TIN PLATING GLOSS OR MATT?? 1

[maya04]

hi,
can someone please advise the difference between matt and bright tin plating from:
1. corrosion point of view
2. soldering (still using little Pb)
it is applied on aluminum for soldering
WHAT IS PREFFERED?
thanks

 

[kenvlach]

Matt tin is better for solderability due to a lower level of organics (brighteners & levelers). Matt tin is usually better for corrosion resistance, too, for the same reason, but corrosion resistance depends mostly on freedom from porosity and thickness. Matt tin also has lower internal plating stress, so less likely to develop tin whiskers. Finally, reflowing lessens porosity and improves brightness of matt tin.
ASTM B545, 'Standard Specification for Electrodeposited Coatings of Tin' includes tests for adhesion, porosity, solderability, etc. and references the following:

ASTM B678, 'Standard Test Method for Solderability of Metallic-Coated Products.'

ASTM B253, 'Standard Guide for Preparation of Aluminum Alloys for Electroplating' gives substrate preparation such as zincating.

http://www.astm.org

Decide on your needs and any applicable electronics industry standards, then discuss choice of a suitable plating chemistry with a 'big name' supplier such as

http://www.atotech.com/start.php3?cl_my_id=672657

http://www.enthone.com/

http://www.macdermid.com/electronics/finalfini_immersiont.html

 

[nigelt]

As an aside, it is my understanding that when tin plating components that will be conducting RF energy, dull tin is likewise preferred. The presence of organic surface levellers in the plating interfere with the surface conduction of RF resulting in un-necessary losses.

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