Hi Frank! I am in complete agreement with everything you have said, and I didn't mean to sound as if I thought all designers didn't care about how their designs come together on the manufacturing floor. But I would have loved to have the designer who put this out to the floor actually have the chance to sit down and do what he asked us to do in this design: http://stevezeva.homestead.com/files/Quad_Stack.JPG Might have had second thoughts about designing something like this. BTW, these are 0402's... Steve -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Frank Kimmey Sent: Tuesday, December 20, 2011 3:44 PM To: [log in to unmask] Subject: Re: [TN] QFP center slug over signal vias I think you would be surprised to see how many Designers would agree. As a Designer, I want to have the best possible understanding of how things are made and/or repaired. Surprisingly, or not it seems Management does not see any value add in allowing Designers to better understand what they are trying to do. Since we seem not to be allowed on the floor, then the best we can hope for is good communication between Assembly, Fab and Design. Unfortunately, most of that communication never reaches the Designer (it tends to get stopped at the Design Engineer, Quality Engineer or Process Engineer, etc.) Try inviting the Designer in for a tour and I bet you will get Engineers whose jobs are to tell the PCB Designer what to do. I can't speak for all PCB Designers but I know that those who I work with would love a chance to learn how to do better designs. Also, we are seeing more Engineers designing PCB, this is another issue as they are not specialists who have that extra pride in being a PCB Designer. And as we all know, they are smarter than us so we need to just do as we are told whether we agree or not as to the proper way to design a PCB. Just a PCB Designer's opinion, FNK Frank N Kimmey CID+ Manager - PCB Design Powerwave Technologies Inc. Mobile - 916-670-0645 -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Steve Gregory Sent: Tuesday, December 20, 2011 12:03 PM To: [log in to unmask] Subject: Re: [TN] QFP center slug over signal vias I think there should be some sort of requirement for a designer to spend at least a few weeks on the manufacturing floor before they start laying out boards... -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Phil Bavaro Sent: Tuesday, December 20, 2011 2:52 PM To: [log in to unmask] Subject: Re: [TN] QFP center slug over signal vias I agree completely. Sharing the pain always is a good learning experience. -----Original Message----- From: Joyce Koo [mailto:[log in to unmask]] Sent: Tuesday, December 20, 2011 11:10 AM To: Bavaro, Phillip @ MWG - TW; TechNet E-Mail Forum Subject: RE: QFP center slug over signal vias If you ask the designer to (1) tape the kapton tape on a piece of clean glass (cleaned using IPA and DI, followed by IPA rinse and dry)(2) cut into small pieces of the size using knife - under microscope if it is necessary, (3) put the piece on to the PWB at desired location using tweezers with proper ESD protection/with ionized gas blow on his hands. I am sure you will never, ever see the same mistake again from the whole design group (the words get around very very quickly ;-). My 1.92 cents. Joyce Koo Materials Researcher - Materials Interconnect Lab Research In Motion Limited Office: (519) 888-7465 79945 Mobile: (226) 220-4760 -----Original Message----- From: [log in to unmask] [mailto:[log in to unmask]] Sent: Tuesday, December 20, 2011 1:39 PM To: Joyce Koo; TechNet E-Mail Forum Subject: RE: QFP center slug over signal vias Yeah, that was my first solution but unfortunately it is too small to put Kapton on reliably (.006" x .015"). I tried to get it die cut but could not get a quote. -----Original Message----- From: Joyce Koo [mailto:[log in to unmask]] Sent: Tuesday, December 20, 2011 10:32 AM To: 'TechNet E-Mail Forum'; Bavaro, Phillip @ MWG - TW Subject: RE: QFP center slug over signal vias Based on my book, solder mask is not consider as valid dielectric for signal. (Kapton tape would be). Joyce Koo Materials Researcher - Materials Interconnect Lab Research In Motion Limited Office: (519) 888-7465 79945 Mobile: (226) 220-4760 -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Phil Bavaro Sent: Tuesday, December 20, 2011 1:26 PM To: [log in to unmask] Subject: [TN] QFP center slug over signal vias We found an existing design which has a device (QFP with center slug) that has too small of a center slug pad on the PWB. Within the corresponding area where the center slug pad should have been, the designer put some signal vias. Therefore the only thing preventing the signal via from shorting out to the center slug (ground) is the solder mask. No failures to date have been reported, even after a 20g vibe test. Is this a violation of J-STD-001 or perhaps IPC-2221 -6.3.4 regarding minimum electrical spacing? ______________________________________________________________________ This email has been scanned by the Symantec Email Security.cloud service. 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