PCB component Zero orientation. - Page 1
Forum section: electronics / general

author: stephen Jones
author_rank: Newbie
timestamp: August 29, 2023, 01:29:50 pm
content: When I add a new component to my PCB package, do I use the IPC-7351 Specification to define its zero orientation, or its orientation on the reel, I seem to find a lot of conflicting information. I have also tried using the Fab3000 ability to generate Pick and place information, and the orientation it comes up with does not match the specifications outlined in IPC -7351 so I am not sure what I should be doing, or does it matter as the PCB assembler will sort it out?

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: August 29, 2023, 01:35:30 pm
content: For consistency probably best to follow whatever your PCB package uses for other parts in its library.PCB assemblers will check & fix as needed, but will be happier if it's consistent

author: SMTech
author_rank: Frequent Contributor
timestamp: August 29, 2023, 02:59:43 pm
content: Either follow existing library parts in your CAD library so you are some way consistent or start from scratch and use IPC. Orientation in tape doesn't mean much, that changes if the parts optionally comes in tube or a different tape width. It can also change between manufacturer tape orientation of SOT26 etc often vary by 180, as a contractor I typically wit until the job is kitted before verifying these details as finding that detail in datasheets sometimes requires excessive effort.On our essemtec pick and place I create new packages using existing Essemtec models, almost universally this requires a 270 degree rotation on any IC's and is very annoying but quick to apply because it is consistent. Had I noticed what was happening when the machine was new I might have overridden Essemtec weird defaults but at the time we were importing files not from CAD but another pick and place machines own strange format (which did base its rotations on feeder presentation). 2 pin devices are typically correct although for a while we had one client who had those out by 90degrees too, much more annoying because they'd clearly realised at some point and changed it, but not across the entire library.Its been a while since I used the Gerber to placement file tool in Fab3000 but I think it prompts you when you generate something to denote the pin1 location and possibly again when you output as to the convention.

author: MR
author_rank: Regular Contributor
timestamp: August 29, 2023, 03:24:28 pm
content: Can anyone give an example of his EDA Application?Default Altium -- 0° for 0402 is vertical - while according to some IPC standard it's supposed to be horizontal (I did not check if there's an option to change the smd angle origin.).Yes it's no big deal, my PNP Application has a group setting for 0402/0603/etc. to adjust the PNP Database rotation for the entire PNP file/components which are assigned to that group.

author: SMTech
author_rank: Frequent Contributor
timestamp: August 29, 2023, 03:43:06 pm
content: Interesting, I don't use it myself but we use Altium for our own designs and zero degrees on 2 pin devices is output to IPC - horizontal pin1 left and always has been, I didn't need to ask someone to change anything. Everyones data importer will work slightly differently but on ours things get messy when otherwise identical packages are in incoming data with different package names for no apparent reason. Then there are translation rules handling this that have orders of precedent. Essemtec for instance will use a rule for a matching internal part number first and they are part number specific rather than package specific.But yes as a CEM I do try and verify all rotational data, it's easier the less there is to check and easy to miss something if the data has random exceptions. Worse is incorrect center definitions.

author: jayx
author_rank: Regular Contributor
timestamp: August 29, 2023, 10:53:04 pm
content: Not sure which IPC-7351 revision you're talking about, but I think in rev B pin 1 was specified in upper left, which apparently was a mistake. IPC-7351C which was never released and was replaced by IPC-7352, supposed to introduce two options for rotation (called "level"): A (pin 1 upper left) and B (pin 1 lower left).Seems that level B is more common as it's been like that in IPC-SM-782, also IEC 61188-7. But in fact the most important thing is to keep it consistent, so don't mix level A and B in your library, othervise it will be a nightmare for CEM.There is a free document with both levels drawings for a various components:https://www.pcblibraries.com/Products/FPX/UserGuide/download/Footprint%20Expert%20Surface%20Mount%20Families.pdf

author: Matt-Brown
author_rank: Regular Contributor
timestamp: August 31, 2023, 04:15:54 pm
content: I have seen many odd rotations specified. For passive caps and resistors dont get a default of 360 (seen that too many times).0 pin 1 left, pin 2 right is what we use for our Jukis.Having said that on sots I dotn like how Juki define theirs.We usually go feed direction (tape punch holes) to left, so sot-23 is almost always 0 if center pin is to left, then rotate counter clockwise to get to 90 etc.We as contravt manufacturers usually have the cad oepn and compare all rotations to the customers pick and palce and adjust accordingly.As a side note: we do a first off the machines on double sided tape and then check all rotations against what either the customer has supplied for parts, or our own purchasing group have bought. There are too manyoptions for different orientations in tape, or tubes, or matrix trays