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I'm working on a new design (still laying out the components) and I have a chance here to reduce the size of the PCB by roughly 40%-50% if I use the other side for a QFP-100 IC (so it's heavy and will probably need gluing) and a few passives.

The PCB is 4 layers so savings are worth it, but I was wondering, if I used both sides and made the PCB smaller, how much extra will I pay for assembly? 2x? Will I be actually saving anything with those extra assembly costs, or might I end up paying more?

PS. I'm not sure I can get a quote right now, because I haven't finished the PCB yet, and they might need more info before they give me a quote, so I'd appreciate it if anyone with similar experience would share their thoughts with me, thanks.

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  • \$\begingroup\$ There are a few more parameters, which are also important: size of the PCB, quantity (number of boards in the production run). \$\endgroup\$ – Nick Alexeev Oct 6 '14 at 19:24
  • \$\begingroup\$ @NickAlexeev This specific PCB is ~1.0"x1.5" small run maybe (100-1000), it would be nice to have a rule of thumb. \$\endgroup\$ – mux Oct 6 '14 at 19:57
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    \$\begingroup\$ Why don't you ask 2 or 3 fabs even if you haven't finished the PCB ? It won't be a real quote, but if they are nice and willing to do business, they may answer about a price difference or how they charge the PCB fab and assembly. \$\endgroup\$ – zeqL Oct 6 '14 at 20:39
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As a single data point in this area, I just did a comparison with a company called Bittele (who build their boards and do assembly in China). They quoted US$3815 for the assembly of 1000 fairly simple single sided boards (components on only one side) and US$3976 for the same specs but a double sided board (components on both sides).
Therefore the cost difference (in this case) was US$161 for 1000 boards or $0.161 per board.

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  • \$\begingroup\$ Just to make sure I understood correctly: the price difference you quote is between having components on one side vs. having components on both sides? \$\endgroup\$ – Timo Oct 12 '16 at 8:04
  • \$\begingroup\$ @Timo That's correct. The difference between having components on one side vs components on both sides. I'll modify the answer a bit to make that more clear. \$\endgroup\$ – MattClimbs Oct 12 '16 at 10:25
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    \$\begingroup\$ @m.Alin I on the other hand understood that that's exactly what the OP was asking? \$\endgroup\$ – Timo Oct 12 '16 at 10:28
  • \$\begingroup\$ @MattClimbs Ok, that's good to hear, as I might also at some stage be needing assembly of a board that really has to have components on both sides, and I was afraid that the price difference in assembly would be big. \$\endgroup\$ – Timo Oct 12 '16 at 10:29
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    \$\begingroup\$ FYI on production boards I have seen it is pretty common to flip half the boards in the panelization. You then don't need a second stencil or pick n place setup and the only extra step is to flip the panels once they come out of the oven and send them back through the line again. \$\endgroup\$ – Jon Sep 5 '18 at 20:35
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When looking at PCB assembly, the price is driven primarily by the number of operations and the cost of solder stencils unless they have invested in a solder printer but even then there is going to be setup fee for each side.

If there are components on only one side of the board, then the assembler will only need a single solder stencil; for two sided two solder stencils are required (obvious, I know, but it is a cost driver).

Double sided means twice through the pick and place machine, so you will end up paying for the extra process step.

You will need to trade off the cheaper raw PCB fabrication cost (you get more PCBs per panel) vs. the increased cost of assembly.

Note that if you panelise the PCBs (so they can all ship to you on a panel) it will be possible to manufacture them this way (the entire panel gets each side soldered in one pass per side) and the cost per PCB in assembly can come down (single sided would need twice as many panels).

There are trade-offs in this, and it is not easy to determine the lowest cost route without specifics.

Note that if your QFP does need gluing, it will be seen as an extra process step by the assembler. It may not need to be glued down; if the surface tension force of the solder exceeds the weight of the part, it will not fall off during the second pass. Consult the assembly house.

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