Homebrew PCBs

On Mon, 21 Dec 2009 14:06:38 -0000, you wrote:

>--- In Homebrew_PCBs@yahoogroups.com, "leon Heller" <leon355@...> wrote:
>>
>> ----- Original Message ----- 
>> From: "blalor76" <blalor@...>
>> To: <Homebrew_PCBs@yahoogroups.com>
>> Sent: Monday, December 21, 2009 12:31 PM
>> Subject: [Homebrew_PCBs] Eagle design rules for Pulsar toner transfer
>> 
>> 
>> > Morning, all.  I'm wondering if anyone has a set of design rules I could 
>> > use with Eagle to help increase the likelihood of creating a layout that 
>> > will work well with the toner transfer method and Pulsar's 
>> > PCB-Fab-in-a-box.  Pulsar's site claims that you can do traces as small as 
>> > 6mil, which seems much smaller than I need at this time.  For my layout 
>> > thus far, I'm using 16mil traces which seem to be able to squeeze between 
>> > DIP pads without too much difficulty, but I'm not sure how far apart 
>> > traces should be from one another and from pads/holes to avoid shorts, and 
>> > how large the pads/holes should be to avoid tearing them up when drilling.
>> 
>> You have to suck it and see; there are just too many variables with TT. 
>> That's why I prefer photo-etch.
>
>Ok, so taking the etching method out of the equation, I still need to drill out the holes without ripping them up.  Is that just a function of the size of the annular ring?  

Yes, and speed of drill and sharpness of drill.  Faster and sharper
the better the hole.  You might want to increase the size of the pad
itself a bit.  I find that 0.056 to 0.066 pads work well for
resistors, capacitors and the like with hand assembly.  I've increased
the size of the pin header pads a trifle because my boards tend to be
slightly overetched.

IC pads are oval and left as is.

0.016 is fine, 0.012 is ok, 0.010 has problems depending, but may be
put to the overall preparation of the board.  

Shorts are not the problem, but voltage flashover can be, as well as
current carrying capability.  If I do through holes with eyelets, I
find that for my purposes, 0.024 to 0.030 clearance is acceptable.
Some things, though, are on a per design basis.

I've done 100 pin TQFP with 0.5mm spacing on the pins, but it's still
at the limit of  how I do boards.

Harvey

>
>
>
>------------------------------------
>
>Be sure to visit the group home and check for new Links, Files, and Photos:
>http://groups.yahoo.com/group/Homebrew_PCBsYahoo! Groups Links
>
>
>