Hello, Since I cannot get a very clear picture from your email, I can only provide some hints for your reference: 1. Verify aspect ratio>=1.5 and area ratio>=0.66: I am not sure what does that mean? 2. Try type 4 solder paste: We currently use type 3 No-Clean solder from Kester. 3. Make sure PCB have no wicking problem. The Rambus PCB are bought from the shell on the market. 4. PCB solder pads have acceptable solderability: They are gold plated and contaminated free. 5. If PCB is ENIG finish, make sure there is no "Black Pad" defect: I need more education about the term "ENIG" and "Black Pad" 6. PCB bow and twist in with specs (>.7 preferred). They are within spec. 7. If CSP solder ball is 63Sn/37Pb, than I think solder paste is not a key point for open solder joint : It is 63Sn/37Pb, no clean solder paste from Kester. 8. Verify your reflow profile is within the specs (according to solder paste vendor) They are in spec. 9. Cross-section to verify the IMC layer is in standard thickness: We did cross section them and found out the in-sufficient solder join or even NO solder join at all on a few pads. 10. The pads on PCB should be a copper defined instead of soldermask defined to prevent potential crack: They are gold-plated. 11. Pay attention to your process to verify NO excessive tension to your board (e.g. depanel, handle etc.): We use DEK 265 series to (Horizon and Infinitive models) print the solder. Printing at 15-20 mm/s. 12. Try to find where the open have (before wave or after). If via hole under CSP haven't been plugged, wave solder sometimes can cause open by remelt the solder joint: The in-efficient solder firstly found after screen-printing. 13. Ask your component/PCB vendor to do the failure analysis, they maybe have much more experience than you: We are trying. Hope this helpful. It is helpful. However, we still need more information. Until this moment, we still think solder paste, stencil apperture, print speed and pressure, and the stencil thickness could be the cause. We are not sure yet. Best regards, > -----Original Message----- > From: My Nguyen [ mailto:[log in to unmask] > <mailto:[log in to unmask]> ] > Sent: Wednesday, December 12, 2001 2:43 > To: [log in to unmask] > Subject: [TN] Inefficient solder on Toshiba micro > BGA > > > Hello all, > > Problem description: > > Been happening on Rambus - part number tc59rm81xmb. > Ball diametter: 0.5 mm; ball pitch: 0.8 mm, ball > height: 0.4 mm. Pad size: 0.3 mm (11.5 mils) > 5-10% of the time (we run huge amount of them) > failure modules came from opening soder join or no solder join > at all. As we inspect the screen printing process > (we > use 5 mils stencil - Dek screenprinting, cleaning > rate: 2 per print, cleaning cycle Wet-Vacuum/Dry), > we > found un-event solder deposit. Some pad even has > very > little solder or no solder at all. > > Stencil is electro-polish; Diamond shape aperture, > 13.5 mils open used trapezoid shape. > > We afraid that if we open the apperture bigger, then > we may have bridging or solder ball. If we reduce > the > stencil to 4 mils to reduce the blockage or > resistance, then we may have in-efficient solder or > many other problem relating thin stencil (damage, > short-life, etc) > > What would be your solution? > > Thanks, > > Stacy > > > ATTACHMENT part 2 image/gif name=std_logo.gif __________________________________________________ Do You Yahoo!? Check out Yahoo! Shopping and Yahoo! Auctions for all of your unique holiday gifts! Buy at http://shopping.yahoo.com or bid at http://auctions.yahoo.com --------------------------------------------------------------------------------- Technet Mail List provided as a free service by IPC using LISTSERV 1.8d 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 delivery of Technet send the following message: SET Technet NOMAIL Search previous postings at: www.ipc.org > On-Line Resources & Databases > E-mail Archives Please visit IPC web site (http://www.ipc.org/html/forum.htm) for additional information, or contact Keach Sasamori at [log in to unmask] or 847-509-9700 ext.5315 ---------------------------------------------------------------------------------