Date: 20010108 From: Bob Paddock <firstname.lastname@example.org> To: Multiple recipients of the Chipdir mailing list Subject: Re: Manufacturing questions
I have a question about electronics manufacturing. I may need to arrange to manufacture some quantity (10K to 50K units) of a design, but not having dealt with this quantity before I am unfamiliar with the services that are available.
Some places only deal in large volumes, some places only
deal in small volumes, there can be different issues.
I know that Semions (sp?)/Infinion has a contract division
that does volume stuff.
I work for a company that does the lower volume stuff,
generally under runs of 5000, this is written from that
Can anyone recommend references on the processes involved or some firms that do this sort of work (PCB assembly)?
Do they like to receive PCBs and parts and perform the assembly, or will they source these themselves?
It is usually better to let the contract house to source
their own parts. They will buy a far higher volume worth of
parts than you alone will.
If there are parts that are unique to your job then you
should supply them.
Doing a 'kit' of parts always cause problems with stuff that
is out of date, especially firmware issues.
What mechanical requirements exist for the PCB to make assembly easier for pick and place machines or any other processes that might be used?
Spacing to allow for the flying heads to 'fit', not all that
much. The foot prints of the parts are more important to
get proper solder flow. There are also issues of placing
proper targets for the test equipment.
Its a 50/50 call on if it is better to let the contractor do
the PCB layout (they will charge you for this) or you supply
it. The both have there advantages and problems.
If the contractor does it, you can be sure it will fit their
equipment, but maybe you have 'noise' issues or RF issues
where your own layout would be better. Some melding of the
two are the best option.
What sort of cost might I be looking at for placing the parts, soldering (wave or reflow process)?
This is actually the smallest part of a contract job, which
surprises most people, see below for details.
Can the firm that does assembly advise me on these points?
The good ones can, if they can't move on, as it is in their
best interest to help you. However some places do charge
for doing 'Request For Quotes', its mostly a issue of paying
for the time.
Any advice would be appreciated.
This is a insider view of why things cost so much:
The first item to consider is how well put together is your
design package. Does your Bill of Material specify parts
fully? For example I was given a BOM that said "C1
Capacitor". The customer got mad when I asked what value it
was. It should tell me the value, the tolerance, the
voltage. If there is a existing PCB layout it needs to give
me a exact foot print, or a industry standard reference. Do
you require a exact part (higher cost) for some reason like
approval issues UL, FCC, MSHA etc, or can I use what I
already stock (costs are lower because I buy by the
tens-of-thousands a month).
A simple .1uF cap can cause problems if your approval paper
work says its a purple-one for example, and we use a blue
one (inspectors want thing to LOOK EXACTLY THE SAME), or
maybe it doesn't matter at all for this application, you
need to document issues like this.
Do you have full design prints that show complete parts
layout, a good schematic? If not I'll have to draw them,
this takes time and costs. Just because YOU know where the
parts go, doesn't mean that the person building it for you
does. A schematic is not required to simply build the
boards but if you want us to test them then it is.
Is there any regulatory issues that need dealt with? Do we
have to seek FCC Part 15 for you?
Its your design, we just build it, but when it doesn't work,
it always seems to be 'our fault'. We do look for obvious
problems, but some customers get mad when we point out
problems. Do you want us to test it once it is built? This
takes our time. Do you have a test fixture that you can
supply or do we have to design and build it?
Does your board 'fit' our equipment? For example, to go on
the automated test line you need to have references targets
on the PCB for alignment. If there are no alignment
references things get done by hand, taking more time, raising
Is the board SMT? If so we need to have a paste stencil
made at a costs up to $500 for large boards. We pass this on
to you. There are other setup fees that may come up
depending on the job. Does your part spacing allow
clearance for the flying 'head' that places the parts?
Does your job require us to get tools or equipment that we
might not have? Frequently we will eat this cost, but if it
seems likely that you are the only job that will ever need
it, then we pass this on to you.
The stuffing of the boards is usually the smallest part of
the time, it is the up front setup, and tear down items that
take time, testing and documentation that drives up the
As you can see there are many places where time must be
spent, that generally get over looked when you are 'doing it
your self', because you consider your time 'free'.
For comparing companies you need to find out their policies
on giving you quotes. Do they charge for this? Some do,
some don't, we decided on a case by case bases. We usually
have some up front one time fee to cover the one shot items,
SMT stencils for example, but some companies 'hide' these
costs by raising the cost per board.
We've had people leave us "because you cost to much" only to
return after a time saying "we got what we paid for". Keep
this in mind if nothing else.
For locating companies in your region, start by asking at
your local computer store, vocational school/technical
collage, or Amateur Radio Club. There will be a person some
place at one of them that can point you in the right place.
You might also want to look up "The American Contract Show"
organization that puts on regional shows every year:
Date: 20010109 From: Bob Smith To: Multiple recipients of Chipdir mailing list Subject: Re: Manufacturing questions
Bob Paddock gives good advice, but I have only a couple of things to add:
Good luck, Bob Smith
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