TMDSLCDK138: Footprints with thermal relief

Fidel Herrera

Part Number: TMDSLCDK138
Other Parts Discussed in Thread: OMAP-L138

Hello,

I am having a look at the board design archives of the TMDSLCDK138, available here: http://www.ti.com/lit/zip/sprcaf3

I have noticed that some padstacks contain a termal relief flash archive. Here I have attached a screenshot so you understand what I mean:

As you can see, there is a file in the flash field of the thermal relief called "BLANKTHERM_4C". However, a rectangle is selected in the geometry field. I assume there is something wrong with this. In any case, when I export the libraries of the .brd archive I get no file called "BLANKTHERM_4C" and therefore I can't recreate the footprint.

My concern is that the footprint may be wrong. However, I have used several gerber viewers to examine the gerber files of the board and none of them shows any thermal relief shape in those pads.

So my questions are:

-Do the padstacks actually have a thermal relief?

-If so, why doesn't it show in the gerber files?

-Can I find those flash archives somewhere to correctly reconfigure the footprints?

I hope I have explained myself correctly.

Thanks,

Fidel.

over 7 years ago

0 Yordan Kovachev over 7 years ago

TI__Guru**** 161600 points

Hi,

Just wanted to let you know, that this has been forwarded to the design team. They will post feedback as soon as they have any.

Best Regards,
Yordan

0 Yordan Kovachev over 7 years ago in reply to Yordan Kovachev

TI__Guru**** 161600 points

Hi,

I don't have the exact ifno, but can't you get this from the LCDK layout files:
www.ti.com/.../getliterature.tsp

There should be a cadence PCB layout in the zip above and you should be able to measure the OMAP-L138 footprints from it.

Best Regards,
Yordan

0 Fidel Herrera over 7 years ago in reply to Yordan Kovachev

Prodigy 80 points

Hello,

That's the archive I have been using. Problem is if you look at the screenshot I attached in my previous post there is a flash archive in the thermal relief which teoretically serves to define the shape of a thermal relief pad. That thermal relief is actually non-existent in the gerber files nor it shows in any layer of the pcb, a fact which confuses me.

Either way, the QFN layout guide discourages the use of thermal relief figures in the ground pad vias. http://www.ti.com/lit/an/sloa122/sloa122.pdf (page 3) so I guess the gerber files are correct. I just want to make sure. There are other vias with the same problem.

Regards,

Fidel.

0 Yordan Kovachev over 7 years ago in reply to Fidel Herrera

TI__Guru**** 161600 points

Hi Fidel,

Sorry, I don't have so detailed information about the device. Let's wait for the HW designers to provide their feedback.

Best Regards,
Yordan

0 Bill Taboada over 7 years ago in reply to Fidel Herrera

TI__Mastermind 42545 points

Hi Fidel,

I've looked at both the cadence file and the gerber and I find the square thermal pad under the part as expected in both. Below is a capture of the gerber view of the top two layers showing the square thermal pad in the center of the part and beside it is just the ground layer. The square pad appears to be present on the top layer and the vias without thermal relief are present on layer two. This is what I was expecting to see so I am trying to understand the issue you are highlighting.

Regards, Bill

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TMDSLCDK138: Footprints with thermal relief