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What are some good methods to populate moderate numbers of pcbs (20-100), without the aid of a pick and place machine?

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    \$\begingroup\$ do you have a stencil for solder paste? \$\endgroup\$ – Kortuk Jun 14 '10 at 23:22
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    \$\begingroup\$ Can you tell us a bit more about the PCB? Does it have solder mask? surface mount? through hole? How big/complex is the PCB? \$\endgroup\$ – Kellenjb Jun 14 '10 at 23:40
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    \$\begingroup\$ I have to agree, can you tell us what kind of board, if it is all through hole, a stencil is worthless, but if it has all surface mount components then you will save years of your life. Are they 0603 footprint, or 1206, another big difference. And solder mask is always a big deal. \$\endgroup\$ – Kortuk Jun 15 '10 at 2:43
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Avoid through hole parts. Don't put components on both sides of the PCB.

Apply solder paste with a stencil, arrange components, bake/reflow.

(update) Here's a great video series from a guy who built 100 little dev boards in 10 days. http://fletchtronics.net/blog/100-bumble-bs-10-days

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    \$\begingroup\$ You can get a stencil from stencilsunlimited.com or integratedideas.com. Of course, as Kellenjb pointed out, this works only if you have a limited set of conditions: soldermask, smt, and pitch are all important in making this work. If you only have to do 20-100, and they're only a couple inches square, you'll get it done by hand with a good iron long before the stencils come in the mail. If you're doing this as a business, plan for stencils, or look into a cheap (relatively) pick-n-place for small jobs. (ex. manncorp.com/pick-and-place/mc384) \$\endgroup\$ – Kevin Vermeer Jun 16 '10 at 3:58
  • \$\begingroup\$ Are Stencils useful for single pcbs or are they only useful when you have multiple un-panelized pcbs? \$\endgroup\$ – stbtra Jun 18 '10 at 16:05
  • \$\begingroup\$ You can use a stencil for a single board, but it takes about the same time to stencil and reflow a panel of several. Manual placing is also quicker as you can place all instances of each part, reducing time swapping between different tapes etc. The combination of tapes stuck down and a foot-operated vacuum pickup can save a lot of time (hint - it's hard to pick parts from tape with tweezers) - with practice you can get down to a couple of secs per part for repetitive placements of the same part type. \$\endgroup\$ – mikeselectricstuff Jan 8 '11 at 1:33
  • \$\begingroup\$ Just watched that video - this really isn't the way to do it efficiently. For a board that size you want to panelise them in a v-scored panel (v-score rather than routed so you can snap out easily) maybe 4x8 boards (hand reach when placing is the first limitation on size), and reflow the whole panel in a toaster oven. \$\endgroup\$ – mikeselectricstuff Jan 8 '11 at 1:43
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If your board is reasonably small, use the soda can method to make a stencil. It's always good to panelize your boards but once the panelized board is over a certain size, i.e. bigger than a soda can, then this doesn't work anymore. Of course, you could always buy a similar thickness sheet of aluminum from McMaster-Carr, then you're only limited by the sheet of paper your laser printer can handle.

For populating boards, save your wrists and your sanity and invest in a cheap manual pick and place. I found that suction pens are ok but nowhere near as handy as a full fledged x-y-z (plus rotation) stage with foot switch for vacuum. There are a few options out there but I found this one to be the best bang for your buck by far. Here's my setup... note the footswitch should be on the floor :)

My pick and place setup

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