Homebrew PCBs

----- Original Message ----- 
From: "Ronald Vanschoren" <yahoogroups@...>
To: <Homebrew_PCBs@yahoogroups.com>
Sent: Tuesday, March 28, 2006 7:53 AM
Subject: [Homebrew_PCBs] Solder Pads and other questions


> Hi,
>
> I am currently starting to make my first PCBs and would like to make my
> own Eagle library to work with (mainly for photo-etch boards and hand
> soldering) because the build in one is not easy to work with. I am full
> of questions now as this is the first time I really need to go into
> detail about packages and solder pads.
>
>
> What is a good source to find information about the solder pads required
> for the most common packages? It is quite easy to find for e.g. SO8 and
> stuff, but the info on 0603, 0805, and 1206 resistors and SMT and
> through hole capacitors is harder to find. The only thing I could find
> for resistors was here: http://www.mouser.com/catalog/625/478.pdf and
> these pads are way smaller then the ones in the default Eagle libraries.

http://www.ipc.org/

These footprints are for reflow soldering. For hand soldering it's a good 
idea to make the pads longer.

>
> About capacitors. Are there default sizes as with resistors? I can't
> seem to find a list of available capacitor packages. I've also looked
> for through hole capacitors and there seems to be a lot of difference in
> packaging to.

0.1" and 0.2" covers most of the ceramic ones I use.

>
> I've been told that SO8 from one manufacturer is not the same as from
> another one. Don't these kind of packages have default sizes then?
>
> About SMT resistors again. The 0603 etc give a clue about the size in
> hundredths of inches, but most information I find on the net is in
> metric measurements. Are the 0603 packages rounded to 1.6mm x 0.81mm
> these days or are there two kinds of 0603 resistors around?

They are all the same size.

>
>
> About through hole pad sizes. I've read somewhere that for through hole
> components a drill size of 0.8mm is recommended, with a round copper pad
> of (at least) 1.3mm. Is that big enough for hand soldering? Why would I
> choose a round pad above a octagonal shaped one? Some documents advice
> to use oval pads for DIP packages, is that true and why is that?
>

0.8 mm or 0.7 mm are fine for IC pins and sockets. I use 0.7 mm and 0.6 mm 
for vias. Pads should be bigger for single-sided boards than for PTH. Also, 
hand drilling isn't very accurate and a larger pad than usd for CNC drilling 
is advisable. I often add teardrops to pads to make things easier.

Oval pads for ICs make it easier to put a track between them.

Leon
--
Leon Heller, G1HSM
leon.heller@...
http://www.geocities.com/leon_heller