Steve, the reason that there is controversy regarding HASL thickness specs is because the sites or lands to be soldered are different sizes. The process reality is that geometry of the individual sites is the primary influence on thickness control in Hot Air Leveling. A brief overview may help. A clean, fluxed copper surface is dipped in molten solder (460f approx.) while the metal is still molten it is withdrawn thru a pair of air knifes. Each of the individual sites on the circuit now coated with liquid eutectic metal will offer more or less resistance to a fixed air pressure from the knifes. For example; a ground plane say .250" x .250" will offer less resitance to the air leveling than a .015" x .070" QFP site that is adjacent to it. Consequently, the QFP site will be slightly thicker and have less pull away at the leading edge or what we call, (surface tension phenomena). The process is repeatable given a consistent geometry. The parties need to agree on a particular site to be measured. (critical QFP lands make an ideal candidate.) The location on those sites to be measured. (near the center) The method used for measurement (XRF) x-ray flourescence Envoila, we can now issue a spec that everyone can live with. (somewhere around 200 microinches +/- 100 microinches) The IPC could be more specific than "coverage and solderable" but, it will require some cataloging of common sites. The above, im sure was sufficiently boring as to have run off the faint of heart. Now, perhaps you can help me answer a question that has made me crazy for some time; If the goal here is pure planarity, i'm having a problem with quibbiling over microinches on the solder coating when, the compnents can be +/- .004"! and this is after we gob on... what, .005" of solder paste? Can you put this into perspective for me? Hope this helps, and thanks in advance Mark Simmons, V-Score Central ################################################################ TechNet E-Mail Forum provided as a free service by IPC using LISTSERV 1.8c ################################################################ To subscribe/unsubscribe, send a message to [log in to unmask] with following text in the body: To subscribe: SUBSCRIBE TechNet <your full name> To unsubscribe: SIGNOFF TechNet ################################################################ Please visit IPC web site (http://jefry.ipc.org/forum.htm) for additional information. For the technical support contact Dmitriy Sklyar at [log in to unmask] or 847-509-9700 ext.311 ################################################################