PCB Auto-routing software: Cadence Allegro / SPECCTRA

[deef]

Hello,

In the past, I've always hand-routed my boards in software from a netlist and rats-nest. Obviously, it's a tedious and horrible way to do it.

Now, I'm looking for a software package to do all that hard work for me. Up until now, I've been using Cadence's Orcad Capture/Layout to make schematics then translate them into boards.

Does anyone have any experience with Cadence's Orcad Allegro for automatically turning my netlists and parts into fully routed circuit boards? In a perfect world, I'd love to just define a bunch of parameters and DRC specifications then press a button for the process to begin. But, I know it's never that easy

So, what do you folks think about Orcad Allegro/SPECCTRA? Also, if not Orcad, what's your favourite PCB design studio?

Thanks,
deef

 

[TurboXS]

People seemed to be very polarised on auto-routers.

We use Altium and you need to set up lots of design rules for the autorouter if you want it to auto-route reasonably.

HOWEVER there is a lot of work in placement and tidying up up the auto-routed board that some would perfer to just do it all by hand.

 

[itsmoked]

Turbo is dead on.

This has been discussed a lot, recently enough, to still be completely valid responses.

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Keith Cress
Flamin Systems, Inc.-

http://www.flaminsystems.com

 

[Comcokid]

The circuit boards I personally do have analog or RF, unusual shapes, or are restricted to double sided where I want one side (as much as possible) to be ground plane. Since I started doing PCBs with red/blue tape on mylar, (in the pre-Smartwork era). I've continued to hand-craft the boards I design using Protel/Altium with the interactive manual-router.

However, I worked at a company where they used an outside design house. One design was crammed with RF, Analog, multiple FPGAs, high-speed clocks, fine-pitch connectors. I designed using ORCAD schematic, wrote up a 10 page document describing signals and my thoughts, and accompanied by a AutoCad drawing/sketch of the board outline, mounting holes, possible connector locations for daughter boards, etc. The outside design house used full-blown Allegro with a high-end autorouter, and would turn the completed multilayer board layouts around in just a few days.

It is astonishing what can be done with the high-end routers in the hands of a PCB designer who specializes in the software package. The question is, will you be using the autorouter enough to become proficient at it?

 

[melone]

Autorouters are wonderful in moderation, and with PLENTY of supervision. Expecting to "reasonably" route a board from scratch with an autorouter is subjective. An autorouter is only as good as the rules that the user provides. In other words, put enough constraints in it to yield an accpeptable result, but not too many to prevent it from routing.

One method that I've found that works pretty well (using Cadence Spectra and/or Mentor Hyperlynxs) is to autoroute in stages, verify routing is acceptable, tweak by hand when neccessary, then lock the traces down to prevent rerouting. Sure this takes a bit longer, and isn't as exciting as pressing a button, crossing your fingers and hoping for the best, but it seems to work reasonably well for my level of complexity. (6 to 12 layers, with 1 to 4 layers of HDI on either side, 3 mil space / trace, etc.)

Hope this is helpful!

 

[MacGyverS2000]

Quality board layout engineers will spend years learning how to set up the rules properly for an autorouter, and even if you put yourself into it full time you can expect several months of tweaking to get something reasonable. Even the great guys don't just press a button and expect quality out of the box. If you've never set up rules before, you'll spend several weeks getting something that looks nice, press the button to get 90%, then spend the next several weeks tearing up and rerouting tracks to get to 100%.

An important question is "What size boards are you routing, and what is their density?"

If you're routing a 3" square dual-layer board with 50 components, an autorouter is probably going to be more of a hinderance due to the amount of time it will take to set up. If it's a 12" square 12-layer board with 2,000 components, an autorouter will only help you if you spend the time setting it up correctly.

Me? I do all of mine by hand up to 4 signal layers, TSSOP/0403 packages packed fairly dense. Anything beyond that and the autorouter gets to take a shot.

Dan - Owner

http://www.Hi-TecDesigns.com

 

[zappedagain]

About five years ago we did a complex but low speed (about 10000 nets) digital design in Allegro on an 9" x 11" PCB. With an experienced Allegro designer the PCB worked well on an 8-layer PCB.

About a year later we had a new designer lay out a similar design. He chose to do it by hand and got the same performance level on a 4-layer PCB. This design had more engineering time but a significant cost savings on the bill of material.

I haven't found an autorouter that I like yet (although I've never worked with a package that cost over $20K either).

 

[cbarn24050]

I use a router by Bartell, a german company, It's at least 10 years old. Ive never failed to get 100% routing success. Vutrax, an americasn company, used to use it on their systems but they make their own now. Both systems are highly recomended.

 

[MacGyverS2000]

cb, What is the complexity level of your boards? # of layers? Trace/space? BGA?

I could always get 100% route on an 8-layer board 12"x12" with 10 components, but then that's not very challenging

Dan - Owner

http://www.Hi-TecDesigns.com

 

[cbarn24050]

Not so dense these days now we have the microcontroller. One to hand has 80pin flat, 28 pin soic, 32 pin dip, 2 off 20pin dips, 2 40pin headers plus descretes. 2 layer, 3"x 2".

 

[melone]

100% hookup does not a good design make....

 

[MacGyverS2000]

I believe that should be 100% hookup does not a good design guarantee...

Dan - Owner

http://www.Hi-TecDesigns.com

 

[cbarn24050]

Its not the softwares job to do the designing, not yet anyway.