Also look at IPC 7095 and 7094, there is a lot of good information on reliability issues with using soldermask-defined pads. Paymon, this is where soldermask is considered to encroach into the solder joint. Read particularly IPC 7095 section 8.4.3, and again Werner Engelmaier also has written some excellent articles on the influence of soldermask on reliability of BGA solder joints. -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of John Burke Sent: Friday, March 30, 2007 12:54 PM To: [log in to unmask] Subject: Re: [TN] Solder Resist Encroachment onto BGA pads I suspect a lot since all of the work on solderability/reliability in regard to wetting angles was done many years ago. Is Werner on the forum? John John Burke (408) 515 4992 -----Original Message----- From: Paymon Sani [mailto:[log in to unmask]] Sent: Friday, March 30, 2007 10:15 AM To: TechNet E-Mail Forum; John Burke Subject: RE: [TN] Solder Resist Encroachment onto BGA pads Thank you John, is there any studies on this? Paymon -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of John Burke Sent: March 30, 2007 12:45 PM To: [log in to unmask] Subject: Re: [TN] Solder Resist Encroachment onto BGA pads Actually yes. If you put solder resist over the lands for the BGA you have by definition a joint defined by the resist system. Effectively this will give you a 90 degree wetting angle which is - you guessed it a stress riser. So a joint with solder mask defined joints will be more liable to crack under stress. John John Burke (408) 515 4992 -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Paymon Sani Sent: Friday, March 30, 2007 9:02 AM To: [log in to unmask] Subject: [TN] Solder Resist Encroachment onto BGA pads Hello All, Does anybody know why IPC does not allow any solder resist encroachment onto the BGA copper defined lands for PCBs? ------------------------------------------------------------------------ ---- ----------- Confidentiality Notice This e-mail and any attachment(s) are intended for the individual or entity to which this email is addressed and may contain information that is confidential. If you are not the intended recipient or an employee or agent responsible for delivering this e-mail to the intended recipient, please be aware that any dissemination, distribution or copying of this communication is strictly prohibited. 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