Homebrew_PCBs

I was wondering how many of you folks use fillets in your PCB patterns where two traces, or any two edges for that matter, meet at 90 degrees.
 
I was looking at some commercially produced patterns and they seem to frequently employ fillets.  This is I presume to prevent cutting in of the pattern at 90 degree corners when the board is etched.  For a pattern produced on a computer it's easy enough to add them in.  Would it make any difference if one is using the toner transfer method?

Thanks in advance for your comments.

John

On 27 Jul 2014 17:01:43 -0700, you wrote:

>I was wondering how many of you folks use fillets in your PCB patterns where two traces, or any two edges for that matter, meet at 90 degrees.

I almost always bevel at 45 degrees. I rather wish that Eagle had a
"constrain to 45 degrees by moving both ends" behavior as an option.

>
>I was looking at some commercially produced patterns and they seem to frequently employ fillets. This is I presume to prevent cutting in of the pattern at 90 degree corners when the board is etched. For a pattern produced on a computer it's easy enough to add them in. Would it make any difference if one is using the toner transfer method?
>

I was told many years ago that traces had a tendency to break if they
were at 90 degrees (that was the expression they used). In theory, I
can imagine that etching through at the 90 degree junction may be a
problem. As such, I will avoid 90 degree joints (even T joints) and
bevel at 45 degrees.

I suspect that it was a result of etching (and etching *in* at the 90
degrees inside point), since they used photoetching (KPR) and had
production etching capability in house.

Therefore, the toner transfer method would not make a difference, one
way or another.

(or so says logic and my memory).

Harvey

>Thanks in advance for your comments.
>
>John

The MITER command will let you quickly turn a: wire-90-wire into: wire-45-wire-45-wire. You can apply it to any wire join, it doesn't have to be 90 degrees. Just click and drag the join.

--Rick

 

I was wondering how many of you folks use fillets in your PCB patterns where two traces, or any two edges for that matter, meet at 90 degrees.
 
I was looking at some commercially produced patterns and they seem to frequently employ fillets.  This is I presume to prevent cutting in of the pattern at 90 degree corners when the board is etched.  For a pattern produced on a computer it's easy enough to add them in.  Would it make any difference if one is using the toner transfer method?

Thanks in advance for your comments.

John

Hi John,

On Mon, Jul 28, 2014 at 10:01 AM, hudakjm@... [Homebrew_PCBs]
<Homebrew_PCBs@yahoogroups.com> wrote:

>
> I was looking at some commercially produced patterns and they seem to frequently employ fillets. This is I presume to prevent cutting in of the pattern at 90 degree corners when the board is etched.

I reckon use of fillets to prevent overetch in the corners is a
historical thing. These days it's mostly done for aesthetics. I
supply thousands of PCBs a month commercially, and filletless right
angles are not a problem at all.

It may still be relevant for home etching though, where timing and
process chemicals are not controlled as strictly as in commercial
production. I suggest making a test board that you can use to explore
how well the home etch process works for you. All the best!

Mitch
http://www.hackvana.com/guide

While it is technologically no problem, 90° trace corners just look
unprofessional and lazy.
A machinist will always chamfer or at least de-burr edges, otherwise
the part is not finished.
So I use 45° rules almost exclusively, with all corners mitered. Also
gives shorter connections.

Pulsonix has a "pull tight" command that, with the routing rules set
correctly, makes it look nice using the shortest length while
maintaining clearances.

In contrast I never teardrop pads unless requested specifically.
I just haven't seen the benefits to bother for my own designs.
Even in thermal cycling on single sided boards the solder broke before
the pads lifted.

I also don't fillet or miter the inside edges of T connections.

What I do is use rounded corner pads instead of square corner for SMT.

I would like to make an "old school" rounded trace design once.
So far I haven't had the chance to put one into production.

ST

On Mon, Jul 28, 2014 at 3:45 AM, Mitch Davis mjd@...
[Homebrew_PCBs] <Homebrew_PCBs@yahoogroups.com> wrote:

> Hi John,
>
> On Mon, Jul 28, 2014 at 10:01 AM, hudakjm@... [Homebrew_PCBs]
> <Homebrew_PCBs@yahoogroups.com> wrote:
>>
>> I was looking at some commercially produced patterns and they seem to frequently employ fillets. This is I presume to prevent cutting in of the pattern at 90 degree corners when the board is etched.
>
> I reckon use of fillets to prevent overetch in the corners is a
> historical thing. These days it's mostly done for aesthetics. I
> supply thousands of PCBs a month commercially, and filletless right
> angles are not a problem at all.
>
> It may still be relevant for home etching though, where timing and
> process chemicals are not controlled as strictly as in commercial
> production. I suggest making a test board that you can use to explore
> how well the home etch process works for you. All the best!
>
> Mitch
> http://www.hackvana.com/guide
>
>
> ------------------------------------
> Posted by: Mitch Davis <mjd@...>
> ------------------------------------
>
> Be sure to visit the group home and check for new Links, Files, and Photos:
> http://groups.yahoo.com/group/Homebrew_PCBs
> ------------------------------------
>
> Yahoo Groups Links
>
>
>

"Stefan Trethan stefan_trethan@... [Homebrew_PCBs]"
<Homebrew_PCBs@yahoogroups.com> writes:

> In contrast I never teardrop pads unless requested specifically.

