Label：Membrane Switch, Circuit, Silk Print Screen
Jan 5, 20212020
Circuit silk print screen production is the most important factor reflecting the inherent quality of membrane switches. Circuits are restricted by parameters such as current, resistance, withstand voltage, insulation, and life span. This is also a concrete manifestation of the penetration of screen-printed products into functional and high-tech fields.
To ensure the function of the circuit, we should first ensure the print screen of the printed circuit.
The requirements of the circuit parameters and structural elements in the circuit for screen printing are described below.
1. The resistance of a wire made of the same thick conductor is inversely proportional to the cross-sectional area of the wire. The current it passes is proportional to the cross-sectional area. Its contact point resistance is proportional to the thickness of the contact.
It can be seen that the thickness of the circuit printed in the membrane switch is the basic condition to ensure the performance of the switch. Under general conditions, the thickness of the circuit pattern should not be less than 30 microns.
2. Because the printed circuit pattern of the membrane switch is made up of particles of conductive metal (usually silver), in its printing material, the barrier between the resin binder and the metal particles, the barrier between the impurities and the conductive particles, and the barrier caused by the mesh of the screen during the screen printing process to the circuit pattern, etc., will affect the density of the conductor pattern, thus affecting the performance of electrical parameters.
To ensure the compactness of the printed circuit layer, in addition to the thickness of the printing screen, on the other hand, it is necessary to consider how the printing screen screen allows the printing material, especially the flake silver particles in the silver paste, to pass smoothly. Therefore, we need to choose a slightly thicker mesh with a larger aperture ratio.
3. The smoothness of the circuit pattern is to consider the impact on the electrical parameters and not for the appearance. Dirty wires may reduce the insulation resistance of two adjacent wires. Especially in high temperature and high humidity situations, the migration of silver ions will extend along the sawtooth, causing short circuits between wires and failure of switches.
In summary, the principle requirements for making circuit printing screens can be summarized as: the screen film should be thick, the mesh should be thick, the aperture should be large, and the edge should be smooth.