Werner and anyone else not tired of this subject, I ran out of steam this morning at about 0200 and, as it's too cold to enjoy golf here, I thought I'd rejoin what always is, to me at least, an interesting subject - HASL. I pose the following for consideration starting with some paraphrasing of industry experts including you Werner: When using a tin-lead solder eutectic, the tin reacts with the metal surfaces (I still want to return to this term as meaning an object?s area having not depth with regard to diffusion and intermetallic formation), to be soldered, to form an intermetallic compound. This ?metal? (does it ever stop being a metal?) layer can be a very high tin concentration on the solder side and a very high copper concentration on the other side. These intermetallics can become brittle and weak ? when excessive (how much is excessive and under what conditions to they become so, specifically, and do they REALLY become excessive?). When they are excessive, solder joints becomes susceptible to failure under mechanical stress as vibration or shock. To produce high quality/reliable solder joints, the IMC must be as thin as possible. The HASL process simply is a ?coffin nail? that can and should be avoided. Again, it is, in my opinion, wasted. I think of it this way in light of so many alternatives as OSP?s, ENIG, etc. If the HASL process is not well managed (as is often the case when operators, reduce conveyor speeds attempting, futilely, to effectively cover copper surfaces, the first step to a ?thick? IMC is begun. Then, in subsequent soldering operations (wave, reflow, hand, touch-up, repair, rework, and modification) the layer thickens and the failure mechanism is promoted. Is this correct or possible? If so, the IMC must be as thin as possible. Most recently, over the past few years (more than 25 but I ain?t saying), I have been asked by clients to help evaluate quick turn board shops promoting lower costs and faster deliveries. Who doesn?t take advantage? The first place I go, after the sit down pow wow, is the lab. In many smaller operations, not well managed but still offering cheap boards with fast deliveries, chemistry log-books still sit there dusty containing hand written data never having been entered into even a simple Excel spread sheet and turned into even simple range charts, never mind XbarR charts. Seldom do I ever see evidence the HASL flux chemistry or solder purity has bee analyzed. The reason I bring this up is because this is where it all starts and often ends as poor quality PCB?s often incapable of supporting soldering operations capable of producing initial quality solder joints or those reliable in any manner. So, again, when an excessively oxidized board is introduced to an ill managed HASL process, creative attempts often are made to make acceptable solder termination areas. The effect is either ?ruined? as a non wetted/wettable solder surface OR one that has excessive IMC formations (again, how much is too much?). With all this, I?ve seen some of the most excellent HASL surfaces coming from well managed operations. I mean they?re flat, ?shiny,? (pardon that one), and totally support good solder joint formation. So, I guess, my complaint is why risk it? It?s just not worth it, nor is it necessary. Earl --------------------------------------------------------------------------------- Technet Mail List provided as a free service by IPC using LISTSERV 1.8d To unsubscribe, send a message to [log in to unmask] with following text in the BODY (NOT the subject field): SIGNOFF Technet To temporarily halt delivery of Technet send the following message: SET Technet NOMAIL Search previous postings at: www.ipc.org > On-Line Resources & Databases > E-mail Archives Please visit IPC web site (http://www.ipc.org/html/forum.htm) for additional information, or contact Keach Sasamori at [log in to unmask] or 847-509-9700 ext.5315 ---------------------------------------------------------------------------------