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December 9, 2009

SN96 Solderability Issues

We have been hand soldering a connector using 63/37 solder. The connector has bright electrolytic tin as the finish.

Recently we switched to SN96 and have been experiencing solderability issues. We sent samples to an independent test lab and had them run solderability testing using both 63/37 and SN96 with RMA flux.

The 63/37 samples all passed and the SN96 all failed for de-wetting. As a side note the tin is plated on at 150 micro-inches thick and the connectors are approx. 2 months old.

Can you shed any light on this problem?

B. R.

Experts Comments

It is possible that you damaged the plating by operating your soldering stations at too high a soldering temperature.

I would suggest evaluating a direct power soldering system operating at a lower tip temperature.

Edward Zamborsky
Regional Sales Manager
OK International Inc.
Mr. Zamborsky serves as one of OK's technology advisers to the Product Development group. Ed has authored articles and papers on topics such as; Low Volume SMT Assembly, Solder Fume Extraction, SMT Rework, BGA Rework, Lead Free Hand Soldering, Lead Free Visual Inspection and Lead Free Array Rework.

I would be suspicious of the condition of the connector pin surfaces.

Perhaps, because of age the parts need to be re-conditioned. You do not mention the type of solderability test, i.e.. dip-and-look vs. wetting balance.

We use a wetting balance (MUST III, GEN3 Systems) in our process development lab and often find that wettability curves will vary with different solders, fluxes, temps and time profiles.

IPC/EIA J-STD-003A and other solderability tests call out a specific profile, solder and flux - in this manner the part being tested is the variable. By using variable solders and fluxes, without establishing a base line for the wettability of the part, there are too many variables for a sound decision.

First determine the quality of the parts, then determine the effects of the different solders and fluxes.

Kevin Valentine
Sales and Service Manager, Americas
Nordson SELECT
Kevin Valentine is the Sales and Service Manager, Americas of Nordson SELECT and has over 25 years of experience in the electronics manufacturing industry. Kevin's expertise is in production manufacturing automation, equipment setup and operation as well as process engineering. For the past 15 years Kevin has focused specifically on soldering issues relating to selective soldering, component solderability and lead tinning.

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