1

CTIS # 29946

Prepared By John Yurtin

Updated 2-9-2005

Connection Systems Training

Terminal Plating

2

Having a good technical understanding of the design and performance of terminals can help you properly apply them within the vehicle. Plating should be clearly understood as to it reasons and effect on performance.

This training help you understand why we plate terminals and the significance of the platings used.

Excellence

Performance Goal: Do it right the first time, every time

Method: Innovation and continuous improvement

3

Agenda

Why Use Plating Types and Selection of Plating Contact Physics & Technology Gold vs Tin Plating Fretting Corrosion Analysis Of Wear Lubricants Field Observations Plating Mix Guidelines Summary

4

MAXIMUM TYPICAL ROUGHCONTINUOUS PLATING COST POSSIBLE PLATINGS Advantages Disadvantages

Plating Type OPERATING THICKNESS (microns) RANKING FOR MATING PARTS Why use this type of Plating Why do we not use this type of PlatingTEMP (C) (1=low cost)

NO PLATING 85 N/A 1 Bare Low Cost Unstable resistance leads to intermittenciey or overheating(BARE Tin or Tin-Lead Need high force terminals and low currentCOPPER ALLOY) Silver Need 12V circuits

TIN 125 1.9 to 6.9 3 Tin or Tin-Lead Relatively low cost Susceptibility to fretting corrosion is main weaknessELECTROPLATE Silver Good resistance to environmental degradation Contact properties degrade quickly above 125C

Susceptible to tin whisker formation

TIN 125 4 Tin or Tin-Lead Relatively low cost Susceptibility to fretting corrosion is main weaknessReflowed 1.9 to 3.3 Silver Good resistance to environmental degradation Contact properties degrade quickly above 125C

Shiny appearance

Tin 125 0.5 to 2.0 3 Tin or Tin-Lead Relatively low cost Susceptibility to fretting corrosion is main weaknessHot Dipped Silver Good resistance to environmental degradation Contact properties degrade quickly above 125C

Shiny appearance Can have large thickness variationLead is being phased out

TIN-LEAD 125 1.9 to 6.9 4 Tin or Tin-Lead Relatively low cost Susceptibility to fretting corrosion is main weaknessELECTROPLATE Silver Good resistance to environmental degradation Contact properties degrade quickly above 125C

Shiny appearance Very high friction - plating is very soft

HARD GOLD 125 0.5 to 0.75 6 Gold Resists fretting corrosion Relatively high costELECTROPLATE Gold-Flashed Pd Good resistance to environmental degradation Contact properties of hard gold degrade above 125C

Diffused Gold Bettr friction and wear properties than tin Can crack when formed

SILVER 150 2.5 to 5.0 5 Silver Resists fretting corrosion Can have poor friction and wear propertiesELECTROPLATE some gold-based coatings Good high temperature properties Turns black when exposed to open air

Less expensive than gold Electromigration is a concern with small centerlines

GOLD-FLASHED 150 6 Gold Resists fretting corrosion Relatively high costPALLADIUM 0.1 minimum GOLD, Gold-Flashed Pd Good high temperature propertiesELECTROPLATE 0.5 minimum PALLADIUM Diffused Gold Cost is similar to hard gold electroplate

Good friction and wear properties

DIFFUSED GOLD ON 150 Refer to specs. for 7 Gold Resists fretting corrosion Relatively high costPALLADIUM-SILVER TMI305 or DGR156 Gold-Flashed Pd Good high temperature properties Single source(CLAD INLAY) Diffused Gold Good formability

Types and Selection of Plating

5

Why Use Plating?

Field Vehicle Interface Resistance Cumulative Distribution at 4 yearsPassenger Compartment

Plated vs Unplated

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

0 10 20 30 40 50 60 70 80 90 100

Resistance in mohm

Cu

mu

lati

ve

%

Plated

Unplated

6

Contact Probe Testing

Function:Measure surface electrical resistance

Uses:

Evaluate contact material systems

Compare aged material systems

Specifications:Force: 0 -1kg range, 1 gram resolution

Displacement: 100 cm range, 0.3 m resolution

Instrumentation: 4-wire m meter

Computerized motion control and data acquisition

Gold Probe

Tip

Test Sample

X - Y Sample

Positioner

Load Cell

Electrical Isolation

Low Noise Motor

20X Gear Reducer

Programmable Precision Table

7

Contact Resistance of Terminal Coatings

0.1

1

10

100

1000

10000

100000

Brass Stainless Nickel Tin Gold Silver PlatinumClad

Gold PdClad

Gold-flashed

PdPlating

Co

nta

ct

resis

tan

ce a

t 1N

Initial1 wk at 150C

Goal is 10 milliohms

Properties of Terminal Plating

8

Contact resistance is a function of contact force and material.

