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I have a Pro Micro board (very small -- see pic below) and it has connector holes in the printed circuit board.

Best Non-Solder Connection (Easy and Removable)

I'm wondering the best way to make non-solder connections for doing my prototype work. By best, I mean easily removable while maintaining solid electrical connection.

Are there pre-made connectors for this type of connection?

What Part Is Most Conductive / Best Electrical Connection?

Also, how can I know I have a good connection? Is it the inside of the hole that has the conductive metal, outside of hole?

Front / Back Separate Traces?

And, are the front and back of the holes electrically connected normally or do they have separate traces normally?

One Idea: Would It work Very Well?

What if I had header pins pushed into a breadboard and then up through those holes? Then I connect my wire to the top of the header pin? Would it be a solid enough connection? Or would it not make enough electrical connection?

ie - would header pins make connection inside of holes and would that be enough electrical connection?

Edit -- I Wish They Made Banana Plugs That Fit This Wouldn't it be cool if you could use a banana plug type of connector. Then just plug in each one and put wire in hole and clamp it down?

banana plug

pro micro 5v board back of board

UPDATE 11-11-2017 Interesting that in the time since I've posted this someone came up with a solution similar to what I was thinking with banana plugs: Hammer Header Male - Solderless Raspberry Pi Connector It's really for use on a RPi Zero but it's the type of snap-on header I was interested in at the time.

However, the installation is not easy so it may not be practical. Take a look at what you have to do to install it : https://learn.pimoroni.com/tutorial/sandyj/fitting-hammer-headers Probably easier to just solder on the header pins.

Update 2 - Dec. 10, 2021

I just saw the following on Twitter & just thought I'd update it here. This is for 1mm holes.

using fishing line

Someone replied and showed that there is now a product someone is releasing that attempts to solve this:

1mm banana plugs

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    \$\begingroup\$ Normally you'd solder headers or sockets to the holes, then connect to those. You can even plug it into a breadboard. \$\endgroup\$
    – pjc50
    Aug 1, 2016 at 20:44
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    \$\begingroup\$ Personally, I'd go with header strips, or just solder. Prototyping can be annoying enough without worrying about whether your connections are good. You should be able to solder/desolder near infinitely, and you clean up with desoldering braid. \$\endgroup\$
    – Scott Seidman
    Aug 1, 2016 at 20:55
  • \$\begingroup\$ I appreciate those comments/suggestions. I was wondering if I could just keep soldering / desolder without destroying the little board. (If I'm careful enough, it's good to know that is a standard operating procedure.) \$\endgroup\$
    – raddevus
    Aug 1, 2016 at 21:02
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    \$\begingroup\$ If you're not confident with it, practice, and make sure you have OK tools. Also, when you're talking about a $20 platform, you probably want to have more than one around for prototyping anyway, in case you fry an important DIO. \$\endgroup\$
    – Scott Seidman
    Aug 1, 2016 at 21:06
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    \$\begingroup\$ Copper traces on PCB are not rugged enough to withstand plugging/unplugging. Neither soldering/desoldering. This is why we invented dozens of solutions (sockets, edge connectors and goldpins being few examples) \$\endgroup\$
    – Agent_L
    Aug 2, 2016 at 11:35

13 Answers 13

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Use grabber test clips, which are basically like smaller alligator type clips.

Mini Grabber Test Leads

Though regular alligator/crocodile clips may work, depending on the size or how many side by side ones you need. I have some really mini ones.

enter image description hereenter image description here

Yes, the pads should be plated on the inside as well as the top and bottom, electrically connecting them.

No, just pushing a standard 0.1" header into the hole won't work. They are not offset holes, or push fit tight. They are generously loose. Some people have used rubber bands but that's not very secure.

