With the rapid development of communication and electronics industry, the production of silicone rubber keypads has also become a mature technology. These keystroke products by the high temperature silicone rubber molded, forming the required key surface, and then after spraying, screen printing, red stripping and other processes formed. Here is a preliminary discussion of this screen printing process.

First, the characteristics of silicone rubber keys

As the key material of silicone rubber, the hardness is generally around 45 °, the printing of a single key surface convex, concave single plane and plane, all for the field line printing. In addition to the printing requirements of accurate location, graphic clear, but also requires ink for printing silicone rubber, ink layer to a certain thickness, strong adhesion and wear resistance, high temperature baking does not change color and so on. Therefore, it made screen printing technology more special technical requirements.

Second, screen printing process 

Screen printing plate-making methods, the main photosensitive plate-making method, that is, directly to the photosensitive gel coated on the Internet, after drying to form a certain thickness of the photosensitive film into a graphic carrier, the process is:

Select the network → select the box → Stretch → clean the screen → drying → coating photosensitive plastic → exposure → development → printing

Specific process is as follows:

1. Mesh box

General use of aluminum, light operation, the intensity is not easy to deformation. Stretch net with cyclohexanone before wiping net frame, remove the residual grease and dirt, and then wipe industrial alcohol, and finally washed with water, and then dry the mesh box. Screen printing plate operation, the need to repeatedly dry, so dry conditions and cleaning should be strictly controlled.

2. Stretching

The first choice of screen, rubber screen printing using nylon mesh, ink over a good rate of tension constant, the selection can cover the edge of the frame and more outside the network frame 6 ~ 10Cm of the screen, with a pneumatic stretching machine Stretching , And with a tensiometer six-point test, to achieve the required tension, coated with a universal adhesive so that the wire mesh in the screen frame, with hot air to speed up the drying, about 5mInR after the sticky, you can turn off the stretcher, the Excess screen glued to the outside of the screen, in order to facilitate the screen to maintain the fastness. Cut off the excess screen, with cyclohexanone, industrial alcohol to clean the mesh surface after drying. If stretching tension is not stable, may cause fonts offset and fuzzy, chord surface of the substrate caused by ink layer thickness difference. Plane orthographic printing requires a large screen tension, a curved surface of the printing surface tension with a small screen, process application of the screen tension range is 3N / Cm ~ 7N / Cm. General tension of the screen life is short, the process should be selected according to the need: Printed conductive ink with 100 mesh straight silk screen, printing orthography, color with 200 ~ 300 mesh diagonal screen to ensure that the ink layer thickness and graphics The integrity of