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If I would like to indicate to the PCBA manufacturer that a solder jumper position is to be "bridged" with a solder blob, what is the preferred way to indicate this? I have thought of the following options

  1. Paste Layer Data - indicate coverage (conversely, no paste if no jumper)
  2. In Component BOM - Indicate population of position and let PCBA figure it out.
  3. Manually or specifically indicate, e.g. in engineering drawing.

A second question is if this is something that would normally be done during smt processing or manually afterwards.

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    \$\begingroup\$ Places that I have seen do it manually after SMT. Also, in some MILSPEC applications they were bridged with a lead submerged in solder. Therefore, I would say in engineering drawing. But also, it sounds error prone, to be honest. I am also curious. \$\endgroup\$ Commented Feb 5, 2019 at 21:28
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    \$\begingroup\$ Why not ask the manufacturer where they would expect to see it? \$\endgroup\$
    – Eugene Sh.
    Commented Feb 5, 2019 at 21:35
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    \$\begingroup\$ it can de done at the SMT step by placing "zero-ohm" resistors. \$\endgroup\$ Commented Feb 5, 2019 at 22:24
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    \$\begingroup\$ zero ohm "resistors" have the advantage of being the only fully automated "pure software" solution, at least unless your assembly house is using a paste printer or a wave soldering machine. Doing it on the paste layer is going to be harder to get right, and would require purchasing a new stencil for each configuration change. While if your pad designs and process can't get a machine-placed 0-ohm resistor right, you have greater problems as they won't get the rest of the resistors right either... \$\endgroup\$ Commented Feb 5, 2019 at 23:01
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    \$\begingroup\$ Suicidally dangerous unreliability can be achieved by any desired method that may well work most of some of the time. If your boards are NEVER "reworked", the surface tension and related environmental conditions are always "just so" and .... having a solder bridge as a production component may even work, often. Otherwise ... . \$\endgroup\$
    – Russell McMahon
    Commented Feb 6, 2019 at 1:22

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The first and last of your three points are as good a way of doing this as any.

If you draw a bridge on the solder paste layer, then there will be paste placed there. You would need to make sure that the gap between the jumper pads is small enough, the pads themselves are not too large, and there is enough solder paste. You can test this out with a test board, or as your PCBA if they have any tested spec. By using the solder paste layer, the bridges will naturally form the desired bridge during reflow.

Alternatively, adding an additional information file with your assembly job is quite common. You can for example provide a too-scale drawing (even gerber file) of the location of all solder jumpers giving infomation as to which should be bridged and which shouldn't. A summary list can also be added to the BOM.

In fact doing both is a great option because it allows for the bridges to be primarily acheived during reflow and then verified during inspection. As part of the board inspection you simply state that the solder bridges should be in place as indicated in your diagram. Any that aren't can then be corrected by the PCBA house manually as a rework step.

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