My apologies to Dan, Susan and all... I PRESUMED to know that Susan was referring to sequentially laminated blind via's. The "filling" with resin occurs in this type of blind via. As Dan mentions, we also have done the controlled depth drill variety, which do not fill with resin. The removal of resin I mentioned previously, is in regard to thermal via's with a large area of metallization used to absorb and displace heat from a device. In the case of TAB devices, they are glued to this "heatsink". In the use of seq. lam'ed blind via's, the resin in these holes has been known to swell during thermal cycles. In this case. the resin interferes with a device mounted or glued directly to the metallization. Regards, [log in to unmask] ______________________________ Reply Separator _________________________________ Subject: Re[2]: Blind Via's in MLB's Author: [log in to unmask] at internet_gateway Date: 2/19/96 3:19 PM I don't understand the need to 'depth drill after lamination to remove some of the resin'. However, nearly all of the blind-via work that we do is controlled-depth drilled at the same time through holes are drilled and processed, essentially, the same as non-blind-via product. Regards, Daniel Buxton Mfg. Engineer _____ /____/\ _______|___ \/| /________ /_| |< Continental Circuits Corp. / ______||_ </| 3502 E.Roeser Rd. | / | /___| |/ Phoenix, AZ 85040 | | |___|_____/ Voice(602) 232-9133 Fax(602) 268-7386 | \/_____ /| E-Mail [log in to unmask] \_________|/ ______________________________ Reply Separator _________________________________ Subject: Re: Blind Via's in MLB's Author: [log in to unmask] at INTERNET Date: 02/19/96 2:27 Susan Here's my opinions: 1) REAL ESTATE. When holes only go halfway or part way through a board, the hole and associated pads don't take up space on all layers. This gives more routing room to designers to run traces, where a normal through via would not allow. 2) & 3) Blind and buried via's "typically" get filled with resin during the lamination step(s). I can't imagine a case where you prevent the holes from becoming filled. 4) I wouldn't say they are required to be capped with plating and or soldermask. As part of the natural process after lamination, boards see an e'less deposition (direct platers, no offense) and electroplate of coppers. This tends to "cap" the blind via's. I have seen cases of "thermal via's" actually being depth drilled after lamination to remove some of the resin. During thermal cycling, the resin will soften and "move" and can cause the plating on the surface to break away or lift. I would offer some pictures of the above conditions, but I'm not very skilled in ASCII art, as are some of our fellow `netters. Please feel free to call me to discuss or perhaps I could FAX you something! Regards, Tom Bresnan Product Eng'g Mgr MULTEK 16 Hammond Irvine, CA 92718 714.951.3388 714.951.8794 FAX [log in to unmask] ______________________________ Reply Separator _________________________________ Subject: Unidentified subject! Author: [log in to unmask] at internet_gateway Date: 2/18/96 12:09 PM ding Blind Vias in multilayer printed boards. 1) Why would someone want to use them? 2) If used are they always filled? 3) When does the filling operation take place? 4) Are they required to be capped by plating or solder mask? I am looking at a lot of multilayers with blind vias and need some help in understanding the manuf process. Thanks, Susan Mansilla Robisan Laboratory