Thanks everyone, for taking the time to respond. That was a new one for me. (its interesting what I take for granted until something goes wrong!) one more question: Is there a difference between soldermask material and silkscreen material? Aren't they both just colored epoxies? (ok, two questions!) Jack . On Mon, 8 Aug 2011 08:51:36 -0700, Bob METCALF <[log in to unmask]> wrote: >White mask historically has performed different than it's green >counterpart. Depending on the pigment used to make it white, it can have >an affect on cure, but also the initial exposure step that created the >image (I'm assuming we are talking about a liquid photoimagable solder >mask). If the UV light does not cross link the mask enough in the initial >exposure step the developer will "attack" the mask more in the development >stage and diminish performance during the assemble process. > >In addition to insuring the proper curing steps are observed, which could >include a UV cure, I would make sure they are tack drying and exposing the >white mask to the manufactures recommendations. If the fabricator is >simply using the same steps used to process green mask, this could be >creating your problem. > >Regards, > >Bob Metcalf >Western Regional Manager > >Atotech USA Inc >1750 Overview Drive >Rock Hill, South Carolina 29730 USA > >Mobile: 714-334-7667 >e-mail: [log in to unmask] >Internet: www.atotech.com > >Managing Director: Kuldip Johal > >-----Original Message----- >From: TechNet [mailto:[log in to unmask]] On Behalf Of Jack Olson >Sent: Monday, August 08, 2011 7:47 AM >To: [log in to unmask] >Subject: [TN] White SolderMask > >Greetings, > >Have any of you experienced mask problems like the ones shown in these >pictures? > >http://frontdoor.biz/PCBportal/WhiteMask.jpg > >The bottom picture shows exposed copper, and I believe there is a copper >plane on the top layer. >(this has happened to different boards, different lot codes, but MIGHT be >the same batch of mask) > >What I'm wondering is, is it more likely that the problem is related to >the >fact that the mask is WHITE, or that it is some other problem? >If the properties of white mask are different, maybe it doesn't adhere as >well to the surface? I remember back in the olden days they used to ask us >to break up solid copper planes so the mask would stick better to the >laminate, but I haven't heard of anyone having problems with that for a >long >time. > >The supplier said they baked some bare boards and ran them through the >oven, >and the problem went away, but we are reluctant to just blindly add a >permanent baking step if there are other considerations. > >Jack --------------------------------------------------- Technet Mail List provided as a service by IPC using LISTSERV 16.0 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 or (re-start) delivery of Technet send e-mail to [log in to unmask]: SET Technet NOMAIL or (MAIL) To receive ONE mailing per day of all the posts: send e-mail to [log in to unmask]: SET Technet Digest Search the archives of previous posts at: http://listserv.ipc.org/archives For additional information, or contact Keach Sasamori at [log in to unmask] or 847-615-7100 ext.2815 -----------------------------------------------------