Taping 2.54mm rectangular connectors

[kuon]

Do you know any gadget to tap stacked 2.54mm dual row rectangular connectors?

I often work with boards that have expansion boards with no pass through header, like this:

https://www.beyondlogic.org/wp-content/uploads/2020/02/BeagleBone-CAN-Cape-678x381.png

I am wondering if you have any idea on solution to "tap" some pins? I usually solder but for prototyping it would be nice to have a fast solution without soldering.

[Whales]

Solder doesn't make a good contact material.  It's uneven and can have residues (like flux) left on it. 

It might be better to make a middle stackable board that goes between the two?  Alas that's only good for production, for one-offs it's still annoying.

[gwideman]

First -- by "tap" do you mean "tap into"? Ie: you're not talking about tapping some threads, for mechanical mounting purposes, for example.

Assuming you're referring to tapping into the signals on the inter-board connector, is this for a permanent purpose? Or for temporary testing?

As @Whales wrote, you would ideally want an interposer board.

If this is for temporary testing purposes, then for Beaglebone (which I think is what you have in your photo) you could simply get a couple of stacking headers (Adafruit has them). Then solder some wires to the pins you want to monitor, and away you go. 

For bonus points, you could knock out a PCB that holds a single such stackable header, and breaks out all the pins to a hole pattern on one side of the header. You would use a pair of these to gain access to all pins of both connectors of the Beaglebone.

For some similar situations, with enough googling I've sometimes found "Some Guy In A Garage" who's already done the work.

[kuon]

I should have given a few more details.

This is taping signal, hooking it to my prototype board.

I linked the beagleboard as example as I work with it right now, but I had this issue with different boards (arduino, raspberry, TPM header on PC motherboard...).

The interposed board is the "clean" solution, but I would need to make one for every header I use. I was looking for something modular. I guess I can try to build something for a few pins that I can put side by side.

[gwideman]

I should have given a few more details.

This is taping signal, hooking it to my prototype board.

I linked the beagleboard as example as I work with it right now, but I had this issue with different boards (arduino, raspberry, TPM header on PC motherboard...).

The interposed board is the "clean" solution, but I would need to make one for every header I use. I was looking for something modular. I guess I can try to build something for a few pins that I can put side by side.

I guess you mean your intent is tapping into the signals on the connector.

You mention hooking signals to a protoboard, so I guess this is for a purpose more permanent than just test and diagnosis, but less formal than creating a product.

I think making a board with a stackable connector, that routes the traces out to the side of the connector, is a robust way to go. And if you make it in some convenient length, you can combine two or more to serve a longer connector, or snap or cut it off to serve a smaller connector, or complete a long one.

On such an "interposer" board you'd have to make sure that the ends are tight enough to allow successive interposers arranged end-to-end to continue the pitch of the pins -- perhaps that's obvious!

In googling for "stackable header connector breakout board", I was surprised not to see exactly that sort of thing readily available.

A lower-tech possibility is to simply get some stackable connectors and solder them to a protoboard -- the type with a regular array of individual plated-through holes. That gives you a board and connector assembly that can interpose between the two existing boards. You can then use thin wires to connect to the pads of the pins you want to tap into, and route those wires to wherever you like on your prototype circuit.  Wire-wrap wire is a good candidate for this sort of thing.

[berke]

If the signals aren't too fast, you could use ribbon cable with crimp-on headers.  Say your connector is 2×40.  You get 80 wire ribbon cable, crimp one connector at one the end, another at the middle, and a third one at another end.  You use the connectors at the two ends to connect your original boards, and you use the middle one to probe.

EDIT: Fix number of wires, 2×40=80

[2N3055]

Are we talking about test points here?