Dougal, Very good point. We have done no experiments to determine if the matte finish is inferior to the glossy finish with regard to contamination. This was strictly conjecture on our part. Are you able to share the mask material that you have found particularly compatible with immersion white tin, if not to the whole forum at least off-line? Regards, Seth Goodman Goodman Associates, LLC [log in to unmask] -----Original Message----- From: TechNet [mailto:[log in to unmask]]On Behalf Of Stewart, Dougal Sent: Thursday, August 23, 2001 3:52 AM To: [log in to unmask] Subject: Re: [TN] White Tin Immersion tin (white tin) is a particularly aggressive process for bare board fab - it is operated at high temperature, long immersion times and uses two chemistries that find it easy to work their way through the soldermask resin structure, namely MSA and Thiourea. There are lower MSA versions available which reduce the attack, but we now use immersion tin as the metal finish to benchmark soldermask performance. We have identified a soldermask that stands up well to the immersion tin process and meets all the requirements on SIR and e-corrosion, but surface preparation before coating, and screening technique do have an influence on the ability of the mask to perform. With reference to your comment on the mattness of the ink, their seems to be a big rift in the understanding of the effect of mattness on contamination, and too many generalisations made. The way that the matte is achieved is different with different masks, even by the same manufacturer, so I would rely on data, not theory, when you want to know if it has an effect. You can't beat real undisputable facts ! Dougal Stewart Director of Technology Development, Viasystems Europe tel: +44 191 206 2081 mob:+44 780 221 1958 The information supplied here is a personal view, and may, or may not reflect the view of my employer. --------------------------------------------------------------------------------- Technet Mail List provided as a free service by IPC using LISTSERV 1.8d To unsubscribe, send a message to [log in to unmask] with following text in the BODY (NOT the subject field): SIGNOFF Technet To temporarily halt delivery of Technet send the following message: SET Technet NOMAIL Search previous postings at: www.ipc.org > On-Line Resources & Databases > E-mail Archives Please visit IPC web site (http://www.ipc.org/html/forum.htm) for additional information, or contact Keach Sasamori at [log in to unmask] or 847-509-9700 ext.5315 ---------------------------------------------------------------------------------