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Electronics => PCB/EDA/CAD => Topic started by: ocset on March 21, 2018, 03:45:26 pm

Title: Distance of bottom layer SMD pad to thru-hole pads
Post by: ocset on March 21, 2018, 03:45:26 pm

Hello,
Please can you confirm that for a offline power supply board (50w) with surface mount components on the bottom, and thru-hole on the top,
the SMD pads must be at least 3mm away from the thru-hole pads.
I just wiondered if Wave and reflow soldering techniques have changed so that they can be closer?

Title: Re: Distance of bottom layer SMD pad to thru-hole pads
Post by: ocset on March 23, 2018, 06:28:34 pm

Thanks, i am not talking about regulations...i am speaking about the manufacture of the board in the cheapest way.
For a board with smd bottm, and thru hole top, it is difficult to  wave solder the thru-hole pins if they are too near to the smd pads.....i was wondering how far do the smd pads have to be away from the protruding thru-hole pins in order to make the wave soldering easy and cheap.

I am assuming that the smd bottom components get mounted first....in the manufacture (pcb assembly) process

Title: Re: Distance of bottom layer SMD pad to thru-hole pads
Post by: tautech on March 23, 2018, 06:45:13 pm

As you can make your own custom pads I see no reason why you can't make the design very compact (same net) however the possibility of doing rework should be given high priority in any layout and sadly these days it isn't.  :--

Title: Re: Distance of bottom layer SMD pad to thru-hole pads
Post by: PCB.Wiz on March 23, 2018, 08:28:04 pm

Quote from: treez on March 23, 2018, 06:28:34 pm

Thanks, i am not talking about regulations...i am speaking about the manufacture of the board in the cheapest way.
For a board with smd bottm, and thru hole top, it is difficult to  wave solder the thru-hole pins if they are too near to the smd pads.....i was wondering how far do the smd pads have to be away from the protruding thru-hole pins in order to make the wave soldering easy and cheap.

I am assuming that the smd bottom components get mounted first....in the manufacture (pcb assembly) process

Surely the one to ask is those actually doing the PCB assembly ?!
Wave soldering clearances I would expect to vary, depending on the direction of solder wave travel.
Typically they would place the SMD parts with glue-dots, then wave-flow the fully stuffed board last.

Title: Re: Distance of bottom layer SMD pad to thru-hole pads
Post by: katy201607 on March 24, 2018, 02:17:25 am

 depending on the direction of solder wave travel is correct