Cleanliness as Part of a Process Qualification

Cleanliness is a critical factor in product performance and reliability and should be given special attention during qualification. The qualification of a process for cleanliness is three-fold.

Three Steps for Process Qualification

• Electrical assessment of residues in high-humidity environments

• Ionic analysis that separates and quantifies ionic and organic residues

• A process control tool to monitor and provide pass/fail determination

Secondary Processes are Important, Too

Producing test specimens as close to the final product as possible is critical to conducting a successful, accurate qualification. Building a test coupon with only primary paste and reflow, or wave soldering process, will only give you half the picture. Secondary processes such as rework/repair and localized cleaning are just as important and must be evaluated as well.

Electrical evaluations, such as SIR, that involve defined pad-to-pad or hole-to-hole spacing can be difficult to accurately perform on product assemblies. This is the reason that test coupons have been developed for electrical and mechanical assessments of assembly processes and materials.

Using the Umpire 2 Test Board in Process Qualification

The Umpire 2 test coupon allows for evaluation of through-hole as well as top- and bottom-side reflow processes. Assembly requires glue attachment of SMT components on the bottom-side. Footprints are included for 1206, 0805 and 0402 SMT packages, as well as BGA, QFN, QFP and DIP components. The Umpire 2 also includes IPC B-36, B-24 comb (both with and without solder mask) and Bellcore electromigration patterns. In addition to paste and reflow, glue cure, and wave solder process evaluation, there are also areas of the test coupon that lend themselves to hand soldering, localized cleaning and the use of temporary solder mask blocking during primary wave soldering. These features make the Umpire 2 ideally suited to addressing both ionic analysis (bag extraction followed by ion chromatography testing) as well as electrical assessment (SIR test patterns).

Foresite suggests sending the Gerber files to your board fabricator to have them produce your Umpire 2 test coupons with the same materials and processes as your production boards for an accurate representation of your product. This will also allow you to address any potential bare board issues (e.g. cleanliness, solder mask porosity) as well.

For more information, or to acquire Gerber files, Umpire 2 boards or component kits for your process qualification, contact us.