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The Healthy EC Dev-Rev1 PCBs came in the other day.  I wanted to know how our old toaster oven would work as a reflow oven without any modifications.  Using an old toaster works well enough that I’ll use this technique again!  The tedious part continues to be -and will always be without a pick and place machine – is the placement of solder and placing of chips.  Although it is a great time to relax and listen to music.

I set the toaster to 475˚F and warmed it up for 10 minutes.  After putting the solder mask and placing the chips, I popped it in the toaster for ~ 90 seconds….and out comes….

Healthy EC Oven Reflow

not bad.  There were two 0805’s that needed to be re-soldered, like the tombstone job on R18:

tombstone Chip

and my old friend the MCP3901 needed cleanup:

 

MCP3901 cleanup

but these were minor – and easy – to clean up.

To evolve my soldering technique, I note:

  • I used too much solder.  I tend to place a glop that covers a pad.  After playing with a stencil, I believe a better method would be a light covering – more like a smear – than a glop.  
  • The paste I am using – as Brent from Osh Stencils noted based on an earlier post on using stencils is very (very) liquid.  I was hoping it was because I had removed the solder paste from the refrigerator an hour before so that it would be at room temperature as Dave (EEVBlog) advised in this video.  No, the paste I am using – Chip Quik Low Melting Lead Free Solder Paste – is liquid.  
Brent suggested Kester EP256 solder paste.  I plan to try this solder paste.
 
After I ran this experiment, I asked the question on the /Ask/Electronics subreddit:
Yesterday I placed chips (on top of solder paste) on a pcb and stuck it in my toaster oven for 90 seconds. Everything seemed to work great. I just turned the toaster to 475F. There was no profile.What are the problems I will run up against with a PCB who has had its chips attached in such a “pop tart” like way?
I got some great advice (link) that I will apply moving forward.  I also ordered a new toaster oven for my family :-).
 
 

 

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