SMT007 Magazine

SMT-June2016

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94 SMT Magazine • June 2016 by Stephen Las Marias I-CONNECT007 I recently sat down with Integrated Micro- Electronics Inc.'s Joemar Apolinario, engineer- ing manager; Aurelio Bantigue, DFM engineer; and Rodney Bebe, process engineer, to get their insights on the solder paste printing process. They discussed the challenges and key consid- erations to make when dealing with tighter tol- erances and finer pitches in line with the con- tinuing miniaturization trend in the electron- ics manufacturing industry. They also talked about the impact of solder pastes in the print- ing process, and the criteria for their selection and qualification. Finally, they highlighted de- sign and process strategies to get the best solder paste printing results. Stephen Las Marias: Please talk about the solder paste printing process and the challenges you face. Joemar Apolinario: The solder paste print- ing process is the most challenging process in the SMT operation because majority of the de- fects—around 60 to 80%—are coming from this process. These include non-wetting, insufficient volume, and short (solder bridging). Factors that greatly impact the solder paste printing quality may vary from the stencil design, the solder paste type, the machine capability (pa- rameters), setup and tooling, and even the engi- neering skills of those who handle this process. The challenge is that the devices now are getting smaller and smaller. We also have the complex products—those boards that combine critical components such as BGAs and ICs, which require finer pitches and smallest diam- eters—and non-critical components. The third challenge is the reliability. We have products that require higher reliability—and those are very sensitive to solder cracks or voiding defects. For most of the defects that we have en- countered, the solder volume being deposited to the pad does not meet the requirement. Las Marias: How do you address those challenges? Aurelio Bantigue: From a DFM standpoint, what we have done so far is we review the stencil de- sign or the aperture design for each of the com- ponents. In our view, we consider both the PCB design and the components that will be mount- ed to the board. We recognize that the trend is toward smaller components, and the challenge is the appropriate aperture design for smaller pins and pads. What we can do is consider the appropriate solder volume. But the more chal- Solder Paste Printing: A User's Perspective FEATURE INTERVIEW Joemar Apolinario Rodney Bebe Aurelio Bantigue

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