[EE] Optimal hole/pad size for double-sided TH components

[Electron]

Hello,
some of you here have a lot of experience. What is in your opinion the
optimal hole and pad size for TH components on a double-sided PCB, to
help flow of solder from one side to the other?

And how does it change if the rheofore is round or square?

Is there an optimal formula to calculate min/max hole and pad sizes,
so one can, basing on the constraints (e.g. need to pass some traces
inbetween pads) decide in the most effective possible way the size
of drill hole and pad?

Thank you.

Kind regards,
Mario

PS: please don't tell me that CADs calculate it automatically.. I want
to learn, too.

[David C Brown]

The hole minimum holes size is determined by the component lead diameter.
Your PCB manufacturer will give you minimum annulus size, minimum track
width and track-track and track-pad clearances (which will be different for
surface and buried plane). Typical feature size for a not very fine PCB is
10 thou. A quick example. A typical quarter watt resistor will have
leads of about 20 thou diameter so a hole of 25 will be about right. Then
a pad of 50 thou gives you a 12.5 thou anulus. With pads on 100thou
centres you can run two 10 thou tracks between pads with 10 thou
clearance.. Or for the ubiquitous 0.64mm square connector pins you might
go for a 40 thou hole in a a 62.5 thou pad which would allow 1 12.5thou
track between pads with 12.5 thou clearance.

But it does get difficult if you have different clearance rules so for my
low precision boards I tended to use 62.5 pads, 12.5 clearance and 12.5
track widrh. Hole size to suit components. But the crucial thing is to
know what your manufacturer can do.

__________________________________________
David C Brown
43 Bings Road
Whaley Bridge
High Peak Phone: [phone]
Derbyshire eMail: ***@gmail.com
SK23 7ND web: www.bings-knowle.co.uk/dcb
<http://www.jb.man.ac.uk/~dcb>



*Sent from my etch-a-sketch*

Post by Electron
Hello,
some of you here have a lot of experience. What is in your opinion the
optimal hole and pad size for TH components on a double-sided PCB, to
help flow of solder from one side to the other?
And how does it change if the rheofore is round or square?
Is there an optimal formula to calculate min/max hole and pad sizes,
so one can, basing on the constraints (e.g. need to pass some traces
inbetween pads) decide in the most effective possible way the size
of drill hole and pad?
Thank you.
Kind regards,
Mario
PS: please don't tell me that CADs calculate it automatically.. I want
to learn, too.
--
http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive
View/change your membership options at
http://mailman.mit.edu/mailman/listinfo/piclist

[Jean-Paul Louis]

Mario,

It has been a while since I last dealt with design guidelines, but on top of my memory is 7mil clearance for the hole (0.007inch /0.3mm), and a minimum annular ring of 6mil (0.006inch/0.25mm) or 12mil(0.012inch/0.5mm) larger than the hole.

The hole clearance must be larger if you plan to use wave soldering.

The best way to confirm that would be the IPC document on through hole soldering.

Post by Electron
Hello,
some of you here have a lot of experience. What is in your opinion the
optimal hole and pad size for TH components on a double-sided PCB, to
help flow of solder from one side to the other?
And how does it change if the rheofore is round or square?
Is there an optimal formula to calculate min/max hole and pad sizes,
so one can, basing on the constraints (e.g. need to pass some traces
inbetween pads) decide in the most effective possible way the size
of drill hole and pad?
Thank you.
Kind regards,
Mario
PS: please don't tell me that CADs calculate it automatically.. I want
to learn, too.
--
http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive
View/change your membership options at
http://mailman.mit.edu/mailman/listinfo/piclist

Just my $0.02,

Jean-Paul
N1JPL