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PCB-July2014

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July 2014 • The PCB Magazine 57 only a few applications read ODB++ reliably, there are countless more that read Gerber with near-perfect reliability. This is because: • The Gerber format is simple • Its specification is well-written, easy to read, detailed and precise • Most of its implementations are mature • As it is so widely used, the implementations are thoroughly field tested, so most bugs have been ironed out • The format is supported by excellent free viewers such as GC-Prevue Advocating the adoption of a new and much more complex format to eliminate simple bugs is a very curious solution indeed. Consider only that a CAD software developer struggling to produce a simple Gerber file correctly is not miraculously going to write a bug-free implementation for the more challenging ODB++ format. If one wants bug-free software it is best to stick with Gerber, as Gerber is a simpler and more mature format than ODB++, it is far less prone to bugs, and its bugs are far easier to find and resolve. Switching to a new imaging format introduces a whole raft of new issues and bugs that would take many years to sort out. Imaging software is complex and takes a long time to get right. Adopting ODB++ to solve bugs in Gerber output is like using a sledgehammer to swat a fly: The solution is far more damaging than the issue ever will be. Table 1 summarizes Coates' claims regarding the benefits of ODB++ vs. Gerber: Here is my take on the aforementioned benefits: 1. False. A simpler, more reliable format in fact needs less diagnostics 2. False. An error can be more easily identified in a simpler format. 3. False. ODB++ is not miraculously error-free. 4. False. IPC-356 supports the actual customer net name. It may be that the software Coates uses does not display it, but this then is a problem in that software. 5. False. Gerber has negative apertures and so can handle planes perfectly. (I should add that this is the first time I see the claim that ODB++ is more compact than Gerber!) If these are the benefits of ODB++ and the reasons for adopting it, then Coates' argument collapses. More importantly, Coates omits to mention the difficulties in adopting ODB++. Over the 20 years that ODB++ has been available, it has taken just 10% of the market share, with Gerber accounting for the remaining 90%. If ODB++ offers all the advantages espoused by Coates in his article, there can only be one of two reasons for its minimal uptake: • The PCB industry consists largely of morons • There are downsides to using ODB++ As I do not think this great industry is in the hands of morons, I believe that there must table 1. GERBER—THE SMARTEST WAY FORWARD continues

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