SMT007 Magazine

SMT-Apr2016

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April 2016 • SMT Magazine 27 bEsT-PracTicE ProcEss PrEParaTion for Pcb assEmblY The first step is to obtain the available prod- uct data from design. This can be challenging because of the many variations of native CAD data formats. Many process preparation tools in use today are unable to use the native ECAD for- mats, which has led to alternative data formats: so-called CAM data exports, such as Gerber files. These unintelligent formats, however, are not designed to hold anything other than very simple information about the product design. Using these formats with limited information then requires an extensive reverse engineering of a sample product to gather enough useful data to be able to complete the process prepara- tion stages. This is a significant bottleneck to the process and inevitably results in frequent mistakes being made. A better alternative is to use the standard in- dustry format ODB++, which can be easily ex- ported from almost any CAD system and con- tains all of the required information for assem- bly process preparation. It is a quick and easy transfer completed in a few minutes compared to days of needless engineering work recreating what was already known to the designer. How- ever, a complete process preparation system will also need to cope with the CAM formats of information such as Gerber files, should these be the only ones that are made available to the manufacturing operation. Tools that can assist with the reverse engineering process can make a significant difference in the time needed with the minimum number of mistakes. Using the reverse engineering method should only ever be the last resort. Qualifying the product Data Model against the BOM Once the product model information has been derived from the design tools, it needs to be qualified against the manufacturing bill of materials (BOM). One PCB design can service many products and variations, so it's important to be able to differentiate between these vari- ants to ensure that the product is built correct- ly. The BOM needs to be used to define which placements and other components should exist for any particular variant, and what the actual materials used will be. The BOM is based on the PCB design data, Figure 2: Data preparation using industry standard oDB++ transfer from eCAD creates a more streamlined and error-free process.

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