds information to the “fixture/summary” and“fixture/details” files. The information is initially identical in the two files:

The efficiency value is a measure of the number of nodes that required more than onewire. If multiple modules are used, there will be cases where each module needs access toa node on the board (for example: Vcc or Ground). In this case, one probe will havemultiple wires. This is reflected as a lower efficiency value. (This value is lower inPowered test systems where a node maybe connected to both analog and digitalresources.)


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Fixture Tooling

Fixture Tooling does some resource management for you.

• Fixture Tooling determines the length of wire needed for each wire-wrapoperation.

• It counts the number of wires connected to each probe or personality pin. Themaximum number of wires is three.

• The software adds the inter-module wiring required in all fixture applicationsof more than one module.

• Fixture Tooling also adds additional personality pins to the fixture. Thesemight be needed in the future if an ECO occurs.

• The Fixture Tooling software generates reports and files that describe how tobuild the fixture and files that will assist in troubleshooting any fixturingproblems in the future.

• Inter-module Wires added by Fixture Tooling• Autofile

When a fixture is loaded, the Autofile is automatically read by the system.− It identifies the board file associated with the fixture, msi’s to that

directory, loads and runs the “testplan”.• The standard Fixture wiring includes the Autofile.

− The system will generate an Autofile code automatically or you candefine your own.

− The system starts with the number 4094 and counts down toward theminimum value of 11.



Board Placement

Probe Select


Fixture Tooling



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− Other autofile codes are reserved for diagnostics fixtures and otherAgilent applications.

− Each fixture must have a unique autofile code.

• Fixture EnableThe jumper, “Fixture Enable” must be installed for the test to run.

− If this jumper is sensed by the testhead, it accepts the fixture as beingpresent and loaded correctly.

− If the enable jumper is not found, the operator is given a prompt aboutthe fixture being misloaded.

• Safety DisableThe Safety Disable jumper must be present in the fixture for the powersupplies to be powered.

− If this jumper is not present, the power supplies are disabled.There are applications where this jumper is very handy such as in theevent that a board needs to have a safety shield to prevent dangerousshock to the operator.

• XL & XG module interconnectionsWhen an ASRU tests a device on the PC board, it needs access to all nodesassociated with that device. The software provides the S and I busconnections to the device under test.

− But guard points might be in another module, with a different ASRUcard.The modules need to be interconnected. The GOUT (guard bus) andLOUT (guard sense bus) connections in each module must be tiedtogether. The Fixture Tooling software identifies which modules need tobe interconnected. It then assigns the appropriate personality pins andwires.

Extra Personality Pins

Fixture Tooling also allocates additional personality pins.

• These are provided to make ECOs easier to accomplish.• When the allocations are complete “extra” locations are added by Fixture

Tooling.• The software will keep track of these resources and when a fixture change is

required, these extra personality pins will be used. The algorithm does notassign a fixed number or percentage of extra p-pins, but typically, it is on theorder of 10%.


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Fixture Tooling Outputs

Fixture Tooling modifies the following files:

• “fixture/fixture.o”

• “fixture/details”

• “fixture/summary”

The “fixture/details” file includes:

• A list of the Test Cards used in testing this PC board.• A summary of the fixture wiring.

− If the mean wire length is 12 inches, there is probably a problem.− If the standard deviation of the wire length is nearly equal to or greater

than the mean value, there may be a problem.− If the overall fixturing efficiency is less than 85%, there is probably a

problem.• A table shows the ground wire length for test cards that had “critical”

connections associated.

The “fixture/summary” file includes:

• The information that appears in the Test Consultant Message Window alongwith additional information that is not displayed. This includes:

− A summary of the fixturing resources (number of pins, probes, wirelength...).

The Fixture Tooling software amends the “fixture/fixture” file:

• Each node now shows the location of the personality pin with the PINSstatement.

• It also adds the WIRES information that lists the Bank/Row/Column wherethe personality pin is located, the color wire, its gauge and length.


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The Files for the Fixture Builder

These files are also important to the programmer who has to modify a fixture.

