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- เผยแพร่เมื่อ 18 ก.ค. 2012
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Dave does some measurements on what effect "PCB tinning" has on the resistance of a PCB trace.
Mike's video: • Does putting solder on...
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Used solder wick makes excellent heavy current wire, don't throw it out!
Great for replacing those burned open traces - Ha, ha!!
Exactly
Yes i do it all the time lol
Amen. There is larger braided copper as well, as well as added wire - or *copper bezel strip.* This latter can be had in widths up to 1/2 inch /12.7mm, and 14 thou/.35mm, from RioGrand (jewelry supply).
Neatest way, in my thinking, (for *really* simple boards; *much* simpler than these, even) would be to plate up an added 4-6 thousandths/0.1 - 0.15 mm of copper. Plating isn’t that hard, if you can give it time in the bath.
It's a poor man's lithium cell strap.
It's possible that the PCB I used had 2oz copper, so the difference with solder would be less. The trackwidth will also make some difference due to the rounding at the edges.
They are the same numbers. Do the math correctly and understand the terminology used. A "40% increase" from 18ohms IS a "28% decrease" from 25ohms. A very common mistake people make when dealing with "percentage increase" and "percentage decrease" terminology. It depends entirely what direction you are talking about, which is why I used the two different figures.
That's why I hate percentages. I know they work differently depending on whether you're going up or down, but I don't trust myself to get it right. Also, they're sorely abused by journalists: HEADLINE: X causes 30% increase in Y! Well, if the initial likelihood was one in a million, that's not a big thing, but if it was one in three--oh dear! I know you're not a maths geek, but maybe you could do a video on how to calculate percentages from both sides.
@@markschwarz2137 fck to journalist's headlines and their clickbates! Most of them aren't graduated in sciense nor in physics. It always depends of what you decide\take as the 100% (the whole "1"). As I found out recently, most of people can't even add a pair of natural fractions! They simply don't know how to do it! Although each one of them went to elementary school! It's awful!
Talking simpler, it entirely depends of what NUMBER you decide as the 100% (taxes calculation is the common example for this)
@@markschwarz2137 if you lose half your money, thats 50%(decrease). if u wanna go back to what you started with, you now have to double your money, thats 100% (increase).
@@Cassiusisback How does that work when all the numbers are zero? LOL!
the fun way would be to load the strip til it burns off and then load a tinned strip and see how many amps it takes to burn that one :)
Eric Hope I'd like to see that :P
That would be the fairest and most complete way to test how well this actually works as decreasing the resistance only indirectly suggests an increase in current carrying ability. Plus, it would be neat to watch the smoke and fireworks.
I think you just hinted at an advantage of tinning: it increases the thermal mass of the trace and improves heat dissipation, thus increasing the amount of current the trace can carry without heat-related failure.
i worked in the power supply industry for most of my life. We always used 2oz copper for our PWB's and always left the solder mask off high current traces to increase the current carrying of those traces. Our kirsten jet solder machine left a pretty thick coating on wide traces. i would guess this halved the resistance of the traces from what I experienced..
The world needs more Daves, people that know what they're talking about and are ready to prove or disprove their knowledge.
At higher frequencies, the resistance could paradoxically increase, due to the skin effect. (Perhaps already from tens of kHz.) That would also be worth measuring.
The bigger the blob the better the job.
Probably also works with hot glue...
Sounds dirty !
@@jfk4229 ey Kenneth
Love the work you do Dave, even going back and watching older videos there is great content.
"Lead free rubbish" made my day.
So many faulty devices due to lead-free solder.
You can’t get away with too much of that on protoboard if you need it to stay flat. The solder contracts, and warps the ends of the board upwards.
If I were doing a post-production mod to a board, I'd lay down a bare copper wire over the trace then solder it down. Anything in parallel will help, but copper+solder has lower resistance than just tin/lead.
what if you wanted to draw 25A at 5v ? would 3mm solid core copper wire work ?
What I sometimes do is reusing some wasted copper wick to reinforce the trace when I run out of small sections of solid-core copper wire kept from domestic electrical works.
@@petegrimsby - yes 3mm2 will work better than 2mm2 wire.
Either can handle the current you mention, but thicker = less voltage drop.
