2016 Flexrigid design rules as success factor · IPC2223 use B Saving Area = saving Cost...

Flex-rigid: design rules as success factor

Webinar April 5th 2016 Speaker: Andreas Schilpp

content

1• System advantages of Flex-rigid (summary)

2• Which rules have to be regarded?

3• Design Chain – 24 important points

4• Examples for good and less good designs

06.04.2016 page 2 www.we-online.de

System advantages of Flex-rigid

Miniaturization

• additional assemblylevels

• option folding

• savings in area forconnector footprints

• savings in weight

• integration of interfaces

Signal integrity

• calculation withreference layerpossible

• impedancediscontinuitiesavoided

Reliability

• less contacts

• wiring error lesslikely to occur

• less mass

• simplified testability• simplified assembly


Which rules have to be regarded?

� Standards and legal

requirements

� commercial aspects

� mechanical impacts and

dependencies

� Environmental conditions and

mission profile

� production related design rules

Contribution to Succes


Mechanics & System

80%

Circuit &

PCB20%

Which topics have to be regarded?

� PCB related Design Rules Contribution to Succes

06.04.2016 Seite 5 www.we-online.de

Circuit &

PCB20%

Which topics have to be regarded?

besides others:

� Flexibility versus Stability

� IPC2223 use B

� Saving Area = saving Cost

� Environmental and operating

conditions

�� total Know-how is needed –

a lot more than the pure design

rules or as a design guide

Contribution to Succes


Mechanics & System

80%

Design Chain


Hint to our last Webinar from March 2016:

24 important points for your development

Design Chain



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Target: „First Time right“ – avoid „late engineering changes“

Today: Where are the most 3D related Points in the Chain?

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06.04.2016 page10 www.we-online.de

Product idea, Concept and Technology ChoiceModular Approach��Integrated ApproachFlex or Flex-rigid?

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Flex-rigid or Flex

Flex features

� typ. high volumes

� Real-to-real Production

or small Sheets

� typ. 12 x 18 sqinch or smaller

� PE and PI Foils

� Coverlay and flexible Soldermask

� Stamping

� stiffener glued

� no THT components or connectors

� special assembly


Flex-rigid features

� small to big volumes

� Sheet Production

� typ. 18 x 24 sqinch

� PI Foils and rigid Materials

� Soldermask, Coverlay and flexible

Soldermask

� typ. Milling

� rigid areas for assembly

� all kind of components

� standard assembly

Flex-rigid instead of Flex


Alternative: rigid-flex-rigid structure 2-layers 1F-1Ri,

Standard thickness 1,6mm

• delivery in an array

• no problem with high volumes

• THT connector with standard assembly and soldering

• second copper layer as option for routing

• ZIF-contact by depth controlled milling easy

• improved stability and handling

Price 2 Flex-rigid: € 1,20 per pcb (@5K)

Flex „1F“ �� Flex-rigid „1F-1Ri“

Origin:: single layer flex with 0,3mm thick contacts for

insertion into a ZIF connector.

• delivery as single pcb (very small!)

• high volumes critical due to small production sheet

• assembly and soldering of THT connector by hand

• glueing of stiffener for ZIF contact by hand

• packaging difficult (bulk goods!)

• Quality issue: crack at THT pin!

Price1 Flex: € 1,95 per pcb (@5K)

��

• Standard solderpaste printing• Standard assembly

• Standard soldering (no hand soldering!)

• Standard production in Flex-rigid• no ENIG on inner layers needed

• no openings in coverlay needed

• no Vias in Flex

All Components on rigid areas



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Functional Specifications for Mechanics & Elektronics & Software, Size

Requirements for the PCB derived from the SystemStart-up may be only „DIN-A4 page“ �� high risk of late engineering changes!


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Mission profile, Reliability Requirements, Life Span

use B – continous bending application


Sensor head: rigid-flex-rigid structure, 4 layers 1Ri - 2F -1Ri

Problem: Interrupts at the flex-rigid transition after 500.000 cycles

Solution: Change in stack-up to a 1F-3Ri, geometrical Changes

Result: easier is better

Stopp testing after 2,1 Mio. Cycles: Function i.O

use B – continous bending application

� Bending form, Radius, bending cycles? � 3D Models are very helpful!



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„Do you provide only Gerbers oradditional 3D drawings or

models???“


Mechanics, Assembly and Fastening of the PCB, Shock and Vibration

Fastening of a flex-rigid PCB - Vibration


NO fixation of one rigid area

… leads to resonanceand destruction evenwith Rigid-Flex!

Option „Lift-off“ with Flex outside


Saving area and material by folding


� Arrange flex extensions to save space, if necessary combine multiple extensions, use fold technology

Save area by optimization in 3D


Save area by optimization in 3D

Flex arm #3a – RFQ of a customer / Proposals


�� folding for

final shape !

drawing or scetch of system assembly is always very helpful !

Fläche sparen durch Optimierung in 3D

Flexausleger 3b


�� folding for

final shape!


15Material Choice for the PCB bare board – as general as possible, i.e. acc. IPC

do not specify supplier and type (using Standards improves quality & price)

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PCB Layout

DfM, Design Rules, Annular Ring

move crossings into rigid areas


2 flexible layers inside 1 flexible layer outside

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Reliability in Design and Layout

IPC 2223 A good example!

Regarding reliability it is importand:

� to do plastic-suited Design

� processing-suited Design

� Fastening

� Avoid Vias in Flex

in general !

NO contacts and plated through holes in flex areas



use big radii. �

We recommend the use of a bending tool

and a pre-bending of Semiflex pcbs prior

to the final assembly

�



short multiple flexible layers



23Further processing of a flex-rigid pcb

Download „Drying recommendations“

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Drying prior to assembly / soldering

� Problem:

� Solution

Other possible cause:

� Do not dry in a stack!

� Use an oven with exhaust system!



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Array separation and transport

Which possibilities does your production has?

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Array Separation with stamping - Transport


Quelle: Fa. acd

�

Additional Information


… to this subject as well as forother basic knowledge have

been already covered by

several Webinars in detail

You could find that in our

Webinar Archive or at

Summary

Flex-rigid by nature is a very reliable Technology.

The development of an electronic system

� could be very complex

� requires a lot of different disciplines.

� Networking and communication is fundamental

� WE likes to support you in a project

� You are running an optimization loop?

WE would like to help you!

� Please contact us as early as possible!


Thank you for your attention!


2016 Flexrigid design rules as success factor · IPC2223 use B Saving Area = saving Cost...

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