I've got a project BOM costed out and I know my PCB costs. Without sending my project out for quote I'd like to be able to estimate the assembly cost by number of SMT components placed and the number of through holes (for connectors) requiring hand soldering. Assume these are assembled in the US. Assume I know the fixed costs for stencils, pick and place programming, etc.
Anybody have some ballpark figures which might help here?
We usually have 100 units assembled at a time. I usually have a 64 to 100-pin QFP, a few 8 to 20-pin SOIC chips, and many 0805 resistors and caps.
I estimate $0.07 to $0.08 per pin/pad. That usually gets me a ballpark figure of what the assembly houses will charge. This does not include the tooling and setup charges. They run between $200 and $500, depending on the assembly house.
Edit We use assembly houses in New England (USA).
Won't fit in a comment field, so:
Note that you say "assembled in the US" - but this would apply only if expressly stipulated, as many companies with a US front end use Asian assembly or Indian or ... . I can recommend a well priced and highly competent and conscientious assembler in Serbia and can suggest a SD, CA company who assembles in all of USA, mainland China and Taiwan.
Very much comment only:
US: $More than China to $Much more than China.
Use following as a very rough guide only.
China:
Reasonable rule of thumb is 1/3 cent US ($US0.00333 cents US) per pad or termination for SMD. Through hole fits inside that cost as long as percent through hole termination points is small compared to SMD termination points.
The above "formula" just happens to come out very roughly right in many smaller cases. It is not a true reflection of costs in extreme cases. eg 2 terminal devices such as capacitors and resistors would be costed at 2 x 0.33 cents = 2/3 cents each. An 0805 1% metal film resistor costs somewhere around 0.1 cent in manufacturing volumes so the assembly cost swamps it. Whereas an eg SOIC14 pkg would cost at 14/3 ~= 5 cents and a SOIC8 at 8/3 ~= 3 cents whereas an eg TQFP44 would cost at 44/3 ~= 15 cents. The resistor install cost may be able to be worked on and the TQFP cost, as some aspects of pick and place costings scale approximately linearly with pin count and/or package size and others are very non linear with size.
When quoted for Taiwanese manufacture via a local NZ middleman who claimed a modest markup % on costs I have had quotes for many times the cost of what can be achieved directly in mainland China.
There is a huge assumption that your design is even manufacturable, or that it will be possible to get high yields. QTA shops who build prototype qty's less than $5K worth need to assess all your DFT, DFM errors and assess the risks of fallout from solderability to testability. Learning curve rejections and rework costs can well exceed the BOM cost in 1st run prototypes and the NRE for screens, machine setup, ATE fixtures and process design is strongly dependant on the complexity of the design and ability for DFT to do fault isolation quickly. i.e. self test vs ICT vs FT etc. Don't be too quick to assume the cheap cost unless you can commit and prepay volumes or take a risk on low cost & cross your fingers on yield. Either they need to be desperate for business or you are willing to take huge risks on field failures.
