• Electronic circuit miniaturization is continuing for integrated circuit improvements.
• High speed computer system and optical communication system required new package technology with high propagation speed and high wiring density.
• For high computer system the used high density package is the way to reducing machine cycle time.
• It can be achieve by reduction in propagation delay for single between large scale integration (LSI)
• Key point for packaging is the lower dielectric constant material and higher gate density on substrate.
• Optical communication system required 

 
- small size

• To reduce inductance and capacitance with might cause electrical cross- talk at high speed
• It necessary to use new technology with high- wiring density
• For high speed communication system, the essential feature are high speed, small size.
• To reduce inductance and capacitance with might cause electronic cross-talk at high speed.
• It necessary to use new technology with high-wiring density.
• For high speed communication system, the essential feature are high speed, small size and high performance.