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  • \$\begingroup\$ Great answer and answers many of my questions and offers a non-solder solution. Thanks very much. \$\endgroup\$
    – raddevus
    Aug 2, 2016 at 0:36
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    \$\begingroup\$ I'm marking this as the answer simply because it addresses my original question about non-solder solution with grabber test clips which are the best possibility for that and because it answers my other questions as well. Thanks very much. Very helpful. \$\endgroup\$
    – raddevus
    Aug 2, 2016 at 3:37
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    \$\begingroup\$ @daylight Just be careful about shorting things together, that's a real risk doing it this way and may end up costing you more than a soldering iron if you damage your hardware. \$\endgroup\$
    – Steve
    Aug 2, 2016 at 12:08
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    \$\begingroup\$ @daylight Just make sure you use solder with rosin flux in the core. Soldering without flux is a pain even for someone who knows how to solder. \$\endgroup\$
    – Steve
    Aug 2, 2016 at 19:16
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    \$\begingroup\$ @kuhaku they are spring loaded. Push the top part and the metal clip is exposed, and the spring tension keeps it locked on the part when you let go. \$\endgroup\$
    – Passerby
    Sep 3, 2017 at 17:31
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Solder a pin header

enter image description here

Typically you solder pin headers to these boards. Either male or female. With male pins, you can solder them with the pins pointing down, so you can put them in solderless breadboards.1

1. This may ruin the breadboard strips

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    \$\begingroup\$ If you want to use the board in a breadboard without ruining it, look for "machine pin headers". \$\endgroup\$
    – user39382
    Aug 1, 2016 at 20:53
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    \$\begingroup\$ I've not had issues with rectangular pins ruining my breadboards, but others' experiences may vary. \$\endgroup\$
    – Ignacio Vazquez-Abrams
    Aug 1, 2016 at 20:54
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    \$\begingroup\$ @IgnacioVazquez-Abrams Works well for me too, but I don't want anyone to ruin their crappy breadboard by taking my advice, so I thought it would be prudent to warn against the practice. \$\endgroup\$
    – pipe
    Aug 1, 2016 at 20:57
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    \$\begingroup\$ @daylight: Don't try alligator clips for anything smaller than LilyPad connections. \$\endgroup\$
    – Ignacio Vazquez-Abrams
    Aug 1, 2016 at 21:43
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    \$\begingroup\$ @ignacio micro alligator clips are tiny enough. \$\endgroup\$
    – Passerby
    Aug 1, 2016 at 23:54
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For me I would rather use these PCB terminal blocks, which you can easily remove and connect your wiring without worrying about loose connections every time.

enter image description here

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  • \$\begingroup\$ Those look promising. I push them through the holes and connect wires, right? If those make good connections with the "holes" then these would be a top choice for me. Thanks. \$\endgroup\$
    – raddevus
    Aug 2, 2016 at 0:37
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    \$\begingroup\$ Are those actually available in the 100 mil pitch and 25 mil square pin size normally used for headers, which is what the poster needs? I've never seen them that small. \$\endgroup\$
    – Jeanne Pindar
    Aug 2, 2016 at 2:24
  • \$\begingroup\$ @JeannePindar Good question that I was wondering about too. I tried to find them that small but couldn't. Thx \$\endgroup\$
    – raddevus
    Aug 2, 2016 at 3:36
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    \$\begingroup\$ @daylight - these are intended to be soldered or put into some kind of socket that is itself soldered. You might get marginal contact with a very careful chosen plated hole size, but don't count on it, and the finished sized of plated holes has some manufacturing variability. \$\endgroup\$
    – Chris Stratton
    Aug 2, 2016 at 15:13
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    \$\begingroup\$ Yes they can be found in 0.1"/2.57mm size, but those are rarer/more expensive. The normal ones are 0.2"/5mm spaced, and that's what's pictured. These are not press fit though, and are expected to be soldered. \$\endgroup\$
    – Passerby
    Aug 2, 2016 at 19:31
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A search turned up an option called "press fit" pins and headers. Here is a picture of one from the whitepaper my Google search turned up:

enter image description here

The problem with this is you still need to connect to that header somehow. You might as well solder a single-row pin header in and use jumper leads as in other answers, though. It really is the best way.

