Lets break in it into 2 areas, Electrical circuit performance
and Manufacturing (DFM).

Electrical routing should be the first concern, because it
doesn't matter how manufacturable the board is, if the circuit
don't work..

What would be the thermal resistance of the additional traces?
Do some delta T's. The board has all ready reached steady state
in the reflow and doesn't the soldermask work as a solder stop.

What kinda of soldering process are we talking ??

I would agree on not makes the traces too wide..

Food for Thought
--
Lou Dallara   Techno Visionary          Reduce..Reuse..Recycle
http://www.waterw.com/~ldallara       http://www.arcosanti.org

jdeking <[log in to unmask]>


OK, I'll take a leap;

1) A pad having MORE than two traces either
  a) Is a "T" intersection, typically undesirable (re: RFI control or
normal analog circuit magick) but not necessarily catastrophic;
b) Or, potentially contains acid traps due to acute angles.

"a" is the more likely reason in most cases. Analog circuits can be very
sensitive to layout and routing geography.

2) However, TWO traces to a pad is quite acceptable, particularly if a
trace needs to connect to a pin, and another on the other side of that
pin; to continue the trace through said pad is preferable to creating a
stub trace and routing around the rest of the component to the second
pad.

3) Exceptions: cases of excessive heat drain on very small components,
or larger components with very wide traces. Use thermal webs when
possible in such cases (meaning, you have to use multiple connections to
the pad).

4) In other words, you can (and, you can't) use multiple traces into a
given pad. It all depends on the situation and the circuit. This is why
we get the big bucks ;) we're in charge of getting this right.
"If it smokes when we plug it in, put in an ECR and blame the layout
guy"
--
Cap'n Jay the Red
"In wildness is the preservation of the World" - Thoreau


-----Original Message-----
From:   Louis Dallara [SMTP:[log in to unmask]]
Sent:   Wednesday, August 13, 1997 10:09 pm
To:     [log in to unmask]
Subject:        Re: [DESIGNERCOUNCIL] Connections from land patterns

 << File: vcard.vcf >> Jo Ann;
I don't think you can generalize like that, I've never heard it
express that way, the number of connections would depend on
the circuit flow, i wouldn't want to be wrapping traces around to
minimize connections..
Anybody else want to jump in :)
Lou
JoAnn Amerson wrote:

> Hi folks!
>
>
> I was told that it is best to limit the number of tracks leading
> to/from a pad
> to one.  Two at the most and three is highly discouraged.  Can anyone
> verify
> this for me?  Are there any specs that apply?  I asked a fellow
> designer and
> he'd never heard it before either.
>
> Any and all responses are welcome.
>
> JoAnn L. Amerson
> Design Librarian
> Red Lion Controls, Inc.
> E-mail: [log in to unmask]
> Voice: (717) 767-6961 ext 6308
OK, I'll take a leap;

1) A pad having MORE than two traces either
  a) Is a "T" intersection, typically undesirable (re: RFI control or
normal analog circuit magick) but not necessarily catastrophic;
b) Or, potentially contains acid traps due to acute angles.

"a" is the more likely reason in most cases. Analog circuits can be very
sensitive to layout and routing geography.

2) However, TWO traces to a pad is quite acceptable, particularly if a
trace needs to connect to a pin, and another on the other side of that
pin; to continue the trace through said pad is preferable to creating a
stub trace and routing around the rest of the component to the second
pad.

3) Exceptions: cases of excessive heat drain on very small components,
or larger components with very wide traces. Use thermal webs when
possible in such cases (meaning, you have to use multiple connections to
the pad).

4) In other words, you can (and, you can't) use multiple traces into a
given pad. It all depends on the situation and the circuit. This is why
we get the big bucks ;) we're in charge of getting this right.
"If it smokes when we plug it in, put in an ECR and blame the layout
guy"
--
Cap'n Jay the Red
"In wildness is the preservation of the World" - Thoreau


-----Original Message-----
From:   Louis Dallara [SMTP:[log in to unmask]]
Sent:   Wednesday, August 13, 1997 10:09 pm
To:     [log in to unmask]
Subject:        Re: [DESIGNERCOUNCIL] Connections from land patterns

 Jo Ann;
I don't think you can generalize like that, I've never heard it
express that way, the number of connections would depend on
the circuit flow, i wouldn't want to be wrapping traces around to
minimize connections..
Anybody else want to jump in :)
Lou
JoAnn Amerson wrote:

> Hi folks!
>
>
> I was told that it is best to limit the number of tracks leading
> to/from a pad
> to one.  Two at the most and three is highly discouraged.  Can anyone
> verify
> this for me?  Are there any specs that apply?  I asked a fellow
> designer and
> he'd never heard it before either.
>
> Any and all responses are welcome.
>
> JoAnn L. Amerson
> Design Librarian
> Red Lion Controls, Inc.
> E-mail: [log in to unmask]
> Voice: (717) 767-6961 ext 6308