Homebrew PCBs

Hi,

With the (thermal toner transfer) boards I've done so far, I've drilled
after etching.

Even though I'm using a good drill press, the drilling played havoc with
the fine pads, and left me with having to either:

 1. buy a conductive pen ($35 here - ouch!) and hand-repair the
    pads/traces, or
 2. use soldering technique and (in some cases) thin wires to bridge the
    damaged connections

So this time, I tried drilling before etching. Worked much better - in
cases where the holes and pads acquired imperfections, these were easily
corrected by dabbing the etch-resist pen gently into and around the
(0.8mm) holes.

I'm quite happy with the result, and would recommend drilling before
etching as an option which can reduce time/pain.

Comments anyone?

-- 
Cheers
David

I usually drill after etching, but I did one today where I drilled it 
first. It won't lift the pads, but I was worried about scratching it. I 
like drilling after because of the dimple in the center.

Mickey



David McNab wrote:

>Hi,
>
>With the (thermal toner transfer) boards I've done so far, I've drilled
>after etching.
>
>Even though I'm using a good drill press, the drilling played havoc with
>the fine pads, and left me with having to either:
>
> 1. buy a conductive pen ($35 here - ouch!) and hand-repair the
>    pads/traces, or
> 2. use soldering technique and (in some cases) thin wires to bridge the
>    damaged connections
>
>So this time, I tried drilling before etching. Worked much better - in
>cases where the holes and pads acquired imperfections, these were easily
>corrected by dabbing the etch-resist pen gently into and around the
>(0.8mm) holes.
>
>I'm quite happy with the result, and would recommend drilling before
>etching as an option which can reduce time/pain.
>
>Comments anyone?
>
>  
>

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.

ST

----- 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 

---
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On Fri, 10 Jun 2005 13:33:06 +0200, Leon Heller  
<leon.heller@...> wrote:

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


for some reason that doesn't work nicely with my sw. on oblong pads.
I'm usually to lazy to use the function, it won't make a too-small pad  
sufficiently large anyway ;-)


ST

Stefan Trethan 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.

Right you are, as I discovered the hard way when drilling my first board.

I do need traces to pass between pins on DIP chips, which rules out
setting larger pad sizes in Eagle.

What's worked as a compromise is to simply drop huge diameter vias on
top of the pads wherever possible, preferring oblong shape, and
resorting to octagonal wherever space is an issue.

If I got desperate enough, I'd touch up the artwork in The Gimp before
transferring to the board.

So far, so good.

-- 
Cheers
David

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:<<
David:  If your drilling does that much damage to the  copper, then clearly, 
the tip of your drill-bit needs work!   A  reasonably-fresh carbide tip will 
NOT damage even a rather small pad at  all!.            Jan  Rowland

 


[Non-text portions of this message have been removed]

In a message dated 6/10/2005 6:26:24 A.M. Central Daylight Time,  
stefan_trethan@... writes:

. . .  Even though I'm using a good drill press . . .<<
Stefan:  This line reminded me, if you make some arbors  and a "table" to 
receive the ends of the bits, a good drill-press will work to  set the plastic 
collars on carbide PCB bits!  

 


[Non-text portions of this message have been removed]

On Fri, 10 Jun 2005 20:31:05 +0200, <JanRwl@...> wrote:

> Stefan:  This line reminded me, if you make some arbors  and a "table" to
> receive the ends of the bits, a good drill-press will work to  set the  
> plastic
> collars on carbide PCB bits!


I had this thought too, but i do not own a good drill press ;-(
I know i ought to get one, but i can do many things with my drill stand  
and a very good power drill in it, and i refuse to buy a cheap press as i  
fear the motor would be inferior and i would be disappointed. the drill  
stand is lever operated, it is no good to precisely press small increments.

ST