hi! got a question about cold solder? what does it really mean? does it affect the operation of your circuit?

 

If your solder does not make good contact with the component lead and the pcb then you have a cold solder or cold joint.
it does affect the performance of your circiut as sometimes the circit will work normally and other times it wont due to lack of good contact between the component and the pcb path.

 

Cold solder joints are more often called dry solder joints.

 

cold soldering might somewhat sound like cold welding (which is one method of welding) but they are not related even in principle.

 

many failed solder joints are called cold solder - basically the result of bad a solder joint. heat not being thoroughly applied to both connecting surfaces, or when all of the solder has not completely reached the liquid state, or solder which has been reheated excessively.

 

This is for lead based solder. It's easy to see. Take a wire, strip and make a loop in it. Strip and loop the other end thru that loop so they are connected but loose. Now mount this in a stable place (vice) but were you can jiggle the wires. Solder that connection then heat it up again while agitating the wire but not enough to splatter solder off the connection.

If you do that with the wires still and with good cleanliness, proper application of solder it will be smooth and shiny with good wetting and flow.

The one you jiggled will look frosted and lumpy and also may be high resistance. Even if it works it will fail from use and can fail with increased resistance or an open and you won't easily see these problems. If the connection fails with increased resistance it can be very hard to discover why the circuit fails. I've also seen them only fail when the connection heats up, usually from having to operate at increased load so the thing would work until it needed to work hard then die.

Now with lead free solder the only way for a hobbyist to tell if you have a good connection is following all the rules of lead solder precisely, using the recommended amount of heat and examining the shape of the solder connection carefully. I do recommend making the same experiment with lead free solder if you intend to use it.

If you have scrap boards you can also try to make good and bad connections to see what good and bad look like. It helps if there is a properly trained person to look at your work and evaluate it but they are hard to come by.

If you are a student see if your teacher has access to get J-STD-001? where? is the latest revision. It's normally expensive and is the industry, military and aerospace standard in the US. It has a LOT of good pictures and explanations.

It's harder to screw up eutectic solder and I'd recommend you use it over 60/40. I am unsure if there is a eutectic lead free solder.

 

A "cold solder joint" occurs when a solder joint has either not been heated sufficiently, or more frequently, the connection has been disturbed when the solder is cooling during it's "plastic" state. This causes crystallization of the solder, which has a much higher resistance than a properly made joint.

63/37 solder, also known as SN63, has been very popular for years. In this alloy, there is no 'plastic' state; during cooling, the solder transitions directly from the liquid state to solid, which greatly reduces the likelihood of a cold joint.

However, with the concerns about putting more lead in the environment, there is a transition to lead-free solder, such as SN96, which contains mostly tin with a bit of antimony. It requires more heat to get to a liquid state than SN96, and has a wide 'plastic' temp range - but no lead. Pure tin is unsuitable due to the growth of "whiskers" - crystalline extrusions which form over time when electricity is applied to a circuit - which is why antimony is added.

 

Cold solder means it is dry solder means it is resistive. So your will effect dpend on position. It may give losses or break to your signal.

 

My old college teacher used to make us solder connectors, then he'd come around and ream on them to break them apart. Then, he would state that we didn't let it wet properly... He was nuts anyways

Steve