Any tricks to attaching a wire or pin to a testpoint?

Question

More and more often, I find myself needing to tear apart a device to seek out and connect to serial pads. These pads typically give me access to the underlying operating system for research or tinkering, of which I'm perfectly comfortable with.

What I'm not comfortable with, though, is making the necessary hardware connections. That is, while I own soldering tools, I'm deathly afraid of using them. As a software guy, I really just want to get in, look at some bits, and get out, without any lasting damage.

Are there some tricks of the trade to attaching pins/wires to a testpoint or non-throughole pad without solder for short-term use? Perhaps a wire with a flat conductive circular tip that would yield nicely to, say, tape or hot glue?

Example pad site:

Answer 1

The best trick is not a trick at all. It's using a thin solder and flux. Once you've identified the pins you need to use, that is. If heat is a concern, use a low wattage soldering iron. After all, these are fairly small (area wise) isolated pins. These things are made to be soldered. Surface mounted parts go through 270°C degree solder profiles!

Aside from that, Pogo pins are a good choice, but there are some more creative options.

Since there is no scale to the picture to say how big the pins are, it's hard to suggest a size of wire to use. Let's use 24awg. Since one point (TP12) is tied to ground, you can grab that anywhere on the board. The other (TP11) looks to be a Vcc type, so you can grab that from anywhere that voltage is at, or don't use it if not needed. So the two important ones are TP9 and TP10. In either case, you strip the wire a few MMs, then you hammer the ends flat, to give them a bigger surface area. Since they are near the edge, a nice flat clamp will hold them in place. (or plastic covered paperclip, or a clothspin, depending on how much space you have to work with) You want the pressure to be on the wire, not the coating, other wise the wire will lift up and you will not have solid contact.

Imagine this but with wires:

Another option is blu tack, fun tack (A reusable gum... putty thing. Just check the stationary aisle or an office store, there is different colors and names but it all works the same). Again, flatten the wire points, then use a big thing of blutack to hold them in place. I suggest taping the wire down an inch away just to take some pressure off though. Non-conductive (I can't say that all kinds are) and doesn't really burn. It's great to hold things in place for soldering too.

Answer 2

I would say pogo pins

attached to a small peg that can "bite" the pcb, similar to the following but using smaller pegs with one pin in the tip of each one.

Answer 3

A wild thought: attach wires to small steel nails with decent size heads, put a strong magnet on the other side of the board and just place the nailheads against the pads. If the magnet is strong enough, the connection will be reliable. However I have no idea how well the board will operate in the resulting magnetic field.

Answer 4

With properly-sized alligator clips, if the pads are near the edge, you could use them.

Another option is to attach wire leads to the pads with electrical tape. In any case, you will want the board + wires to remain perfectly still once they're set up.

If you're trying to work on many copies of the same board, you could rig up some sort of clip that presses leads onto pads in the same place, and connect your wires to those removable leads.

The main problem you'll have is maintaining electrical connectivity with all the pads, which can easily be messed up by bad placement or even the slightest bump to you connecting wires/clips.

Answer 5

[This started as a "don't be a yellowbelly afraid to solder" comment. But, I've run out of room.]

Note that the TP9 through TP12 are test pads, and there are no components on them. This means that you are very unlikely to burn a component, while you try to solder to these test pads. The only tangible failure can occur if you overheat the pad to the point where the adhesive, which holds the copper to fiberglass, fails. Even then, you would probably only lose the pad, while the device under test (DUT) remains operational.

Use leaded solder. Leaded solder melts at a lower temperature than lead-free solder. Modern (last 3 years or so) circuit board materials boards are designed to withstand higher lead-free temperatures. If you use leaded solder, this will give you additional margin for avoiding overheat.

Have solder wick, so that you can break solder bridges, if you hake them.

Answer 6

Few links I found helpful.

How to solder. http://www.talkingelectronics.com/projects/Solder%20-%20How%20to/HowToSolder.html Well explained the common mistakes and how to avoid parts damage.

soldering in SMD circuits. http://www.instructables.com/id/How-to-Solder-SMD-ICs-the-easy-way/

Besides them,

Some-other suggestions:

1. Could use a PCB-holder or PCB-cradle, that allows using both hands. That could enhance both accuracy and speed. The second hand could be used to hold the parts on proper place.

2. Could use a Magnifying screen. fresnel-lens magnifiers are now very popular.

3. Could use good quality tweezers, such as Watchmakers forceps or Jewelers forceps.

4. Pointed-tip for soldering iron sold separately. A pointed tip, matching with the iron, could be bought.

5. Soldering and desoldering really needs fine manual-skill , calmness and concentration. Lot of practice on scrap boards required.