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Testing solder joint
Hi all,
I have done some soldering on my gameboy advance and have created a dry joint, I would like to know if is possible to test a solder joint using a multimeter if so how and what make is recommended (I don't need anything fancy). Thanks Grant |
"Grant" wrote in message ups.com... Hi all, I have done some soldering on my gameboy advance and have created a dry joint, I would like to know if is possible to test a solder joint using a multimeter if so how and what make is recommended (I don't need anything fancy). Thanks Grant Just look at it, if it's dry it'll look dull. Don't use lead-free solder if you can help it, that stuff is crap, even after years of soldering I still can't make a nice joint with it. |
"James Sweet" bravely wrote to "All" (26 Oct 04 05:20:19)
--- on the heady topic of " Testing solder joint" JS From: "James Sweet" JS "Grant" wrote in message JS ups.com... Hi all, I have done some soldering on my gameboy advance and have created a dry joint, I would like to know if is possible to test a solder joint using a multimeter if so how and what make is recommended (I don't need anything fancy). Thanks Grant JS Just look at it, if it's dry it'll look dull. Don't use lead-free JS solder if you can help it, that stuff is crap, even after years of JS soldering I still can't make a nice joint with it. It is possible to test the resistivity of the joint using a milli-ohm meter. It's may be a hard to find gadget though so one could alternately inject 1 ampere of current and measure the voltage drop using the 200mV scale of a dmm. i.e. a 7mV reading equals 7milli-ohms. The acceptable resistivity of the joint would depend on the amount of expected current. Generally speaking anything below 50 milli-ohms would be okay. However, for large currents I'd want less than 10 milli-ohms. i.e. 10 amperes at 10 milli-ohms is 100 milli watt. An ideal 1 milli-ohm or less might not be easily achieved. However if the component lead is bent flat over the conductive trace it may be much closer to zero ohms than if left floating in solder as is common. A*s*i*m*o*v .... Power is obtained by current meeting resistance |
"Grant" wrote in message ups.com... Hi all, I have done some soldering on my gameboy advance and have created a dry joint, I would like to know if is possible to test a solder joint using a multimeter if so how and what make is recommended (I don't need anything fancy). A dry, grainy looking blob is not good. Add some good flux and reheat it .... usually works fine. |
Thanks for the advice guys
Grant |
We all know it when we see it. It's got a fairly characteristic look to it but ... A) What, physically, is a cold solder joint? and B) What are the electrical characteristics of a cold solder joint? TIA Norm |
"Norm Dresner" wrote in message ... | | We all know it when we see it. It's got a fairly characteristic look to it | but ... | | A) What, physically, is a cold solder joint? It is an unwetted connection between solder and other metals. Think blobs of water on a greasy pan. | and | | B) What are the electrical characteristics of a cold solder joint? Variable. Sometimes they work for 10 years then fail. Usually they make intermittent connection. Sometimes they make no connection at all without external pressure. N |
On Fri, 29 Oct 2004 22:29:37 GMT, "Norm Dresner"
wrote: We all know it when we see it. It's got a fairly characteristic look to it but ... A) What, physically, is a cold solder joint? If I remember correctly, a good solder joint should create an actual chemical/physical change/bond at the surfaces of the lead and the solder pad. The metals actually join chemically. A cold solder joint likely would not accomplish this. Just a guess, sort of an educated one, maybe. Tom and B) What are the electrical characteristics of a cold solder joint? TIA Norm |
"NSM" wrote in message news:AFCgd.39769$9b.12504@edtnps84...
