Bridging across solder jumpers during reflow.

[phil from seattle]

I have been using 3 pad solder jumpers on a number of board I have designed.  Usually, I run a trace between the default pads. If the user wants to switch, they have to cut the trace and solder bridge the other pads. Making my customers cut traces is a source of problems.

I would like to switch to having a solder bridge created during reflow rather than a trace that needs to be cut. This will make it a lot easier to switch the jumper.

How should I go about doing this?  Create a mask layer area that spans the two default pads? Is that sufficient? Will that cause a bridge?

[tooki]

I have no experience on whether your suggested approach would work. (Sometimes, it’s hard to make solder jumpers work, even by hand with a soldering iron. I’m sure there is some specific jumper geometry that works better than rectangular pads. I’ve seen chevrons, for example.)

What definitely works is to just use 0 ohm jumpers. Easy to install, easy to remove.

[phil from seattle]

What definitely works is to just use 0 ohm jumpers. Easy to install, easy to remove.

Thanks for replying.  Yes, they do.  The problem is you have to make them reasonably big - 803.  And desoldering them to move is almost as big a challenge as trace cutting.  I'm pretty skilled at board rework and I lose over half the resistors I desolder.

[langwadt]

What definitely works is to just use 0 ohm jumpers. Easy to install, easy to remove.

Thanks for replying.  Yes, they do.  The problem is you have to make them reasonably big - 803.  And desoldering them to move is almost as big a challenge as trace cutting.  I'm pretty skilled at board rework and I lose over half the resistors I desolder.

if it is just a 0 Ohm resistor  it doesn't really matter if you lose them, just make a solder bridge, so smaller is easier

for assembly it seem easier to make different parts DNP than changing the paste mask to change solder bridges

[Doctorandus_P]

I would like to switch to having a solder bridge created during reflow...

That would be difficult to do reliably. You can start with making the narrowest gap that your PCB manufacturer can manufacture, and combining it wit a solder mask aperture that is bigger then the pad to encourage bridging, but I guess it will still be unreliable.

Maybe using a 0 Ohm resistor for the factory, and then combine it pads that can also be used as a solder bridge to override it manually is a good combination.

[abeyer]

If they really can't be expected to use a soldering iron, why not 0.1" headers and a removable plastic jumper? or a dip switch? those were always the standbys for easy user config.

[phil from seattle]

If they really can't be expected to use a soldering iron, why not 0.1" headers and a removable plastic jumper? or a dip switch? those were always the standbys for easy user config.

They are expected to solder various connectors onto the board.  Small SMDs are a challenge.

Dip switches and 2.54mm headers are possible but are big and space is limited. And, dip switches add cost, especially spdt.

[tooki]

What definitely works is to just use 0 ohm jumpers. Easy to install, easy to remove.

Thanks for replying.  Yes, they do.  The problem is you have to make them reasonably big - 803.  And desoldering them to move is almost as big a challenge as trace cutting.  I'm pretty skilled at board rework and I lose over half the resistors I desolder.

803?

You mean either 0805 or 0603, right?

Anyway, as langwadt said, who cares if you lose it? You can either use a new one, or (with a footprint optimized for solder bridging) then bridge it by hand.

0805 and smaller are easy to remove with just a big blob of solder on an ordinary soldering iron tip.

Anyhow, the key idea here is that if you optimize the footprint for manual jumpering, you can still use a 0 ohm jumper for reflow, but use manual jumpering for later modification.


Another option is jumpering with through-hole wire jumpers.


With that said, if the users are really so unskilled that they can’t cut a trace or desolder a resistor, it really may make sense to use switches or headers+jumpers. You don’t have to use expensive SPDT switches, just use multiple SPST.