The Role of EDA Tools in Creating Fab Notes


Reading time ( words)

When discussing fab notes, there’s a lot of focus on what designers should and should not include in the package. But what is the role of EDA tools in this process, and can intelligent data formats streamline the tasks and help eliminate fab notes that are less than fantastic? In this interview, Pat McGoff, market development manager for Mentor, a Siemens Business, speaks frankly about fab notes and what EDA tool companies like Mentor can do to automate this process.

Andy Shaughnessy: What do you think are the biggest problems that PCB fabricators face regarding designers’ data packages?

Patrick McGoff: The biggest problem with the designer’s data packages is the confusion they often cause. Like other contract suppliers, PCB fabricators make every effort to be as accommodating as possible in terms of what kind of design data they will accept. I can remember when fabricators would take in a scanned image of a PCB and digitize it to reproduce the board.

Today, when we say, “Send us the Gerber files,” what we are really saying is “Send us the Gerber, drill, and netlist files, along with drill drawings, route drawings, stackup drawings, and notes,” and that’s just for the fabricators. Contract assembly providers need even more data and information. The problem with this legacy approach is that there are frequently discrepancies between the various files. The netlist file or drill file often does not match the Gerber data because they came from different systems and might not even reflect the correct revision of the design.

Shaughnessy: When there are problems with the fab notes and other data, what is the typical process that the fabricator goes through to resolve these issues? How does that impact the job?

McGoff: When a fabricator sees a discrepancy in the data provided, or if there is incomplete information, they put the job on hold until it can be resolved. The problem is that the delivery clock doesn’t start until the data package is complete and accepted. That five-day turn is sitting in the starting block waiting for the technical query (TQ) communication channel to do its thing. The CAM engineer notifies the manager of the issue, and the front-end manager notifies the salesperson, who then informs their point of contact at the customer side. Then, that information is conveyed to the designer, and only at this point can the correction and clarification process begin. All of this can easily take several days to resolve, so the designer pays for a five-day turn but gets the boards back in eight days.

It’s even more problematic if the fabricator misses a discrepancy in the data package and runs with the erroneous set. This raises a lot of questions, such as, “Which is the go-to file: the Gerber data, the drill file, or the netlist?” Do all your fabricators have the same understanding? Who is responsible for the scrap when that does happen? I believe the larger question should be, “Why would you ever leave the potential for that kind of discrepancy in your process?”

To read this entire interview, which appeared in the August 2020 issue of Design007 Magazine, click here.

Share

Print


Suggested Items

Beyond Design: How to Handle the Dreaded Danglers, Part 2

10/12/2016 | Barry Olney, In-Circuit Design Pty Ltd
In Part 1, I deliberated on how dangling via stubs distort signals passing through an interconnect and also decrease the usable bandwidth of the signal. This is due to the via stub acting as a transmission line antenna, which has a resonant frequency determined by the quarter wavelength of the structure. The conventional solution to this problem is to back-drill (or control depth drill) the vias to bore out the via stub barrels, so that the via stubs are reduced in length if not completely removed. This month I will look into all the possible solutions.

The Gerber Guide, Chapter 3: The PCB Profile

11/30/2015 | Karel Tavernier, Ucamco
The profile defines a simple region in the 2D plane. The proper way to do this is to specify a closed contour: The inside of the contour is the PCB, and the outside is not. It is that simple. Note that such a simple region is solid, without holes. By definition then, a profile cannot have holes intentionally placed within it. These are superfluous and represent an unnecessary and complicated duplication given that drill holes are well defined in the drill/rout file. One can view cut-outs in a PCB as still part of the PCB, just as much as the drill holes are.

TTM: Consult Fabricators Early for PCB Designs

07/02/2015 | Andy Shaughnessy, PCBDesign007
Recently, I attended the Designers Council “Lunch and Learn” at Broadcom’s office in Orange County, California. One of the speakers at this event was Julie Ellis, a field applications engineer with TTM Technologies. She sat down with me to discuss her presentation and some of the ways fabricators can assist PCB designers.



Copyright © 2020 I-Connect007. All rights reserved.