Dave Bergman Perhaps you will forward following info to the member who needed data on getting the holes filled in his center located heatsink. It appears that the six sheets of prepreg are a bit short when it comes to filling 0.25 inch. I know that voids are often experienced when I have triedt to fill 0.010 with 4 sheets. You can play with the press cycle and try to close the press at just the right time when the outer edge resin is still a bit stiff and the center section is at a low viscosity; hopefully pushing the trapped resin in the holes A safer method is to squeege a thixotropic filled resin into the holes of the oxide treated heat sink and it will fill them about 80%. Then let the filler resin at least harden and partially cure at room temperature so it will not run all over during the final cure. Then you can follow your previously described process or you can finish the hole filling with the preprg during the multilayer lamination process. A small amount of the filler material may be left on the surface by squeegee drag, but if it is a good insulator and will not create any problems. If you are later drilling thru the holes and plating them through the filled resin will have better resistance to cracking than the unreinforced resin that came from the prepreg. Arlon and several other companies sell hole-fill material that it used for the same purpose that you require. Phil Hinton Hinton "PWB" Engineering *************************************************************************** * 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] * ***************************************************************************