Archive of the former Yahoo!Groups mailing list: Homebrew PCBs

----- Original Message -----
From: "Stefan Trethan" <stefan_trethan@...>
To: <Homebrew_PCBs@yahoogroups.com>
Sent: Friday, June 10, 2005 12:24 PM
Subject: Re: [Homebrew_PCBs] drill before etching?


> On Fri, 10 Jun 2005 05:04:42 +0200, David McNab <david@...>
> wrote:
>
>> Even though I'm using a good drill press, the drilling played havoc with
>> the fine pads, and left me with having to either:
>
>
> If that is the case you definitely have too small pads.
> Remember the pads are not only for electrical connection, but also for
> mechanical mounting, and nothing is more annoying than a PCB with the pads
> lifting off.
> You surely understand they must be MUCH bigger in non-PTH boards as the
> plating acts like a rivet that holds things together - and still i have
> managed to pull PTH padstacks out with improper soldering, so they were
> too small too. Most PCB software is set to tiny pads meant for PTH boards.
>
> Make bigger pads, make oblong pads if the spacing doesn't allow more, for
> example, for a 100mil pitch DIL IC you can make 4mm long pads which still
> look good.
>
> I tend to make bigger pads for components that are either mechanically
> large, are connectors, or have many pins. This helps those components that
> have the highest stress (e.g. electrolytic caps are often pulled/pushed by
> handling of the board because they are higher), And helps the parts that
> are hard to desolder.
>
> If you make oblong pads, it is best never to go with the trace into the
> pad in the center at right angles to the orientation of the pad. I have
> had the fault that drilling did cut the trace free from the rest of the
> pad, but it was not visible easily. So always go into one of the ends of
> the pads.

I often use 'teardrops' on my home-made PCBs. The Pulsonix software I use
can add them automatically.

Leon

---
[This E-mail has been scanned for viruses but it is your responsibility
to maintain up to date anti virus software on the device that you are
currently using to read this email. ]