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: 01663 733236 Derbyshire eMail: dcb.home@gmail.com SK23 7ND web: www.bings-knowle.co.uk/dcb *Sent from my etch-a-sketch* On 18 November 2017 at 15:37, Electron wrote: > > 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 > --=20 http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .