Soluble multi-block copolyimides having pendant carboxyl groups were prepared by one-pot polycondensation in the presence of γ-valerolactone/pyridine catalyst, and used for the electrodeposition coating on copper foil and substrates. Polyimide compositions for electrodeposition coating consisted of the pendant carboxyl-containing polyimide, neutralizing agent, organic solvents and water. In practice aqueous electrodeposition baths were prepared by stirring a mixture of a solution of the polyimide in N-methyl-2-pyrrolidone (NMP), γ-butyrolac-tone, cyclohexanone, anisole, N-methylmorpholine and water. The electrodeposition coating under a fixed voltage in the range of 5-100V for 0.25-5min provided polyimide films with high levels of appearance, smoothness, and denseness on copper sheet and complex shape material. These polyimide compositions for electrodeposition coating had good keeping quality for two weeks.

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Ag was electroplated on Cu seed layers with underlying Ti/TiN layers using a cyanide plating solution with a pulse waveform. The electroplated Ag films had the resistivity of less than 2.0μΩcm. For the Ag films with less impurity and, thus, with lower resistivity, grains were grown to about 2μm diameters by 350°C annealing. The strength of Ag (111) texture was strongly inherited from preferred orientation of underlying TiN and Cu. The Ag films were highly (111) textured at elevating annealing temperature. When Ag plating started, Cu dissolved and, thus, voids were formed and water remained in them, which caused peeling between Cu and Ag during annealing. This suggests that Ag plating needs electrochemically noble metal seed layer. Finally, we have demonstrated Ag damascene processed interconnects for ULSI global lines.

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Via-filling by copper electroplating with direct current (DC) using a low copper concentration bath was studied. The effect of additives on the copper deposits was also studied by using a Vickers hardness measurement and glow discharge optical emission spectroscopy (GDOES) . Via-filling was achieved with the low copper concentration bath under the selection and combination of additives. Combination of polyethylene glycol (PEG 10mg/dm³), bis (3-sulfopropyl) disulfidedisodium (SPS 10mg/dm3) and Janus Green B (JGB 10mg/dm³) as additives in the low copper concentration bath were found to be a most effective for the void-free filling. The Vickers hardness of copper deposits using various additives were measured and found out the comparatively same hardness values obtaining from additive free bath. From GDOES analysis, the component of additives in the copper films was localized at the upper part of the deposited copper films. In this report, mechanism of via-filling by copper electroplating is also discussed.

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The application of glyoxylic acid as an alternative reducing agent to formaldehyde for full build electroless copper plating process was investigated. Excellent mechanical properties of deposits were obtained with the conventional additives, which were used for the formaldehyde bath. The rate of the Cannizaro reaction of glyoxylic acid was reduced by using KOH instead of NaOH and by maintaining a low bath pH. The solubility of potassium oxalate, which is the by-product salt of the plating reaction and Cannizarro reaction, is much higher than that of sodium oxalate. The bath life of the KOH bath was five times longer than that of the NaOH bath. The test boards plated with developed electroless copper plating solution showed an excellent level of reliability for the through hole interconnection.

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In order to improve joint reliability of Sn-Ag-In-Bi solder with Bi more than 5%, the effect of Bi addition content and P addition to Sn-Ag-In-Bi lead-free solder on mechanical properties and joint strength has been investigated. The tensile strength increases with Bi addition up to 10%, on the other hand the elongation decreases with Bi addition up to 6%. At Bi addition more than 10% and 6%, the tensile and elongation are constant. There is no P addition effect to mechanical properties of Sn-Ag-In-Bi. The joint strength of Sn-3.5Ag-3In-6Bi decreases by about 20% after annealing at 100°C for 1000h, but the joint strength does not decrease with annealing time by 90-340ppm P addition to Sn-3.5Ag-3In-6Bi. The P addition to Sn-Ag-In-Bi has effect that the growth of reaction layers is inhibited.

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A new wafer-level chip-size-package, which realizes high reliability at low cost, has been developed. The package contains a stress-relaxation layer, so it can achieve a lifetime of over 1000 cycles under a -55/125°C temperature cycling test for its solder joints, even when the package contains a large chip of about 100mm² and is mounted on a FR-4 motherboard without an underfill assembly. To realize such reliability above, the stress-relaxation layer was optimized, by using finite element analysis, to have a thickness of 75μm and a Young's modulus of 1000 MPa. The stress-relaxation layer is formed by printing to lower the cost of manufacturing the package. The high reliability of the designed package was confirmed experimentally. Under temperature cycling test, none of 50 test samples failed even after 1400 cycles, and the lifetime to 50% failure for the samples was more than 3000 cycles.

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BGA joints of Sn-3.5Ag and Sn-3.5Ag-0.75Cu lead-free solders on the substrates plated by Electroless Nickel/Immersion Gold were studied. Solder ball pull strength was measured by hot bump pull method, and it is found that the pull strength of Sn-3.5Ag-0.75Cu was higher than that of Sn-3.5Ag. P-rich layer was observed at the jointed interface by cross-section analysis using EPMA. The P-rich layer of Sn-3.5Ag-0.75Cu was thinner than that of Sn-3.5Ag. In the case of Sn-3.5Ag-0.75Cu, intermetallic compounds (Cu, Ni) 6Sn5 were formed, and they prevented the diffusion of Ni to solders, and inhibited the concentration of P at the jointed interface. As the result, P-rich layer was hardly formed, and this is considered to be a reason for high pull strength of Sn-3.5Ag-0.75Cu solders.

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Recently, demands for card-type Products has be growing. So, package is demanded not only to be smaller and lighter. But also its thickness is needed to be extremely thin. We have developed an ultra-thin package (0.5h-FLGA) with a package thickness of 0.5mm (Max) . The technical features and characteristics are described in this paper.

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We have evaluated the joint reliability of some kinds of components jointed with Zn system solder. The tested components were CSPs with Sn-Ag-Cu-Bi solder balls, TSOPs with some platings, and Chip components with some platings. The evaluation was carried out by the temperature cycle test (TCT) . As the results, in case of CSPs, we obtained good joint resistance even after TCT 2000cycles. And also in the case of Chip components, we obtained good joint strength even at 1000cycles. On the other hands, in the case of TSOPs, the joint strength TSOP which has 42alloy lead plated with Sn-Pb was weaken.

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A fine pattern for high frequency use has a serious problem about its RF signal loss. In order to cope with this matter, we proposed a new type of electrode applied by combination of sintering Ag and electroless plating Cu. The pattern is formed by etching a sintering Ag film, and its surface is covered with electroless plating Cu. The design rule is 30/20μm and its thickness is 10μm. Especially, it was a key point that the cross section became corner-less around shape. We found that the RF performance was affected by the thickness and the shape. We confirmed that this electrode is applicable for a new MMIC.

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We present the results of the stray light noise suppression experiment in the laser diode (LD) /photo diode (PD) integrated units for optical pickup use. The use of dummy PD elements have proven to be effective in removing the diffusion current generated by the stray light. Because they can trap the stray light and re-combine the photo-generated carriers, multiplex reflection is avoided. Moreover, stray light irradiating photosensitive elements of the PD can be effectively prevented by establishing a partition between the LD and the photosensitive elements. Preliminary experiment shows that the partition installation lowered the noise level to less than 40% comparing with that of no partition.

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