If I understand correctly, you deposit solder paste under the component during the initial build. After reflow, the paste solidifies and makes contact with the bottom of the component for heat transfer. Your question is what to do when replacing the component. How do you replace the solder bumps under the device. Is the body of the component ceramic or metal? If ceramic, when you remove the devise the solder bumps should remain intact, nice and flat. Why not leave these bumps as is and place the component, contacting the existing bumps while soldering? If the case is metal, and you disturb the bumps during removal, how about reapplying solder paste, placing the component and reflowing it with a hot air terminal? Another option is to change the drawing to allow the use of a thermal adhesive for rework. Jim Marsico Senior Engineer Production Engineering EDO Electronics Systems Group [log in to unmask] <mailto:[log in to unmask]> 631-595-5879 -----Original Message----- From: Becerra Alejandro [SMTP:[log in to unmask]] Sent: Wednesday, April 24, 2002 4:54 PM To: [log in to unmask] Subject: [TN] Repair of Circuit with Solder Paste below Hello to All, We have a circuit that requires solder under it because in order to have a good thermal dissipation. The circuit is a QFP48. When assembled in the line, the stencil has apertures in the body of the component in order to apply solder. We have tried to manually apply the solder with an iron tip, but after cross-sectioning the repair component we have found that sometimes the solder is not in contact with the component. What could be the appropriate procedure to repair this component? Regards, Alejandro Becerra --------------------------------------------------------------------------------- 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 e-mail to [log in to unmask]: SET Technet NOMAIL 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/html/forum.htm for additional information, or contact Keach Sasamori at [log in to unmask] or 847-509-9700 ext.5315 ---------------------------------------------------------------------------------