Question for specctra experts

[igorsat]

By default specctra uses only two decimal places, but I would like to set grid for vias with higher precision. Let’s say I would like to set grid spacing to 6.6716 mils. How do I do that? If I change the units to microns I can get additional decimal place but that’s it. I’m browsing documentation, but I can’t find a command.

igorsat

 

[mr.anderson]

Which version of SPEC*TRA you are using?

 

[igorsat]

By default I route all PCBs by myself, but I was persuaded to try auto-router after 3 years by a coworker who is using it (we have version 10.2) for simple designs. I thought they improved significantly in that time, but I guess they didn’t. After four hours of gate-swapping I ended with very simplified design, from the routing point of view (896 pin xilinx BGA connected to BGA SRAMS), but spectra was unable to complete it on 6 layers (4 signal 2 plane). I spend a day setting up do files trying all exotic things I could think of but this auto-router simply isn’t capable enough. After that I gave up and route the design by myself in a day.

Now I have a board with 0.8mm pitch BGAs and some tinyBGAs with even tighter pitch, so I thought I would give auto-router another try, but it can’t place vias between BGA pins, because I can’t setup via grid accurate enough. In general the design is pretty simple and it isn’t a challenge for the brain, so I thought this is ideal for auto-router, but…

After several hours of searching and trying various settings I gave up and turn with the question to this message board. I still think I will end up routing design by myself…

igorsat

 

[mr.anderson]

Well, I checked it in SPEC*TRA v15.0, using All*gro as PCB editor, all works fine with precision down to 10 micrometers and probably less too.

What is your PCB editor? The design resolution is typically set by the PCB editor in design file (something.dsn) that gets exported from PCB editor to SPEC*TRA. So, you probably should check your PCB editor settings or increase the resolution in .dsn file by hand (in string like " (resolution MM 10000)").

HTH,

 

[igorsat]

I’m still using good old P*CAD2001. It is showing 2 or 3 decimals in editor, but in file positions are stored with 7 decimals. The problem is, if the board is large (20x30cm) and the origin is in the left-bottom corner and if the grid is set to only 2 or 3 decimal places then vias in the upper-right corner will not be placed between the 0.8mm pitch BGA pins, regardless if microns are used as a main unit.

I will try to locate the “resolution” string as you suggested.

igorsat