Contact area and contact pressure influence wear properties and resistance to contaminants

Goal is to design for the highest contact pressure that will meet requirements for the maximum number of mating cycles

– Typically 2 to 4 large radius contact spots

– Ten mating cycles typical for tin and silver-plated terminals

– Hard gold or gold-flashed palladium used when more mating cycles are required

Contact Technology

9

Contact Resistance Calculations

RConnection = Rbulk + R film + R constriction

Rbulk = resistance of the terminal material

R film = resistance from oxidation, corrosion, etc.

R constriction = resistance through a clean interface (good approximation for ring terminal resistance)

R constriction =

Rc = Constriction Resistance in Ohms

= Resistivity of Contact Material (Plating or coating) in Ohm-cm

H= Hardness of Contact Material in kg/mm2

W= Contact Force in kg

10

Contact Force & Contact Resistance

11

White-Light Profilometer – Used to study fretting and wear

damage

Coupon Wear Tracks

DimpleFretting

Under High Power

Dimple-on-Coupon configuration for fretting tests

Fretting Under Low Power

Fretting Under High

Power

Analysis of Wear

12

Fretting corrosion - The formation of oxidized wear debris caused by microscopic relative motion between contact surfaces.

(generally10 to 100 microns movement)

Fretting Corrosion - Definition:

Contact Interface Review

13

Fretting Machine Operation– Sample holder

– Feedback loop

– Debris particle

Contact Physics Infrastructure

Sample

NormalLoad

Sample holder

Position sensor

Electrodynamic drivers

Aluminum rodTower

14

Contact Physics InfrastructureFretting Wear

• Basic research

» Fretting parameters

» Power

• Applied research

» Material comparison

» Lubricant evaluation

0.001

0.01

0.1

1

10

100

0 1000 2000 3000 4000 5000

Fretting Cycles

Oh

m

Unpowered

0.001

0.01

0.1

1

10

100

0 1000 2000 3000 4000 5000

Fretting CyclesO

hm

Powered

Unpowered

Powered

Fretting

Wear

Tracks

15

Lubricant Requirements

General Requirements– Ability to withstand terminal operating temperatures

– Environmentally acceptable

– Ability to be applied and detected easily

– Chemically compatible with all terminal and connector housing materials

– Should remain on contacts to help reduce friction and wear

– Non-conductive

– Non-corrosive

– Low cost

16

Contact Lubricants Sliding Wear

A graph showing changes in the coefficient of friction under sliding wear conditions for un-lubricated and lubricated conditions.

The addition of Nyosil M25 lowered the coefficient of friction– Decreasing the frictional force

– Lowering the insertion force

0

0.2

0.4

0.6

0.8

1

0 2 4 6 8 10

Sliding Wear Cycles

Co

eff

icie

nt

Of

Fri

cti

on Not lubricated

4 l Nyosil M25

17

Effect of Lubricants on Fretting

Tin Plated Dimple&Flat After 1 Week @ 150C

0.0001

0.001

0.01

0.1

1

10

1 10 100 1000 10000 100000 1000000

Fretting Cycles

Res

ista

nce

(O

hm

s)

No Lube

High Perf. Grease

18

Connection System TechnologyVibration Analysis

Vibration is a challenging requirement to design around because of the variables

– Frequency

– Intensity

– Duration

Vibration Simulation Program– Complete for the Micro64 Connection System

– Development started for 100W Connection System

» Terminal contact geometry

» Natural Frequency

» Actual testing

Design of Experiments– Lubricants

– High flex cable

– Bolt together connection

– Rubber mounts

19

Micro64 Vibration Simulation Data

20

Micro64 Vibration Simulation Data

All ECMs On Engine Known Pass Limit 16.6Grey Area 16.6-24.5

Known Fail Limit 24.5Duration Input Output Evaluation

Hours/Axis G rms % Severity Pass-Fail ReasoningProfile 7 100 34.9 132.7 100.00% Fail 132.7>>24.5Profile 6 10 9.94 33 24.87% Fail 33>24.5Profile 5 22 12.5 24.7 18.61% Fail 24.7>24.5Profile 4 8 12.6 22.3 16.80% Grey* 16.6<22.3<24.5Profile 3 100 5.02 15.4 11.61% Pass 15.4<16.6Profile 2 6 9.96 15.3 11.53% Pass 15.3<16.6Profile 1 50 9.82 14.5 10.93% Pass 14.5<16.6

*In actual testing, Packard did pass

21

Connection System TechnologyVibration Analysis

Vibration profiles need to be evaluated individually for each Connection System

– Multiple variables make it difficult to compare profiles

Vibration Simulation is conservative estimate of connection system performance

– Enables us to do an intensity vs frequency analysis

» Mounting geometry

» Dampening/rubber mounts

Work closely with OEM’s and Module suppliers to design the most cost effective system that will perform in the specified environment.

