Challenge
Good Printability
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Table of contents
What is printability?
Recently, demand for a small and light portable device, such as smart phone, has been increasing, and electric devices are expected to be miniaturized, light-weight and high-functioning.
To meet these expectations, deice must have a lot of components in a small area. To obtain stable print results in such small areas, it is essential to select appropriate solder powder size and to use optimal printing condition for the selected solder paste.
Market demand
The market demands improved print position accuracy and consistent solder paste volume to achieve accurate printing in high-density design PCBs.
Approach to improve printability
Selecting appropriate solder powder size
Solder powder size of the solder paste is standardized by IPC J-STD-005A and divided into Type 1 (largest) to Type 7 (smallest). Type 4 is the mainstream today. However, micro-grain solder powders, such as Type 5 and Type 6, are drawing attentions to adopt to increasing demand of fine-pitch printing. It is known that combination of the solder powder size and stencil aperture to obtain stable printability is 0603 chip component for Type 4, 0402 chip component for Type 5 and 03015 or 0201 chip component for Type 6, respectively (chip sizes are metric).
Selecting appropriate stencil thickness
Metal stencil thickness and aperture size to obtain a good printability is
Aspect ratio (Sum of the areas of stencil side walls/ stencil aperture area) is 2.0 or less
And
Area ratio (Stencil aperture area/ sum of the areas of stencil side walls) is 0.6 or more.
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