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Packaging technologies for those devices have also been evolving towards higher performance and higher density. Anisotropic Conductive Film (ACF), which is pasted with insulation adhesive dispersed equally with conductive particles, is essential for packaging substrates and driver ICs. The use of highly conductive particles of uniform size is essential for achieving higher performance and lower resistance.
We manufacture these highly conductive fine particles of uniform size by wet reduction method, which was developed jointly by Hitachi Metals, Ltd. and Akita Prefectural Resources Technology Development Organization. It is a potential technology that enables the higher performance and higher density required for next-generation electronic components.
Demand for mobile devices, including smartphones and tablet PCs, has been growing rapidly. It is expected to continue growing, mainly in emerging countries.
Mobile devices are evolving towards higher resolutions, multifuntional, and lower profiles. Packaging technologies have also been evolving further towards higher performance and higher density.
Anisotropic Conductive Film (ACF), which is essential for packaging substrates and driver ICs, is a connecting material consisting of insulation adhesive dispersed equally with conductive particles. The use of highly conductive particles of uniform size is required given the higher performance and higher density mentioned above.
From collaboration with Akita Prefectural Resources Technology Development Organization, Hitachi Metals has developed a wet reduction method for manufacturing spherical metal particles.
As shown in Figure 1, the particles having smooth surface are completely spherical, uniform in size, and highly dispersive. The limited variation in the particles is also apparent from the result of the measurement of particle size distribution with the laser diffraction method shown in Figure 2.
In addition, conductive fine particles are required to maintain stable conductivity, even in a harsh environment. In response, we have established a uniform Au plating technology to plate large quantities of fine Ni-P particles having large specific surface area, which has been deemed difficult. It can be confirmed from a cross-sectional image of the film formation of Au plating, which is shown in Figure 3, that an Au plating layer of an even thickness is formed on the particle surface. And it was confirmed in an accelerated test (125ºC/95 RH%, 0.2 MPa; RH stands for relative humidity), by which we evaluated the changes of particles, that the volume resistivity increases only around two times compared to the initial resistivity even when the Au film around the particle is extremely thin at 15 nm or 30 nm (Figure 4).
Currently, we offer fine particle samples in the range of 2-30μm in diameter, mainly for the anisotropic conductive application. Please feel free to make an inquiry.