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Subject: Tear drop routing
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shiva
Posts: 57
Online: User is Offline
2/26/2008 3:05 AM  
How can i do tear drop routing for vias and pads? Presently we are using Allegro studio v.16.0. If anyone known this, please let me know. Thanks, Shiva.
cadpro2k
Posts: 45
Online: User is Offline
2/26/2008 2:23 PM  
Here's my process, and don't think I'm joking.

1) output data to the vendor.
2) include a note on the fabrication drawing that states the vendor can add theiving and teardropping if necessary.

You need to understand why you 'might' need teardropping. It's mostly needed for small traces that enter pad, and it helps to protect the traces from cracking at the transition. If you're not going below .005" lines, you most likely don't need teardropping.

Now, teardropping... This practice reared it's ugly head (like 45 degree routing) over a company (PADS) making it easy to do in routing. This is almost a default on PADS designs, and most times is not necessary. So, using Allegro, don't be deceived, and believe it's required because you saw a PADS database.

Personally? In PADS I have it add teardrops. In Allegro I don't have it in the database, but do add the note to the drawing (just in the offchance SOME manufacturer doesn't have good controls over their processes. So, I never do it in Allegro (but add the note).

Good day.
Mitch
jch teyssier
Posts: 25
Online: User is Offline
3/03/2008 11:51 PM  
I do my tear drops in allegro and it work s fine.
By doing it, i insure that tear-dropping is possible on all locations. If not, i lokk why tear drop is not genrated (bad pad entry, entity to close), correct it and re-lauch gloss process for tear drop.
I let manufacturer add tear drop (fab note) only in heavy time pressure (prototypes)

The less the manufacturer modify my desin, the better is! (In some idea, i don't want manufacturer to add copper balancing: they can't kwon isolations area and keepouts!)
dominic_obar
Posts: 3
Online: User is Offline
3/05/2008 12:40 AM  
i agree with teyssier. run GLOSS and only few vias, pads and T's will be left without teardrops/fillet if the GLOSS PARAMETERS are set correctly so that it matches the spacing of objects in your design. you can readjust the gloss param (max. offset, fillet angle, etc.) then add fillet individually the objects that were left without teardrops/fillet. at least the process im describing applies to allegro v15.5.1 but i believe it has not changed much in v16.0.
shiva
Posts: 57
Online: User is Offline
3/06/2008 12:57 AM  
Thanks for your comments. I like to konw how can i put teardrops. Is thereany way? Can anyone tell me the path?

Regards,
Shiva.
jch teyssier
Posts: 25
Online: User is Offline
3/06/2008 11:47 AM  
As writen above, use GLOSS command (in 15.7: Route->Gloss
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Forums > Silicon-package-board > PCB Design > Tear drop routing


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