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We are designing a product that will hopefully sell many thousand units, and now I am at the stage of specifying what parts to use.

We require three inter-board connectors, one with 10contacts and two with 4 contacts. Instead of using two different sizes, we can just use three of the ten contact connectors. The ten contact connectors cost 30% more than the four contact connectors at volume. So the obvious choice is to spec for two different parts on the BOM.

But more BOM lines increases the PCBA assembly cost, and increases the inventory of components we have to hold.

What has the greater effect on unit cost, reduced BOM lines, or reduce BOM cost?

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closed as too broad by Dmitry Grigoryev, PeterJ, Daniel Grillo, Dave Tweed May 11 '16 at 21:08

Please edit the question to limit it to a specific problem with enough detail to identify an adequate answer. Avoid asking multiple distinct questions at once. See the How to Ask page for help clarifying this question. If this question can be reworded to fit the rules in the help center, please edit the question.

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    \$\begingroup\$ Why not consolidate some of the interconnects so that you only need 2 10-pin connectors? \$\endgroup\$ – Ignacio Vazquez-Abrams May 11 '16 at 3:47
  • \$\begingroup\$ The two 4pin connectors are on different boards. I could make one large board, but then it is a weird shape and will probably increase manufacturing cost. \$\endgroup\$ – SonderEng May 11 '16 at 4:45
  • \$\begingroup\$ Why don't you just calculate the price of using 3 10-pin connectors and the price of using 1x10-pin and 2x4pin connectors, and pick the cheapest option? \$\endgroup\$ – Dmitry Grigoryev May 11 '16 at 11:44
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The obvious answer to your question is that it really depends on a number of factors. You have to weigh the cost per part versus the cost per BOM line to determine the most cost effective approach.

On thing that can be said though if you are working on BOM line item minimization is to first concentrate your attention on those lines with the lowest part costs. This will almost assuredly be first in the SMT resistor category followed closely by the low capacitance valued SMT capacitor category. The biggest gains will come here. Think seriously if you have 10K and 12K resistors if you can have both lines be the same value....even if that ends up being that you end up specifying 1% resistors for both line items.

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If these parts are hand-placed, the build cost impact of 2 different part numbers is probably small. If they are machine placed, reel sizes may mean it is irrelevant (3 identical reels, or 1 plus 2).

Unless you can make cost savings by buying in bulk, you are optimising the wrong part.

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