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| Reply To: | Leadfree Electronics Assembly E-Mail Forum. |
| Date: | Thu, 23 Sep 1999 08:19:53 -0700 |
| Content-Type: | text/plain |
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All,
I wanted to add that Sn25Ag10Sb has been used for many years in high volumes for soldering power die on to Cu heatsink/leadframes. Yes, this solder is quite strong and brittle, especially compared to Sn37Pb and similar solders. However, the Ag-Sn and Sn-Sb intermetallics are not the normal cause of failure in these packages. The most common failure mode is die cracking during cooling of larger die due to the large CTE mismatch and high solder strength. In general, if the die survive the initial cooling then they can be thermally cycled thousands of times without failure.
Regards - Marty
On Wed, 22 Sep 1999 16:24:27 -0700 Kirk D Mueller <[log in to unmask]> wrote in response to Doug Rohm:
I thought the problem with tin and silver was the formation of brittle
Sn-Ag intermetallics when the silver content exceeded 10 % by weight.
Kirk Mueller
Doug Romm <[log in to unmask]> on 09/22/99 08:48:13 AM
All,
Several of the Pb-free options being offered for use in both solders and
component lead plating include silver (Ag), for example Sn/Ag. In the past
some users of IC components have had concerns/problems with use of Ag in
components because of silver dendrite growth. Is there any concern about
use of Ag in these Pb-free alternatives? If not please provide a brief
technical explanation of why not.
This question may have been raised previously, but I can't find the answer.
Best regards, Doug Romm
Martin (Marty) Weiser, Ph.D.
Product Manager - Plated & Discrete Products
AlliedSignal Electronic Materials (formerly Johnson Matthey Electronics)
Spokane, WA
(509) 252-2757 (phone)
(509) 252-8617 (fax)
[log in to unmask]
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