Tell me about getting boards assembled

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kk6gm
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Posted by kk6gm: Thu. Sep 15, 2011 - 06:11 PM
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Please...

Being more a software guy, I've never had to deal with this. But now I've got a few board designs made up (PCBs in hand) and I want to have them assembled. Some thru-hole, some SMT. I want to get small quantities made up for now, say 50-100 boards - with expections of larger quantities later.

So what is the process? Who obtains the parts? Assuming I supply the parts, what is the assembly house going to want (e.g. if each board needs one particular cap, do I just send them the strip I get from Mouser with 100 of those caps?) How do I link various bags/tapes/reels of parts to what goes on the board where?

Any and all advice you can give will be most helpful.

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Learning and Information, General Electronics
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ka7ehk
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Posted by ka7ehk: Thu. Sep 15, 2011 - 07:16 PM
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It varies a lot with the assembly house.

There is a local one (near Corvallis,OR) which will purchase and stock parts for you. Of course, that costs, but you may "save" by not having to deal with that. They also have "house-stock" parts for some standard things, like 5%, 1/4W, leaded resistors.

These places appear to be enough different that the only thing that makes sense is to talk, directly, to several until you find one that is a good fit.

Jim

Jim Wagner Oregon Research Electronics, Consulting Div. Tangent, OR, USA http://www.orelectronics.net

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hobbss
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Posted by hobbss: Thu. Sep 15, 2011 - 07:22 PM
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I suppose a lot depends on your vendor (and country). In the U.S., assembly houses will accept your kits, or kit the boards for you. Most houses charge ~25% in component costs (i.e., 125% of the cost of the components for kitting and fees) as a flat rate for kitting. However, this is often offset by the fact that, since they buy in such bulk quantities, their prices are often lower than what you can buy components for. If you are going to provide kits, make sure you know their requirements (i.e., minimum of four inches of tape for any taped components, and any overages for package sizes (typical: 25% for 0402, 10% for 0603, 5% for 0805, etc). Also, if you are providing kits, you do not need (and actually should not) separate the components into individual kits -- send in bulk. When you order the assembly, include at a minimum, a bill of materials including reference designator and part numbers. In addition, if possible, include a pick and place file (xy centroids, with rotation) and a IPC-386 file, and an explicit Assembly Drawing. Basically, the more information you provide, the less chance there will be a mistake.

In terms of pricing, there will be an NRE (for a stencil and for programming the pick an place machine), a flat rate per board (decreases with increasing number of boards, increases with number of components), and an additional fee (anywhere from $0.30 to $1.00) for each through hole component. Also check to see if they charge extra for things like BGAs or fine pitch components.

Edit:
Jim -- you wouldn't happen to be talking about Screaming Circuits, now, would you?

Also, if letting them kit, be very clear on the acceptability (or lack thereof) of substitutions.

Science is not consensus. Science is numbers.

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ka7ehk
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Posted by ka7ehk: Thu. Sep 15, 2011 - 07:40 PM
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Screaming Circuits is SE of Portland in the town of Molalla. Our local one is much smaller - MegaTech.

That is another point. The big houses, like Screaming Circuits and their brethren typically have a much more formal process and are more rigid in their requirements. The small places, like the MegaTech I mentioned, certainly have "rules" but have a lot more flexibility. The small ones will often do first and second round prototyping. They will often purchase boards for you. If the board is SMT, they will purchase the solder screens for you but may just do it by hand on the initial builds (if the quantity is really small, say under 10, and it does not involve really fine pitches). But, for really small runs, they may hand-apply paste but use a machine to place individual parts. It all depends.

Jim

Jim Wagner Oregon Research Electronics, Consulting Div. Tangent, OR, USA http://www.orelectronics.net

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Chuck-Rowst
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Posted by Chuck-Rowst: Fri. Sep 16, 2011 - 03:21 PM
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kkogm,

Take my free advice and find yourself a trusted EE friend with production experience to help you with this. There are plenty of ways to get "burned" for first-time entrepreneurs on the customer side of the electronics sub-contracted assembly business.

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