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AdBemt
Posted - 26 Feb 2020 : 21:58:02 Hi
I'm currently changing my footprint library to be IPC-7351 compliant. But this creates a problem, as reloading this footprint in a existent design creates a rotation of all the effected parts.
Is there a way to modify the orientation angle of a group of parts in one go? Rotation is not helping as all the parts are rotated around one point.
Help is greatly appreciated.
4 L A T E S T R E P L I E S (Newest First)
jameshead
Posted - 28 Feb 2020 : 07:18:08 In the real world assemblers don't really care what rotation you used as long as you are consistant. Differnet component manufacturers are a mixture of orientations in tapes. Most assemblers I've discussed this subject with would prefer customers to keep to one rotation standard for all devices rather than have customers having different footprints for different devices from different manufacturers aligned differently on reels.
Most competant assembers use CIM software that will analyse a customer suppled centroid CPL and automatically change the rotation (theta) value to be suitable for their assembly lines based upon the footprint entry the customer has included in the centroid CPL file and the component manufacturer and reel they have details for. They create rules for each customer. Telling an assembler you're using IPC-7351 and either Rotation A or Rotation B makes this learning and setting up easier and quicker for them.
As to why there are two rotations this is what I've learnt from an individual who was on the IPC-7351 committee when the original rotation A standard was included and when the rotation B standard was added, so it's really hear-say so take away from it what you will.
The original IPC-7351 standard was going the way of what is now the Rotation B standard until the meeting for the final vote when one member of the committe then made the case for changing the rotations to what is Rotation A and was able to persuede a slim majority of members present to adopt the Rotation A standard.
When the revised IPC-7351 standard was developed the Rotation B was added as a large number of people who'd adopted IPC-7351 had ignored the particular part of the standard for rotation and carried on using their own standard which in a large majority of cases happened to be what is now Rotation B.
feynman
Posted - 28 Feb 2020 : 06:46:59
quote:Originally posted by AdBemt
I think it would be better if there is one default way for the default rotation.
That ship has sailed, I guess. There is the IPC standard in two flavours now, the IEC standard and the EIA standard. In addition to that there is a lot of software that uses none of the above standards. The best you can do is keeping at least your library consistent. Either way the assembly shop has to spend a lot of time figuring out the rotation you used.
AdBemt
Posted - 27 Feb 2020 : 20:46:25 Oke thanks for the tip. I think this could do the trick for me.
you have a point about the 7351B rotation levels. The A and B level are a little bit confusing. It feels a little bit like the IPC has problems making up there mind. I think it would be better if there is one default way for the default rotation. I notice that different EMS company also has another preferences for the rotations.
jameshead
Posted - 27 Feb 2020 : 10:44:46 Have you absolutely set upon a particular rotation level? The first incarnation of IPC-7351 had only one rotation whereas the revised IPC-7351B has two different rotations: Level A and Level B. The newer Level B standard fits better with the supplied Pulsonix libraries and displays better with the aspect ratio of a widescreen monitor.
One thing you could investigate is to output a CSV file before you change footprints in a design, then edit the CSV file in Excel to change the rotations.
Then reload the design with the new footprints, and use "Import Component Placement CSV Data" under File > Import Design Data
I've not tried this myself. Just reading your query I thought this might be the way I'd go about doing it.
