DipTrace PCB PAD shape - Page 1
Forum section: electronics / beginners

author: iamnothim
author_rank: Regular Contributor
timestamp: March 27, 2013, 05:56:32 am
content: Hi,I've been setting up my component and pattern libraries in DipTrace. All my components are thru-hole. I have 30-50 set up, but I'll only need a dozen. That's because I keep screwing up my calc's and I am accumulating components.In the Pattern editor my options for PAD shape are Ellipse and Oval. Which should I pick and why isn't round an option? (I think I'v picked oval)I've followed AMPDOCTOR's rules of thumb for PAD size and spacing. Do I use ANSI or ISO drill bit sizes?I tend to like my units to be mm, but all the drill sizes are in 1000ths, and that's what the doctor ordered. Is that more acceptable?Here are AMDOC's suggestions."The thumb rule I like to use is 1w resistors get 700thou (1.78mm) pad to pad spacing, 1/2w 600 (1.52mm), 1/4w 500 (1.27mm), etc. Ideally you want about 100thou (0.25mm)between the bend and the body. This should be approximately IPC standard but I may be wrong so don't quote me on that. With respect to the pad and hole size, take the nominal lead diameter and add 12thou (0.3mm) and round up to the nearest drill size for your hole, then double that value for the pad size. As far as component to component spacing, I tend to lay out 1/2w and 1w resistors with about 200 thou ( 0.51mm) spacing between them, and 1/4w at around 150 thou (0.38mm). While you can get them closer, if you've got the board space use it. This makes getting in and out with an iron a snap if you need to do any rework or repairs."The lead bend from body at .012" is a bit tight. I am bumping that way up to 0.100" per bend.I do not have a handle on the layers and process of making a board. I think I understand the PAD and the silk (outline). I'm good with assigning a pattern to a component. And when I ran a trial of make a PCB from my schematic, it had no errors and actual looked like a PCB. I'm going to save those questions for later to see what I can figure out on my own.Thanks ya'll for the help and support.

author: Kremmen
author_rank: Super Contributor
timestamp: March 27, 2013, 10:29:55 am
content: Quote from: iamnothim on March 27, 2013, 05:56:32 amWhy not delete the failed ones? Who need or wants faulty components that only mess your designs up if you use them by accidentQuoteRound is a special case of ellipse and oval, where x=y so you don't need "round" separately.QuoteNot in any real sense. Diptrace comes with a lot of imperial dimesioned stuff out of the box, but i don't use anything but metric. I have defined a metric snap grid in all the tools and all components are defined in metric and metric only. Original Diptrace components that i use, i tend to migrate into a library maintained myself, and convert everything to metric and standard gridsQuoteA dimension is a dimension, whatever the units may be. Use what makes you happy, that is what i doQuoteOK, later with the layers then.BTW you did notice there is a board for Diptrace specifically? Consider moving there.

author: iamnothim
author_rank: Regular Contributor
timestamp: March 27, 2013, 04:16:14 pm
content: Hey Krem,What I can't figure out is the relationship between PAD shape and solder. Ellipse vs Oval. Does it flow better with one shape v the other?Units... that's what I was thinking, and I find metric is easier too. However all the bits are in thou's. but that's an easy spreadsheet conversion. As to ISO v ANSI. I've decided to pick ANSI since I hate the United Nations. I'm also guessing ANSI bits are easier to find.Parts, I figured if they are in my inventory I might as well make a component and a pattern for later. With my transformer problem (121 VAC vs 115) I was buying these high watt resisters as big as cigars..... (3.3 Ohm, 10W) Now I found thick film. Paying my dues. I still have those issues but that's for a different thread too.A DipTrace board? Now that's a novel idea. Why didn't I find it?? Because I'm too stupid to look.thx.

author: Kremmen
author_rank: Super Contributor
timestamp: March 27, 2013, 08:18:52 pm
content: Quote from: iamnothim on March 27, 2013, 04:16:14 pmPad shape is a factor in wave soldering where the board is immersed in solder. Some pad configurations are more prone to solder bridging and then it is an advantage to be able to adjust the pad shape to prevent that. I don't know if there is that much difference between ellipse and oval. I tend to use oval only but maybe very big circular pads come out right only as ellipses, i never tested.QuoteWell i don't feel quite that strongly about the UNAnyway ISO/IEC works for me but there is nothing really broken in ANSI either.If we are talking about drill bits here, most datasheets give the thru hole diameters in mm also. And these days they seem to be and easy series of .1 mm increments btw say .5mm to say 1.5mm or so. Only vias in high speed multilayer boards are significantly smaller, down to .2mm or so.Quote

author: iamnothim
author_rank: Regular Contributor
timestamp: March 27, 2013, 10:37:57 pm
content: Cool...I'm good.Thx for the info.