Abstract
Flexible circuit boards are widely used in smart consumer electronic devices. In this paper, a novel methodology, which is different from the traditional etching and screen printing methods that generally rely on screen printed conductive ink as a conductor to form the required circuit in a dielectric film, has been reported. Liquid metal was directly injected into biocompatible polymer microchips, based on the air-diffusion mechanism, in order to prevent the circuit board from being directly exposed to the outside environment. The liquid metal circuit board that was produced had good thermal conductivity because the thermal conductivity of gallium is about 60 times that of water and 1000 times higher than that of air. In addition, the liquid metal circuit board has good ductility and repeatability, which is required to meet the extreme deformation that is experienced in most electrical applications. The proposed method has the ability to fabricate irregular circuit boards and complex patterns with channel-lengths as high as 4 m or channel-widths as small as 30 μm. This method can not only solve the problem of the traditional circuit boards being difficult to modify and repair, but it can also effectively protect the circuit and realize high fidelity of the circuit.
Highlights
Flexible printed circuits (FPCs)1 are a type of very reliable and high quality circuit boards
In order to characterize the stability of the flexible liquid metal circuit board, the flexible circuit board was repeatedly stretched to 120% of its original length
The results showed that the flexible circuit board had strong stability, and it could be used in the production of a practical circuit board
Summary
Flexible printed circuits (FPCs) are a type of very reliable and high quality circuit boards. It is currently difficult to manufacture irregular patterns in a complex circuit.3,8 For these materials, metals that are liquid at room temperature can be injected, which have good ductility, elasticity (with excellent recovery behavior), stability, and high conductivity values. The problem of the low heat flux of traditional flexible circuit boards and fatigue fracture caused by repeated bending has been solved. This method solves several problems with filling channels with liquid metal that occurs in the previous approaches.. In order to meet the requirements of different functional devices in practical applications, it is necessary to complete the filling of more subtle, complex, and irregularly patterned circuit boards. The graph of the change in the resistance of the circuit board with the increase in temperature has shown that the resistance values of the metal circuits varied less with temperature
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