Hi Lee,

        It sounds like you are getting "burning" (local current densities
are too high) on the panel.
        There are a whole list of things which could be causing this.

        What current are you running?
        It might help if you can lower your Amperes per Square Foot (err,
Meters).
        Depends on the chemistry you are using.

        How steady are your power supplies?  I'm assuming DC.

        Have you inspected the boards prior to Sn/Pb plating?
        They could be getting burned in some preceding (copper) step.

        Can you change the design or are you locked in?
        You might add nonfunctional pads in the troublesome areas.

        During plating, the panels don't sway towards the anode bars, right?
        I've seen panels burn on the bottom or the edge (especially on one
side more than another) when it wasn't mounted in the tank correctly.

        Some thoughts,

        Hans

~~~~~~~~
Hans M. Hinners                                 WR-ALC/LYPME Bldg. 640
Materials Engineer                                      380 Second Street,
Suite 104
Manufacturing Eng. Sec.                         Robins AFB GA 31098-1638
912-926-1970 (Voice) 468 - 1970 (DSN)   912-926-7974 (Fax)
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> Hello, all
> I have difficulty in Sn/Pb plating beacuse deviation of Sn/Pb thickness is
> severe.
> and where the pattern is dense the deviation is more severe.  
> 
> Does anyone know the good way decrease the thickness deviation?
> Is it possible to decrease the plating thickness deviation of the dense
> pattern part  
> 
> within +- 1㎛?
> I want to the way and the eqip, chemical ....
> I'm waiting...
> Good bye all  
> 

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