[PCB_FORUM] Re: Via at SMD Thru

Yes - this is NOT a bug.

The GUI system in SPECCTRA is not designed to be a complete collection of available SPECCTRA commands.

Via-in-SMD THRU is a newer added Rule and is an hierarchical rule so can be applied to Classes, Nets, etc as desired.

All SPECCTRA commands are equally available from the Command Line, DO File, embedded DSN rules or the SPECCTRA GUI (and, in this case, only as long as they're included in the GUI).

Regards,

David


At 10:36 AM 8/29/2005, Baumstark Michael-EMB043 wrote: 
Chris:

What you have observed may not actually be a BUG, at least in terms of functionality. It sounds more like you are reporting the lack of rule generation from the GUI menus. Whereas a manually constructed rule actually does behave as you interpret the rule syntax to be defined.

As I recall from several years back from Specctra 9.01 (UNIX) days, the GUI features (via at SMD- thru, etc.) were added primarily as a new shortcut mechanism to faciliate via-in-pad controls as a quick switch setting, PCB wide, instead of having to use the then and still working method to call out every padstack and allow a specified via for via-in-pad (for our purposes this was restricted to micro-vias only and legal just about anywhere a micro-via would fit). It appears that you may have uncovered one of those undocumented features, or more correctly stated, added functionality within the rules heirarchy missing the GUI menu picks. It may have been an intentional "oversight" to keep other GUI menus in heirarchy rules less cluttered due to the practical application at the PCB level. (But this is very good to know and thanks for posting your observation.) Did you actually test out the functionality when you applied this rule to a class for fanout and/or autorouting? It seems you have said so: but just double checking.

I have discovered that you can perform a number of commands on the command line that is syntactically correct and will stack up in the rules.do log file just fine as well as replay later on without error; however, I believe that not all commands actually work. Mostly I stick to the GUI menus lately or at least adhere to the syntax that can be generated from a GUI, so this observation is a dated statement.

If you discover that this is working, it may be worthwhile to keep track of those commands that work, AS well as those that do not, especially when there is not a supporting GUI driven command.

I suspect that Cadence will log your "Bug" observation, but due to a number of significant functionality enhancement requests already on queue, this one item may be a low priority line item. So in the meantime, if it does work as expected you can tuck it into our "Bag of tricks" as an undocumented Bonus feature.

P.S. - I will assume that you are well versed in allowing through-hole vias within SMD pads and in particular your design group "DFM Guidelines" will allow them in BGA pads under certain "manufacturing" conditions?


Sincerely yours,

Michael Baumstark

Staff PCB Designer - BSEE, CID+
Motorola - Advanced Product Technology Center

-----Original Message-----
From: icu-pcb-forum-bounce@xxxxxxxxxxxxx [mailto:icu-pcb-forum-bounce@xxxxxxxxxxxxx] On Behalf Of Christopher Nunn
Sent: Wednesday, August 24, 2005 4:23 PM
To: icu-pcb-forum@xxxxxxxxxxxxx
Subject: [PCB_FORUM] Via at SMD Thru

Hello group,

I have uncovered what I think is a bug in SPECCTRA.

I am trying to route a BGA pin top side to a bottom side SMD component. I want the thru via to be placed in the SMD pad. The nets are power and ground and have been set up as CLASS POWER.

In specctra, in the GUI interface, I see a button under the PCB/Rules/Wiring/General for "Via at SMD Thru"
The same button does not exist under CLASS/Rules/Wiring/General. HOWEVER, when I manually type at the command line: rule class POWER (via_at_smd on (grid off) (fit off) (thru on)) specctra understands it and does what I intended it to do.

It seems impossible to accomplish this through the GUI interface.

Can anyone else confirm this?

Thanks,
Chris Nunn



David Price

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