Look at the size of the (flat) wire inside a 25A fuse... that's your minimum.
It's all about the voltage drop, but most critical is the length. At 25A the 3mm2 will give a huge drop over 10 meters, yet the drop will be about 100 times lower over just 100mm.
Is that due to skin effect?
@@thedevilinthecircuit1414 - is WHAT due to the skin effect?
The idea of increasing conductor cross section is to reduce resistance. In the case of low voltage DC circuits, there isn't any skin effect anyway.
I have also done this on the top side taking advantage of the solder paste process. It's also more consistent with strips that are not in the same direction of wave solder flow.
I also resubscribed because you have answered back to every response I've left and I value that level of interaction with your community.
You're absolutely correct. You should never try to cool solder artificially as it can lead to a poor joint. It's well known by plumbers also that if you cool a soldered joint quickly, it also fails quickly...
I use this practice too, the idea is I can get over double the current through thinner tracks, and it reduces the pcb area required. Pile the solder on thick, then while hot re-work by running the iron along the trace to get a neat smooth tube of solder., easy It look like it been wave soldered. Obviously time to do this is limited or the pcb will over heat and can be damaged where track may start to lift.
This was great having both Mike and yourself do a in depth look on the same subject.
Ohms law rules there, silly to think it doesn't make a difference. Also what affects the current handling too is how much heat the trace can lose. If there's no solder mask the heat loss is greater resulting in less heating and therefore lower resistance. Add solder to that and you have a resistor made up of the solder in parallel with the trace. Even if the resistance of lead/tin is greater (145nohmm/m vs 17nohm/m or about 8.5 times greater) at 35um the copper is so much thinner that the solder only has to be 0.2mm (average) to have an equal resistance which would halve the trace resistance. Obviously the average thickness of the solder in Dave's video is more than that so the 40% he stated sounds very reasonable if not understated.
goatstaog
Sadly in HiFi circles fraudulent statements are allowed. BTW, the output impedance of the amplifier and the total resistance of the wire between amplifier and speaker does make a difference to sound quality if it's > 0.2Ohm. that's why active speakers perform so much better than conventional speakers. Note that 0.2Ohms between the actual terminals of the driver and the pins of the amplifier is what I'm talking about. Because conventional speakers have around 1/2 to 2Ohms in the crossover network, the cable actually can't make it any worse, and spending crazy amounts of money on cable is a suckers game.
Christ those people... resistance of a wire depends upon the material, length and the cross-sectional area.
So of course PCB tinning increases current carrying capacity!
I tinned the internal antenna of my wifi dongle and I got a faster connection.
Is there any kind of design rule to follow using this HASL finish? , i mean the rule its 40mils per Amp however if i get a 40mils HASL finish track, can i actually put 2 Amps on that?
亮星王 hah... :D
akkudakkupl Typically referred to as MALT - material, area, length, temperature.
Jason Bone Which itself is MERMAID - Mnemonic that Encourages Rote Memorization, Actually Intelligence-Destroying.
Such things should be self-evident from the simplest considerations regarding physical flow. It saddens me that this mnemonic exists.
Yes, good point.
great test Dave, I use this method on some of my boards too.
@Benjamin Phelps A 40% increase in resistance is the same as a 28% decrease in conductivity. It just depends whether you're talking about gaining resistance by removing copper or reducing it by adding copper. The ratio is the same, it just depends whether you start with the higher or lower resistance when calculating and expressing the percentage change.
I always do the same way. Thanks for the experiments. Great video!
I appreciate your efforts.
Thanks , I actually learned something practical today . Cheers
Thick tin also helps cooling small but hot components by increasing surface area.
Small power supply's often have diodes that have their hot end(they literally have one)stuck in a big surface of copper board surface thick in solder.
More surface is more cooling and better heatconduction.
I do this all the time on the ac heat and motor control side of hottub control boards and there is a drastic decrease in board failure from high amperage
Good on you for writing captions before youtube autogenerated them to help the impaired. That's a nice touch for your channel bro.
Another great one, keep'em coming.
Excellent video, I will have it into account when I make power supplies.
