Solder Bump

Most widely used method in forming the solder bump on PCB pad is electroplating and screen printing. Though electroplating method can be applied for the finely patterned pad, the control of concentration ratio of ternary compound solder is not easy. Currently, lead, which is one of the main components of conventional solder, is restricted due to its environmental pollution and lead-free solder becomes the hot issue among the package companies. Various lead-free solders have been developed and most of these lead-free solders consist of more than three components. On the other hand, it is very difficult to form the bump on the finely patterned pad by using the screen-printing, but the technique that can be applied to 175mm pitch pad has been developed by continuous efforts. Since it is easy to control the component of solder paste, the screen-printing technique is advantageous to adopt lead-free solder. In flip chip connection for Au/Ni bump, solder ball is also used instead of ACF. The flip chip interconnection process using solder ball is reliable than ACF, though it is more expensive. The cost in forming the solder ball by screen-printing is lower than by electroplating. So screen-printing technique can be applied in flip chip interconnection required more reliability. Microscale Co., Ltd has been developing the lead-free solder in cooperation with KAIST.

Bump Height : 122 Bm

Bump Diameter : 143 um

Pitch : 250 um

Material : 63Sn/37Pb

3Sn/97Pb

UBM : TiW / Cu