Re: gEDA-user: Hierarchial refdes vs. board assembler

[Steve Meier <smeier@xxxxxxxxxxxxxxxxxxx>]

This process as written below should be captured into the geda wiki. I
do think the cost of the components is a hudge cost driver for a pcb
assembly!

However, the shop I primarily use for complex hierarchical boards with
bga's of over 1000 pins has no problem with the hierarchical refdes.

They can take the xy text file and program their P&p machines just fine.
The flying probe tester is another issue. For the flying probe they need
to know the location of each pad and each expossed via and request the
pad's ascii file format. Side project has been to see if I can translate
back and forth between pad's ascii and pcb... I have made considerable
progress from pads to pcb.

One suggestion I have is when approaching a shop tell them up fron you
are using pcb an be ready to explain that it is an open source program.
Check to see that they can handle the gerbers. This seems not to be an
issue these days but still. Check to see that they can handle your
refdes scheme. Better to have them agree up front then for them to use
it as an issue to delay your boards.

This might actually also be a good project for the wiki. A standard
format rfq which defines our requirements.

Steve Meier


Bob Paddock wrote:
>> They won't get my business again, as this crap is costing me a great
>> deal of time -
>>     
>
> I wrote the message below for a different list last year,
> when someone wanted to know why getting a board built
> by a CM cost so much more than the parts cost when bought
> from DigiKey.  It will give you lots to think about when
> picking a CM.  If you can, pick one where you can go and
> see the place for yourself.
>
> I'm actually surprised your X3/R1 made it all the way to the P&P
> machine before one of the CM's "Systems" barfed.  Usually
> your BM is entered near the front of the process so your
> job can be quoted.
>
>
> ===============================================
>   
>> Is there a rule of thumb for estimating the cost of getting circuit
>> boards assembled?
>>     
>
> In a past life I worked for a large Contract Manufacture,
> http://www.matrc.com .  I don't mean this to a plug for them,
> but the tour of the place is helpful for the discusion:
>
> http://www.matric.com/tour.html
> http://www.matric.com/info/tour/smt.htm
>
> To a CM it is all about *Time*.  When it comes to parts, the actually part
> cost is really insignificant as far as cost contribution goes.   Most of the
> cost goes to the time it takes to setup and teardown.
>
> For a broad brush overview of cost steps:
>
> One shot fee for getting your project into the system.  Someone
> has to enter your BOM, and schedule into the amourphys blob
> known as "The System".  Any change that you do triggers
> a recalculation, that you either payfor or is amortized
> across your boards.  Every future order you place will have
> a small "trigger few" to pay for someone to enter your order.
>
> Included in that is a  fee for someone to do a time analyze of the number of
> operations that your project will require.  A unit time value is assigned to
> each operation, and each operation has a cost, that is, as far
> as I know, calculated by Magick (All CM's use Magick for this step
> to my knowledge).
>
> If you supply the parts there will be fees for entering a carrying
> fee per new part number into The System.  Some cost analysis guru at GM,
> long ago, decided to simply have a number in The System carries
> a charge of $50 or so per year.  The accountants just love
> to beat up the engineering department for "we have to many
> parts in the warehouse".  Company owner wants to keep
> inventory turnover high.  Also cost for physically getting
> your parts into The System, such has putting them
> in the warehouse, typing in the data etc.
>
> There will be a scrapping fee to get your stuff
> out of The System if you take your project someplace
> else.
>
> Those None Recurring Engineering (NRE) fees you either
> pay for up front, or it is amortized across the number of boards.
> This is why the range can seem so different between different
> CMs.  Some hide the fees, some don't.
>
> Also when you supply the parts the price of each part
> will be market up by a *minimum* of 33% (More Guru
> calculations).  If you don't mark the price up by
> this amount you lose money each time you touch the part.
> You are changed for the use of the warehouse space,
> like renting a storage unit.
>
> Now lets say you let the CM supply the parts.  In general
> this will get you a lower per part cost for the commodity parts.
> As they will be using 100,000 0.1 uF 0603 caps a day,
> the pick and place machine will have that loaded.
> So you don't have to pay for loading your reel of
> much smaller volume part.  Also the CM will have
> negotiated a much better price than you got
> from Digikey.  The downside here is that you lose
> some measure of control, which can be a problem
> if you have to meet UL/MSHA/FDA etc. regulations.
>
> Which reminds me there will be extera charges
> for projects that involve the pain of FDA paperwork,
> such a per lot tracking etc.  Other acronyms
> apply as well, UL, FCC etc.
>
> There is a fee for having the solder paste stencil made.
>
> Now that the NRE's are out of the way, lets build
> a Thousand Widgets.
>
> Someone answers the phone and enters
> an order into The System to build a Thousand Widgets.
>
> The System checks the warehouse to see if all
> of the parts area available.  Your order
> is then routed to Purchasing to get the parts
> that are not available ordered, or routed
> to planing to get your order into the build
> que.
>
> When your build hits the top of the que:
>
> Someone pulls the parts from the warehouse,
> at the minimum your PCB; time.
>
> Your bareboards are put in an oven and baked to drive out any moisture,
> you pay the handling and electricity; time.
>
> Your parts are loaded on the Pick&Place machine; time.
>
> The board go from the oven to SMT Assembly; time.
>
> Someone pulls your stencil out of the rack and puts it in the paste machine.
> Past is applied to your board; time.
>
> Your board is put into the Pick&Place and your parts are mounted;
> paste, electricity
> and time.
>
> Your board then goes through the IR reflow oven for soldering; electricity and
> time.
>
> The boards are then cleaned; fluids and time.
>
> Any of your parts left on the P&P are removed, and put
> back in the warehouse, when Widget #1000 comes out
> the end of the machine; time.
>
> The stencil is cleaned.  You pay for whatever the cleaning
> fluid is and time.
>
> The stencil is put back in the rack; time.
>
> If your boards are in a array, they are then cut apart.
> It is cheaper to build arrays, but it adds this cutting fee; time.
>
> If there are parts that could not be mounted in the P&P machine
> they are done by hand, or put through the wave solder machine,
> then cleaned a second time.  There is a big hit in costs for
> anyting done by hand such as connectors, transformers,
> cable assemblies etc. Time.
>
> The boards then go to Quality Control for the level of inspection
> that you paid for.  Simple visual to full functional test.  Time.
>
> Boards leave QC and go to shipping where they are put
> in Anti-Static bags and cardboard boxes and shipped off
> to you.  Time.
>
> You pay the shipping one way or the other.
>
> There could also be Added Value items such as your boards
> are put in an enclosure.  You pay for someone to do it right
> down to the number of seconds it takes to tighten down the
> screws.
>
> By now you probably have gotten the idea that Time is important.
> When you were looking up stuff in the DigiKey catalog were you
> billing yourself the time it took to do it?  Probably not...
>
>   
>>  The 500 piece cost for the electonic parts from Digi-key is
>> about $4.20
>>     
>
> Did you include the Anti-Static Bag, the yellow Anti-Static
> Sticker that seals the bag, the solder (price of metals is going up every
> day), and any board cleaning fluid chemicals / deionized-water in that price
> of $4.20, and the time to do those items?  I didn't think so...
>
> A good CM knows the cost of every operation and will be around a long time.
> A new CM doesn't know his costs.  Hence the wide variation in CM quotes.
>
> Matric developed a reputation for being a high price CM, and customers
> would leave based on cost, rather than value.  However many of them would
> return after a while saying "we got what we paid for", and never left again.
>
> In the end my advice is to analyze the value of the services you are paying
> for, not the cost of the parts.
>
>   



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