Process Perspective on Cleaning Array Packages
The people at Austin American Technology have been cleaning surface mount array packages since they were first tested some 30 years ago. Early array packages generally had a generous space provided by pins or columns to compensate for thermal expansion coefficient (TCE). Early testing identified the reliability concerns associated the early solder joint failure in the corners of array packages without compliant metallurgical connections. Read more.
Development of High Energy Systems
Solder balls quickly replaced the pins and columns as they were less expensive and were more manufacturing friendly. They came with there own particular problems. Collapsible balls (they melt) or non-collapsible (they don’t melt) were the flavors of the surface mount array packages in the 1990’s. The non-collapsible ball gave a little more cleaning space, but did not self-align as well as the collapsible version of the interconnect on larger packages. Both were relatively easy to clean until the I/O count went beyond 100 and then things get more challenging. In the late 1990’s Austin American Technology introduced and patented a high energy inline cleaning and drying system with vastly superior cleaning, rinsing and drying energy capable of cleaning these array packages. Read more. Click here for Product Information.
Development of New Cleaning Verification Systems
Cleanliness verification of array packages remains a concern today because it is hard to visually inspect under surface mount array packages. Ionic cleanliness testing using the Resistance Of Solvent Extract (ROSE) test became more important to assess cleanliness especially on impedance sensitive or high frequency circuits with array packages. The issue with ROSE testing is that the new fluxes were rarely soluble the Isopropyl and water mixture used to dissolve and measure the remaining flux residue. To solve this problem Austin American Technology introduced and patented the Mega Ion cleaner/tester with multi-solvent capability.
Development of New Cleaning Design Standards
QFN’s now dominate as the small array package of choice. Cleaning under these packages does not get much harder. QFN’s come in mutiple types of leadless pad-to-pad designs that make cleaning flux both difficult and unpredictable. QFN’s require high energy cleaning systems and good board design to provide the confidence that the highest reliability and performance can be achieved. Austin American Technology has lead and participated in industry studies to develop new design guidelines for effective cleaning of assemblies with QFN’s. Read more.
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