Matt: I have seen this same or similar condition on gold features. We
use a different LPI than you, applied by a DP10. Ni and Au are electrodeposited;
150u" and 30u" respectively. This happens only on a certain style of consruction
and in our case had nothing to do with developing, although we went up and down
that road quite a few times. If you would like to discuss this further contact
me.
                                                Regards
                                                        Michael Barmuta
                                                        Staff Engineer
                                                        Fluke Electronics
                                                        Everett Wa.
                                                        425-356-6076


On Thu, 12 Feb 1998 13:42:10 -0800 Matthew Byrne wrote:

> From: Matthew Byrne <[log in to unmask]>
> Date: Thu, 12 Feb 1998 13:42:10 -0800
> Subject: [TN] Re[4]: [TN] Soldermask developing
> To: [log in to unmask]
>
>      I am using Taiyo AUS-5 on electrolytic nickel gold.  Yes, we would
>      like to do selective plating, but the parts cannot be bussed.  We are
>      required on this part to use electrolytic full-body gold & the Taiyo
>      mask.
>
>      Electrolytic gold is not very smooth when examined microscopically.
>      There seems to be many cracks & crevices to get into & trap material.
>
>
>      Matt Byrne
>      HADCO
> ______________________________ Reply Separator
_________________________________
> Subject: Re: [TN] Re[2]: [TN] Soldermask developing
> Author:  "TechNet E-Mail Forum." <[log in to unmask]>, [log in to unmask] at
> SMTPLINK-HADCO
> Date:    2/11/98 11:33 PM
>
>
> You did not specify whether your gold was electrolytic (usually a thicker
> deposit and less porous) or the electroless Ni/Au (usually thinner [up to 5
> microinches] and more porous). I would expect that there would be no problems
> with developing mask off the electrolytic gold and there could be more
> problems with the more porous electroless Ni/Au.
>
> Most people who use gold circuitry will selectively gold plate (electrolytic)
> or will plate the electroless Ni/Au after the solder mask has been applied and
> cured. Let's face it, gold is expensive and the less you can get away with and
> still satisfy the customer, the better for the bottom line.
>
> I have not heard of developing LPI mask off of gold (not a whole lot of
> experience here, either). Perhaps, you may need to develop more aggressively
> or look at other LPI solder masks.
>
> Larry Fisher
> Dexter Electronic Materials
> [log in to unmask]
>
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