Mechanism of Solder Joint Cracks in Anisotropic Conductive Films Bonding and Solutions: Delaying Hot-Bar Lift-Up Time and Adding Silica Fillers

Abstract

Micron sizes solder metallurgical joints have been applied in a thin film application of anisotropic conductive film and benefited three general advantages, such as lower joint resistance, higher power handling capability, and reliability, when compared with pressure based contact of metal conductor balls. Recently, flex-on-board interconnection has become more and more popular for mobile electronic applications. However, crack formation of the solder joint crack was occurred at low temperature curable acrylic polymer resins after bonding processes. In this study, the mechanism of SnBi58 solder joint crack at low temperature curable acrylic adhesive was investigated. In addition, SnBi58 solder joint cracks can be significantly removed by increasing the storage modulus of adhesives instead of coefficient of thermal expansion. The first approach of reducing the amount of polymer rebound can be achieved by using an ultrasonic bonding method to maintain a bonding pressure on the SnBi58 solder joints cooling to room temperature. The second approach is to increase storage modulus of adhesives by adding silica filler into acrylic polymer resins to prevent the solder joint from cracking. Finally, excellent acrylic based SnBi58 solder joints reliability were obtained after 1000 cycles thermal cycling test.

Effect of Servo-Pressurized Mode on Soldering Process Characteristics of Micro-Parts

“…At present, an inverter pulse heating power supply is used for HBS because it can achieve precise control of the welding temperature and welding time. However, the pneumatic pressurization method [4], [10], [11] is used for most of the current hot-bar soldering. This pressurization method has the disadvantages of high-pressure fluctuations and a process pressure that cannot be adjusted.…”

Pseudo-tricolor typed nanobelts and arrays simultaneously endowed with conductive anisotropy, magnetism and white fluorescence

“…At present, anisotropic conductive films (ACFs) have been widely used by researchers because of their many practical advantages, such as flexibility, reliability, simplicity and environmental friendliness. 1–3 Type I ACFs have been widely used in the electronic industry, which conduct electricity unidirectionally along the Z -axis and insulate along the X – Y plane. 4 Type II ACFs have the characteristics of different conductivities in two perpendicular directions along the X – Y plane, which are still in the laboratory research stage.…”

A Review: Solder Joint Cracks at Sn-Bi58 Solder ACFs Joints

“…Aiming at replacing the socket-connectors, FOB assembly is attracting more and more attention, due to a lower thickness (about 50 μm) and a higher fine-pitch capability (under 100 μm) [5]. So Google started to use FOB in mother board assembly to partly take place of connectors, as shown in Figure 1.…”