Another JLCPCB issue

the tape, so that makes horizontal zero degrees".

Jon Elson -- Thanks. I printed that out. A perfect example of why (as a beginner) much of the process was frustrating. That statement is NOT something that is clear (at all) to a novice. My software places horizontal at 90 or 180......so there you go......and then there's a circle with 0 at the top........so again, there you go.

Silly me.

If you are not sure how your board is to be manufactured, you're at an extreme disadvantage expressing this information to anyone else.

Before you set board edges on a blank layout, you should already have a pretty good idea just how the board is going to hit the assembly line in its panelized (or otherwise) form - and just what automated steps are available/required, from JLCPCB or any other vendor/internal department you may be aiming for.

As previously stated "as off bandolier is 0 degrees".

RL

tirsdag den 13. april 2021 kl. 17.58.44 UTC+2 skrev legg:

there's an IPC standard for CAD,

but afaiu you can't necessarily thrust that an assembler or footprint follows it

I know exactly how it will be manufactured. I give the manufacturer my design files and if there are any concerns they ask me. So far it has worked very well.

Not for me. Every contact assembler I have worked with has handled the panelization to suit their processes. That's how it works best. They do what they do well and I do what I do well. I give them design files that meet a standard and they know how to implement my design on their equipment.

So how many degrees does the part get rotated? That's what they need to program the machine. You still haven't explained how they figure that out from the number I give. You are ignoring that they orient the board in the machine to suit themselves. I have no control over it and I can't factor that into my data. So trying to assume an orientation of the part on the reel is still not adequate information.

You also have not explained how to decide the rotation direction and another fly in the ointment is how to specify the rotation of parts on the bottom side not to mention the X,Y directions for the bottom side. JLCPCB gets around that sticky wicket by not assembling parts on the bottom side. I'm not so lucky.

This document is amazingly limited. They address the one issue of "where is zero degrees?" ignoring the issues of rotation direction or anything else. Very incomplete.

A contract assembler will interpret your drawings to fit their machines - fair enough.

However, in PCB artwork, the original instructions are encoded in your files, to anticipate intended later assembly methods and machinery.

The IPC reference given is drawn from industry practice - it doesn't define it.

Orientation of the part, on tape or bandoliers shows up in the part mfr's spec, to determine 0 degree placement. Pick and place rotation is +xdeg clockwise or -x degrees anticlockwise, in a fab line moving from left to right. For pick and place with feeders on both sides of a production flow, the vendor has to re-interpret the -/+ degrees for his machine, based on the dispenser's orientation.

The accuracy of your CAD dootprint, in accurately reflecting the mfr's part packaging data w/r to orientation is your responsibility. Same with establishing pin numbering for schematic/layout coherence.

If you count on somebody else doing this for you, every time, you will eventually be disappointed

RL

I have ordered assembled PCBs from JLCPCB a number of times, and only minor adjustments to the orientation was needed. I guess they have a DFM tool that checks the PnP file up against the orientation of their line, and adjust that automagically

Your statements contradict themselves. You say the IPC reference is "industry practice" then you say industry varies. You then say that positive rotation is clockwise without indicating if that is IPC standard, "industry practice" or just JLCPCB. Well, it can't be JLCPCB as they rotate counter clockwise...

You say there are no standards, then you provide a description of the standard while not addressing rotations on the bottom of the board. You didn't describe the orientation of the board in all this however. So it won't make any difference what rotation I assume for the parts if the board rotation is not known.

As to counting on the CMs fixing rotation problems, from JLCPCB's web page, "If you don’t know how to change the file, please just place your order, our engineers will review and fix the rotation and polarity of the components based on the silkscreen markings before assembly."...

Your batting average is not so good in this matter. Even JLCPCB doesn't agree with you much.

This is exactly why standards are created and used. Well, used by most other than JLCPCB.

Industry practise precedes the IPC standard. Hence variation in practise.

As long as JLCPCB publishes its practices, there is no issue.

Don't mislead the OP.

RL

I'm glad you finally understand. What you say now goes against your prior post which clearly indicates what you seem to think is a standard. BTW, IPC does produce standards. They have a large part of their web site devoted to it. Check it out.

Wow! I've been doing a little digging with JLC and they are even more perverse than I realized. Not only do they use unconventional conventions for the rotation direction and the zero degree orientation of the part, they use an unconventional orientation for the orientation of the tape in establishing the orientation of the part.

Every data sheet I've found orients the tape from left feeding to the right. JLC seems to orient the tape from the bottom of the page feeding toward the top of the page. To find this information you have to read a FAQ article titled, "Does the red dot means pin 1 in the placement previewer?" This article seems to be saying the red dot in the preview is not necessarily pin 1, rather just a reference that they set.

Why can't these guys get on board with the rest of the world?

I don't know why everyone else is having problems, but I just got a set of boards back and everything was placed correctly, and I didn't have to tweak *anything*. I "just" used the JLC plugins for kicad... ;-)

Is there such a canned solution for Altium? I don't feel like learning a new PCB program (and I just paid for a license update).

yeh ditto

doesn't look like it handles the special rotation, the kicad plugin I've used fixes the rotation with a table of common footprints and how they should be offset

Thanks!

My boards were shipped yesterday. First assembly I've done but now that I know the process and their "uniqueness", further orders will be a cinch. The pain was "almost" worth the price -- alas, amazing what they are giving me for 148 bucks shipped. 4 different small boards. 30 pcs each, one with (35) 0805 passive components on it.

And she was right about "don't worry about it". In the preview, my parts were all over the place, not even close to where my Sprint software placed them.

My electronics hobby has gone from going through the trash at Raub radio/tv repair in 1963 to this. -- pretty amazing.