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I agree, Mike, there are indeed some really neat
SMD devices and tools out there - but, most are just too expensive for the
hobbyist. I drooled over several nights just pouring over
them.
Yes, many article on the web about supposedly how
to do that. The critical parameters seem to be squeegee angle with the
board, thickness of the stencil, hardness of the squeegee, viscosity of the
solder paste, and pressure of the squeegee on the stencil. Probably
others, but those are the ones I recall.
Just pick and place machines that just pluck those
SMD components off of reels and place them on the board are one of the items
that caused a bit of drooling.
But, on the other hand if a solder paste run smears
or is other wise unsatisfactory, you can clean off the board with alcohol and
have another try at it. {:>) Nothing is locked in until you stick it in
the oven. After that then a lot of work to change/remove anything in the
wrong place.
Ed
----- Original Message -----
Sent: Friday, February 16, 2007 9:03
PM
Subject: [FlyRotary] Re: SMD Printer
Photo 2
We
produce and test a lot of boards that are all SMDs and fine pitch devices.
Getting that solder paste on the correct thickness is an art form. Even with a
tightly controlled manufacturing process and state of the art equipment, there
are often problems. I saw a real nice pick-n-place machine for placing
somponents on circuit boards go at auction for $500. It was probably worth 100
times that. If I were in California, I'd have bought it. Mike
LaFleur
-----
Original Message ---- From: Ed Anderson
<eanderson@carolina.rr.com> To: Rotary motors in aircraft
<flyrotary@lancaironline.net> Sent: Friday, February 16, 2007 6:25:18
PM Subject: [FlyRotary] Re: SMD Printer Photo 2
Hi Bill, there are a number of places that will
make stencils - but cheaper plastic ones a bit harder to find.
You take a CAD drawing for your circuit board -
most use DXF format but they can be make from Gerber files (my Circuit Board
drawing software does not produce gerber files, but will export a DXF
file).
I then eliminate anything in the DXF file that is
not a pad or pin that I want solder on. Then e mail the file
to this company/guy. http://www.pololu.com/ attn : Jan
Malasek They use a laser to cut the stencil based on your DXF file and
ship it to you. Oh, they first send you a PDF of the proposed stencil
for one last check by you before cutting the stencil.
The one I got matches even the 30 pins of a fine
pitch socket with pins only 0.25mm apart, so I was pleased. You can see
some result of the laser heat on the plastic so its not quite as clean as with
a metal stencil - but quite good for the price.
Ed
-----
Original Message -----
Sent:
Friday, February 16, 2007 4:52 PM
Subject:
[FlyRotary] Re: SMD Printer Photo 2
Ed,
Very nice printer you made -- how do you get your
stencils?
Bill Schertz
KIS Cruiser # 4045
-----
Original Message -----
Sent:
Friday, February 16, 2007 2:55 PM
Subject:
[FlyRotary] Re: SMD Printer Photo 2
Hi Bill,
To answer your question, Yes. And I am
certain they can be made to do the job. In fact, before the stencils
arrived on the SMD scene, it appears they used a "Mesh screen" which I
understand is very close to what the silkscreen printers do.
But, the "mesh screen" approach was limited
by the smallest pitch of pins they could resolve to, so they went to the
stencil approach.
With the solder paste method (from what I
think I understand) appears to require some consistency of pressure for
best results. That lead to my adjustable springs to put the squeegee
under consistent pressure - supposedly once I find that magic pressure
setting then consist good result will follow.
Lots of ways to skin this cat.
Ed
-----
Original Message -----
Sent:
Friday, February 16, 2007 3:41 PM
Subject:
[FlyRotary] Re: SMD Printer Photo 2
Ed, That looks like innovative and neat work. Now the apparatus
begs the question, have you ever looked at a standard silkscreen jig
from the art store to do the same job? The design you made is
considerably tougher, but some of the silkscreen machines are pretty
well framed using hardwood. FWIW (which probably aint
much)
Bill Jepson
-----Original Message-----
From:
eanderson@carolina.rr.com
To: flyrotary@lancaironline.net
Sent:
Fri, 16 Feb 2007 11:19 AM
Subject: [FlyRotary] SMD Printer Photo
2
This shows one of the two side mounts of my SMD
solder paste printer which is attached to the MSD nylon strip which
rides in a groove inside the cheap T track. The T track is simply
screwed to the 1/2" slab of aluminum. The acorn nut provides tension
through a 1/4" threaded rod and keeps the pull-handle gripped between
the two sides and provides tension on the side plate which puts side
pressure on the MSD strip in the T rail. More pressure makes the
device slide slower and less makes it faster.
The squeegee holder can pivot to either put the
squeegee down on the bed or to hold it up off of it after a solder run
and you want to move the squeegee holder back to the other original end
of the board without smearing your deposited paste.
The second photo shows
where the squeegee holder would be positioned after a "solder-run" was
made. I would then rotate the squeegee up 1/8" inch out of contact
with the bed and move it back to the other (starting) end of the
bed.
Ed
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