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help! min. gap between PCB and chassis???

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bollsakkie

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If I have an IC(through hole type) soldered onto a PCB, what is the minimum gap that I need to have between the PCB and the metal chassis (that the PCB is housed in) so that I can ensure that there is no "arcing" or discharge between the pin and the metal chassis?
Are there any standards relating to this?

Thanks in advance for your help!



https://obrazki.elektroda.pl/81_1178700715.jpg
 

i think 6.5mm to 7.0 mm required.

IEC-60950 standard

try this link
 

Assuming that your board handles only low to intermediate voltages, aka less than 100V, then arcing is not a concern. The bigger problem is board flexing and the pins touching the bottom of the chassis. This sort of problem is handled in a couple of ways. Best method is to use large stand-offs to insure the board is quite a distance from the chassis. The second method is to use cutters to insure all leads protrude only a minimum length from the board and use shorter standoffs. The third method is to cut the leads to a minimum length and place an insulator between the PCB and the chassis. Plastic sheeting makes an acceptable insulator. I have often used the plastic sheets that are used for overhead transparencies. These sheets are fairly thick and come in nice big sizes, yet are easy to cut. Some very low cost designs even use cardboard as the insulator. This too works, but is sensitive to humidity problems. If the cardboard absorbs moisture, it can cause weird leakage paths anywhere it touches the PCB.

How low can you go? I have seen successful designs using the insulator method with a board standoff of 0.125 inches or about 3mm.
 

How big the gap is depending your circuit's voltage and frequency.

I do not know about the standard, but for low voltage (up to 20...30VDC) and low frequency (below 1MHz), a gap of several milimeters is good enough.

I saw in the industrial equipment, where the gap is always maintained by sleeves on the bolts that used to fix the PCB to chassis, these sleeves are typical 15...20mm long.

nguyennam
 

bollsakkie said:
If I have an IC(through hole type) soldered onto a PCB, what is the minimum gap that I need to have between the PCB and the metal chassis (that the PCB is housed in) so that I can ensure that there is no "arcing" or discharge between the pin and the metal chassis?
Are there any standards relating to this?

Thanks in advance for your help!



https://obrazki.elektroda.pl/81_1178700715.jpg

There is no concern for arcing. The spacing between chassis and pcb can be 5mm or even less, which is plenty for your purpose.
 

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