To-263-n

[Denisl]

WE RECENTLY USED THE TO-263-5 FOOTPRINT FROM THE PCBSTANDARDS LIBRARY. HAD SOME COMPLAINTS FROM ASSEMBLY THAT THE OVERALL HEIGHT WAS A BIT SLIGHT. AFTER LOOKING AT THE DATA SHEETS FOR THIS PACKAGE I CONFIRMED THEIR ANGST. THE 5 SOLDER LANDS ARE A TAD SHORT AND THE THERMAL PAD DOES NOT EXTEND FAR ENOUGH NORTH. JUST THOUGHT YOU'D WANT TO KNOW.

[Denisl]

Here is the correct one.... <g>

[Tom]

Denis,

Thanks for the heads up. The original TO-263-5 was built per the attached datasheet from National Semiconductor. National Semiconductor has different dimensions than the Texas Instruments part.

If you compare National Semiconductors "Lead Position Overlay" dimensions with the dimensions on the pcbstandards documentation you will see that they are right on the money.

We had a meeting regarding this part and the TO-263-5 land pattern and we decided not to make two different TO-263-5's but to make one (larger) land pattern that will fit both parts. The new land pattern will be available today.

One note: When using the pcbstandards library, please compare the "vendor data sheet" component dimensions with the "pcbstandards documentation" component dimensions. And above all alert us (like you did) when there is a discrepancy. In this case, the maximum overall length of the National part is 14.35 and the TI part is 15.49. That alone is an alert.

[Denisl]

WOW! What a wonderful resource. You guys are the best! Thanks for your promt attention to this issue and the quick resolution.

By the way, I found the JEDEC data on the TO-263. It is JEDEC MO-169A. I have not yet taken the time to do a dimensional comparison to the National/TI versions of this part, but I'd bet that neither of them exactly match the JEDEC standard.

Again, thanks for the quick resolution.

[Tom]

Denis,

I have been researching the TO-263 family of components and have come to the realization that there isn't a standard. JEDEC has the MO-169A document, but no component manufacturer follows their specification.

I also found more information from IPC and their data is different then JEDEC's.

I also located several component manufacturers datasheets and no two match. What a mess. The TO-263 family comes in 2, 3, 5, 7, 9, 11 and 15 pin packages. There are several different versions for each different pin quantity, which makes it even more difficult.

Our only course of action is to build a separate "customized" land pattern for each specification. We're completely upgrading this component family documentation for pcbstandards and building all the necessary land patterns. The current SOT-23-5 in the pcbstandards library will only work for the National Semiconductor part LP3962/LP3965, but the others are on the way.

[Denisl]

Arrrrgh!
<start rant>
Why do they bother with a "standard" if no one follows it? I'll spare all the expletives that come to mind.. It's like the ol' SOT-23. There was originally just one package, numbered as the industry has always numbered semiconductor packages, counter-clockwise. Then, they started using the SOT-23 for dual diodes and LED's. Everybody came up with their own (incorrect) numbering scheme. Just drives me crazy! How is the PCB design community supposed to establish "Standard Libraries" when the semiconductor industry connot conform to PUBLISHED standards?
</end rant>
I guess you're beginning to see that this is a huge problem. While you're looking at the variations of the TO-263, be sure to examine Linear Technology's "DD-PAK" ... it's another variant of the TO-263.

[Tom]

Well the TO-263 component family is sure interesting. We have completed our investigation and have updated our library and documentation with the following sixteen TO-263 decals:

TO-263-2N
TO-263AB-2N
TO-263D2-2N
TO-263AA-3N
TO-263BA-3N
TO-263NS-3N
TO-263AB-5N
TO-263BB-5N
TO-263NS-5N
TO-263TI-5N
TO-263AC-7N
TO-263BC-7N
TO-263NS-7N
TO-263BD-9N
TO-263AD-11N
TO-263AE-15N

[nnewman]

Tom
Where are the library updates you mentioned? I just checked the library files and the last update was 8/4/02.

[randychase]

Originally posted by nnewman
Tom
Where are the library updates you mentioned? I just checked the library files and the last update was 8/4/02.

Check back in a few hours or subscribe to the updates thread. The person who does the updates was on vacation last week.