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  • \$\begingroup\$ I didn't read the whole thing. It's possible special equipment is necessary to install these. It appears to be more of a permanent manufacturing technique as opposed to prototyping, though. \$\endgroup\$
    – Steve
    Aug 2, 2016 at 3:03
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    \$\begingroup\$ No special equipment is needed for some (most?) press fit headers especially a single or double row (instead of those multi row connector ones in the white-paper), but from what I recall reading, some (most) will damage the board if removed. But then there is mill-max.com/new_products/detail/129 and I'm sure some others. \$\endgroup\$
    – Passerby
    Aug 2, 2016 at 4:34
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Normally you solder a male header to the board, and if you aren't plugging them directly into another board, you connect them with either ribbon cables or jumpers that have individual sockets on the end. enter image description here These jumpers are available in m-m, f-f, and m-f configurations. You could get the connectors and make them yourself, but that requires a special crimping tool.

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    \$\begingroup\$ Soldering a female header is also an option. Much preferable imho as you can use bare wire as jumpers if needed. Male headers need f-f or f-m to use for prototyping, or wire wrap. \$\endgroup\$
    – Passerby
    Aug 2, 2016 at 4:35
  • \$\begingroup\$ Do you have a good keyword to search for on Digikey to find cables like this? As embarrassing as it may be, I've had great trouble finding this kind of cabling. \$\endgroup\$
    – Cort Ammon
    Aug 2, 2016 at 18:45
  • \$\begingroup\$ @CortAmmon dupoint or breadboard cables. You probably won't find them on Digikey, check eBay or the usual china resellers (aliexpress, dx, etc) \$\endgroup\$
    – Passerby
    Aug 2, 2016 at 19:28
  • \$\begingroup\$ I found those on Adafruit. I used to make my own (still do for production stuff) but these are cheap and convenient for prototyping. \$\endgroup\$
    – Jeanne Pindar
    Aug 2, 2016 at 22:59
  • \$\begingroup\$ And I just found that they are sold on Mouser as Adafruit brand "jumper wires" \$\endgroup\$
    – Jeanne Pindar
    Aug 2, 2016 at 23:06
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Solderless connector

Need: Normal size paperclip and one standard jumper (plenty on your old hard drives.)

  1. Crimp paperclip with vise grip pliers, and adjust if needed to just fit snugly into the hole in the PCB.
  2. Cut paperclip to length and insert long end into jumper.
  3. Insert crimped end of paperclip into hole in PCB.
  4. Use other side of jumper for standard male prototyping cable connectors.
  5. Leave in place, which has the advantage of not constantly inserting/removing a connector and thus wearing out the hole.
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    \$\begingroup\$ this is essentially a diy press fit connector. \$\endgroup\$
    – Passerby
    Nov 11, 2017 at 17:18
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I’ve found that aluminum foil will do the trick for a through-hole when I don’t feel like soldering or want a temporary pin. I wrap the tip tightly in some foil and gently twist as I insert it. Add a little electrical tape for insulation and stability as needed.

enter image description here

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  • \$\begingroup\$ That's an interesting one. Thanks for sharing. \$\endgroup\$
    – raddevus
    Mar 22, 2022 at 17:51
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What about a stepped header like this one? Sized such that the via will land on one of the steps. Then the flat surface of the vias can make contact with the steps.

enter image description here

Links: Samtec BBS-106-G-A

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What Part Is Most Conductive / Best Electrical Connection?

Usually you solder to the circular 'pad'.

Front / Back Separate Traces?

No, normally they're plated through.

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If your module doesn't have headers you can have someone add them (when you're purchasing them) or you can add them yourself. This goes along with what @pipe suggested above but rather than placing into a solder-less breadboard one would make connections like you can see below.

There is not an easy way to wrap the wire into the holes themselves. Possible but prone to user error since you'd have to do it yourself with no tools.

Wire Wrap Prototyping

This does require you to purchase wire-wrap wire, a decent stripping tool, and a wire wrapping tool. If you look on eBay they're dirt cheap compared to what you can get them for new from Digikey (or the like)

The connections are robust and I've made some serious product prototypes before ever spinning a board.

