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A question about using oversized leads in solderless breadboards got me thinking about how I damaged a breadboard back in my hobbyist days, and whether there's any difference in how cheap or expensive breadboards might react to oversized pins, which would mostly be down to what contact material they use.

The three material options I can think of that would be reasonable are spring steel (perhaps for very cheap ones), beryllium copper, or maybe phosphor bronze, either nickel- or tin-plated or just unplated.

I would expect that they would specify the contact material in the datasheet, the same way connectors almost always do. But I've been unable to find any breadboard that does so! When they do have a material specification, it's just specifying what plastic the plastic parts are made out of. So I ask here: What contact materials are typical for breadboards to use? Does it vary between manufacturers, between cheap and expensive ones, or does everyone pretty much use the same?

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Some specify phosphor bronze. Also this one. There are others, generally name-brand with commensurately high price tags.

If they don't specify, I would expect brass or perhaps spring steel with nickel plating. You can distinguish with a magnet (the brass - or phosphor bronze- would be slightly magnetic due to the plating). One I tested appears to be brass- non-magnetic and takes a set easily. Often you can just peel the double-face tape back on the back and extract a contact strip with tweezers for testing.

The main difference would be that brass is not as springy as phosphor bronze so the contacts may get loose if something too big is forced into the holes. It's also much cheaper.

There are other ways to damage contacts or get intermittent contact in these things, so whether it's better to buy cheap ones and throw them away when they get flaky, or expensive ones is not all that clear to me, and would depend on usage. Some people seem to have an awful lot of trouble with them- not sure if it's the user or the product.

Another way to damage them would be to put too much current through the contacts, which can cause them to lose their temper (the metallurgical property that makes them springy, rather than to make them emotional).

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    \$\begingroup\$ I find the cheapest ones often have intermittent contact right out of the box, and I often have to search around for the tightest points on the springs. With the expensive ones, I find sometimes it's too hard to push pins into the springs. The latter is the more acceptable failure mode for me, as it's much easier to know when the contact is good. \$\endgroup\$
    – Scott Seidman
    Commented Jul 25 at 14:27
  • \$\begingroup\$ I'm surprised phosphor bronze is chosen over beryllium copper; is phosphor bronze much springier? As I recall, contacts on connectors seem to always be beryllium copper, outside of a few exceptions. \$\endgroup\$
    – Hearth
    Commented Jul 25 at 15:20
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    \$\begingroup\$ @ScottSeidman The hobby products have tended to go downhill in quality over time IME as the buyers seek out products based on price alone. I have not bought one of those things in maybe 20 years (probably have gotten a few for free by various means). They were a thing in the late 1970s, so they've had a long run. Eg. alligator leads from Radio Shack used to be reasonable quality, the worst ones now are worse than useless. I made some myself with silicone wire and Keystone clips to have something that wasn't a few strands of the thinnest wire, badly crimped into a crude clip with jaws akimbo. \$\endgroup\$
    – Spehro 'speff' Pefhany
    Commented Jul 25 at 15:48
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    \$\begingroup\$ @ScottSeidman Schools are definitely a place where I would spend the money on decent equipment. And probably throw them away regularly since they'll find some way to damage them regardless. \$\endgroup\$
    – Spehro 'speff' Pefhany
    Commented Jul 25 at 16:01
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    \$\begingroup\$ Absolutely. Every year I yell at our circuits lab instructor who doesn't seem to discourage students from removing the clips from scope probes so they can cram them right into a breadboard. Trashes the breadboards and scope probes at the same time. \$\endgroup\$
    – Scott Seidman
    Commented Jul 25 at 16:40

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