Mike's example had several unknowns. Like the amount of copper used, and it's original value without solder. The amount of solder can vary massively between boards. My amount was not arbitrary, I did a minimum amount and a maximum amount based on a known trace width. That gives us typical max and min figures to work with.
Excellent. You get to have all the fun!
On some high power boards (Eg UPS etc) I've seen strips of the mask removed rather than the whole track area. I wonder if this helps the solder to pool due to surface tension on the edge and so overall a greater amount of solder then letting it flow over a large surface area? that as a technique would certainly be more predictable as a manufacturing process
interesting! I have seen a few boards with the traces with solder on them and actually wondered if it was done for this reason.
I wonder if a bit of paste-flux would have helped wick more solder off there? (it does add to the stink-factor!) Cool video!
You only need to worry about this type of stuff when making loads of pcb's. the calculations involved would be nutz due to all the variables, such as width of track and the surface tension molten solder would curve to, then it's cross sections resistance etc etc. if your making a few boards, just solder a bare wire along the trace that can hadle the amps. Keep it simples. hope this helps
I think a fair bit of it is that the extra solder also has the ability to dissipate or absorb heat. This is especially important for pulsed currents.
This testing is perfect!
Any chance that you'll try the difference in current support for tinned versus untinned?
Did you calculate or measure the true thickness of the copper trace?
I have seen huge deviations from the specified thickness.....
What about immersing some stranded copper wire in the solder. I have seen this once, but no testing. It will be more $$, but what if it is a case that's worth it?
THANKS DAVE!!
Wow, how much braid did you end up using? That seems like drudgery.
what I were told in a university class, was that the chemical tinning as well as the solder mask, lowered the maximum amount of current that could be past through the trace, by thermally isolating it from the air.
what are your thoughts on that?
actually I have done this in my line of work, Equipment repair. A type of unit that always burn on the board where the fuse and a large inductor is due to power demand down the line and other issues (like bad design). Which I am not complaining about since correcting manufacturer fault is a source of income for me. so anyway, after fixing the blackened and burnt PCB I add solder between the fuse and conductor. I followed with thermal scan which shows the heat migrating from the fuse clips on to the inductor.
The pros and cons for PCB manufacturing differ from PCB repair a bit. Years back I repaired quite a few power supplies in a certain model of Panasonic Laser Printer. There was a trace that was improperly sized around one of the pads. It would get hot and desolder the wire sometimes lifting the pad from the PCB. To fix it I stripped the solder mask back about 1/2 inch & soldered a 16 gauge wire along the trace. At the pad I made a loop with the wire to give plenty of area and strength.
It would be interesting to see how much effect the trace width has and plot any resultant curve... More in-depth analysis really needs a way to evenly and consistently coat the trace with different thicknesses.
I also wouldn't mind seeing it with surface mount processing. where you leave a gap in the soldermask, and leave a gap in the stencil. we found that with 2oz copper the 5mil thick stencil really didn't have any practical difference with the operation of the board (we never went this detailed into measuring trace resistance), and the extra solder did cause a number of other problems, especially with conformal coating adhering to it.
I also found an article at the time (sorry, this was a while ago so I can't reference it) that says solder is about 6x the resistance of copper, so a 1 oz trace (35um, or 1.38mils) a 5 mil stencil (assuming the whole stencil gets filled with solder at the end) the solder will give 30-40% reduction in resistance. right in the middle of what you measured!.
Thanks for doing the numbers!
adding more conductive materials in parallel will of course lower resistance...........
I wonder how much difference 2% silver would make.
The equation of resistance where the area of the material (thikness) is important supports your statements..
If the board is lead-free solder, there is a risk of breakage / cracks forming from CTE or vibration issues. I have an under-seat self powered subwoofer which failed because a big open region of tinned solder cracked.
In power supplies I often see thick jumper wires following the same path as the PCB traces, in an effort to provide additional ampacity to that portion of the circuit, either in place of tinned regions or to supplement them. They often terminate near the solder termination of compenents which are carrying high current.
Great investigation. I have never liked solder wick, solder sucker FTW!
I think lead free solder would be even better than 60/40 for reducing the resistance as the resistivity of tin is about half that of lead. Not sure how to calculate the resistivity of an alloy of tin and lead - does one just average them out or is there some more complex calculation?
