Matthew,
I've worked on this in a previous life. The more important
parameter was how clean (is) are your developer rinse(s). I've also
observed this affinity you talking about in the grain boundary mainly.
To your question try this if you can.
cascade developing, keep the rinse clean, running rinse, rinse
temperature.
Regards,
> ----------
> From: Matthew Byrne[SMTP:[log in to unmask]]
> Reply To: TechNet E-Mail Forum.;[log in to unmask]
> Sent: Tuesday, February 10, 1998 4:15 PM
> To: [log in to unmask]
> Subject: [TN] Re[2]: [TN] Soldermask developing
>
> Has anyone every had experience developing solder mask on gold
> plated
> boards? We get the impression that the mask has an affinity for
> the
> gold. It leaves stains that are very hard to remove. We see
> them
> after developing, & are looking for a method to remove them
> before
> curing.
>
>
> Matt Byrne
> HADCO-Owego
>
> ______________________________ Reply Separator
> _________________________________
> Subject: Re: [TN] Soldermask developing
> Author: "TechNet E-Mail Forum." <[log in to unmask]>, [log in to unmask]
> at
> SMTPLINK-HADCO
> Date: 2/9/98 12:50 AM
>
>
> With standard sodium or potassium carbonate developing solutions
> (generally
> 0.9 to 1.1%), feed and bleed systems for LPI solder masks are
> maintained at a
> pH level of 10.7 to 10.8. Since the initial makeup of the developing
> solution
> in the holding tank with DI water is in the range of 11.0-11.2 pH, the
> system
> is fairly easy to control by feeding directly into the developing
> sump. A
> number of companies make feed and bleed systems for controlling
> developing
> solutions. The feed rate is usually controlled by pH of the solution
> in the
> sump.
>
> These days, a number of companies (Surfact-Tek, Morton, Dexter, etc.)
> offer
> "doped" developing solution concentrates that are designed for the
> liquid,
> photoimageable (LPI) solder masks. These concentrates contain amounts
> of
> sodium or potassium hydroxide that increase the pH of the operating
> solution
> in the sump (up to 12.0 pH), increase the loading capacity of the
> developing
> solution and allow for better development of the solder mask out of
> the holes
> (important if screening is used to apply the mask).
>
> Whichever way you go, I'm sure you will have success with using the
> feed and
> bleed method to control your developing with your LPI solder mask.
>
> Hope this helps.
>
> Larry Fisher
> Dexter Electronic Materials
> [log in to unmask]
>
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