AN0001
Application note revision 1.6
www.Proto-Advantage.com
Circuit Assembly Instructions for Proto Advantage PCB and Stencil Kits
1.0 Board and Stencil Kit Details
Whether you have a toaster oven, a hot plate, or a professional reflow oven, use our laser cut 4 mil (0.1 mm) thick
stainless steel stencils to apply paste and reflow any surface mount chip. All you need is one of our adapter
boards (example: PA*, IPC*, or FPC*), the corresponding stencil (example: PA*-S, IPC*-S, or FPC*-S), one of our
mini-squeegees, and one of our mini-tubes of solder paste. We manufacture and stock the largest selection of
adapter boards in the world, and can adapt almost any IC package to DIP.
For the demonstration in this application note, we have used a low cost toaster oven. Usually the cheaper ones
are best since they have manual controls. This one has a manual control knob allowing temperature to be set
from 95°C (200°F) to 235°C (450°F), perfect for a low temperature (Sn42/Bi57.6/Ag0.4) or leaded (Sn63/Pb37)
reflow process. For prototypes, we usually recommend low temperature or leaded solder paste as it makes reflow
easier due to the lower liquidus temperatures. Most lead-free packages are backwards compatible with a low
temperature or leaded solder process. The only exception being lead-free BGA packages, which can still be
soldered using a low temperature or leaded process, but require a higher liquidus temperature, usually around
217°C (420°F), to be exceeded for at least 30 seconds to ensure the lead-free solder balls melt.
Figure 1 below shows the syringe of solder paste, IPC* adapter board, stainless steel stencil (4 mil thick), and
mini-squeegee for reflowing ICs in the lab, at work, or at home. Figure 2 shows the other equipment you will
need: isopropyl alcohol, paper towels (or lint free wipes if you have them), toaster oven, temperature probe,
compressed air (optional), tweezers and Scotch® tape.
Figure 1:
Proto Advantage Board and Stencil Kit.
Figure 2:
Other equipment you will need.
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2.0 How to use the Board and Stencil Kits
2.1 Unwrap your Stencil
First, unwrap the stencil. 4 mil thick stainless steel should be handled with care as it can bend if abused and it
has sharp corners. Despite the need to handle it carefully, keep in mind that every production assembly house in
the world uses stainless steel stencils because they are the best. They provide the most accurate apertures, best
solder paste location and are reusable for thousands of boards. Keep the stencil and simply re-order the bare
PCB next time you want to assemble another IC in the same package. The syringe of solder paste can be kept at
room temperature for up to a year.
2.2 Clean the PCB and Stencil
Using a small amount of isopropyl alcohol on a sheet of paper towel, wipe the PCB footprint and stencil clean.
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2.3 Affix the Stencil to the PCB
Position the stencil over the footprint so that all pads are visible through the stencil apertures. Tape the top edge
of the stencil in place over the unassembled PCB using low residue scotch tape (Name brand 3M Scotch® tape
works best).
FOR SMALL ADAPTER PCBs: ones with less than 32 DIP pins, or less than 1.6” in length,
refer to Appendix A for additional instructions.
2.4 Apply the Solder Paste
Apply a bead of solder paste at the top end of the stencil, just below the tape.
Drag the mini-squeegee from top to bottom to spread the paste. Take only one pass with the squeegee, applying
even pressure to ensure the paste fills the stencil voids completely.
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2.5 Remove the Stencil
Lift the stencil with a pair of tweezers and remove the tape.
2.6 Inspect the Solder Paste Deposited
Visually inspect the solder paste to ensure it is on the pads and a uniform volume has been deposited. It should
look like the paste in the image below. It doesn’t have to be perfect, since the solder will flow and bond to the
pads and pins during the reflow process. If you are not satisfied with how the paste was deposited, wipe off the
paste using paper towel with isopropyl alcohol on it, clean the stencil with paper towel, isopropyl alcohol, and
compressed air, and simply start over.
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2.7 Place the IC Chip into the Solder Paste
Place the IC chip in the correct orientation on top of the paste, using the pin 1 silkscreen marker dot on the
PCB. Keep the board upright and do not tip or jar the board. Any shock or tipping may shift the IC and could
cause shorts to form during reflow.
Visually inspect the IC chip placement. It should look like the placement in the image below. If you are not
satisfied with how the chip is seated, lift the chip off, clean the chip using paper towel with isopropyl alcohol on it,
clean the board using paper towel with isopropyl alcohol on it, clean the stencil with paper towel, isopropyl alcohol
and compressed air, and simply start over.
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© 2007-2016 Proto Advantage
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