Hello FreeCalypso community, I am pleased to announce that as of about 16 hours ago, the FCDEV3B PCB fabrication process is now underway. I have settled on using the selective surface finish combination (OSP for SMT pads, ENIG for plated through holes), which appears to be the standard used by the cellular industry. More precisely, I don't know what the cellular industry uses *today* for their 3G/4G stuff and for "modern" GSM/2G chipsets from MTK or Spreadtrum, but at least the OSP + selective Ni/Au finish *was* the cellular industry standard in the days of Calypso and Calypso+ chipsets. Neither I nor Harald Welte have been able to find out *why* the industry does or did it this way, but the historical fact is that this practice has been very consistent for both production and prototype board runs, hence doing likewise for our boards is the safest choice.
In any case, the FCDEV3B PCB fab process is now underway, and the bare PCBs are expected to arrive some time in mid-to-late February. The next steps are: * While the PCBs are being made, we need to get the BGA reballing of Spansion flash+pSRAM chips started in parallel. Being opposed to RoHS as a matter of principle, I am going to have our boards assembled with traditional SnPb solder paste, using a reflow soldering process at the lower temperature appropriate for SnPb, *without* subjecting our boards and their components to the crazy high heat of RoHS reflow. For the other 3 BGAs I got parts with SnPb solder balls, but the Spansion part could only be obtained with RoHS solder balls. The latter won't melt properly with a lower temperature SnPb reflow process, hence they need to be reballed. This reballing process can be done in parallel with PCB fabrication, and the remaining balance in the FreeCalypso account after the PCB fab order should be sufficient to cover this reballing - I just need to get back in contact with the people who told me they could do it (back in the early summer) and get the ball rolling. * Once we have the PCBs and the reballed flash+pSRAM chips, we'll be ready to go into assembly - I already have all other parts physically on hand. I don't know yet whether or not we'll need additional funds at that step - I will need to have another discussion with the SMT assembly shop about costs when we get closer to it. Hasta la Victoria, Siempre, The Mother _______________________________________________ Community mailing list [email protected] https://www.freecalypso.org/mailman/listinfo/community
