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shadders
United Kingdom
224 Posts |
 Posted - 29 Oct 2014 : 18:34:46
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Hi,
Not sure if Number One are interested - i used their footprint for a TO-264 based transistor and the PCB outline is 16mm width. The actual Jedec width of the transistor is 20mm.
Perhaps a single transistor use is not an issue, but can be a problem if you closely pack the transistors.
Regards,
Shadders. |
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Iain Wilkie
United Kingdom
1015 Posts |
Posted - 29 Oct 2014 : 21:10:34
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One of the problems with other people's libraries ..... You cannot trust them, you need to double check them always. I have also come across big variations between different manufacturers footprints for the same types devices.
I tend to generate all my own footprints as and when rather than use libs, then I know it's going to be correct, or if it is wrong, I only have myself to blame !
Iain |
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rvpilot
United Kingdom
51 Posts |
Posted - 30 Oct 2014 : 09:16:03
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Totally agree with Iain. I've had a number of costly board re-spins due to using the libraries out-of-the-box ! (i.e. wrong size footprints, SOT23 transistors with wrong pinouts, micro's with swapped pins, etc)
I now have specific PCB footprints in the manufacturers library (i.e. NXP_SOT23, ST_SOT23, etc) as different manufacturers do vary their footprints or devices have non standard lead lengths.
I also create EVERY component I use and verify the PCB footprint against real components and have built on that over the years ... and verify using a proprietary 3D generation tool (creates the PCB from the Gerber or CAD file, then places STEP models on it to verify pad layout and clearances), BEFORE I sent to manufacture !
It's a bit of work up front, but I've not had to do a board re-spin due to bad libraries in over 8 years now ... touch wood !! |
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Iain Wilkie
United Kingdom
1015 Posts |
Posted - 30 Oct 2014 : 09:56:09
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The SOT23 problem is forever on going.... due to non standard pinning conventions. If you have multiple libs with the same named "SOT23" footprint, unless you enable and disable the relevant libs you will end up with a mis-configured SOT23 part. This is due to the library structure using 3 libs to create the component when you use it rather than a single "component" lib that contains the footprint and schematic intimately linked. This is the Achilles' Heel of the EASYPC tool in my opinion, but unfortunately is there to say forever.
Iain
PS ... RVPILOT .... what is the 3D tool you are using ? |
Edited by - Iain Wilkie on 30 Oct 2014 09:58:03 |
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rvpilot
United Kingdom
51 Posts |
Posted - 30 Oct 2014 : 11:06:00
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Iain,
That's why I prefix the footprints with the manufacturer name and the only thing I share across all components is my schematic symbols.
The tool is a complete utility I wrote myself that imports Gerber or GenCAD output files and generates a full 3D model using Alibre Design Professional (now Geomagic Design Elements). I'm also working on a ODB++ importer. It's useful for not only validating parts, but creates a perfect PCBA model ready for designing the enclosures, etc. (looks good in documentation too !)
The tool also creates my BOM's (with variants based on an OPTION component values, i.e. OPTION=USB) it's similar to the new BOM Composer, but more specific to my output format and exports in xlsx or docx formats.
I might turn it into a product if I can write a few more 3d exporters, i.e. SKETCH-UP, STEP, etc. |
Edited by - rvpilot on 30 Oct 2014 11:08:57 |
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Iain Wilkie
United Kingdom
1015 Posts |
Posted - 30 Oct 2014 : 13:48:01
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Rvpilot .... sounds like you have something of interest and if you do turn it into a product, I for one would be interested.
The 3D output in EPC is pretty basic so something like this could be very handy.
Iain
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Benno
Netherlands
79 Posts |
Posted - 30 Oct 2014 : 21:16:05
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rvPilot, if you make it into a product and the price is reasonable it is a +1 for me too.
I was looking into creating something like that myself, also using Gerber and standaard mfg 3d models. That way the tool is independent from any other tools. |
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shadders
United Kingdom
224 Posts |
Posted - 31 Oct 2014 : 14:01:31
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HI All,
Thanks - yes - that is what i will do in future.
I usually check the footprint for the pin spacing, but the outline caught me out in this instance, luckily before sending to PCB manufacturer.
In general, the build your own libraries is the better option.
Regards,
Shadders. |
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toni9999
United Kingdom
39 Posts |
Posted - 03 Nov 2014 : 08:04:37
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Definitely interested in this rvPilot.
Hate having to wait on the mechanics department to to assembly drawings for me. |
Edited by - toni9999 on 03 Nov 2014 08:05:14 |
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Topic |
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TO-264 Footprint