"Norm Dresner" wrote in message ... | | We all know it when we see it. It's got a fairly characteristic look to it | but ... | | A) What, physically, is a cold solder joint? It is an unwetted connection between solder and other metals. Think blobs of water on a greasy pan. | and | | B) What are the electrical characteristics of a cold solder joint? Variable. Sometimes they work for 10 years then fail. Usually they make intermittent connection. Sometimes they make no connection at all without external pressure. N A cold solder joint is when the part being soldered was not heated enough for the solder to grab on to it properly. |
"Master TV" wrote in message om... | A cold solder joint is when the part being soldered was not heated | enough for the solder to grab on to it properly. I spent 30 minutes watching a skilled tool and die maker try to resolder the radiator from his car with more and more heat and failing each time. I finally asked him to let me try. I carefully cleaned all the parts, using wire brushes and acid flux and washing it all thoroughly afterwards, a process taking over 15 minutes. I then soldered it in less than 10 seconds. It isn't just heat that does the job. It's a combination of materials, cleanliness, flux and heat. I've soldered everything from litz wire to bus bars and preparation is the key. BTW, if you want to test your soldering, try soldering pieces of flux cored wire solder together. If you are really good you can build your own mini Eiffel tower. N |
"NSM" wrote in message news:j0Tgd.51427$9b.42072@edtnps84... "Master TV" wrote in message om... | A cold solder joint is when the part being soldered was not heated | enough for the solder to grab on to it properly. I spent 30 minutes watching a skilled tool and die maker try to resolder the radiator from his car with more and more heat and failing each time. I finally asked him to let me try. I carefully cleaned all the parts, using wire brushes and acid flux and washing it all thoroughly afterwards, a process taking over 15 minutes. I then soldered it in less than 10 seconds. It isn't just heat that does the job. It's a combination of materials, cleanliness, flux and heat. I've soldered everything from litz wire to bus bars and preparation is the key. You are very much correct except that it is heat that does the job. The cleaning is necesary for the heat to occur where you want it. BTW, if you want to test your soldering, try soldering pieces of flux cored wire solder together. If you are really good you can build your own mini Eiffel tower. N |
"Leonard Caillouet" wrote in message
news:DH6hd.1067$ep3.915@lakeread02... "NSM" wrote in message news:j0Tgd.51427$9b.42072@edtnps84... "Master TV" wrote in message om... | A cold solder joint is when the part being soldered was not heated | enough for the solder to grab on to it properly. I spent 30 minutes watching a skilled tool and die maker try to resolder the radiator from his car with more and more heat and failing each time. I finally asked him to let me try. I carefully cleaned all the parts, using wire brushes and acid flux and washing it all thoroughly afterwards, a process taking over 15 minutes. I then soldered it in less than 10 seconds. It isn't just heat that does the job. It's a combination of materials, cleanliness, flux and heat. I've soldered everything from litz wire to bus bars and preparation is the key. You are very much correct except that it is heat that does the job. The cleaning is necesary for the heat to occur where you want it. Only partially. The cleaning is also necessary to create a surface to which the solder *can* bond. It won't bond to an oily/greasy surface nor to most oxides. Only to bare metal. Norm |
"Leonard Caillouet" wrote in message news:DH6hd.1067$ep3.915@lakeread02... .... | It isn't just heat that does the job. It's a combination of materials, | cleanliness, flux and heat. I've soldered everything from litz wire to bus | bars and preparation is the key. | | You are very much correct except that it is heat that does the job. The | cleaning is necesary for the heat to occur where you want it. If that were true you could solder aluminum to aluminum - or bananas. I can solder aluminum to aluminum with regular solder, but it isn't heat that does the trick - it's oil. N |
On Sun, 31 Oct 2004 09:32:36 -0500 "Leonard Caillouet"
wrote: "NSM" wrote in message news:j0Tgd.51427$9b.42072@edtnps84... It isn't just heat that does the job. It's a combination of materials, cleanliness, flux and heat. I've soldered everything from litz wire to bus bars and preparation is the key. You are very much correct except that it is heat that does the job. The cleaning is necesary for the heat to occur where you want it. I gotta disagree with this. A good solder joint requires both sufficient heat and surfaces that are clean enough to alloy with the molten solder. Surfaces that are fairly clean will be cleaned up sufficiently to solder by the flux, but the fluxes used in electronic work are fairly mild ones. That the different metals actually alloy at the junction can be seen in greatly magnified photographs, where the % of different materials can be analyzed as a function of depth. The alloyed layer of solder over iron is extremely thin, but the alloyed layer between solder and copper is much thicker, but still less than .001". It's all a matter of the relative melting points and solubilities. Like many other things, good preparation is responsible for success much of the time. When the manufacturer sells a component they guarantee that its leads will be solderable for some period of time, often something like 6 months. While the solderability usually lasts much longer than that, it is often prudent to do something that will remove oxides from the surface if you are working with very old parts. For tinned leads, all we need is an occasional break in the oxide to allow the solder underneath, then it will work its way along the surface and float the oxides to the surface of the solder. To answer the original question, a cold solder joint is one where at least one of the pieces being soldered together did not get solder actually flowed and alloyed to its surface. This may still give both mechanical and electrical contact, but neither is reliable over time. The name (cold solder joint) actually comes from the fact that cold solder joints often arise when something small is soldered to something large. The disparity in thermal mass allows the small object to heat up and accept the molten solder quickly, leaving the large object still below the melting point of the solder. Until both objects are above the melting point, there is no chance of getting a good solder joint. Likewise, you can get the same effect when one part is badly oxidized. If the solder can't break thru the oxide layer, we can never get a good joint, no matter how warm we get the parts. In fact, a typical beginner's mistake is to assume that the solution is more heat. While this may seem obvious, the most common result of raising the temp too high is to burn the flux, as it has been raised outside its useful temp range. - ----------------------------------------------- Jim Adney Madison, WI 53711 USA ----------------------------------------------- |
