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Dendrite after pure tin plated on alloy

Now I have a problem about dendrite after pure tin plating on raw material are alloy42 and copper plated Nickel. The machine that run electroplating is MECO machine. The machine type is blet and plated by strip to strip. the plating thickness is 400 -800 microinches. The current density is 20-25 A/dm2. Please suggest me to corrective this action.

Sommat P.
Hana Semiconductor Co.,Ltd - Thailand
2005

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2005

Please describe the problem appearance (e.g., roughness, spangles or other grain effects, whiskers?).
" Dendrite" usually refers to a tree-like solidification pattern. Does the problem occur immediately (upon plating), after heating (post-plating bake or solder reflow), or after some time period? Is this bright tin or matte (dull) tin? Also, is humidity/temperature exposure testing involved?

Stresses due to organic brighteners may facilitate whisker growth, causing many companies to specify matte tin. Excessive Cu6Sn5 formation under certain heating and aging conditions causes stresses and a pronounced grain effect.

A study "Whisker Testing: Reality or Fiction?" by P. Oberndorff et al. of matte tin plating on Alloy 42 (low thermal expansion Fe-42%Ni) indicates nickel underplating (rather than copper) will minimize the above problems. http://www.st.com/stonline/leadfree/testing.pdf

Ken Vlach [deceased]
- Goleta, California
Finishing.com honored Ken for his countless carefully researched responses. He passed away May 14, 2015.
Rest in peace, Ken. Thank you for your hard work which the finishing world, and we at finishing.com, continue to benefit from.

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Hello,
Dendrites or filaments visible after plating can be attributed to few factors. It is more likely to occur on Copper alloy material specially Olin 151 (due to presence of Zirconium) but Alloy 42 and Nickel base material will also grow dendrites. Pre-treatment/preclean process play an important role in dendrite growth. Make sure they are properly maintained and in optimum conditions. Plating chemical efficiency and additive mechanism are also factors to consider. Please look at your filters. There maybe loose fibers flying around the plating cell that can stick on the frames and plated over by tin.

Germie Maravilla
- Laguna, Philippines
2005

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Dendrite occur immediately after plating on two packages only that molding is white compound (the component has titanium dioxide). We're going on solving this problem. Our current action is "Tin strike" before tin plating. The inspection result of dendrite is improvement but it's solved incompletely. Now we're monitoring for multiple lots and also optimize tin strike condition.
Please you suggest us for tin strike operating condition or other way to get more good result.

Nontalee C.
Hana Semiconductor (Ayutthaya) Co., Ltd. - Thailand
2005

Try chopped dc plating. We already encountered same problem in our company ( Tin copper plating on copper base ). Our initial countermeasure was the change of base metal etching. But later the problem reoccurred. We tried chopped dc plating of 9 sec on and 1 sec off. It was effective.On:off Timing may vary depending on bath additives.

Rose Buds
- Batangas, Philippines
May 23, 2008