Electronic packaging material

     BCB(benzocyclobutene) has been commercialized since the 1990s as an advanced electronic packaging material.

CB has two types: photosensitive (negative gum behavior) and non-photosensitive (also known as dry etching). The monomer of BCB is liquid, which is converted from liquid to solid by heating and solidifying. The BCB monomer is synthesized through a series of diene reactions, and a BCB solid polymer is formed with high polymerization and crosslinking. Many of the basic features of BCB. BCB has low dielectric constant and excellent thermal, chemical and mechanical stability. Rewiring, wafer level encapsulation, passivation, MCM intermediate dielectric layer, etc. play an important role in lC packaging.

The advantages of BCB for wafer bonding are as follows:

1) height leveling ability: for line and spacing of 25 pressure m, flatness is greater than 80%.

2) low curing temperature: 200-300 ℃, can even under 180 ℃. Can use the hot plate and rapid solidification (250 ℃ 300 ℃ x1h or X1min). No catalysts or by-products are required during curing. Shrinkage can be neglected during curing (5-6%).

3) good bonding performance and high bonding strength.

4)BCB can also be photoetched or etched for selective paste.

5) the solidified BCB is transparent to visible light (transmission rate is up to 90%), so it can be used in optical devices.

6) the solidified BCB can resist the erosion of many acids, bases and solvents and is suitable for fluid applications. However, BCB can still be eroded by strong oxidizing acids (H2SO4:H2O2=3:1).

7) low water absorption is favorable for airtight sealing.

8) the dielectric constant is relatively low, which is favorable for rf-mems and other wafer level packaging.