22

Connection Systems Training

Gold Plating vs. Tin Plating

23

General Guidelines - Gold vs. Tin Terminal Plating

When do we use tin-plating?– Terminals with contact force over 5N (280MP and larger)

– In areas where tin’s resistance to vibration has been proven

– Some customers specify gold-plated terminals for low-current circuits, but we have seen no physical low current limit for tin-plated terminals

When do we use gold-based plating?– When mating connector or device uses gold

– When low terminal contact force causes fretting and wear issues with tin. ( typically around 5 N)

» Gold normally used for 100W, Micro64

» Gold-to-gold or tin-to-tin used on Micro-Pack 100, 150MP, and GT depending on severity of the environment

– When max. continuous operating temperature exceeds 125C

» Regular “gold-plating” not acceptable above 125C

» Special, silver or gold-based coatings used for 125C to 340C

24

Acceptable Plating Combinations

Tin-Plated Terminals– Compatible with mating terminals coated with tin or tin-lead

– Tin-to-silver is similar or slightly better than tin-to-tin

– Tin-to-gold not recommended

» Tin oxide can build up quickly on contact spots and cause increased resistance.

Gold-Plated terminals– Compatible with mating terminals coated with gold, gold-flashed palladium,

and gold alloys

– Gold mated to silver-plated terminals can be compatible, depending on terminal design

– Gold mated to tin plated terminals not recommended – (see above)

25

Connector Testing – Gold vs. Tin

C-4006 VALIDATION RESULTS UNSEALED MICRO-PACK 100 CONNECTORS

Dry Circuit resistance measurements

0

5

10

15

HEAT TMPCYCL

HUMID SHOCK VIBR DUST

TEST DESCRIPTIO N

MA

X.

DR

Y C

IRC

UIT

RE

SIS

TA

NC

E (

mo

hm

)

TIN GOLD

SPEC. LIMIT

Gold and Tin perform about the same if connector

and terminal designs resist

fretting corrosion

26

Fretting Corrosion - Definition:

Fretting corrosion - The formation of oxidized wear debris caused by microscopic relative motion between contact surfaces.

(generally10 to 100 microns movement)

27

This is fretting corrosion!

Fretting Corrosion

28

Effect of Terminal Contact Materials

FRETTING AT 20 Microns, 1N, 8 Hz

0.0001

0.001

0.01

0.1

1

10

1 10 100 1000 10000 100000 1000000

FRETTING CYCLES

RE

SIS

TA

NC

E (

Oh

ms

)

2.5 MICRON TIN

0.5 MICRON HARDGOLDCLAD Au/PdAg

2.5 MICRON SILVER

29

Conclusions

Gold plating is normally used for low contact force connections that are susceptible to fretting corrosion

Tin plating can be used in many automotive connections if fretting corrosion is eliminated

Are most connector troubles caused

by vibration?

Severe Vibration can cause harmful wear of contact interfaces

Mild vibration can cause fretting corrosion

Thermal changes can cause movement and fretting

Steps in the development of fretting corrosion on a tin‑plated terminal interface

Fretting Corrosion

31

What about Plating and Lubricants? Gold Plating will result in improved performance

Gold to Tin is not recommended by Delphi and other industry experts. (AMP clearly does not recommend tin to gold interfaces!) (http://www.amp.com/products/technology/metrology.stm)

Lubricants can reduce the effect of fretting

Thermal changes can cause movement and fretting

Fretting Corrosion

This is fretting corrosion!

Fretting Corrosion

Sensor terminal after GMI12590

Fretting corrosion can be caused by micro-movement from temperature changes as well as from mechanical vibration.

Fretting Corrosion

Symptoms of connections with fretting corrosion

– Problem disappears after connector is bumped

– Changing the device (sensor, computer, etc.) makes the problem go away temporarily

– Problem appears when the weather changes

Field Observations