• traceThis file combines all the information about the fixture in a single file and isused during troubleshooting. The information includes the probe’s location(X-Y and device.pin), the number of wire-wrap wires connected to it, thecolor of those wires and where those wires should go. If there were a fixtureverification error, use the “trace” file to debug the fixture.

• drillAn Excellon Format 2, version2 file that most machine shops will recognizeand use in the construction of a fixture, specifically, drilling the Probe Plate.It includes the probe locations (completely through the Probe Plate), thealternate locations (partially through the Probe Plate), the personality pinlocations and locations for Tooling Pins.

• drilltopAnother Excellon file, this one is dedicated to drilling the Top Plate in theevent top side TestJet Probes are used and you used the Test Consultantsoftware to determine the exact locations for these probes. It only includesholes in the Top Plate, no other information. If the fixture does not includetop side test probes, there will not be a “drilltop” file.


fixture/ trace!-----------------------------------------------------! AGILENT FIXTURE TRACE REPORT <date & time>! fixture/trace!-----------------------------------------------------FIXTURE TYPE: Agilent Simplate Express...!----------------------------------------------------- (Pin) [Probe] <Length>!-----------------------------------------------------Node Name 1AProbe [2 11.77 44.7] On Device: u1.1Wire Color: Blue Guage: 28 Path (2 20.00 61.0) <6.5> [2 11.77 44.7] Use Digital Drv. ASRU Detector Shorts Test

...Node Name CLOCK_ENABLEProbe [2 16.84 27.1] On Device: r5.2Wire Color: Blue Guage: 28 Path (2 18.00 48.0) <3.5> [2 16.84 27.1] Use GP Relay...


Fixture I 8 - 23

• drillsupAnother Excellon file, this one is dedicated to drilling the Support Plate. Themajor difference between this one and the “drill” file, is that the “drill” fileincludes information on drilling “blind” holes and holes for the personalitypins. The “drillsup” has only the list of drill locations to match the probe siteson the board and tooling pin locations.

• insertsLists information to assist in the loading of the drilled Probe Plate. It tellswhich holes receive probe sockets, which ones receive personality pins andwhich Tooling pins to use. In the case of different spring force probes, itdefines which force probe to install in which receptacle.

• wiresThis file is designed for the people who actually do the wire-wrapping. Thereare two styles of presentation (defined in Board Consultant).

− Manual: The wiring operations start at the center of the board and workout from the center to limit the number of wire-wraps that will requirethe operator to “dig for the pin” among previously installed wires.

− Automated: The wiring order is based on the length, gauge and color ofthe wire. Automated wire-wrap machines center the wire-wrap gun overthe target pin so that there is no need to “dig for the pin”.

• differenceThe “difference” report is part of the “details” file. This report lists all thewiring changes as “wires to remove” and “wires to add”.

Note: If you have not built a fixture yet, if you see the software removingwires and adding wires, you are forcing it to adapt to a fixture that does notexist. This is not as efficient as letting the software create the fixture withoutany limitations.

During the lab, review the “fixture/trace” and “fixture/wires” files. The “trace” filecontains the maximum information possible about each node.


Fixture I 8 - 24

Bank Row Column

The BRC or Bank Row Column reference is a way of navigating the fixture and testhead.The numbers reflect which Bank is involved, which Row in that bank and which columnon the row. Thus the node 1A, described at BRC 22061 is in Bank 2, Row 20, Column61.

Likewise, Clock_Enable has a connection at BRC 21848 or Bank 2, Row 18, Column 48.

For the Double Density Pin Card, this original numbering scheme did not work very well.Therefore, the numbering on the Double Density cards uses the original numberingscheme for the original row of pins, and inserts an extra 1 into the pattern for the secondrow of pins. Thus if these were Double Density Pin Cards, BRC 220161 would refer toBank 2, Row 20, Double Density row 1, Column 61.

The Bank1 node at 11848 is shown as a white dot on the drawing, at Slot 6 of Bank1.

• Notice it is on the Control Card.• Notice this is a different resource than the corresponding pin in Bank2.

