--------------------- Forwarded message: Subj: Re: GEN: Blind via Fill Date: 96-12-08 15:10:48 EST From: Dryfilm To: [log in to unmask] It is extremely difficult to completely fill blind vias without having resin squeeze out on the surface of the panel. The practice of allowing the resin to flow onto the surface and removing it by sanding is fairly common. There are some potential dangers in this process, such as removing too much copper from the plated surface. This method rarely results in consistantly filled holes; some will be even with the surface, while some will have a slight depression; others may remain above the surface. Generally, a slight depression at the via hole (<1mil) is acceptable. The makers of Pacothane make a product called Paco-Via. Paco-Via is a conformable release sheet used in place of Pacothane or Tedlar on a blind via layer. It conforms to the hole, and completely prevents resin from flowing onto the surface of the layer. The via holes will fill nearly level with the surface, thereby eliminating the need to sand the panel to remove resin. Although this product is a little more expensive than Pacothane, my experience with it has been excellent and I believe the cost is justifiable from a quality and manufacturing perspective. Mark Dowding Regional Technical Specialist Insulectro *************************************************************************** * 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] * ***************************************************************************