Developing the stencil printing process for 01005 lead-free assemblies

This paper presents the implementation of 01005 components in a wireless module mass production. Several modifications in processes, material, and equipment were required. A number of manufacturing related issues needed to be addressed. One particularly significant issue for use of 01005 technologies is solder paste printing and the reason is lack of manufacturing experience. Many manufacturers have spent much time and money determining the optimum process conditions for using 01005 components. All of the 01005 manufacturers recommended using an electroform stencil for very small aperture size and fine pitches. This is required a change from the standard manufacturing process that utilizes a laser-cut stencil printing and it is also one of the more expansive stencil fabrication processes. For some manufacturing processes this may be difficult. However, the current state of the art for laser-cut stencil technique of solder paste is very limited for these extremely smallest components due to laser-cutting quality. In right of this need, we carried out to evaluate if the enhanced laser-cut stencil with post-treatment such as electro- polishing can perform as good as or better than the electroform stencil. The designed experiments are conducted to determine the effect of electro-polishing on the print performance of enhanced stencil for 01005 small apertures. The results showed that the standard laser-cut stencils could be strengthened through optimized electro-polishing treatment after laser-cutting process. This enhanced laser-cut stencil showed acceptable paste release performance and it is low- cost alternative to electroform stencil for 01005 small apertures. The work described in this paper also examines the release performance of type-3 and type-4 pastes from electroform and enhanced laser-cut stencils. Results of this test showed that paste release performance is significantly better for type-4 comparing to type-3 pastes.