Printed Circuit Design & Fab - February 2009 - (Page 30)

MATERIAL rEGiStration adVaNCed registration Systems An integrated registration control system can provide feedback for continuous improvement, increasing overall process yields. by NEIL CHILToN Whether we operate in boom times or an economic downturn, improving yield remains the major challenge for all PCB companies. In the good times, higher yield means higher capacity, shorter lead times, improved factory utilization and better profits. In the not-so-good times, it means all of the above plus something much more important: survival. For most engineering managers the scrap pareto will be one of their vital business tools, helping to identify the causes of product failure thus driving improvement. It is a fair bet that you could take a scrap pareto from any shop globally and see the same top five categories – though not necessarily in the same order. It is also a near certainty that “registration” would be included within that top five. However, while a category like “innerlayer opens” can generally be identified in one or two process areas (AOI and E-Test), “registration” is often used as more of an umbrella term with its pernicious effects seen in a number of process areas. The greatest proportion of registration scrap results from having applied incorrect innerlayer scale factors at CAM. The impact of this is costly in technical, commercial and resource terms. The ability to get innerlayer scale factors right the first time at CAM is essential for all manufacturers of multilayer PCBs, and especially those in the quick-turn business. In principle, the correct scale factors to apply at CAM are determinable as a function of material and process influences. The following factors should be considered. ■ The materials used in the stackup • Vendor and resin system • Core structure (glass construction, etc.) • Copper weight and copper distribution (signal, mix, plane, etc.) • Prepregs used (quantity, glass style, resin content, etc.) ■ Press cycle and Process influences ■ Grain/Fill (warp/weft) influence ■ Other factors • effect of adjacent cores, position of the core in the stack, mass lamination vs. pin lamination However, as anyone who has had responsibility for the lamination department in more than one PCB shop will testify, scale factors that are good for a specific set of materials in one shop will likely not be good in another shop. For instance, the influence of the shop’s specific processes – particularly the press cycle – are critically important. Being able to predict scale factors correctly at CAM is generally achieved by one of the following four methods: individual experience, a data-driven intelligent system, godlike powers of intuition or luck. In practice, however, individual experience relies heavily on both god-like powers of intuition and luck, and it is unlikely to be a method of choice. Taking a manual approach to a data-driven system will probFEBRUARY 2009 FiGurE 1. A representation of the non-precision method of analysis and correction. 30 printEd CirCuit dESign & fAB

Table of Contents Feed for the Digital Edition of Printed Circuit Design & Fab - February 2009

Printed Circuit Design & Fab - February 2009 Contents Our Line Market Watch Around the World Happenings ROI Tip Jar BGA Bulletin Interconnect Strategies Final Finsh Forum Defects Database Embedded Active Components In Multilayer LCP Packages Simulation: The Need for Speed Advanced Registration Systems The DC Design Squeeze Ad Index Do You Really Want a Better Autorouter? Designing With Conductive Materials, Part 1 Off th eShelf Marketplace On the Forefront

Printed Circuit Design & Fab - February 2009

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