We have also done extensive studies on the HASL process and I agree with Mr. Holmes 100%. Dennis Mitchell Zycon Corp. [log in to unmask] ______________________________ Reply Separator _________________________________ Subject: Re: FAB: Fine Pitch solder thickness w/HASL Author: [log in to unmask] at corp Date: 4/2/96 10:40 PM We have spent a lot of time studying the HASL process, and in my opinion it is virtually impossible to control solder thickness within tight tolerance. The lower limit of solder thickness on surface pads is generally between 50 and 100 microinches. Thick areas elsewhere on the same board often exceed 1.5 mils. The lower limit you specify is unrealistic, and unneccessary. 0.3 mils applies to plated solder and is not needed with HASL. The real requirements for reasonable shelf life is no exposed intermetallic. This can be achieved at a minimum solder thickness around 50 microinch. Robert R. Holmes Lucent Technologies (Formerly AT&T) [log in to unmask] ------------- Begin Original Message ------------- From: rfpo2.rfc.comm.harris.com!njd (Dill, Norm J) Date: Mon Apr 01 11:13:00 EST 96 Subject: FAB: Fine Pitch solder thickness w/HASL To: [log in to unmask] ('IPC Technet Input') Cc: Bcc: Content-Type: text Content-Length: 732 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