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Lead frame Plating Problem 

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I have been in the lead frame plating industry as a plating engineer for 6 months. One of the problems I always encounter is uneven Ag plating (spot Ag plating). What is causing the problem? Is it coming from the anti immersion bath?

Another thing is the "Ag Oxidation". I found the problem tends to happen when we're using higher duty cycle (90%, 70%..etc) and solve by lowering the duty cycle. Also, especially when we're using copper olin 7025, the problem could come anytime no matter what pulse we use. Could anyone explain what is the mechanism that is causing the problem?

thanks in advance..

deen

Md. Deen
Penang, Malaysia

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Hi Deen,

how often you change your anti immersion? and how many stages is your anti immersion?

anti immersion could contribute to unevenness. it might drag the contaminant into the Ag bath.

Ahmad Nisfu
- Penang

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The anti immersion process on Cu base material before Ag plating that inactivation of Cu surface and almost solution content Ag ionic and cover on Cu material surface to prevent Cu immersion to Ag plating solution as one of contamination prevention.

C C Chen
- KaoHsiung, Taiwan ROC

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February 8, 2012

I am facing uneven plating like as Mr Deen. We purely use copper material, we use brighteners, we use anti immersion chemical with proper control to avoid the chemical dragout to Ag bath.  We also use 1 ms on and 2 ms off plating pulse and with 800 to 1200 ASD current density.
We have studied on current distribution cables to verify it resistant. All seems okay
We still encounter The uneven Ag plating.

AH Kim
- Singapore

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February 10, 2012

Hi AH, Deen,

Possible causes of uneven Ag plating are:

1. Inadequate of surface active agent (conditioner) to enhance Ag deposit uniformity at high current density.

2. Inappropriate/inadequate solution flow from sparger/nozzle.

3. Improper anode-to-cathode ratio and/or too short anode-to-cathode distance.

4. Metallic or organic contamination.

5. Poor pretreatment (water break) prior Ag plating.

6. High free cyanide in Ag bath.


Regards,
David

David Shiu
- Singapore