− The resources on the cards are numbered from the Mother Board.− Therefore, the 48th pin from the Mother Board in Bank1 is not the same

resource as the 48th resource from the Mother Board in Bank2.− The 48th pin in Bank2 is a General Purpose Relay (GP1H, H for high)− The 48th pin in Bank1 is a Ground Connection.− See the On-Line Documentation for details about the resources.

See the Cards In Testhead manual.


Testhead Numbering

BRC: Bank Row ColumnBank 2 Bank 1

Module 2

Module 3

Module 0

Module 1

Slot 1: ASRU

Slot 6: Control

Slot 1: ASRU

Slot 6: Control

Slot 1: ASRU

Slot 6: Control

Slot 1: ASRU

Slot 6: Control MO

THE

R B

OA

RDM

OT

HER

BO

AR

D

Row 1

Row11Row 13

Row 23

Row 1

Row11Row 13

Row 23

Column 78 1 78 1

1A at: 2 20 61CLOCK_ENABLE at: 2 18 48

Double Density node at: 2 20 1 61Bank 1 Node: 1 18 48


Fixture I 8 - 25

Fixture Verification

There are several tools available to assist in verifying the correct wiring of a fixture.Some of these will not be detailed until later modules, but the majority can be explainedhere.

Board Graphics

Before starting verification, you should start the Board Graphics display. If enabledbefore starting the fixture verification, the Board Graphics Display will highlight all thepositions where the probe can be placed to access a node, or the specific device.pin thatthe command wants you to probe.

• To use the Board Graphics Display: in a BT-BASIC window:• msi to the board directory• Execute the command board graphics• In the same BT-BASIC window, issue the desired verification command.

Auto Start

AutoStart is associated with the Special Function Key F7. It has two modes of operation,the default is “manual start” meaning you must press either the foot switch or the STARTkey to initiate a fixture verification test (detailed below). If you choose to use “auto start”the hardware looks for a continuous contact between the hand-held probe and any pointon the fixture. When the software has detected a continuous contact, it automaticallyinvokes the START key for you.


Fixture Verification

Missing ProbesMiswiresOpens and Shorts


Fixture I 8 - 26

verify

The verify command places the guided probe on a location, applies a 100mv sourceand measures where that signal goes. The verify command options:

• verify “node_name”

− You enter the command with a specific node name.− The system provides a list of device.pins where the node can be found.− The testhead applies the 100mv source. It measures all nodes to see

where the signal actually goes.− If it goes to the expected point(s) only, it passes.− If it goes to additional locations, these are reported.− If it does not go to the expected destination, that is reported too.

• verify all

− This command tells the system to test all points on the board,− This command will cause the verification software to sequence through

each component in “board” asking you to place the guided probe oneach pin of the component to verify the connection.

• verify all nodes

− This command tells the system to test all nodes on the board (but not allpoints – that tests each node several times).

− This command sequences through all the nodes in the “board” filehaving you verify each node.

• verify all from “device.pin”

− Allows you to stop the verify all verification. The softwarerecords the current device.pin being verified so that you can return laterand resume verification without missing any points or having to retestlocations.

• verify nodes from “node-name”

− Allows you to stop the verify all nodes verification. Thesoftware records the current node being verified so that you can returnlater and resume verification without missing any nodes or having toretest nodes.

• verify all testjet probes

− This command sequences through all TestJet probes on the board.

• verify testjet probes “device_name”

− This command tests the TestJet probe associated with the specifieddevice.

• verify testjet probes from “device_name”

− Allows you to stop the verification process and resume without havingto retest or miss testing any probes.


Fixture I 8 - 27

verify all mux cards

− The software runs without your interaction. It tests each of themultiplexing cards associated with TestJet Probes. Because the TestJet’selectronics board can be mounted incorrectly, this test also verifies theassembly of each TestJet probe. (The test does not check the polarity ofthe sensor plate, that is done by the verify testjet probescommand.)

• verify mux <mux#> port <port#> module <module#>

− Tests the TestJet Probe associated with the targeted mux/port/module.

find pins

find pins: The function is similar to verify except you do not specify a locationor node.

