The authoritative public forum
  for Metal Finishing since 1989
-----

Tin Alkaline Matte - Plating thickness Accuracy / Wire and Tie (Vs) Jig Plating

Hello, I am Vikram Bidi from Bangalore, India.
We have an application in which - Steel is base material, 2.5microns copper undercoat & Tin Finish to assist solderability.
Alkaline Matte Tin with 4-6microns (Target 4 microns) is essential for the next process(insert/overmolding).

I want to know is it possible to achieve consistent 4-6microns thickness with a target to maintain near 4microns.
If yes, then which method among Wire & Tie plating and Jig plating can give us this result.
What are the critical parameters which have to be controlled to achieve 4-6microns.

Vikram Bidi
Electronics Manufacturing - Bangalore, India
2007

---

Hello Ted Mooney,
Please suggest!

Vikram Bidi
Electronics Manufacturing - Bangalore, India
2007

---

2007

Since I do not know the size and shape of your part, it is hard to say.
1st, you have told us nothing of what you are currently using and what the problem is. Very few people respond to such open ended questions as you pose, because we may say exactly what you are doing now.
Do you do an acid dip between the copper and the tin?
In a cyanide based plating you can tweak the cyanide and the caustic to get desired results but you are not using cyanide. For a sodium stannate bath, typical is 39 gpl of tin as metal in analyses.
Typically, you will get better distribution of your plated tin with a lower amps per square foot and increased agitation. Corners and edges (high current density areas) will plate much heavier than low current density areas!
The lower ASF sill plate slower and will thru trial and error allow you to nail the 4 micron thickness in the average current density areas by varying the plating time, assuming that the load is always the same.
Is this rack or barrel?
You might need rack insulation or robbers to control buildup on the outer edges of the racked parts.
You will notice that this is all general plating knowledge, because you have given us nothing specific to work with.

James Watts
- Navarre, Florida