I have seen a lot traffic on different alternatives to HASL. Most seem to refer to various OSPs or some form of precious metal. However, I would like to offer a different approach.
Several years ago I worked with a pcb supplier who was requested to supply parts with a bare copper finish. No protective coating at all. The last operation in house was to clean the surface, rinse with DI, dry and then parts where immediately packaged in groups of 10 and vacuum sealed. We placed a strip of gray anti-oxidation paper from 3M in the package before sealing. According to our customer, it was easier for them to open a package of 10, and clean before fluxing with a mild sulfuric than it was to fight coplanarity issues of the solder. They had tried an OSP but found it to inconsistent. This practice spread to two other customers before I had left that supplier. I haven't found anyone else even remotely interested in that practice since but apparently it worked for at least 3 customers for over a year without any reported issues.  I'm not sure if it is still being used but I thought I'd share that experience with the net. 

Thanks,

Ed Cosper
Graphic Electronics Inc.
Tulsa, OK

################################################################
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 technical support contact Hugo Scaramuzza at [log in to unmask] or 847-509-9700 ext.312
################################################################