I've had a professionally made PCB fail at a pin junction in exactly the
way that teardrops are meant to prevent, so I tend to always use them on
my boards.

Very interesting thread.

Am I correct in assuming that "tear-dropping" refers to adding either chamfers or fillets where a trace meets a side of a rectangular, oval, or round pad which is wider than the trace?

"palciatore@... [Homebrew_PCBs]" <Homebrew_PCBs@yahoogroups.com>
writes:

> Am I correct in assuming that "tear-dropping" refers to adding either
> chamfers or fillets where a trace meets a side of a rectangular, oval,
> or round pad which is wider than the trace?

In general, yes.

Examples at the bottom of:
http://www.delorie.com/pcb/teardrops/
(click to expand each image)

It appears that the examples on that page show filets at round pads, but not at rectangular ones. Is this the general practice? I would think they would be equally advantageous on both types.

Fri Aug 1, 2014 9:44 pm (PDT) . Posted by:

"DJ Delorie" djdelorie


"palciatore@... [Homebrew_PCBs]" <Homebrew_PCBs@yahoogroups.com>
writes:
> Am I correct in assuming that "tear-dropping" refers to adding either
> chamfers or fillets where a trace meets a side of a rectangular, oval,
> or round pad which is wider than the trace?

In general, yes.

Examples at the bottom of:
http://www.delorie.com/pcb/teardrops/
(click to expand each image)

"Paul Alciatore palciatore@... [Homebrew_PCBs]"
<Homebrew_PCBs@yahoogroups.com> writes:

> It appears that the examples on that page show filets at round pads,
> but not at rectangular ones. Is this the general practice? I would
> think they would be equally advantageous on both types.

Probably, but at the time, the math for pretty teardrops on square pads
was too hard for me to bother with :-)

I think I put teardrops on square pads now, as if they were round pads.

Do you put teardrops or did you mean fillets "on square pads now, ..."?

Donald.

----- Original Message -----
> From: "DJ Delorie dj@... [Homebrew_PCBs]" <Homebrew_PCBs@yahoogroups.com>
> To: "Homebrew PCBs" <Homebrew_PCBs@yahoogroups.com>
> Sent: Monday, August 4, 2014 9:15:33 PM
> Subject: Re: [Homebrew_PCBs] Re: To fillet or not to fillet on a PCB pattern
>
>
> "Paul Alciatore palciatore@... [Homebrew_PCBs]"
> <Homebrew_PCBs@yahoogroups.com> writes:
> > It appears that the examples on that page show filets at round pads,
> > but not at rectangular ones. Is this the general practice? I would
> > think they would be equally advantageous on both types.
>
> Probably, but at the time, the math for pretty teardrops on square pads
> was too hard for me to bother with :-)
>
> I think I put teardrops on square pads now, as if they were round pads.
>
>
> ------------------------------------
> Posted by: DJ Delorie <dj@...>
> ------------------------------------
>
> Be sure to visit the group home and check for new Links, Files, and Photos:
> http://groups.yahoo.com/group/Homebrew_PCBs
> ------------------------------------
>
> Yahoo Groups Links
>
>
>
>

That looks very nice!

Donald.

----- Original Message -----
> From: "DJ Delorie dj@... [Homebrew_PCBs]" <Homebrew_PCBs@yahoogroups.com>
> To: "Homebrew PCBs" <Homebrew_PCBs@yahoogroups.com>
> Sent: Saturday, August 2, 2014 12:44:19 AM
> Subject: Re: [Homebrew_PCBs] To fillet or not to fillet on a PCB pattern
>
>
> "palciatore@... [Homebrew_PCBs]" <Homebrew_PCBs@yahoogroups.com>
> writes:
> > Am I correct in assuming that "tear-dropping" refers to adding either
> > chamfers or fillets where a trace meets a side of a rectangular, oval,
> > or round pad which is wider than the trace?
>
> In general, yes.
>
> Examples at the bottom of:
> http://www.delorie.com/pcb/teardrops/
> (click to expand each image)
>
>

"Donald H Locker dhlocker@... [Homebrew_PCBs]"
<Homebrew_PCBs@yahoogroups.com> writes:

> Do you put teardrops or did you mean fillets "on square pads now, ..."?

I meant teardrops. As in, the code doesn't check to see if the pad is
square. I typically don't use square pads so I was just lazy in my
code.

>> I think I put teardrops on square pads now, as if they were round pads.

I get it. Seeing the photos was illuminating, too.

Thanks,
Donald.

----- Original Message -----
> From: "DJ Delorie dj@... [Homebrew_PCBs]" <Homebrew_PCBs@yahoogroups.com>
> To: "Homebrew PCBs" <Homebrew_PCBs@yahoogroups.com>
> Sent: Thursday, August 7, 2014 11:49:01 AM
> Subject: Re: [Homebrew_PCBs] Re: To fillet or not to fillet on a PCB pattern
>
>
> "Donald H Locker dhlocker@... [Homebrew_PCBs]"
> <Homebrew_PCBs@yahoogroups.com> writes:
> > Do you put teardrops or did you mean fillets "on square pads now, ..."?
>
> I meant teardrops. As in, the code doesn't check to see if the pad is
> square. I typically don't use square pads so I was just lazy in my
> code.
>
> >> I think I put teardrops on square pads now, as if they were round pads.
>
>