Hi again Bob, Here are the pictures you sent to post: http://stevezeva.homestead.com/Microvia_separation.pdf Steve -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Bob Landman Sent: Thursday, November 11, 2010 5:26 PM To: [log in to unmask] Subject: Re: [TN] the reliability of capped vias in pads Thanks Chris. Just sent pictures to Steve G to post. Here are some additional comments from my colleague on the problem he's confronting: 1. there are two types of capped vias: a. through hole vias filled with conductive polymer and b. laser drilled microvias "filled" with copper (the copper is electroplated in a special formulated copper electrolytic solution that selectively plate copper in the vias (the copper plate rate in the vias is 3 to 4 time higher than on the PCB panel) In both types the via is capped with electroplated copper. The copper thickness is about the same as the copper conductors on the CS or PS , that is 50 - 70 micron ( 2- 3 mils). In both types there are some reliabilities problems. He's asking about the second type of vias. Removing a soldered lead component from a capped (microvias) pad may apply a pull force on the vias under this pad and aided by the heating of the region by the touch of the solder iron can seperate the microvia from the capture pad.(i.e the second layer that is under the outer CS or PS layer, see the photos in the attached file (in the photos the laser microvias are not capped). He needs information about failures of boards with capped microvia from people that allow hand soldering repair. Thanks! Bob Landman H&L Instruments, LLC -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Chris Mahanna Sent: Wednesday, November 10, 2010 9:54 PM To: [log in to unmask] Subject: Re: [TN] the reliability of capped vias in pads The 6012C cap requirements are intended to assure a minimal structural feature. As such, IMO wrap continues to be the most important reliability feature. If your fabs are laying down 2-4 mil caps that's a different story. Chris -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Frank Kimmey Sent: Tuesday, November 09, 2010 10:33 PM To: [log in to unmask] Subject: Re: [TN] the reliability of capped vias in pads Bob, I don't know I can give definitive proof of but I am pretty sure (good Engineering reference) capped via in pad can be considerably more reliable in manual rework than standard pad. With the additional copper going through the board it should give considerably better resistance against thermal caused pad lift (more surface area to adhere to board, plus pads on both sides). I would always be more comfortable hand soldering through hole than SMT. Due to the mechanical definitions of a capped via I would expect through hole soldering rules may apply better than surface mount. As to your specific questions, I think those all must be determined internally depending on your available skill levels and reliability needs. Sorry I don't have better, maybe Werner will take a break from golf to answer. Hope it helps some, 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 Bob Landman Sent: Tuesday, November 09, 2010 10:50 AM To: [log in to unmask] Subject: [TN] the reliability of capped vias in pads A colleague asked me for information about the reliability of capped vias in pads: 1) How many allowed repairs? 2) Is it acceptable to hand solder wire lead components on those pads? 3) How many allowed repairs are allowed for hand soldered component leads on thes pads? 4) What is the recommended soldering iron tip temperature? (for lead-free and tin/lead solders) 5) Is the solder tip "touch up" time controlled well enough by the average repair technican when done manually to be acceptable or is only reflow soldering recommended (no rework)? 6) Is the touch up time more variable, longer, when the solder is Lead Free? (I would say yes it is and we only use eutectic tin/lead solder on COTS lead-free boards when we do a repair) 7) Are there any restrictions on placing a via in a pad if the component leads are hand soldered to this pad? Bob Landman H&L Instruments, LLC ______________________________________________________________________ This email has been scanned by the MessageLabs Email Security System. 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For more information please contact helpdesk at x2960 or [log in to unmask] ______________________________________________________________________ --------------------------------------------------- Technet Mail List provided as a service by IPC using LISTSERV 15.0 To unsubscribe, send a message to [log in to unmask] with following text in the BODY (NOT the subject field): SIGNOFF Technet To temporarily halt or (re-start) delivery of Technet send e-mail to [log in to unmask]: SET Technet NOMAIL or (MAIL) To receive ONE mailing per day of all the posts: send e-mail to [log in to unmask]: SET Technet Digest Search the archives of previous posts at: http://listserv.ipc.org/archives Please visit IPC web site http://www.ipc.org/contentpage.asp?Pageid=4.3.16 for additional information, or contact Keach Sasamori at [log in to unmask] or 847-615-7100 ext.2815 -----------------------------------------------------