Even though the solder resistance is higher than copper resistance, the total resistance is lower when a pcb trace is tinned. It's like connecting two resistors in parallel. The equivalent resistance is always lower than the lower value resistor. But all this is valid for DC. If we consider impedance of the timned pcb trace, things get worse as frequency increases.
I've seen some manufacturers solder either a bare or insulated thick or thin wires! as a technique
Will this increase PCB heat temperature if put solder on its trace?
It would be nice to see another comparison for this with Sn60Pb40 and Sn60Pb38Cu2 solder
So if you used a different kind of solder, say one that has silver in it, would that drop in resistance be even higher?
With some PCB board processes a thin coat of solder is electroplated where conductors will be and then the plating is actually used as the acid resist during etching. In these cases there is no bare copper conductors even under the solder mask. The solder plating that is used is very thin of course.
The solder does "leach" some of the copper out and form an alloy with it. Some people even say that solder shouldn't be reused because once the copper gets into it it no longer tins properly. I've never had a problem though. For a while my solder pot contained 100% used solder that was sucked from boards. It's in one of my videos. I doubt though that the tiny amount of copper removed by the solder would be detectable by a meter.
Gotta love ur Pace Fume Xhauster
"Lead free rubbish" Thank you!
Nothing wrong with lead free, it just needs more heat. Its been used as standard in industrial and consumer electronics in the EU for many years now perfectly successfully.
@@cbcdesign001For one-time reflow manufacturing process purpose more thermal stress for electronic components is bearable with the benefit of less poisoned environment caused by improper utilisation of electronics. Less toxic industry for its employees is great either. BTW, actually, Chip Quik desoldering alloy CONTAINS lead (despite its claims that it is suitable "for lead and lead-free" applications - if you delete it completely before placing a new chip, the refurbished electronics still be virtually lead-free, but then the whole point is missing: you still work with lead). As opposite, Field's metal is, actually, lead-free and has practically the same melting temperature, 60°C (but it has up to 51% of pricy indium within - instead of up to 21% of indium within Chip Quik alloy, which isn't cheap as well)
@@cbcdesign001 negative. Everything is wrong with RoHS alloy. You may want to search for "Tin Whiskers", but don't crap your pants when you do.
Hi, thickning the trace with solder is not the only reason to leave the soldermask of. When you leave the soldermask of without soldering you already increase the heat disepation of the trace. So the resistense doent change but you can pas more current true without killing you trace.
Is there any kind of design rule to follow using this HASL finish? , i mean the rule its 40mils per Amp however if i get a 40mils HASL finish track, can i actually put 2 Amps on that?
Whenever I have a problem with an overloaded trace, I like to sweat down a small copper wire the full length of the trace. Well, usually a fine wire, remembering a motor relay board where I used a AWG 14 gauge stripped out of a bit of Romex. Ugly, but it solved the problem.
Seriously, I doubt if silver plating would be worth the expense, since the conductivity of copper is so close to that of silver. But the solder test might result in a warning to those building HF/VHF/UHF power circuits, to go easy on the solder.
Preparing the copper surface before adding he solder may help. It oxides quickly on contact with air.
Thats one of the reasons we use flux or flux core solder 😊
For RF, since solder has higher resistance than copper, would the skin effect cause the resistance to increase?
Moldymeter?
That is AuusieSpeak
Polish subtitles are really good on this one! :)
i think the biggest problem with this technique is the risk of shorts if the solder overheats and melts. i had a cheap usb power brick that did exactly that because i overloaded it horribly and it didn't have any polyfuses or similar. solder holding the pins of the mains plug onto the board liquified, shorted out and pretty much instantly vaporized (aka exploded). after i extinguished the flames and threw the breaker back in i disassembled it to take a look at what happened and the whole case and everything inside it was sputtered in solder...
I think that the solder you use and the thickness of the copper are huge factors.
I wonder how current level affects the resistance. For example, I'm thinking as current levels are increased, the resistance would decrease incrementally relative to the current. Beyond a certain current level the resistance would start to increase because the conductor can no longer dissipate the accumulated heat.
Sir you are really genius
Really awesome test :D
I wonder what the difference would be if you used solderable copper trace repair tape instead of solder tracing and only put a bit of solder on each end of the tape?
