Lead finish composition & Tin plating process
|Standard||85% SN, 15% Pb|
|63% SN, 37% Pb (some Metal Can packages)|
|Au over Ni|
Solder ball composition
For device-specific composition, click here.
Tin plating process
TI’s Tin plate process meets and exceeds qualification and monitoring standards set in JESD201, with Class 1 and Class 2 levels inspection per JESD 22A121. In addition, TI has taken the following actions for Tin plating products to meet JESD201 Class 2 requirement:
- Leadframe base material (alloy) control
- Tin plating control (chemistry, process and thickness)
- Post-plate annealing (150C minimum within 24 hours of plating)
TI uses leadframe materials such as Cu194, Cu7025, TAMAC2, and TAMAC4.
- Tin whiskers arise from stresses in the plating and are known to occur on tin plated or tin-alloy plated parts.
- After plating, an incubation period of several thousand hours may be required before any whiskers begin to grow. The length of this incubation period depends on the lead finish thickness, lead finish grain structure, and on the base metal composition.
- Tin whiskers are a reliability concern throughout the industry due to the fact that they may bridge the gap between leads causing electrical shorting.
- As a whisker mitigation measure, TI anneals all leadframe-based packages with formed leads for 1 hour at 150° C within 24 hours of plating. This is the industry-accepted method for controlling whisker growth.
- For electro-Plated devices, the minimum “as plated” thickness is 7 um, with 15% of thinning allowed after lead trim and form. This thickness conforms to the recognized Tin Whisker Mitigation practices published in JEDEC/IPC JP002.
- Hot Solder Dipped devices are dipped in a SnAgCu alloy to a minimum thickness of 5 μm after lead trim and form. This process is considered "Whisker free" per JEDEC/IPC JP002.
Representative whisker test results per JESD201
|Leadframe Material||Cu7025||TAMAC 4||Cu194||TAMAC 2|
|Stress Test||Timepoint||non- reflowed||Precon Condition C||Precon Condition D||non- reflowed||Precon Condition C||Precon Condition D||non- reflowed||Precon Condition C||Precon Condition D||non- reflowed||Precon Condition C||Precon Condition D|
|TMCL (-40C/ +85C)||500cyc||<11 um||<11 um||<11 um||<11 um||<11 um||<11 um||<11 um||<11 um||<11 um||<11 um||<11 um||<11 um|
ND = Not detected