May be it's because of over baking at the PCBs shop. Check bare boards at stock or at the PCB's shop samples. Check if the legend / marking has discoloration also. Reuven ROKAH e mail: [log in to unmask] Think green before printing this mail... Thanks -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Robert Kondner Sent: Friday, July 30, 2010 6:12 PM To: [log in to unmask] Subject: Re: [TN] PCB Discoloration Hi, No SMT reflow probably means it is simply a variation in FR4 sheets. Is there a spec as to color somewhere? Bob Kondner -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Linda Langley Sent: Friday, July 30, 2010 11:04 AM To: [log in to unmask] Subject: Re: [TN] PCB Discoloration The assemblies come to us completely assembled and had the discoloration. The boards are all hand solder, no SMT. This board gets labeled, PEMs pressed, then hand soldered at our supplier. All the darker boards are in the same date code. The PCB has two signal layers of 1oz copper plated to 2oz separated by the laminate. The finish is Immersion silver. The board thickness is 3.18mm We do not know if the discoloration was a result of the assembly process but are leaning away from this assumption. Linda Langley CIT Training Specialist Jabil Circuit 248-292-6176 -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Steve Gregory Sent: Thursday, July 29, 2010 9:34 PM To: [log in to unmask] Subject: Re: [TN] PCB Discoloration Hi Linda! While discoloration in itself is not a defect, I would be a little worried about these seven boards. Especially since the rest of the lot are not discolored like this: http://stevezeva.homestead.com/PCB_Discoloration1.jpg I don't see any delamination in the photos, but it sure looks like the boards got pretty toasty. I wonder if it was because the boards were sitting over a preheater or hot plate too long. From the looks of the components on the board, most of it was probably hand soldered (those PTH caps converted to SMT couldn't have taken reflow), and I imagine that the solid plane on on the backside of the board was a real heatsink. Preheating the board would have helped with soldering the PEM nuts for sure, but maybe the preheater was set too high. I know a Hakko IR preheater can smoke a board if you're not careful (not that I've ever done that, but I know a friend of a friend who did. Hehehehe). Anyways, those seven boards saw more heat than the rest of them did based on the appearance in the photos. I don't think I'd buy off on them... Steve From: Linda Langley [mailto:[log in to unmask]] Sent: Thursday, July 29, 2010 1:42 PM To: Steve Gregory Subject: FW: PCB Discoloration Hi Steve, Here I go again asking for help from my experts! Can you please post these pictures? So I don't have to bother the whole forum, would you know the name of the board guru that could answer my questions? I am not sure if the discoloration is a defect, is this a form of delaminating? Why would only seven boards turn this color? They are all from the same lot. Any information will be greatly appreciated. Linda Langley CIT Training Specialist Jabil Circuit 248-292-6176 --------------------------------------------------- Technet Mail List provided as a service by IPC using LISTSERV 15.0 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 Please visit IPC web site http://www.ipc.org/contentpage.asp?Pageid=4.3.16 for additional information, or contact Keach Sasamori at [log in to unmask] or 847-615-7100 ext.2815 ----------------------------------------------------- ______________________________________________________________________ This email has been scanned by the MessageLabs Email Security System. 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