Mike's technique was better, because you just added an arbitrary amount of solder. Mike used a real example with a real amount of tin. But thanks for confirming.
The solder deposited is not free: first the solder has to be paid for, and second, all that exposed copper will dissolve somewhat into the solder (which is a problem with wave soldering machines), requiring that the solder be replaced more often, because dissolved copper is detrimental to soldering.
Does the things change repeting the experiment with AC ?
I understand change from is from 50 milli-ohm to 25 milli-ohm, and that is a 50% change, but the overall change is still only 25 milli-ohm. Using Ohms law we can say that power is I^2*R, so if 2 amps are going through the track, thats a change of only ~0.1 watts of energy dissipated by the track. That lower resistance helps for sure, essentially dropping the power dissipated by the track in half, but doesn't the solder also act like a heat sink, which reduces thermal strain on the track?
I'm just planning to build power supply. Thanks for great info
If someone else tries this, how about measuring the thickness of the solder with calipers?
Dave, what about the inductance of the traces? Do they increase with this technique? In a H-Brige high frequency PWM, the inductance of the board is very important...
With high frequency you get skin effect that makes things more complicated.
@@lrmackmcbride7498 only in the MHz range for a PCB like this I would bet, but also depends on the current, hard to ballpark, better to simulate.
@@michelfeinstein .3 mm at 50khz. For short runs at low current it might not be as big of an issue. For a high frequency H bridge, it is definitely an issue. Hence the "keep traces short" mantra. Above 100khz litz wire is a necessity in power applications.
It is possible to solder a thick wire if you want to drain a really high current from a PCB trace.
When you calibrate a 3478 you can only calibrate 2 or 4 wire ohms. The measurement that isn't picked to be calibrated is probably going to fail so that meter might be a little off to show the difference between 2 and 4 wire.
Conductivity of solder is well below that of copper. It takes a lot more microns to make a big difference.
Exelente video!
Woooooa. Hey Mike our Antipodean cousin here has really thrown down the gauntlet. Errors in your analysis ????? Never!!!! What are you going to do next? I've got part of a thermoneuclear bomb in my garage, I'll send it you. Surely a teardown on that would would keep the Crazy Aussie's head down a bit and score you some points. No, seriously guys, this is brilliant stuff I'm learning so much.
2oz double sided isn't that difficult actually. It's not extremely expensive either. It may be out of the realm of many hobbyists, but the 2oz copper is common on high current temperature controllers.
How was this an issue at all? Don't need to know crap about testing with/on solder thickness on PCBs to figure out the answers. Resistance and current of different gauge wires (e.g. 16-gauge vs 12-gauge) is well known, and the principles are directly related... i.e, the same damn thing.
I would also suspect lead-free solder has a higher conductivity?
TheAmmoniacal It's silver based, so off the top of my head, I would guess that it would.
I actually do not understand something. When we do that we thicken only specific area of PCB trace but the rest still remains the same thin copper. So what am I saying is, that if we use thick wire which has e.g. thin coupling to another wire, high current will burn that thin wire joint, yes? So what happens here on unthickend traces on high current? Thanks in advance. :)
I can't understand why people would think it wouldn't make a difference, it's like going from a little thin wire to one that's twice the cross sectional area. Obviously it would be able to carry more current.
I love then both Mike and Dave talk about the same stuff, I get more out of the topic as well
good digging
Strange that there is so much solder, yet the resistance increase isn't significant. The resistance of solder must be quite high compared to copper
I'd have to look it up, but I think the resistivity of solder is substantially higher than copper.
Surely the weakest point in this test are the parts just after where you had the wires soldered for sencing where no solder was applied to the strip?
I think the main reason for the difference is that Mike's board probably was soltered mostly with tin, and Dave's was with tin/lead and pure tin is better conductor.
Maybe tomorrow, it's bugging me! I need to shoot the installation of it.
The thing you aren't considering is if the trace is 10 miles long and half a mile wide there will be a big difference but one normal traces of a few mm it won't make a difference. If you go from 10 pico ohms to 2 pico ohms how much more current are you going to get? No boards have traces as long and as wide as his bread board.