I am not in disagreement at all that preparation is absolutely necessary,
assuming compatible materials to begin with. The point that I was trying to make is that without the transfer of energy causing BOTH parts to rise to the proper temp, you won't be doing any soldering. Oxides, etc prevent the heat more than they do anything else. Preparation allows the heat. Leonard "Jim Adney" wrote in message ... On Sun, 31 Oct 2004 09:32:36 -0500 "Leonard Caillouet" wrote: "NSM" wrote in message news:j0Tgd.51427$9b.42072@edtnps84... It isn't just heat that does the job. It's a combination of materials, cleanliness, flux and heat. I've soldered everything from litz wire to bus bars and preparation is the key. You are very much correct except that it is heat that does the job. The cleaning is necesary for the heat to occur where you want it. I gotta disagree with this. A good solder joint requires both sufficient heat and surfaces that are clean enough to alloy with the molten solder. Surfaces that are fairly clean will be cleaned up sufficiently to solder by the flux, but the fluxes used in electronic work are fairly mild ones. That the different metals actually alloy at the junction can be seen in greatly magnified photographs, where the % of different materials can be analyzed as a function of depth. The alloyed layer of solder over iron is extremely thin, but the alloyed layer between solder and copper is much thicker, but still less than .001". It's all a matter of the relative melting points and solubilities. Like many other things, good preparation is responsible for success much of the time. When the manufacturer sells a component they guarantee that its leads will be solderable for some period of time, often something like 6 months. While the solderability usually lasts much longer than that, it is often prudent to do something that will remove oxides from the surface if you are working with very old parts. For tinned leads, all we need is an occasional break in the oxide to allow the solder underneath, then it will work its way along the surface and float the oxides to the surface of the solder. To answer the original question, a cold solder joint is one where at least one of the pieces being soldered together did not get solder actually flowed and alloyed to its surface. This may still give both mechanical and electrical contact, but neither is reliable over time. The name (cold solder joint) actually comes from the fact that cold solder joints often arise when something small is soldered to something large. The disparity in thermal mass allows the small object to heat up and accept the molten solder quickly, leaving the large object still below the melting point of the solder. Until both objects are above the melting point, there is no chance of getting a good solder joint. Likewise, you can get the same effect when one part is badly oxidized. If the solder can't break thru the oxide layer, we can never get a good joint, no matter how warm we get the parts. In fact, a typical beginner's mistake is to assume that the solution is more heat. While this may seem obvious, the most common result of raising the temp too high is to burn the flux, as it has been raised outside its useful temp range. - ----------------------------------------------- Jim Adney Madison, WI 53711 USA ----------------------------------------------- |
On Mon, 1 Nov 2004 05:55:26 -0500 "Leonard Caillouet"
wrote: I am not in disagreement at all that preparation is absolutely necessary, assuming compatible materials to begin with. The point that I was trying to make is that without the transfer of energy causing BOTH parts to rise to the proper temp, you won't be doing any soldering. Oxides, etc prevent the heat more than they do anything else. Preparation allows the heat. I think there's still disagreement here. The thermal conductivity of metal oxides is actually not that different from the metals themselves, and the oxide layers are so thin that they have insignificant insulating value. OTOH, most of the heat flow occurs after a meniscus of solder forms between the iron and the work, creating a heat flow path that is much large than the point contact that would otherwise be available. This initial meniscus can't form until the oxide layer is broken, so preparation often helps heat flow. However, even if you have another means of heating an oxidized part, like in an oven or infrared furnace, the solder won't flow to an oxide covered part. - ----------------------------------------------- Jim Adney Madison, WI 53711 USA ----------------------------------------------- |
On Mon, 01 Nov 2004 22:54:41 -0600, Jim Adney
wrote: On Mon, 1 Nov 2004 05:55:26 -0500 "Leonard Caillouet" wrote: I am not in disagreement at all that preparation is absolutely necessary, assuming compatible materials to begin with. The point that I was trying to make is that without the transfer of energy causing BOTH parts to rise to the proper temp, you won't be doing any soldering. Oxides, etc prevent the heat more than they do anything else. Preparation allows the heat. I think there's still disagreement here. The thermal conductivity of metal oxides is actually not that different from the metals themselves, and the oxide layers are so thin that they have insignificant insulating value. OTOH, most of the heat flow occurs after a meniscus of solder forms between the iron and the work, creating a heat flow path that is much large than the point contact that would otherwise be available. This initial meniscus can't form until the oxide layer is broken, so preparation often helps heat flow. However, even if you have another means of heating an oxidized part, like in an oven or infrared furnace, the solder won't flow to an oxide covered part. - ----------------------------------------------- Jim Adney Madison, WI 53711 USA ----------------------------------------------- Jim, you obviously were awake in class. Leonard has that "I have to be right" thing screwing him up. |
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