I wrote an article and made a video on wire wrap for prototyping on Circuit Dojo. Feel free to check it out.

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  • \$\begingroup\$ Alternatively, you could also create a pogo pin jig, similar to what you included in the notes that connects to each pin. That would be good for quick programming in a production setting though rather than a prototyping setting. Soldering some headers on and using wire wrap is still the best option IMO! \$\endgroup\$
    – jaredwolff
    Jul 11, 2018 at 3:41
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    \$\begingroup\$ OP asks how to do this without soldering. You can't wire-wrap holes. \$\endgroup\$
    – pipe
    Jul 12, 2018 at 6:47
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    \$\begingroup\$ Yes you can wire wrap holes. Tediously, and depends on location, but it can be done. \$\endgroup\$
    – Passerby
    Jul 13, 2018 at 4:46
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    \$\begingroup\$ @Passerby -- wire wrapping absolutely depends on wrapping around corners for gas-tight connections that are just about as reliable as solder (even more so, IIRC). No corners, no wire wrap. Is this part of the process for wrapping holes? If not, the method uses wire wrap wire for a mechanical correction, but it's not a wire-wrap. If it is, I'd love to see a pointer to the method. \$\endgroup\$
    – Scott Seidman
    Jul 13, 2018 at 17:05
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    \$\begingroup\$ @pipe - to object that this answer involves soldering is an absurd double standard when your very own answer proposed soldering a header to the board. \$\endgroup\$
    – Chris Stratton
    Jul 14, 2018 at 4:47
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The newly added comment is something that's been around for a while; these look like they're just press-fit (specifically the compliant-pin type) direct-wire-to-board connectors, though I've never considered using them for a purpose like this.

Many of them are designed to be non-removable, but the compliant-pin type in particular are probably more easily removed than others. They may damage the plated hole when removed, particularly when inserted and removed repeatedly.

You can find them here; it looks like TE Connectivity's "Amp-in" and "Mini Amp-in" series are probably the most like what you've shown in the image.

A more reusable method (but one that requires altering the PCB) may be to combine wire-mount pin connectors with proper multi-fingered sockets, like this:

enter image description here

(Image source: this page about similar sockets from Mill-Max)

These sockets are soldered into the PCB (they make press-fit ones too), and the pins crimped or soldered onto wires. You'd just have to find sockets that are designed for the right hole diameter, and pins that have the right diameter to mate to them. You can skip the pins, too, if you have the right diameter of solid-core wire. Stranded wire won't make a good connection, though (unless maybe you use a ferrule? I've never tried this, so don't blame me if you do and the connection is flaky!).

Note that the press-fit sockets are in general not removable without damage to the board. The soldered-in sockets can be removed relatively easily with standard desoldering technique, for when you're ready to permanently assemble your finished device. Of course, wires are easily inserted and removed from these sockets any number of times (well, at least a few hundred times; check the cycle life rating!).

Disclaimer: I have no affiliation with either TE Connectivity or Mill-Max, except as an occasional customer. TE's parts just came up in a search, and Mill-Max is a manufacturer whose pin sockets I've used extensively for making test equipment, so I'm familiar with what they offer.

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Press-fit options were already suggested here in the previous replies, but seems these options evolved since then. Here is what looks like exactly what OP meant - non-solder connections for prototype works:

Living without Solder – code, circuits, & construction

I should say I did not try it myself yet, just looked for the same thing and found this. Here are the actual pins mentioned in the blog above:

enter image description here enter image description here

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There is a type of header pin the just snaps in place for temporary use that would be perfect for you. It's not advertised as this but I have used then on many projects and they have saved me tones of time. https://www.sparkfun.com/products/9015

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    \$\begingroup\$ No, that's just a surface-mount pin header. It won't make a good connection with a PCB without being soldered. (And it won't fit at all into the boards the OP is using.) \$\endgroup\$
    – user39382
    Jul 3, 2018 at 19:30

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