1. HASL means hot air solder leveling. After solder mask is applied and cured, panels are fluxed and then the panel are dipped into molten solder (usually 63% tin/37% lead eutectic solder at about 500 deg F) for 3-6 seconds. Then the panels are passed through blowing hot air (usually around 30-60 psi or more and around 600+ deg F) to blow the solder flat and out of the holes. This process puts a tremendous amount of thermal stress on the panels, will usually warp the panels and you have a lot of lead, which is on the environmental hit list these days. On the other hand, you end up with a pretty much flat surface of solder on your surface mount pads and plated through holes and soldering components to this is usually pretty easy (solder solders to solder pretty good!). 2.OSP is a very thin organic coating applied to the surface of copper surface mount pads and plated through holes and inhibits oxidation of the copper. OSP's have shorter shelf lives that HASL, is very susceptible to handling because the coating is so thin (put a fingerprint on an area and it is toast!), and does not take multiple thermal excursion well (solder past fusion followed by wave soldering can cause problems). On the other hand, OSP puts much less stress on the panels, panels don't warp and it is environmentally friendly. So which one do you use? Many people have been successful with both systems and many board shops (probably most) have the capability for processing both systems. It really depends on you and what your needs are. Hope this helps. Larry Fisher Allen Woods & Associates