Pick&place files: Component rotation on the bottom side - Page 1
Forum section: electronics / general

author: Lukas
author_rank: Frequent Contributor
timestamp: February 25, 2020, 12:59:09 am
content: Hello Everyone,I recently added Pick&place export to Horizon EDA (seehttps://www.eevblog.com/forum/eda/horizon-eda-version-1-0!/new/#new), but I haven't been able to conclusively figure out how the zero rotation is defined for parts placed on the bottom side. See the attachment for what I mean: Is Q3 or Q2 at the correct angle? This boils down to whether a component is moved to the bottom side of the board by mirroring it about the X or Y axis.So far I've seen software do both, but is there some kind of standard, or does everyone do whatever they please and it's up to the assembly house to determine the proper orientation?Lukas

author: Deni
author_rank: Regular Contributor
timestamp: February 25, 2020, 07:08:50 am
content: I am not sure that there's a standard, but I prefer Y-axis mirroring. Similar thing to Pin 1 reference location for 0-degree rotation, where I like lower-left corner. Perhaps due to fact that most screenshave better X-axis resolution, so with that kind of orientation you can display part footprint bigger. Our p&p machines (Universal GSM) can transform data any way you want, so it is not that critical.

author: nctnico
author_rank: Super Contributor
timestamp: February 25, 2020, 03:17:39 pm
content: You can ask an assembler but to me the most logical would be to use the coordinates from looking at the top of the board and mark the component as 'mirrored'. This makes checking the XY file versus the design (as seen on the monitor) easy. This is what Orcad's Allegro seems to do. Another issue is the part's origin. Recently an assembler asked me for an placement file which uses the centre of the part as the origin instead of pin 1.

author: Deni
author_rank: Regular Contributor
timestamp: February 25, 2020, 03:44:16 pm
content: All p&p machines use centroid coordinates as a part position reference, no wonder there.

author: Pseudobyte
author_rank: Frequent Contributor
timestamp: February 25, 2020, 04:25:30 pm
content: Here you go! Hope this Helps. Rotation is always from the top in pick and place data.

author: Pseudobyte
author_rank: Frequent Contributor
timestamp: February 25, 2020, 04:39:19 pm
content: As to the standard question. The format is defined in ODB++ as x, y, rot, mirror.When you provide data to a CM they will generally be using some sort of data preparation tool. They will take your gerbers, and your placement data, interpret the rotation mirror and x/y data. They then will correct for tape rotation of parts. As long as you give x, y, rotation, and mirror you should be fine. I would not modify the output of the tool to interpret the rotation based on mirror.

author: Lukas
author_rank: Frequent Contributor
timestamp: February 25, 2020, 08:42:46 pm
content: Thanks a lot for trying this out in Altium. KiCad does it this way as well, so I'll keep the export this way even though it's the other way round in the board editor.

author: Feynman
author_rank: Regular Contributor
timestamp: February 26, 2020, 06:49:59 am
content: I think the convention for part rotation on the bottom side doesn't matter too much (I've seen both). Either way, there is a lot of manual work involved in the assembly shop, since there is no standard format for XY-files.Regarding Horizon EDA I would focus on generation of neat assembly drawings (PDF). I think that's much more important than the actual rotation convention.

author: b2che
author_rank: Newbie
timestamp: December 07, 2023, 12:41:29 pm
content: Hi all, I've been banging my head about this issue today, and enjoyed the nice (and I believe correct) diagram form Pseudobyte (thanks!) However, I think it looks a bit more interesting on a part that is not symmetrical about an axis, so here it is for a SOIC8. You can see the interesting Altium behavior of mirroring over thex-axiswhen moving a part to Bottom. That is, the footprint is mirrored over the x-axis to move it to Bottom, and then the rotation angle is added counter-clockwise as seen from Top.

author: Feynman
author_rank: Regular Contributor
timestamp: December 09, 2023, 05:02:08 pm
content: Here is how Pulsonix does it: