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track size for current

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justin_t

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Hi

What is the standard to calculate track width required for the current flowing through the track. Is there a rule of thumb that people work by?

My application draws 10 amps AC. What size should i be expecting?

Justin
 

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Putting thick lines of solder over the traces helps to increase their ampacity without taking up any more space on the board.
 
Putting thick lines of solder over the traces helps to increase their ampacity without taking up any more space on the board.

Hi Hero999,

I'm afraid for good reason that your suggested method burries a great safety risk. I saw this technique used in a UPS. Caused by a malfunction close to a short the copper traces got so hot that the solder melted and flew through the enclosure. If it piles up high enough it will cause more trouble.

A better way is using stranded wire pretinned and solder it onto the copper trace.

Soldering tin has a resistance of five times copper resistance.

There are also copper strips availabe looking like cattle fences. They have pins every 1/2 inch which can be soldered to the trace without considerably reducing its cross section. They are mounted on the component side and their distance to the board is big enough (approx 1.5mm) to prevent heating the board in case of overload.

Planning for a PCB with high current flow using PCB material with double copper thickness (standard: 35µm, enforced: 70µm) should be considered.

Additionally this method offers reference measuring points for trouble shooting.

Hans
 

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Having sections of track with no solder mask to allow for solder coating & whole of track solder coated have been used in industry for many years. This is pretty common place in many power supplies.
Inverter welders Ive been inside use this practice.
Many commercial manufacturers skimp where they can so solder is a lot cheaper than specialised parts (even wire) & I guess they wear the risk(or some probably don't consider the risk).

I have some of my power supply designs where there is an un-SolderMasked strip on the track to reduce Volt drop on 3.3V supplies & single ended current sensing.

There would not be great risk for all designs,
I Think its ok to solder coat tracks but should evaluate the risk/result & knowing what fault currents might be expected.

I agree soldering tinned CU wire to the track is much better than solder by it self & have used this on jobs ( & repairs)

A technique I use at times it to place a thinner section of track between 2 solder pads so I can control where the track blows when I cannot justify a fuse.

I 'm not trying to disagree but I think there is a "middle ground" here.
 
I have worked on an AEG induction hob which uses a necked down area of copper strip as a 20 amp fuse. The board almost certainly uses extra thick copper and the necked down section is about 2mm wide.
 
Hi Hero999,

I'm afraid for good reason that your suggested method burries a great safety risk. I saw this technique used in a UPS. Caused by a malfunction close to a short the copper traces got so hot that the solder melted and flew through the enclosure. If it piles up high enough it will cause more trouble.

A better way is using stranded wire pretinned and solder it onto the copper trace.

Soldering tin has a resistance of five times copper resistance.
I think it was the lack of a suitable fuse that caused the meltdown more than the technique itself.

Solder does have a higher resistance than copper but the layer is probably five times thicker than the copper trace so it's probably good for double the current.

All your other idea like using stranded wire are good though.
 
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