Friday, October 5, 2012

V3 Progress

No pictures today. Just a bit of a text update.

I've received all the components to complete the V3 circuit board. Surface mount soldering by hand is generally difficult, but the AP2 modules are proving to be the absolute most stubborn pieces to solder that I've had the displeasure of attempting. This is a situation where you need to accept the old adage: "The right tool for the job". I am not using the right tool.

If you attempt to surface mount the AP2 module by hand here is something to keep in mind. There are small through holes for the contacts on the base, just big enough for a fine leg of a resistor to fit down. They also make great test points. If you test and cannot get the solder on your PCB to connect to the AP2 then put a wire down the hole tinned lightly with solder. Heat the wire and keep pushing it down, then alternate heating the pad on your board (the small amount exposed) and the wire while applying pressure downward. Eventually you'll make a connection. Check it with a multimeter. Once you've made a good connection heat the pad and then the wire and put the wire out -- it will pull solder up through the hole and seems to make a very reliable connection.

This is time consuming. I spent about 3 hours trying to surface mount two of these to my PCB and several connections would not connect. This technique takes several minutes per contact, so about an hour to get all the connections working. All of this could have been avoided if I had a reflow oven. Necessity is the mother of invention.

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