EEVblog Electronics Community Forum
Electronics => Beginners => Topic started by: Faringdon on August 18, 2022, 11:26:40 am
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Hi,
We are using this type of pin header to carry 6A of current onto a little daughter PCB containing PFC sense resistors….
Pin header
https://uk.farnell.com/harwin/m20-9990845/header-1row-8way/dp/1022256
Its datasheet, says each pin is rated for 3A of current. However, that presumably means when mated with a socket housing such as eg….
Socket housing
https://uk.farnell.com/harwin/m20-1060800/crimp-housing-8way/dp/865667?MER=sy-me-pd-mi-acce
When soldered direct from one PCB to the other, we presume the current rating per pin is far higher than 3A?
{EDIT: Please note we are not using the socket housing, we are soldering the pin header into PTH's at either end. END-OF-EDIT}
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RTFM 3A is 3A. Why psuh your luck? It wont't melt at 6A but you will are risking a 20mV drop or 20mW of lost power. The mated value may be higher or lower in contact reistance.
6A .03R go figure.
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Soldered to PCB on both sides would be higher, by how much?
Test one connector terminal at 6 amps, it should not be hot
or get hot after time. If it does try 2 terminals.
Jeff
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My apologies, i should have made clear that we are not using the socket housing, we will be soldering the pin header at both ends, as Jeff eelcr kindly alludes.
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I'd find a table of wire sizes to max current based on temperature rise and voltage drop, and see what the max current would be for a wire of this surface area. How much voltage drop you can tolerate will depend on your application and the voltage. A 24 V rail is obviously less sensitive to voltage drop than a 1.8 V rail.
I'd think for the 10mm or so you could get away with more current, but I haven't done the math.
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2-3A is very typical maximum rating.
This is indeed related to the mating of the socket. The contacts are tiny and do not have much force.
But if you just use short pin header, pins directly soldered on PCB both ends, I see really no problem with 6A. You can easily qualify the heating by a simple test since the uncertainty of the contact resistance is removed.
There still is a risk that if you buy another brand, they use different alloy with worse electrical conductivity, but if the PCB-PCB separation is just a few millimeters, it's quite far-fetched. The pins are thick, after all, and the PCBs will act as heatsinks. I wouldn't be surprised if you could pull of something ridiculously high like 20-30A, given the PCB tracks can handle this!
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My apologies, i should have made clear that we are not using the socket housing, we will be soldering the pin header at both ends, as Jeff eelcr kindly alludes.
then it just like a piece of wire, not a header/socket combination
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You can always use more than one pin to conduct the power. You should derate. If it says 3A then back off 20%.
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Bottom line physics is that the current carrying capacity of a conductor is purely a function of heat dissipation (IR heating due to the resistance of the conductor.) If you can remove the heat, then that pin header can conduct 10000A.
To put it differently, it's about temperature rise. The current ratings of different gauge wire is based entirely on the presumed allowable temperature rise. If the temperature of the pin when conducting 6A is acceptable to you, then the pin can handle 6A.