Stencil printing variables

Amicon E1330LV/ Emerson Cuming Unfilled, no-flow fluxing underfill (reworkable) Not applicable Nickel-gold and OSP finishes Syringe, jet dispense, or stencil print Flip-chip, CSP, EGA modest post-reflow cure (offline) required. Reworkable, 300 second reflow cycles 225°C peak. Variable fi-equency microwave curable. 

As with most processes, numerous variables affect the final product. For solder paste deposition using stencils, Chouta and Heck identified 39 variables relating to materials, 32 variables to processes and equipment, and 10 variables to personnel and environment. Among variables critical for the successful stencil dispensing of adhesives are stencil design, the adhesive material and its rheological properties, and the printing process. 

Eor PIP, various PWB variables, stencil apertures, solder paste printing methods and parameters, and component types and insertion methods, have been evaluated for both tin-lead... 

In the solder paste printing process, defects typically are caused by poor alignment between the substrate and stencil, incorrect material selection (substrate, paste type and stencil design), or variations in the amount of paste deposited. Defect elimination relies on the engineer and operator to address these variables and monitor the process. 

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