As a micro-etch (either type) becomes saturated with copper, there is a tendency for it to redeposit copper sulfate crystals, especially when it hits a cold rinse. These tiny copper sulfate crystals will cause dewetting in HASL. It is common practice to follow the micro-etch rinse with a sulfuric acid dip of 5-10% and rinse. This redissolves the copper sulfate. Another fix is to change (persulfate) or regenerate (peroxide-sulfuric) the micro-etch more frequently, to prevent copper buildup in the solution. Also, maintain enough acid in the etch (see supplier) to keep the maximum amount of copper in solution. Patty ---------- From: TechNet-request To: TechNet Subject: Re: HASL Microetch Date: Thursday, September 26, 1996 1:30PM As a HASL service provider we see the entire gambit of solder mask residues. We use a persulfate based etchant at a rate of 40-60 microinches. The trade off is that it is much more difficult to rinse than peroxide/sulfuric chemistries and can cause non-wets if not entirely removed before entering the HAL machine. Michael Holan Process Engineer Radian Electronics Div. [log in to unmask] ______________________________ Reply Separator _________________________________ Subject: HASL Microetch Author: [log in to unmask] at INTERNET Date: 9/26/96 12:57 PM Does anyone have information, opinions or preferably data regarding micro etching with persulfate vs sulfuric acid/peroxide chemistries? We are currently using a sulfuric acid/peroxide based microetch at the HAL line, and are considering alternatives. I have seen some information which suggests a persulfate based chemistry is better at removing solder mask residues. Any feedback would be appreciated. Jim Kenny *************************************************************************** * TechNet mail list is provided as a service by IPC using SmartList v3.05 * *************************************************************************** * To unsubscribe from this list at any time, send a message to: * * [log in to unmask] with <subject: unsubscribe> and no text. * *************************************************************************** *************************************************************************** * TechNet mail list is provided as a service by IPC using SmartList v3.05 * *************************************************************************** * To unsubscribe from this list at any time, send a message to: * * [log in to unmask] with <subject: unsubscribe> and no text. * ***************************************************************************