Research of Electrical Connection Between Chip and PCB Based on Conductive Adhesive Film

Abstract

PCB interconnection is the most common type of electrical interconnection. Solder paste welding is the most widely used type of electrical connection of chip on PCB. In this paper, a method of using conductive adhesive film and connector to realize the mechanical pressure type electrical connection of the chip is proposed, so as to try to solve the problem of overheating and damage in the solder paste welding of the thermal sensitive chip. The thickness of conductive adhesive film is 0.1 millimeter, when it is under vertical pressure, it will be conductive. In this research, the conductive adhesive film and the chip are mechanically fixed on the circuit board by the connector, the conductive adhesive film is placed between the chip and the PCB. The circuit adopts digital power amplifier. The chip in the circuit is YDA138-E in SSOP package, and the connector material is high temperature resistant nylon. Because the clamping force of the connector directly acts on the top of the chip, the stress on the electrical connection position of the conductive adhesive film completely depends on the interference area between the connector and the PCB assembly. And the stress increases with the increase of interference area. With ANSYS simulation software, an interconnection model including circuit board, connector and other devices is established. The static analysis of the circuit model is carried out by finite element method. The range of the interference area is obtained, and to eliminate the interference area under the condition of significantly uneven stress distribution. Because the thickness of conductive adhesive film is very thin, its deformation and stress can be ignored, so only the thickness of the film is used as the compensation of interference area. Take several interference values inside and outside the interval, and assemble connectors according to different value results. In the case of the same input signal, use oscilloscope to detect and collect output electric signals of several circuit boards as sample signals, and take the output electric signal of the circuit under the solder paste electrical connection type as the reference signal. With MATLAB data analysis software, the degree of relevance between the sample signal and the reference signal collected by the oscilloscope is analyzed quantitatively. Finally, it is concluded that the reference signal and sample signal have high similarity in frequency domain. There is a delay in the time domain between the sample signal and the reference signal. The chip can work normally under the electric connection of the conductive adhesive film. and can be used as a reference method to solve the problem of chip overheating damage.