Streamlining new product introduction
management of part libraries to be on the individual machines, significantly duplicating the part data across all production lines.
Figure 4. The solution: streamlined NPI process from design to manufacture.
is inconsistent with the other components. Most PCB manufacturers maintain
a master parts library that contains the electrical data associated with those parts. Being able to enhance this library with the addition of physical package information can deliver significant benefits in component savings. This accurate physical package data can be compiled manually by analyzing individual data sheets, but it is more cost effective to leverage existing component package libraries that have been developed over many years and are associated to the manufacturer part numbers for easy identification and usage. DFM techniques help in a number of
ways to reduce component cost in PCB assembly. Process defects that occur during assembly not only mean increased work in progress (WIP) while the boards are repaired but also mean that replacement components may need to be used, further increasing the component costs. When accurate pin terminus
information is available, it allows the DFM analysis to check the toe-print contact area to the corresponding land pattern on the PCB. Performing this task for each variation on the AVL ensures that any components that are incorrectly sized for the pad can be rejected before they cause significant quality and reliability issues during the assembly process. This analysis can also detect more extreme component selection problems where an incorrect package size has been incorporated in to the mBOM, such as a 1206 package being used on an 0805 land-pattern. Although
more obvious, it is typically not detected until the initial sticky tape run, with the result of this being increased costs to resolve it. Accurate component package
information also provides further benefits for design for test (DFT) analysis. The ability to automatically determine if test points and vias are accessible when in close proximity of component outlines can save expensive and potentially unreliable fixturing at electrical test stations. Seemingly small details, such as the chamfer on the corner of integrated circuit devices indicating pin one, can mean the difference between whether a point is accessible or not. Accurate package pin data can be
further leveraged for flying probe test. The requirement here is to be able to move the probe contact point away from the center of the pad. It is preferred to position the probe contact point at the end of the pad. This provides a more reliable contact point as there is less chance of the probe being deflected off the pad. For pick and place development,
being able to centrally manage placement equipment libraries provides significant benefit in component costs. Each process engineer can leverage the work done by co-workers to speed up the SMT program development process. This is only possible for NPI solutions that provide a mechanism of downloading part data to the machine in conjunction with program recipes for placement locations. Tools that only provide the program recipe require
Initial process development Once a new product is ready to be introduced to manufacturing, its impact on the existing lines must be determined. Most PCB manufacturers today operate in high mix production lines where product changeover is the significant issue, rather than maximum throughput of the line. In other words, sacrifices to throughput are acceptable if it reduces the change-over time. Most PCB assemblers have engineers who use spreadsheets to determine which products should be grouped together, assigned to which lines, and built in which order to make the necessary schedule. The need is to be able to react to constantly changing situations as product build requirements change or material shortages occur with different line availability. Component availability can create
significant problems deciding which products to run down which production line. This is a dynamic situation that can change at any moment. A higher priority product may suddenly need to be produced having an immediate impact on the component needs of the warehouse. Being able to automate the process of analyzing the current line set up to take in to account lot size, priority, change-over time, material needs, number of operators, machine downtime and number of shifts will bring significant benefits in being able to deliver the maximum number of products in the least time. This level of automation allows manufacturers to be able to react to changes in product priorities and material levels so that “what-if” scenarios can be played out quickly and accurately as changes evolve.
Summary Given that the component cost of producing printed circuit boards is the single largest factor, those PCB assemblers that manage the challenges of manufacturing BOMs and AVLs and make them work for them will be the most profitable. Having software solutions in place that allow the most flexibility to deal with the challenges that exist in managing component usage creates a competitive advantage in the market.
Mark Laing is product marketing manager
for the Valor division of Mentor Graphics Corp. He has more than 16 years of experience in the PCB assembly and test industry and holds two
patents. A native of the UK, Mark has lived in the U.S. for the past 11 years.
20 – Global SMT & Packaging – Celebrating 10 Years – December 2010
www.globalsmt.net
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