It often does not make sense to invest in expensive production equipment if you just want to spin a few prototypes and instead outsource your PCB assembly and prototype manufacturing to a reliable vendor. I will give some tips as to what to watch out for when looking for a contract manufacturer.
Many contract manufacturers will offer an instant quote mechanism on their website for manufacture of circuit boards and assembly of prototypes. This will save you time when comparing different vendors. Make sure that the quote system allows you to enter all of the details, such as board material, thickness, copper thickness, milling etc. so that you can get an accurate quote without any surprises later on.
Usually the cost per board will decrease as quantity increases. This is due to the fairly high setup cost of circuit board manufacturing and component assembly. Some vendors will use a system where they combine boards from several customers. This way the setup cost will be distributed amongst several customers. When you manufacture a product, you obviously do not want to have to manufacture a large quantity of boards right away while you refine your design.
One limitation with small-quantity prototypes though is that the choice of materials and material thicknesses will be limited. If you are using a special material then chances are there won’t be any other customers using the same material. In addition, lead time plays a big role in determining cost. A longer lead time allows the manufacturer more freedom in slotting your production. This is typically reflected in lower costs which you will see in the quote section. Obviously if you are in a rush and want to be moved to the top of the pile you will need to spend more money.
Make sure that your contract manufacturer will support the file format for manufacture that you provide. The most common format for PCB manufacture is the Gerber format but some vendors will also accept board files from common PCB software products. Some suppliers also offer in-house PCB design. Even if you design your board yourself, picking a vendor with design services may prove useful in case there is a problem with your files. In this case your vendor can make quick changes which will avoid costly delays.
When subcontracting PCB assembly, ensure that your vendor can assemble all of the package types that your board uses. Some vendors cannot assemble certain type of IC packages such as BGA, chip-scale packages or very small component types. If in doubt be sure to contact your vendor ahead of time.
Some contract manufacturers will carry an inventory of standard SMT and through-hole components. You will save time if you can pull from your vendor’s inventory rather than purchasing each component yourself. Make sure to specify which components you wish to consign yourself when you upload your bill of materials.
Most vendors will also offer manufacture of the SMT stencil which is required for PCB assembly. Be sure to order the stencil right away when ordering the circuit boards themselves to avoid delays.
To ensure that your circuit boards will work, be sure that your vendor is quality certified and offers the tests and board inspection methods that are required. Please note, however, that certain tests, such as ICT testing requires additional time and cost to prepare suitable test fixtures.