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Design007-Apr2018

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54 DESIGN007 MAGAZINE I APRIL 2018 Refining Output Data Packages for Fabricators The Bare (Board) Truth by Mark Thompson CID+, PROTOTRON CIRCUITS One of the biggest issues PCB fabricators face is the completeness (or incompleteness) of the data output package we receive from customers on a new PCB. In this column, I am going to present what is needed, from a fabri- cator's perspective, for a good output package and why. An Industry-wide Problem In a recent I-Connect007 column, The Perfect Customer, my colleague Dan Beaulieu said that fabrication packages are fre- quently incomplete, thus delay- ing the quote process. I believe that this statement is true for ALL board fabricators! Dan also pointed out that many larger customers that pre- viously had their own in- house PCB fabrication no longer have that ability, and as such, much of the tribal knowledge that was shared between their in-house fabrication and the engineering group in those days has disap- peared. So, a lot of this board fabri- cation knowledge has not been passed on to the new generation of engineers and designers. This leads to incomplete or inaccurate output packages that lead to clarification questions prior to quote, which delay the quote process. In this column, I will discuss which files are needed for fabrication and why. The Basic "Must Haves" Let's start with the obvious. Image Data Many design software packages have multi- ple output types of image data. The four most common and accepted are the following: 1. ODB++ is Mentor's data transfer format. Some of the benefits of outputting ODB++ are: a. The IPC netlist is embedded in the data and need not be sent as a separate file. b. Fabricators using Genesis are looking at a true apples-to-apples comparison; what I see on my screen is the same as what the end-user creating the ODB++ data sees. Oddly shaped pads rotated at unusual angles are not always interpreted correctly with some of the older CAM systems, but this is not an issue with ODB++ data. 2. Gerber 274X, Gerber data with embedded apertures is by far the most common output. 3. Gerber X2 is the new- est form of Gerber output. Not all fabricators are able to use this type of data. Much like the 274X data, X2 has the apertures embed- ded, and additional attributes added as well. 4. Gerber 274D is one of the older types of Gerber output. It requires the designer to send a separate aperture file list or wheel, and is a little more cumber- some than the X types of Gerber with the apertures embedded. With this type of Gerber data, the aperture list must be complete or you will get a phone call from the fabricator for potential unassigned D-codes in the file list or wheel. NC Drill Files This is the file with the hole sizes, plating status (plated or not) and the X and Y hole coordinates.

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