• find pins

− Put the hand-held probe on a point and press F1: START.− The 100mv signal is applied to the hand-held probe and the system

looks for which node is receiving the signal.− When it finds that node, it reports it to you. If there are multiple node

contacts, all are reported.− Because the signal is on the entire node, the system cannot report which

device.pin the guided probe is on, but it does list the device.pins on thenode in contact with the hand probe.

• find testjet probes

− Put the hand-held probe on the test via of the TestJet Probe− The software does a serial poll of all the TestJet Probes looking for the

one that you are probing. When the poll is completed, you receive aprompt, including the address (module, mux, port) and associated devicefor that TestJet Probe.

probe “<device-name>”

The “probe” command displays a representation of the device specified.

• probe “<device>”

− When the hand held probe is touching a pin, that pin is shown as a “P”indicating the 100mv signal is currently present of the pin in question.

− When that lead is released, the display shows it as “T” for tested.− Any lead that is not touched, will show an asterisk (*).− Any lead that does not have a probe in the fixture (marked “no_probe”

in “board_xy”) will be identified with a period (.).


Fixture I 8 - 28

Running Test Consultant Multiple times

There are two fundamental reasons for running the Fixturing Software again.

• The first is that the previous run resulted in errors, poor test coverage,excessive number of blocked resources or something that you decided wouldnot allow the process to continue until that was corrected.

− In these cases, the fixture has not been built yet.

• The other case is if there is an Engineering Change to the board.− In this case, the fixture has been built.

Re-running Fixturing Software BEFORE a fixture is built

If the reason for running the software again was identified before a fixture was actuallybuilt, Test Consultant needs to know that the fixture does not exist.

• The key is that the Fixturing Software believes in magic. It assumes that assoon as its reports are generated, a fixture is built. When the fixture reportsare in existence, the fixture exists too.

• Any subsequent software run assumes that there is a tangible fixture sittingon a shelf. Given this, the software will work with the existing fixture,modifying it rather than recreating it.

• This leads to a very inefficient fixture design.


Running Fixture GenerationMultiple Times

Fixture has NOT been built

Remove Fixture FilesRun Agilent IPG Test Consultant

- Software sees no evidence of fixture therefore, creates a new one withoutprovision for non-existent fixture.

Fixture has been built

Keep Fixture FilesRun Agilent IPG Test Consultant

- Software sees the fixture. - Software decides if a wire can be added or removed based on existingtests and fixture.


Fixture I 8 - 29

• To illustrate what can happen, an example:• Test Consultant was run, including the fixturing software.

− Fixture reports were generated, the software assumes a fixture exists.• You discover a data entry error on a digital device.

− The correction is made.• Test Consultant is run again.

− The fixture files describe a fixture (that has not been built) that hasseveral conflicts with the newly entered digital device.

− In one case, the software might recognize the conflicts, issue warningsand mark that lead of the device as not being accessible.

− In another case, the “new” device needs a personality pin, but all the p-pins in the immediate area have either been allocated or will not workdue to multiplexing conflicts. Therefore the closest available personalitypin must be used, unfortunately it happens to be 12 inches away.

• The moral of this story, if there is no fixture yet, do not let the system thinkthere is.

How do you tell tell the software that the fixture does not exist?

By removing the “wirelist.o” and “fixture/fixture.o” files.

• Use a BT-BASIC window to unlink the files:unlink “wirelist.o” | unlink fixture/fixture.o”

Rerunning Fixturing Software AFTER a fixture is built

If Test Consultant is being re-run with an existing fixture due to an ECO, the “wirelist.o”and “fixture.o” files are the only way the system software can know what the existingfixture looks like.

• Given these resources, the fixturing software may generate a modifiedversion of the fixture.

• It may write new “wirelist.o” and “fixture.o” files and add a “difference”report to the “details” file. The “difference” report contains details about anywires that need to be removed and about wires that need to be added.

