Authored By:
Tony Lentz
FCT Assembly
Greeley, CO, USA
Jasbir Bath
Bath Consultancy, LLC
N. Pavithiran (R&D Manager)
Nihon Superior
Ipoh, Perak, Malaysia
Summary
Printing of solder paste and stencil technology has been well studied and many papers have been presented on the topic. Very few studies have looked at how solder paste volume affects solder joint reliability. It is the aim of this work to correlate printed solder paste volume to solder joint reliability.
The circuit board chosen for this work includes a variety of component sizes and types. The components tested are as follows: 0402, 0603, 0805, and 1206 Imperial chip components (1005, 1608, 2012, 3216 metric); PLCC; SOT, and SOIC leaded components. In an effort to determine the lower limit of acceptable solder paste volume, printed volumes were varied between 25 and 125% of nominal. Solder joint quality was assessed using IPC-A-610 standard methods and cross-sectional analysis. Solder joint strength was measured using shear and pull tests. Thermal cycling between -40 ºC and 125 ºC was done for 1000 cycles and solder joint quality and strength was measured again.
In summary, the solder joint reliability data was correlated to printed solder paste volume. This was done in an effort to establish basic guidelines for the printed solder paste volumes required to generate reliable solder joints.
Conclusions
This study gives some guidelines on the effects of solder paste volume for certain components in terms of manufacturing yield and reliability. It is apparent that a wide range of solder paste volumes can be used to create acceptable solder joints, but if the solder volume is too low then solder joints may not be reliable. Changing solder paste volume can induce certain defects but these defects are correctable. It is advisable for PCB assemblers to set up their own standards for acceptable solder paste volume based on the components used.
Initially Published in the SMTA Proceedings
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