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Dendrites after strip to strip plating (pure tin)

2007

We have a problem on dendrites growth after plating specially on fine pitch packages (lead are very close together).

Our machine has only 2 plating cells and the current density is around 20-30 ASD to get a good plating thickness around 10-12 microns. Our pure tin process is run at room temperature only.

What are the possible rootcause for this problem?

Alfred Yu
Semiconductor - Indonesia

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Alfred,
There are a few things I would check out. Make sure the Sn metal and sulfuric acid concentrations in the bath are suitable for the current density and speed you are using. Because anode polarization and stannic Sn generation are common problems in this type of plating, a non-phenol antioxidant (with good stability) is being used in your type of bath with very good results. Are you using a non-phenol antioxidant in the bath? If not, your Sn supplier should be able to advise you. Good Luck!

Mark Baker
Process Engineer - Syracuse, New York
2007

You indicate the growth is happening after plating. Does this mean that the dendrites are growing while sitting on the shelf? If the are you are probably seeing tin whiskering. There are probably people who would be interested in seing your problem if the growth is happening quickly.

Kurt Sammons
- Inman, South Carolina
2007

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Hi Alfred,


Dendrites growth has many factors to consider and therefore you need to go to process of elimination. It can be base material related. (are you plating on copper base?) It can also be due to poor pre treatment. High operating current density can also be a factor but it can be corrected by optimizing the solution concentration and increasing solution flow rate. Surprising that you are operating at room temperature since most pure tin chemistries are operating at slightly higher temperature to achieve good plating when running at high current density. You can check also the metallic impurities particularly Lead. Keep it low. Good Luck.

regards,

Germie Maravilla
- Manila, Philippines
2007

I would like to know where I can get non-phenol antioxidant? My application is tin electro refining in sulfuric acid. I am using an phenol based antioxidant (contain hydroquinone) and cannot retard effectively the generation of stannate ions. My anodes are dark color and similar to mud when I touch it. Should they be metallic white?

Brigitte Peck Ki Laou
Recycle scrape metal - Montreal, Quebec, Canada
2007

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Hi sir,
In my m/c have 4 plating bath, M/c speed is 4.5m/min why many time black patches coming in my m/c ?

Selvaraj Raja
- Singapore
2007

We are plating copper based alloys. we already optimized concentration of the solution & its flow rate. the chemistry operates at room temperature.

Alfred Yu
Semiconductor - Indonesia
January 14, 2008