What things drive up the cost of a bare PCB? At what points do costs take large jumps?
I am sure there are more experienced people to answer here but this is a start:
We have been asking suppliers for quotes on 5000 units for an evolving board.
From initial observations of our piece prices these are some of the things that have varied cost, however I cannot place a percentage contribution for each item:
- Density of your specific board in a panel. Most PCB panels we have been ordering are 18x24 inches. If your board is an irregular size there will be wastage in panel space. Panels can be smaller than this and another common size is 400x350mm (Roughly 16x14Inches) PCB manufacturers will have their preference and set their lines up accordingly.
- Milling complexity, if they can mill out your boards within a straight grid it will take less time, dropping board prices. Similarly with drill-holes and vias. Time making these, tends to push up board prices.
- Layers, it generally means more cost
- Finishes that may be non-standard, some houses prefer single solder-mask colors.
- Copper pour weight.
I only have a hunch that the large cost jumps are on boards that pack into a panel badly, have complex drill and profile requirements and use gold finish.
Hope this sheds some, basic but initial light. Criticism is welcome.
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The best person to answer such a question would be someone in the Fabrication Business. As an assembler here’s what i can add to the list:
- Laurence is correct, PCBs are fabricated in panels, so the more of your PCB the shop can fit on a single panel, the lower the cost.
- I’ve noticed that some shops are more expensive than others purely because of the clientele they serve. If they are setup for large volumes or different IPC class while you are asking for prototypes, then their prices would be higher.
- Having features such as blind vias, impedance control traces, etc. would also drive up cost
Also possibly not relevant to actual PCB cost but sometimes having manufacturers source out PCBs would also be more cost effective since they can use their relationship with their suppliers to get a better cost.
Hooman Javdan
hooman.j@circuits-central.com
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To expand a little on the previous answers from a bare-board manufacturing perspective; there are four main areas that impact price.
i) Material Price.*
Essentially boards are built and priced by the square foot. Generally 18x24 inch panels are the industry standard, although there are other sizes in play for a variety of reasons. The more the board shop is able to maximize on a production panel, the lower the unit cost is. Remember that although the ‘shop’ panel will be 18x24, not all of this is salable real-estate. Typically an area of approx. 1" on all sides is required for plating contacts, registration control features, pinning holes, targets and test coupons. Discuss your particulars with your particular board house and find the best cost solution. Generally the more flexibility you offer them, the better they are able to do on price.
Another thing to keep in mind is total quantity produced and manufacturing yield. Most shops run a minimum number of panels of each job. If you want 100 boards and manage to fit them all on to a single ‘shop’ panel, the board house would likely still produce between two and four panels depending on the complexity. Often when ‘bad things’ happen they happen to an entire panel. Given that set-up is also a cost adder, most shops factor this into the panel optimization calculations as well.
Be careful of material call-outs that limit the board house and their raw material sources. Unless you have a very specific reason, it is better to call out the IPC 4101 ‘slash’ sheet rather than a particular brand name of laminate. Short of this, list your required performance characteristics like Tg/Td/Dk/Df etc.
The same is true of the ‘stack up’ or board construction. Ask for what you need, and leave the board house as many options as possible to give you the best possible performance at the best possible price.
Needless to say, high performance laminate, hybrid constructions, custom lay-up and other similar requirements will add cost. Again, discuss your needs with your board-shop.
ii) Yield Modifiers. Features or characteristics that impact the overall yield, will impact overall cost. Lines and spacing in excess of your board shops ‘sweet-spot’, tight annular ring, high-aspect plating ratios, unbalanced copper or asymmetrical builds all have the potential to impact yields and therefore price. Discuss with your board house – ask for DFM input early in the design phase and tune the design for manufacturing as much as possible.
iii) Process Cost.
‘Extra’ process cost ‘extra’ money. Of course you get what you pay for – ask for what you need. blind/buried/filled vias, sequential lamination, selective surface finishes, secondary N/C functions like controlled depth, back-drills, counter-sinks, pockets, active cavities…all add cost. Discuss the best way of approaching these various requirements with your board-house to avoid undue cost, stress, or surprises.
iv) Class / Quality Adders
Generally boards are build to IPC 6012 class II with most tolerances in the +/- 10% range. Calling out requirements in excess of this specification generally adds to the cost. Typically this involves increased sampling, reporting, inspection, and in some cases directly impact overall yield. Most good shops build to class III and inspect to class II. Ask for what you need, and again, discuss with your particular board-house.
Most board houses are very willing to discuss your particular goals and end requirements and how to best satisfy your particular needs. The earlier in the design phase you initiate dialog, the easier this is. Find a shop that suits your requirements and style, and build that relationship.
Hope this helps shed a little more light.
Best Regards,
Ian
Ian Hanna
Sr. Field Applications Engineer
ITL Circuits
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