Attaching probes to test points

I’ve started playing around with a USB Logic Analyzer and decided to try to read the weight off of my kitchen scale. My first challenge is to cleanly attach the logic probes to the test pads on the board (see attached picture). Without a solid connection, it will be tough to measure signal changes.

A couple of options come to mind:

  • Simply solder small wires to each test point (haven’t soldered in years, but don’t mind learning). Has a high likelihood of damaging of the board.
  • Create some kind of pin grid I could press on the board. I’d create the grid by pushing wires through some type of medium (maybe even cardboard) in the proper pattern so when pressed onto the board, all the pins will make contact. Seems pretty theoretical.

I’ve tried googling and binging but it seems to be a pretty tough combination of keywords.

Any pointers?

Those are bed-of-nails test points, designed for spring loaded pin array in an automated testing machine.
Its possible to solder short wire stubs to each pad for the LA probes.

MarkT:
Those are bed-of-nails test points, designed for spring loaded pin array in an automated testing machine.
Its possible to solder short wire stubs to each pad for the LA probes.

Thank you.

"bed-of-nails" gives me another search term I didn't know. Lead to "pogo pins" which are the spring loaded pins and are available on amazon. Now to find some type of grid hold the pins. Otherwise, soldering will be the answer.

Now to find some type of grid hold the pins.

These are normally a custom made block from the X-Y pad positions in the PCB CAD package.
These are then drilled with a CNC drill in a block of insulating material of the sort used for making PCBs. Your PCB substrate: a guide to materials | Knowledge Centre | Essentra Components UK

Then you need some sort of clamp arrangement to hold the PCB on the bed of nails. The ones I have been involved with are normally hydraulically operated. These are known as “test fixtures” and are a quite expensive part of setting up a production line.

I never solder without using this.

Try soldering without it first, then try using it. Once you try it you'll never go back to soldering without it.

Hopefully no-one's trying to solder without using rosin-cored solder in the first place. Extra flux is
useful, but cleaning the surfaces before soldering is wise too.

Since flux needs to be cleaned off after soldering I tend to use extra rosin only when needed, and use
no-clean solder paste for surface mount work.

The advice on soldering is helpful. I have do have 60/40 Tin Lead Solder Wire with Rosin - 0.6mm because this is small work. Is this appropriate for soldering a wire stub to the pads? I'm tempted to use the clipped off ends of some resistors for the wire stubs.

Also, if I go down the "bed-of-nails" path, I'd probably manually create something like this:

It might be very hard to get the geometry correct without 3d printing it. I could also make a jig that will do 2 or 3 pins at a time instead of all of them.

Fun little project.

Since flux needs to be cleaned off after soldering I tend to use extra rosin only when needed, and use
no-clean solder paste for surface mount work.

Alchohol works just fine for cleaning it off. I've been using it for 40 years and I've never been so busy
I can't spare a few seconds to clean it off. Besides , the no-clean flux sucks bigtime compared to rosin
flux for almost all applications.

It might be very hard to get the geometry correct without 3d printing it.

Take a photograph. I port it into a drawing package and scale it to be the real size of the board. Then pick out the positions of the pads putting cross hairs where you want them.

Next delete the image just leaving he cross hairs and the outline of the board. Print onto paper and glue onto a board. Then just drill at the cross hairs.