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Thanks to a VERY generous
equipment donation by a co-worker of mine (thanks again,
Mendel!), we have a vapor phase reflow soldering setup with
which to build our Dashcomp 1g PCBs. Following is an
account of the first time either Rody or I have ever used vapor
phase reflow, or even seen it in action. (Note: All
images shown below are clickable for a larger image) |
Applying the Solder
Paste
In order to stick the parts to the PCB, solder paste
must be applied. A stencil is used to do this.
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Pasted PCB
The stencil has accurately located the blobs of solder
paste onto the minuscule pads.
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Too Much Paste!!!
If you look at the paste for the microcontroller pins,
you'll see that they're tall, skinny towers o' paste. This
isn't the way it's supposed to be, and it came back to bite us a
little bit.
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Our Soldering Setup
Here is our Multicore Solders "Vaporette" vapor phase
reflow oven, alongside its home-built cooling system. I
used a $9 swamp cooler pump and some Tygon tubing to build a
recirculating water-based cooling system. Worked great!
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Galden HT-200
Perfluoropolyether Fluid
This is some exotic stuff... I actually got it for
a steal at $270 for this gallon ($18/lb), but that's MUCH better
than the $64/lb that the 3M counterpart (FC-70) costs.
This stuff is reclaimed, and is from TMC Industries in
Minnesota.
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"Vaporette" Vapor
Phase Reflow Soldering Oven
As I mentioned, we have a vapor phase reflow soldering setup with
which to build our Dashcomp 1g PCBs. YAY!!! It works
on the principle that the HT-200 is boiled at the bottom of the
vessel by a heater, and the boiling point of the fluid is 200
degrees C. This vapor condenses on the relatively cool PCB
that is dropped into the vapor cloud, which adds a tremendous
amount of heat to the PCB, thereby flowing the solder.
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PCB in the Reflow
Oven, Not Yet Flowed
This PCB is in the oven, but hasn't yet started to flow
the solder. |
PCB in the Reflow
Oven, Halfway Flowed
This PCB is in the oven and has started to flow.
If you look carefully, you'll see molten solder on the right
hand side of the board, and intact solder paste on the joints on
the other side of the board. The "wave" of molten solder
is traveling along the board.
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Rody, the PCB's
Designer
Rody, a watched reflow oven never boils....
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Completed PCBs!
Here they are, as completed as they can get in the
absence of my soldering station (it's buried in the garage
somewhere). The reflow oven worked great, but since we put
too much solder paste on, there are several solder bridges on
the fine-pitch IC's. Oh well, nothing a wick can't fix!
We'll be more careful next time.
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Updates to come
soon! |
