From: NAME: WILLIAM G KENYON FUNC: Chemicals/Electronics TEL: 302-652-4272 <KENYONWG@A1@ESVAX> To: NAME: [log in to unmask] <"[log in to unmask]"@ESDS01@MRGATE@ESVAX> There is a simple way to eliminate solder balls from the assembly process...by making a change in the PWB fabrication process. The fab process to use is called SSD or Solid Solder Deposits. To provide a thumbnail sketch- solder is applied during or after fabrication in sufficient volume to provide the volume of solder needed to make a good solder joint. The "solder" can be applied as plate, paste or liquid solder- depending on the process variation used. If not liquid solder, the "solder" is reflowed. The next step is to flatten the solder deposits to make solder "bricks" on the board. The board is then washed (most of the solder pastes are inexpensive water soluble types) to remove all the residues and ALL SOLDER BALLS. Since no components are present, a simple water washer can be used. Again, no components so ultrasonics can be used without anyone getting worried. A quick visual inspection to make sure all the solder bricks are there and you are done. Screen on a sticky no clean flux, follow with a Mylar cover sheet and you can store the boards for up to one year. Pull off the cover sheet, stack, punch up the right programs on the pick/place and reflow machines and start zero defect ZERO solder ball assembly. No test prints, no solder paste, no stencil cleaning, minimal turn around time on the shop floor when changing part numbers. Don't really need inspection or cleaning either. This process is running now- if may have been used to make your laptop, since it is used routinely to do 10 mil pitch TAB attach for laptop CPUs. There are about four versions of the generic SSD process available, so it is not single source. The SSD concept was first used to make double sided VHSIC boards with 20 mil pitch QPFs in one pass through vapor phase soldering in 1984 with 17 mil pitch the following year....so like many ideas in electronics manufacturing, it has been around long enough that it is safe to adopt it. For global assemblers, the SSD concept is in the documentation publication plan of IEC TC91: Surface Mount & Related Processes. IPC actively participates in the work of this group. Bottom Line: If you want a no clean no solder ball process that will run on fine pitch parts, this might just be the answer for you. While there is an additional cost for the PWBs, the savings at the assembly step more than make up for it, generating a net cost savings. --Bill Kenyon Global Centre for Process Change, Inc. 302 652-4272/-5701 Tel/Fax *************************************************************************** * TechNet mail list is provided as a service by IPC using SmartList v3.05 * *************************************************************************** * To unsubscribe from this list at any time, send a message to: * * [log in to unmask] with <subject: unsubscribe> and no text. * *************************************************************************** * If you are having a problem with the IPC TechNet forum please contact * * Dmitriy Sklyar at 847-509-9700 ext. 311 or email at [log in to unmask] * ***************************************************************************