Introduction to Pd Alloy
- Palladium (Pd) alloy is a common option for spring pin plunger creation.
- The primary demerit of using Pd alloy is the finished plunger cost; so to offset this demerit, Pd alloy should be deployed only when appropriate.
- Pd alloy’s primary merit for IC testing is the alloy’s hardness, helpful in preventing solder migration to the spring pin’s plunger tip.
- The primary targeted results for deploying Pd alloy plungers are:
- Reduced variability of Cres over life of pin
- Improvement of pin tip longevity
- Throughput improvement by less frequent cleaning
But how does the hardness of the Pd alloy impact wear away?
Precipitation Hardening Process
Steps:
- Pre-heat the hardening chamber
- Insert the parts into the hardening chamber for heat treatment in nitrogen
- Cool down in nitrogen

Hardness Measurement Process
Steps:
- The sample is encased in epoxy
- A grinder and polisher are used to remove the material until a cross section is revealed
- Measure hardness by Vickers hardness tester

Hardness vs. Heat Treatment Temperature by Supplier

Breaking Force by Bending Test
- For the breaking force, we are using a three point bending test (flexural) method
- Reading is recorded once the material breaks
- Breaking counts are recorded


Breaking Force and Heat Treatment Temperature

Plunger Tip Wearing by Cycling Test
- Sample pin
- Hardest plunger and moderate hardness plunger
- Single ended pin for 0.35mm pitch
- Spring force is 28gf
- Cycle test
- Two kind of pin insert into same socket
- Cycle test until 200K
- Golden plated flat dummy device
- Measure Plunger Flat Ratio every 25K cycle

Definition of Plunger Flat Ratio

Plunger Tip Wearing

Plunger Tip Wearing After 200k Cycle

Summary
- Pd alloy material hardness and heat treatment condition
- The heat treatment temperature are different by supplier
- The hardest value are different by supplier
- Pd alloy material bending characteristics
- The hardest sample breaks minimum bending force
- Higher heat treatment temperature introduce higher braking ratio
- Pd alloy material wear away characteristics
- Hardest plunger average Plunger Flat Ratio (wearing) is smaller than moderate plunger
- Hardest plunger wearing variation is wider than moderate plunger
- Hardest plunger wearing is worse than moderate plunger
- Moderate hardness Pd alloy material is the best for the plunger