Try baking the affected boards for at least 30 min at 150C. I suspect you are getting some water absorption in the solder mask filler and if this is the case the bake will eliminate the white. If you don't have an oven for baking try using a heat gun directly to the white spots, that could work as well. Regards, Bob Metcalf Atotech Western Regional Manager Cell 714-334-7667 E-Mail [log in to unmask] This e-mail and any attachments hereto are business documents of Atotech USA Inc. and may contain CONFIDENTIAL OR PROPRIETARY BUSINESS INFORMATION. Unauthorized disclosure and/or use of information contained in this email is prohibited. If you are not the intended recipient, you may not read, use, disseminate or copy this message or any other files transmitted with it. From: prashant chopra <[log in to unmask]> To: <[log in to unmask]> Date: 07/10/2013 08:07 AM Subject: [TN] Black solder mask having white patch -- need advice Sent by: TechNet <[log in to unmask]> Hi Everyone, We are using a black soldermask for one of our PWA. After the assembly and aqueous wash cleaning, we see a white patch on the bottom side. This patch is in small area and the top side is all clean. Again this is not happening on all the PWAs. I have attached a picture above for reference. I need expert advice on what can be the issues either from the PWB fabricator end or during the assembly process which can cause this? We are using the black solder mask for first time and we do not have such issue with either green or grey solder mask. Thanks in advance for your help. rgds Prashant ______________________________________________________________________ This email has been scanned by the Symantec Email Security.cloud service. For more information please contact helpdesk at x2960 or [log in to unmask] ______________________________________________________________________ ______________________________________________________________________ This email has been scanned by the Symantec Email Security.cloud service. For more information please contact helpdesk at x2960 or [log in to unmask] ______________________________________________________________________