I have been soldering (prototype quantities) mini-Ball Grid Arrays to FR4 boards with 10-mil diameter solder pads. Co-planarity is a major issue to get these things soldered down. I have had great success using the Precision Pads Technology (PPT) solid solder deposit method to place uniform, co-planar solder on my boards. Two disadvantages?...you need a dry-film soldermask and you need to ship your boards to Florida for processing (or get licensed to do it yourself). The process works GREAT! You can even VP solder J-leaded parts to the board without wicking all of your solder up the leads. Just add flux, place your parts, and reflow. Of course I'm presuming that your HASL solder thickness spec. is rooted in a co-planarity requirement for SMT attachment. ----- Begin Included Message ----- Subject: FAB: Fine Pitch solder thickness w/HASL Our HASL solder thickness spec. is 0.3 to 1.5 mils. Is it unreasonable to expect using a horizontal HASL process that 1.5 mils will be the actual max. on 100% of the pads on both sides of the board, even with fine pitch (< = 20 mils)? My guess is that the surface tension of the molten solder on the fine pitch pads, its low mass and the surrounding geography, make it difficult for the air knives to do consistant leveling. Some of our product mix here is Mil Spec work. Converting the boards with fine pitch on both sides to Au/Ni may be more pain than it is worth. Any inputs on this subject will be greatly appreciated. Norm Dill MQC Specialist [log in to unmask] (716) 242-4210 ----- End Included Message ----- Gary P. --- Gary D. Peterson _/_/_/ _/ _/ _/ SANDIA NATIONAL LABORATORIES _/_/_/ _/ _/_/ _/ _/ P.O. Box 5800, M/S 0503 _/_/ _/_/_/ _/ _/ _/ _/ Albuquerque, NM 87185-0503 _/_/_/_/_/_/ _/ _/ _/_/ _/ Phone: (505)844-6980 _/ _/_/ _/ _/_/_/ _/ _/ _/_/_/_/ FAX: (505)844-2925 _/ _/_/ _/ E-Mail: [log in to unmask] _/_/_/