If there is a fixture, but the “wirelist.o” and “fixture.o” files are removed, the existence ofthe real fixture is likewise removed. Now the fixturing software will start all over again.It is likely that the new version of the fixture will be very similar to the actual fixture butthere will definitely be differences. Therefore, never remove these files if a fixture hasbeen built.


Fixture I 8 - 30

The ECO process

The process followed when Test Consultant runs with an existing fixture.

• The software first removes all resources that are no longer needed. It movesthese resources to an internal list of “available-resources”.

• When additional resources are needed, all available resources are evaluatedfor the best match. This evaluation starts with the list of “available-resources” created or augmented in the first step.

Make two archive tapes of your development.Send one to the people who build your fixture. Save / Protect the other.Many programmers also make copies of the “wirelist.o” and “fixture.o” files and savethem in the board directory, perhaps as “wirelist_orig” and “fixture/fixture_orig”.

Exceptions to the Rule

Having built the fixture you may discover the need to add wires to improve test accuracy.This need may not be seen until you are well into the debug process. There are two basicalternatives to achieving the needed modifications.

• You can manipulate the fixture semi-manually using Fixture Consultant.Fixture Consultant (discussed later) allows you to make changes while thesoftware only shows alternatives based on multiplexing requirements.

• You can modify your test development descriptions in Board Consultant andrerun Test Consultant. Using this technique, the software will manage allaspects of the actual modification.

Examine the “fixture/details” file

Look for changes to the fixture… findn "Diff":

--------------------------------------------------------3070 FIXTURE WIRE DIFFERENCE REPORT <date & time>/home/user1/class_bd/fixture/details--------------------------------------------------------

| From | To | From | ToLength|Ga|Color|(b r c ) |(b r c )| X Y | X Y------|--|-----|----------------|---------------|-----|-----|-----|----Remove 2.8 26 Blue (2 23.00 63.0) (2 22.00 61.0) 4211 -227 5801 -281Add 4.3 26 Blue (2 23.00 63.0) (2 16.00 62.0) 4211 -227 4361 -327

Remove 1Add 1

If a wire is removed from a fixture, the old test may no longer execute properly. Thismeans the old version of the board will no longer be testable. Use Multiple Board


Fixture I 8 - 31

Versions software to keep the existing tests and testhead resources in place whileadapting to a new version of the board. This is discussed next week.

Glossary

There are some additional terms and expressions that you should be aware of beforecontinuing.

• Simplate Fixture: Long wire fixture using one plate for probes and a secondfor pins.

• Simplate Express Fixture: Short wire fixture using a single probe/pin plate.• Probe: Spring loaded nail that connects the fixture to the PC board.• Personality Pin: Pin that connects the fixture to the testhead.• Vacuum Fixture: These are vacuum actuated fixtures. A vacuum is applied

so the PC board is pulled tightly against the Support Plate and together theseare pulled down onto the test probes.

• Support Plate: The plate that the PC board rests on. It has a vacuum gasketbetween it and the Probe Plate and a vacuum gasket between it and the PCboard.

• Probe Plate: The plate that contains the test probes. On the Express Fixture, italso has Personality Pins loaded in it.

• Alignment Plate: On Simplate Express fixtures only - aligns Personality Pinsto testhead.

• Tooling Pins: Pins that the operator mounts the PC board over. These ensurequality registration between the PC board and the overall fixture.

• BRC: The testhead resources are numbered as Bank/Row/Column values orBRCs. There are two formats. The single density pin cards use B RR CC.The double density pin cards use the format B RR 1 CC.e.g.: 11311 would be Bank 1, row 13 column 11. or 214122 would beBank 2, row 14, column 22 on the double density card’s second row.

• ECO: Engineering Change Order. The basic modification of the existingboard to include new features, cost reductions, re-engineering modifications,etc.


Fixture I 8 - 32

Appendix

“fixture/fixture.o” details

For an Express fixture, you must define several details during the data entry phase ofBoard Consultant. Board Consultant copies this information to the “board_xy” file.

