Continue to Site

Welcome to EDAboard.com

Welcome to our site! EDAboard.com is an international Electronics Discussion Forum focused on EDA software, circuits, schematics, books, theory, papers, asic, pld, 8051, DSP, Network, RF, Analog Design, PCB, Service Manuals... and a whole lot more! To participate you need to register. Registration is free. Click here to register now.

What happens when fiducial marks are not on the board?

Status
Not open for further replies.

akhmar

Newbie level 4
Joined
Aug 6, 2004
Messages
7
Helped
0
Reputation
0
Reaction score
0
Trophy points
1,281
Location
Malaysia
Activity points
65
hi all,
in pcb assembly process, the fiducials are required for pick and place machine to load smt components on the board. what if the the fiducials are not on the board, do the components still can be loaded onto the board? does a fabricator add auxilliary fiducial marks to help their fabrication process? cheers
 

fiducial + pcb

Usually, PCB manufacturers add several manufacturing marks. When you send the gerbers you usually send all within the keepouts, but the PCB manufacturer adds the frame, global fiducials and perhaps others like drill calibration, etc. It is the best way to ask your manufaturer about this. PCBs cannot be made without a frame, because it is usually used as holding area at the tinning and plating process, and also the pick and place machines needs an unused area for the transport belt. You can use global fiducials if the required precision is not too high, but if you have small components and fine pitch ones, you will have to use also local fiducials. Otherwise the placing error is too high.

/pisoiu
 

Re: fiducial marks

if the the fiducials are not on the board:
At assembly process, assambly operator will teach his machine several marks which are found on your PCB as reference points. These marks can be a font letter, a corner, a pad or shape which will be used instead of fiducial.


PCB manufacturers won't put any local fiducial.
PCB manufacturers won't put any global fiducial or unused area for the transport belt unless you want them to do so(forex. panelization).
 

fiducial marks

Fiducials should be placed by the layout engineer. They should be named with reference designators such as "FID01", "FID02" etc. One of the fiducials is preferrably used as a primus datum point for the board. The coordinated of the entire board should be changed so that this fiducial is at X0Y0.

(This is also a convenient way to ensure that they are there during layout review before submitting your gerbers)

By giving them reference designators, they can be separated in the pick-and-placement list. This list is then used by the assembly plant. If the board is panelized together with many others, the pick-and-placement list is modified (by the manufacturer) to suit the entire panel.

Fiducials should be placed so that there are no traces un underlaying copper layers. This is important, as the pick-and-placer uses them for board location calibration.

Several size recommendations exist. Check with your manufacturing plant.
 

Re: fiducial marks

Hi

When I setup a Program for Smd mounting if there aren't fiducial marks i try to use any mark that can be ripetible and that cuold be ever on the same position like a Via or a pad or a hole... pick and place uses images to find fiducial marks so you have to find a way to give always the same image.
 

fiducial marks

For the most, it's the design engineer that sends a single image to the manufacturer for them to step and repeat into a panel.
This is the point at which fiducials should be specified to be added.

If you also send a solder paste layer with your data, get the manufacturer to send it back when it has been step/repeated in their front end, with the fiducials added.

This can then be used for best accuracy to make the solder paste screen & placement files.
 

Status
Not open for further replies.

Part and Inventory Search

Welcome to EDABoard.com

Sponsor

Back
Top