What are the requirements for the selection and use of membrane switch printing inks?

What are the requirements for the selection and use of membrane switch printing inks?

Membrane switch circuit printing using conductive ink, conductive ink is mainly composed of conductive filler (including metal powder, metal oxides, non-metal and other composite powder), connecting agent (mainly synthetic resin, photosensitive resin, low melting point plexiglass, etc.), Additives (mainly dispersants, regulators, thickeners, plasticizers, lubricants, inhibitors, etc.), solvents (mainly aromatics, alcohols, ketones, esters, alcohol ethers, etc.). Conductive ink is one of the most critical materials for printing film switches. The quality and price of the ink are directly related to the quality of membrane switch products and the cost of product production. Conductive ink is a kind of functional ink. In printing, there are conductive inks such as carbon paste and silver paste.

Carbon paste ink is a liquid type thermosetting ink. It has the function of protecting copper foil and conducting current after film curing. It has good conductivity and low resistance. It is not easy to oxidize and has stable performance. It is resistant to acids, alkalis and chemical solvents. Erosion: With strong wear resistance, wear resistance, good thermal shock resistance and other characteristics. Silver paste ink is a one-component ink composed of ultra-fine silver powder and thermoplastic resin. It can be used on most substrates and has strong adhesion and hiding power. Low temperature cure, controlled conductivity and very low resistance. The printing material printed on the switch circuit is mostly a thick paste of silver paste, which is a screen printing method and a common material for processing electronic components. However, since most of the silver paste is of a high-temperature sinter reduction type, the silver paste used in the switch circuit must be a low-temperature-curing type silver paste because of the limitation of the temperature resistance of the base material. There are many types of silver paste for printed switch circuits, and the performance and quality are quite different. The properties of silver pastes should be evaluated from the aspects of resistivity, solid content, particle size of metal particles, bonding strength, and curing temperature. Then choose. Because the silver paste is expensive and its quality is related to the electrical properties of the membrane switch, it should be carefully selected. Because the viscosity of silver paste is thicker than ordinary inks, and it also contains metallic solid components, scraping should be done with care. The presence of various solvents and additives in the conductive silver paste has a certain influence on the resistivity. To release them from the conductive circuit, they mainly rely on hot air drying to volatilize them. Drying temperature is generally controlled at 85 °C ~ 90 °C is appropriate, constant temperature in hot air 40min. Practice has proved that dry conductive patterns that are not completely dry are often more than a dozen times higher than the dry thoroughly patterned resistance. Therefore, dry quality is also a major aspect of the quality of membrane switches. In addition, on the metal silver contacts of the switch, conductive carbon paste protective layer should be screen printed, using the characteristics of carbon paste, in order to facilitate the rapid separation after contact closure, improve the wear resistance of the switch contacts, and ensure the switch touch The point can withstand millions of contacts and protect the underlying metal silver contacts from oxidation. The 1 carbon slurry is a non-metallic material. The dense carbon coating can prevent the metal silver from contacting with the narrow gas and hinder the migration of silver ions, thereby effectively protecting the stability of the electrical properties of the switch circuit. When the carbon coating acts on the lead socket, It can facilitate the insertion and removal of lead wires and connection terminals. However, excessively thick carbon coating is prone to spalling failure, so the screen printing conductive carbon paste should not be too thick.

Hangzhou Kaike Electronics Co., Ltd.

Address: No. 2. Dadi Road, Haining Agricultural External Development Zone 314408,

Zhejiang, China

Contact Person: May Wong

Telephone: 86-571-86830690     Fax: 86-571-86687367

Cell Phone: 86-15158112598

Email: May@hzkaike.cn