Printed Circuit Board Assembly & PCB Design SMT Electronics Assembly Manufacturing Forum

Printed Circuit Board Assembly & PCB Design Forum

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IC Contamination

Steve L

#17969

IC Contamination | 22 October, 2001

The solder joint appeared dull and there is dewetting on the PCB after Reflow. The leads of IC we used appeared dull grey before soldering.

Dose anyone happen to know if there is a standard to verify the IC contamination and how to deal with the contaminated IC we have in house?

Appreciate your help. Thanks in advance.

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#17973

IC Contamination | 22 October, 2001

I�m aware of no such standard. There may be something in Euroland [ie, IEC, etc.]

TM-650 �Test Methods Manual� has procedures for measuring various types of contamination, such as: * 2.2.25 �Detection Of Ionizable Surface Contaminants� * 2.2.27 �Cleanliness Test � Residual Resin� * 2.2.28 �Ionic Analysis Of Circuit Boards, Ion Chromatography Method� * 2.2.38 �Surface Organic Contamination Test� * 2.6.3.3 �Surface Insulation Resistance, Fluxes�

The level of these contaminants SB such that the do not compromise the product performance, er words to that effect. Various test labs; such as CSL, Trace, Robisan; help their customers develop guidelines for allowable levels of various contaminants, based on the end-product use, type of test, the manufacturer of the test equipment, and whatnot.

Points to consider: * �Dull� appearance alone is not an indicator of solder connection quality. Dewetting certainly is. Taken together, they indicate something nasty is going on with your assembly. * Some alternate solderability protection materials: - Appear different from SnPb lead solderability protection. - Require soldering profiles different from SnPb solderability protection. [For instance, TI�s site has information of their Pd solderability protection. http://www.ti.com/sc/docs/asl/palladm/index.htm] * Some combinations of board and component lead solderability protection require profile adjustments.

Questions are: * If the component is the problem, why did the board dewet, rather than the component? * What is the coating of the component of concern? Who is the supplier? What does the supplier say about the appearance of the lead solderability protection? * What is the solderability protection of the bare board of concern? * What is the temperature profile taken on the dewetted lead? * What is this component? * What is your process prior to noticing the problem?

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