Std stencil design was used for same pad design with and without via in pad. Nothing special, no math. Best regards, Leo Leo M. Higgins III, Ph.D. Vice President, Technical Operations ASAT, Inc. 3755 Capital of Texas Highway, Suite 100 Austin, Texas 78704 -----Original Message----- From: TechNet [mailto:[log in to unmask]]On Behalf Of Guy Ramsey Sent: Monday, April 24, 2006 7:59 PM To: [log in to unmask] Subject: Re: [TN] Solder joint reliability of BGAs and 0402 chip on blind vias True, but it these tests results came from a study where the solder stencil had been optimized for knowing the attributes of the board. In the CM world these things have a way of dropping in on us. The arithmetic is not complex, but it is also not a no-brainer. -----Original Message----- From: TechNet [mailto:[log in to unmask]]On Behalf Of Leo Higgins Sent: Monday, April 24, 2006 4:52 PM To: [log in to unmask] Subject: Re: [TN] Solder joint reliability of BGAs and 0402 chip on blind vias Some work has been published actually showing better mechanical shock / drop test results for unfilled via-in-pad solder pad structures, even with the common presence of a void in the solder located right in the recessed via. This helps avoid the issue of lifted copper that is often seen over the top of filled microvias. Best regards, Leo Leo M. Higgins III, Ph.D. Vice President, Technical Operations ASAT, Inc. 3755 Capital of Texas Highway, Suite 100 Austin, Texas 78704 -----Original Message----- From: TechNet [mailto:[log in to unmask]]On Behalf Of Bob Wilson Sent: Friday, April 21, 2006 1:11 PM To: [log in to unmask] Subject: Re: [TN] Solder joint reliability of BGAs and 0402 chip on blind vias Yup. Laser drill at 4 mil diameter and fill with good conductive epoxy. When I hooked the board up I eased the fabrication a bit by doing the blinds only from layer 1 to layer 2 and layer 15 to layer 16. (Layers 2 and 15 were flooded GND planes). Boards were fabbed at Hallmark Circuits in San Diego. I talked to them before I routed a signal and the boards worked fine. Bob Wilson CID -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Ted Kong Sent: Friday, April 21, 2006 10:57 AM To: [log in to unmask] Subject: [TN] Solder joint reliability of BGAs and 0402 chip on blind vias Hi all, Has anyone used blind vias on BGAs or 0402 chip packages? Will they form reliable solder joints? Thanks all in advance. Ted __________________________________________________ Do You Yahoo!? Tired of spam? Yahoo! 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