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Troubleshooting the innerlayer process: identifying and maintaining proper process controls is key to improving innerlayer yields.

Article Excerpt
An improved awareness of the relationship between key innerlayer process controls and defect modes can help improve both product yields and overall quality. Whether the process is designed to produce ultra-fine line product or more mainstream innerlayers, each of the steps within the manufacturing process can influence both quality and yield. Identifying and maintaining the proper controls and procedures for each process step is a critical first step to maintain high quality while meeting cost targets. This review of the issues associated with the liquid-resist based innerlayer process will provide an overview of the critical issues.

Material Preparation and Handling

The quality of the copper surface over which the resist is being applied has a primary impact on the process defect level. In general, while liquid resists have a better ability to cover surface defects, dents, scratches or burrs on the copper surface, the surface condition can still lead to formation of defects after etching (predominantly opens).

The key to avoiding such issues is to be aware of the different points at which the copper surface can be damaged. Control of the process starts with clear acceptance criteria for incoming copper clad laminate. This should be combined with appropriate levels of sampling and inspection to confirm that quality targets are being maintained.

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Each time clad laminate is handled, there is another opportunity for creation of surface damage. Both procedures and equipment maintenance schedules for sheet cutting and edge cleaning operations...

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