Now the moment I’ve been waiting for…soldering with a stencil, solder paste and my hot air gun.  I had the solder paste stored in my refrigerator in a cooling bag.  I had taken it out to get to room temperature a few hours before.

The first thing I did was to tape down the stencil.

Taped Down Stencil

Now, spread the solder…

Spread The Solder

Peel off the stencil…

Peel Off The Stencil

OOPS! Way too much solder paste  This was my problem when I was using a solder iron.  I finally figured out that I needed far less solder than I thought.  I haven’t done stenciling before…but I am assuming reflow will suck the solder up.  OK, I’m hoping.


Placed the parts with an attempt to make sure the diodes were placed in the right direction.

TBD: picture of diode next to schematic picture with flow. next to pcbnew picture.



I set the hot air gun at 249˚C and air at level 4.  I used the bigger of the tips I could find.

Healthy pH Shield After Stencil Solder

 Definitely too much solder paste.  This is especially true with the MCP3901.  Using a magnifying lens, I could only find the MCP3901 with shorted pins.

It was easy to remove excess solder with solder wick on one side.  However, the other side became more difficult than I imagined it should.

MCP3901 After Solder Wick

 What added to this was a few of the pins were bent together!  Not sure how I did that.  Definitely points to being more careful with this chip.  I removed the MCP3901

Removed MCP3901

Before replacing, I tried connecting wires to the power jack – due to my screw up in drawing the footprint (see this post).  Alas, there was not enough exposed copper on the PCB to attach the wires.  Given that I can’t get power to the PCB, I can’t test.  Drat.

What’s Next

Staying calm, the next move is to revisit the schematic and layout and update the power jack footprint as well as double check the circuits.