Stencil Printing for Nerds

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Abstract                                                                                                                                                                       Consumer demand has accelerated the pace of the electronics miniaturization trend, compelling assemblers to develop robust capabilities for 01005 components and 0.3mm pitch array packages in order to remain competitive. The process of acquiring these capabilities can be complex, as they involve numerous interactive factors. To optimize the stencil printing and reflow portions of SMT assembly given the challenging new realities, a process evaluation tool has been developed that provides a

turnkey solution for solder paste performance testing. 

The evaluation toolkit incorporates PCB design with some embedded DOEs, a configurator that calculates sample sizes and bill of materials (BOM) costs, a stencil design, a fully integrated BOM for easy programming and feeder optimization, stepby-

step directions for solder paste performance testing, a soldering reference manual, basic statistical reduction of SPI readings, and a score card. The score card is a key element of the concept, as it enables the assembler to customize the selection criteria based on the specific operation.

This paper details the development of the turnkey test model, taking it from an internal test board to a publicly available, production-line ready kit. It discusses component selection, sample size considerations, cost reductions, maximizing test efficiency, and adding intelligence to the data. The overview examines both user and supplier perspectives on testing methods and highlights key  onsiderations for assemblers. It concludes with opportunities and plans for potential future developments to expand the tool’s analytical capabilities.

Abstract

In the world of solder pastes, one size does not fit all, which is why so many different formulations exist. The myriad of options can be overwhelming, and matching the right product to the operation can be confusing, time consuming and costly. 

When a small EMS provider determined it was time to update the SMT process chemistry, they needed to develop a test program that they could execute efficiently while keeping production running and costs under control. The result is a consolidated test plan that gauges key solder paste properties and requires less than one shift of line time per product evaluated. 

This paper reviews the test plan, data collection and analysis processes, and presents the results. It discusses some of the issues encountered during test development and their resolutions or workarounds. Finally, it interprets the findings as they apply