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Advanced registration systems: an integrated registration control system can provide feedback for continuous improvement, increasing overall process yields.

Article Excerpt
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.

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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...

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