I have seen people mistake insufficient reflow temperature for insuffient solder paste on this type part. > -----Original Message----- > From: TechNet [mailto:[log in to unmask]]On Behalf Of My Nguyen > Sent: Thursday, December 13, 2001 1:11 PM > To: [log in to unmask] > Subject: Re: [TN] Inefficient solder on Toshiba micro BGA > > > 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 > ------------------------------------------------------------------ > --------------- > --------------------------------------------------------------------------------- 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 ---------------------------------------------------------------------------------