• Fixture Option information such as the fixture type and size.• The command line BOARD, the name entered must match the name of the

directory. In this case the “angela_bd” directory and file.• If the outline of the board includes several notches, slots or other

irregularities, you can simplify that by selecting a single plane and using it asthe board edge. However, before you over-simplify the board outline, checkwith your fixture builder to confirm that they understand you are simplifyingthe outline.

• The location of Tooling Holes is important to the fixture building process.The software includes keepout regions adjacent to tooling pins because thepin has a shoulder that prevents probes or personality pins from beingmounted immediately adjacent to the tooling pin. The software expects youto define two Tooling Pin locations.

• You define keepout areas to prevent the placement of probes and/orpersonality pins in a specific region of the fixture. The reasons for defining akeepout area will vary, among the most common are to allow for TestJetprobes (done by the software) or to allow for components mounted on theedge or bottom of the board.


fixture/fixture.o! ------------------------------------------------------------! FIXTURE DESCRIPTION LISTER <date & time>! fixture/fixture.o! ------------------------------------------------------------OPTIONSFixture Type EXPRESS;Fixture Size BANK2;...BOARD angela_bd !Note: This name must match the board directoryPLACEMENT 19486, -77677 0.0;

OUTLINE0, 0115750, 0115750, 1285000, 1285000, 0;

TOOLING3750 2500, 6500;3750 113410, 121450;

KEEPOUTS


Fixture I 8 - 33

“fixture/summary” - after Board Placement

The “fixture/summary” file contains all ERRORS and WARNINGS generated by thesoftware while evaluating the “board” and “board_xy” files. The information scrollingacross Test Consultant’s message window while the software runs, is the sameinformation found in the “fixture/summary” file.

NOTE: The “fixture/summary” file is cumulative. The original file generated by the firstrun of fixturing software will be kept and subsequent runs of the fixturing software willappend information to the end of the file. If you want to review the latest run of thefixturing software, you will need to skip past the earlier runs and find the most recentinformation.

--------------------------------------------------------3070 BOARD PLACEMENT <date & time>/home/user1/class_bd/fixture/summary--------------------------------------------------------...The board “angela_bd” was placed at X = 19486,Y = -77677 with a rotation of 0.000 degrees.

“fixture/details”

The third file is the “fixture/details” file. After Board Placement the “summary” and“details” files are identical. As the fixture software continues to run, the two files becomedistinct.

“fixture/summary” - after Probe Select

The “fixture/summary” file now includes a description of fixture requirements, number ofprobes, number of pins, etc.

--------------------------------------------------------3070 Probe Select <date & time>/home/user1/class_bd/fixture/summary--------------------------------------------------------Nodes that are inaccessible or need more probes = 0Maximum probe force density (oz./sq.in.) = 104Number of probes exceeding density threshold = 0...Nodes added to the fixture = 101Nodes marked NO_PROBE or NO_ACCESS in board_xy = 0...

The “fixture/details” file now includes:

• Testhead resources defined as inaccessible or as “blocked pins”


Fixture I 8 - 34

• Personality Pin locations and the probes that block them are listed.Having several Personality Pins blocked is not uncommon and is generallynot a major concern.

During incremental runs of the fixture software, Probe Select might make changes. To see anychanges, review the “fixture/details” file.

“fixture/fixture.o” output - after Module Pin Assignment!-----------------------------------------------------! FIXTURE DESCRIPTION LISTER <date & time>! fixture/fixture.o!-----------------------------------------------------OPTIONS ... BOARD angela_bd PLACEMENT 13111, 38073 -90.0; OUTLINE ...TOOLING ...NODE ADDR0 PINS 22136 -676; PROBES P50 70380, 22980 u302.9;ALTERNATES

80380, 26980 u303.5; WIRES 22136 TO P50 Blue 28 1.00;...

NODE CCLK PINS 22032;PROBES P110 80880, 75480 j301.1;ALTERNATES 75880, 65480, u302.18; 61880, 66480, u301.2; 52880, 48480, ar309.1;WIRES 22032 TO P110 Blue 28 1.00;OTHERPINS 21329 BLOCKED; ... 22341 SOCKETED; ... 21805 DRILLED;. . .