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Packaging | Lead-Free Status | Impact to Customers | Tin Whiskers
Green Compliance | Industry Consortia | Questions & Answers | Literature
- 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, National anneals all of its tin plated, leadframe-based packages for 1 hour at 150° C within 24 hours of plating. This is the industry-accepted method for controlling whisker growth.
- Since thin plating is known to be more susceptible to whisker growth, National maintains a minimum tin plating thickness of 8 microns, with a nominal thickness of 12 microns.
- National packages are plated with the most advanced plating chemistry in the industry for tin whisker control and have been meeting JEDEC 22A121 specifications since 2010.
| |
National |
JEDEC |
| Stress1 / duration |
TMCL(-55/85° C) / 3000 cycles |
TMCL(-55/85° C) / 1500 cycles, min. |
| Stress2 / duration |
Room conditions/ 10,000 hours |
30° C/60%RH / 4000 hours, min. |
| Stress3 / duration |
60° C/93%RH / 7000 hours |
60° C/90%RH / 4000 hours, min. |
| S.S. (screening) |
9 terminations |
96 terminations |
| S.S. (detailed insp.) |
9 terminations |
18 terminations |
| Inspection Tool |
SEM required |
Either SEM or optical |
- In terms of lead-free requirements, the current RoHS Directive exempts leadframe packages with pitches less than or equal to 0.65 mm.
- The following data is collected per the JEDEC requirements given in JESD201:
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 |
12.1 μm |
16.7 μm |
18.9 μm |
24.2 μm |
19.9 μm |
< 10 μm |
14.4 μm |
13.7 µm |
11.3 μm |
32.5 μm |
22.5 μm |
11.2 μm |
| 1000cyc |
15 um |
18.7 μm |
19.4 μm |
25.2 μm |
27.7 μm |
< 10 μm |
22.2 μm |
19.1 μm |
17.9 μm |
35.3 μm |
30.2 μm |
20.9 μm |
| 1500cyc |
19.5 um |
23.3 μm |
19.9 μm |
26.3 μm |
27.8 μm |
20.8 μm |
22.9 μm |
21.8 μm |
19.3 μm |
35.2 μm |
31.3 μm |
23.4 μm |
THST
(55C/85%RH) |
1000hr |
< 10 μm |
< 10 μm |
< 10 μm |
< 10 μm |
< 10 μm |
< 10 μm |
< 10 μm |
< 10 μm |
< 10 μm |
< 10 μm |
< 10 μm |
< 10 μm |
| 2000hr |
11.4 μm |
< 10 μm |
< 10 μm |
< 10 μm |
< 10 μm |
< 10 μm |
16.9 μm |
< 10 μm |
< 10 μm |
< 10 μm |
< 10 μm |
19.6 μm |
| 3000hr |
31.5 μm |
28.9 μm |
< 10 μm |
< 10 μm |
< 10 μm |
< 10 μm |
22.5 μm |
< 10 μm |
< 10 μm |
15.9 μm |
< 10 μm |
36.7 μm |
| 4000hr |
38.7 μm |
32.8 μm |
26.2 μm s |
< 10 μm |
< 10 μm |
< 10 μm |
24.9 μm |
29.1 μm |
< 10 μm |
17.1 μm |
< 10 μm |
34 μm |
Ambient
(30C/60%RH) |
1000hr |
< 10 μm |
< 10 μm |
< 10 μm |
< 10 μm |
< 10 μm |
< 10 μm |
< 10 μm |
< 10 μm |
< 10 μm |
< 10 μm |
< 10 μm |
< 10 μm |
| 2000hr |
< 10 μm |
< 10 μm |
< 10 μm |
< 10 μm |
< 10 μm |
< 10 μm |
< 10 μm |
< 10 μm |
< 10 μm |
< 10 μm |
< 10 μm |
< 10 μm |
| 3000hr |
< 10 μm |
< 10 μm |
< 10 μm |
< 10 μm |
< 10 μm |
< 10 μm |
< 10 μm |
< 10 μm |
< 10 μm |
< 10 μm |
< 10 μm |
< 10 μm |
| 4000hr |
< 10 μm |
< 10 μm |
< 10 μm |
< 10 μm |
< 10 μm |
< 10 μm |
< 10 μm |
< 10 μm |
< 10 μm |
< 10 μm |
< 10 μm |
< 10 μm |
Leadframe Material
| Leadframe Material |
Packages |
| Cu194 |
SOT23, SOT223, DPAK, MSOP, SOIC, SC70, TO252, PSOP, MDIP, LLP |
| Cu7025 |
QFP, TSSOP, TO247, TO-PMOD |
| TAMAC2 |
TO220 ≤ 9 leads, TS263 ≤ 9 leads |
| TAMAC4 |
TO220 ≥ 9 leads |
Packaging | Lead-Free Status | Impact to Customers | Tin Whiskers
Green Compliance | Industry Consortia | Questions & Answers | Literature
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