======== Original Message ======== We are attempting to attach a nickel-plated copper heatsink to a 10 layer PWB per a set of manufacturing drawings that only states that "the heatsink shall be attached with prepreg". It does not call out a pressure, temperature, cycle time, or a type of prepreg. We have assumed that we would need a "low-flow" type of prepreg. We have tried some sample cards with a low-flow prepreg (PC-GF 108V by Westinghouse Fortin) that we have on hand; we have had good registration of the heatsink to card, but the adhesion has not been as good as we would have liked, and the heatsink seems to have been pressed "into" the board (you can feel the outline of the heatsink on the backside of the card). We ran the press at the lowest possible pressure we can for our press (15 lbs). We are looking for suggestions from anyone who has experience with laminating heatsinks to PWBs. Thanks, Marty W. Sheppard / LYPME Manufacturing Engineering Support (912)-926-9632 DSN 468-9632 Fax: (912)926-7974 email: [log in to unmask] ############################################################## TechNet Mail List provided as a free service by IPC using LISTSERV 1.8c ############################################################## To subscribe/unsubscribe, send a message to [log in to unmask] with following text in the body: To subscribe: SUBSCRIBE TECHNET <your full name> To unsubscribe: SIGNOFF TECHNET ############################################################## Please visit IPC web site (http://www.ipc.org/html/forum.htm) for additional information. For the technical support contact Dmitriy Sklyar at [log in to unmask] or 847-509-9700 ext.311 ############################################################## ======== Fwd by: Richard MacCu ======== For a bright nickle plated heatsink a low flow epoxy prepreg can be used but there may be some things you need to try. If the nickle is thick enough, lightly abrade the bond side with 600 Grit sandpaper to roughen the surface. Clean with MEK or toluene. No alcohol or other degreaser these can leave a film on the surface which can act as a release agent. Make sure the package reaches the cure time and temp for adequate bonding but don't over stay. The material you mention can stand a hot press start of 320F, load and keep in the press for 30 mins. The prepreg needs to see about 15 to 20 mins above 300F to get acceptable cure/bond strength. As for the telegraphing of the heatsink into the board. First, accurately calculate the surface area to be bonded and ensure you are at 15lbs per sq in. You may want to reduce to 10 lbs per sq in. If you are over that, place dummy material of the same thickness in the stack to reduce the force pressure on the board. If the press is manually controlled monitor closely, at the lower pressure when heat causes the stack to expand it increases the force pressure quickly. If the heatsink is .020"-.030" thick you should get good conformity at 10lbs with little effect on the board. Use a thermocouple for temp monitoring if possible. Are you using a press pad? Silicone, expanded paper? Use on the heatsink but not under the board since it can cause more telegraphing. Good Luck Richard MacCutcheon ############################################################## TechNet Mail List provided as a free service by IPC using LISTSERV 1.8c ############################################################## To subscribe/unsubscribe, send a message to [log in to unmask] with following text in the body: To subscribe: SUBSCRIBE TECHNET <your full name> To unsubscribe: SIGNOFF TECHNET ############################################################## Please visit IPC web site (http://www.ipc.org/html/forum.htm) for additional information. For the technical support contact Dmitriy Sklyar at [log in to unmask] or 847-509-9700 ext.311 ##############################################################