Dev Log: Wearable Private Cloud

2 PCB down the production line

Last week Hanza, our assemblers, sent two boards down their production line. The first went with just solder paste, no components, to check the quality of the solder mask. They were sufficiently happy with it, to program the pick and place machine to assemble a second.

There are components on both sides of the PCB. Here, the back side has been assembled.

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As the PCB is thin and contains flexible sections, it must go down the line on a carrier. There is one for each side and they have been made by milling FR4 laminate. Here is the second carrier.

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And here is the PCB on it, ready to go down the line for the second side assembly.

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The first stage is screen printing solder paste.

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Then comes the component placement.

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The final stage is to go through an oven, where the board reaches a temperature of 240C and the solder melts.

We x-ray inspected the board.

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The display is monochrome.  Here, I have highlighted some potential issues.

In my last post, I mentioned that the holes in the PCB had not been filled.  Circled in cyan are solder joints which have voids in them.  These voids are caused by trapped air expanding when the boards are heated.  The good news is that none of these appear to be bad.  There are no solder bridges, so no short circuits, and the voids are probably not big enough for open circuits.

In red, I have circled 3 joints where there is a through hole in close proximity.  Here, a substantial amount of solder has flowed down the hole and is not available for joining the component ball to the PCB.  This was expected.  The good news is that there is some solder and that there might still be enough for the joints to work.  If this is so, then we are still on schedule.

We can also report that we’ve tried the charging with these PCB and it worked flawlessly.

Cheers,

Martin Layley
Hardware Engineer

martin-layley

 

 

 

 

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