Usually in order to ensure the conductive effect of conductive adhesives, the resistivity of conductive adhesives will be specially tested, and after passing the test, conductive adhesives can be put into the market, and their quality must be strictly guaranteed. So, how to test the conductivity of conductive adhesives? Let's follow us to find out!

Here's how:

(1) The principle of measuring conductive adhesives uses a constant current (10A, cm²) to pass through the series circuit of the standard resistance and the measured resistance at the same time, and then measure the voltage drop generated on the standard resistance and the measured resistance respectively.

(2) Conductive adhesive test preparation and resistivity calculation take glass or other hard insulating plates with uniform thickness and cut into two kinds of test pieces with standard sizes of 160mm×10mm×2mm and 120mm×10mm×2mm.

Each piece is formed into a group, after surface treatment, drying, the two pieces overlap, and their thickness is finely measured with a micrometer. Each piece is coated with glue, stacked table, and 0.03~0.05mm copper foil or aluminum foil is used as the lead, and the resistance is tested and calculated after the adhesive layer is fully cured. The volume resistivity of the conductive adhesive is calculated as follows: A should be calculated according to the actual measured length of the adhesive layer a and the value of the adhesive layer width b after the failure of each sample. That is, A = ab (accurate to 0.01cm). Each kind of adhesive specimen should not be less than 5, according to the allowable deviation requirements of the trade-off, representing the same test specimen should not be less than 60% of the original test quantity, take the arithmetic average, the significant number of 3 digits. The value measured from each specimen shall not deviate more than 5% from the mean. When measuring, the humidity and temperature at the time of the test should be recorded, and the adhesive layer failure characteristics should be observed in order to determine the quality of the bond. According to the actual working conditions of the bonded parts, the determination of shear strength can be divided into three types: room temperature, high temperature and low temperature.

How to determine the resistivity of conductive adhesives?

Conductive adhesive is determined at room temperature, requiring room temperature at 23 Shi 5 °C and relative humidity of 55% ~ 75%. Determined at high temperatures, the following temperatures can be selected according to requirements: 60°C, 100°C, 150°C, 200°C, 250°C, 300°C, etc. The high-temperature shear strength determination is carried out in a removable electric heating box installed around the upper and lower chucks of the testing machine, and the temperature control system of the electric heating box is the same as that of ordinary adjustable electric heating drying ovens. When the temperature in the box reaches the specified temperature, the constant temperature can be maintained for 20min before the test can be performed.

Conductive adhesive is tested at low temperature, and the following temperatures can be selected according to requirements: 196°C, -100°C, 60°C, -20°C. The principle of low temperature shear strength determination is similar to high temperature determination, and a refrigeration system is installed around the upper and lower chucks of the testing machine, and after reaching the specified temperature, the constant temperature can be tested for 20min. It should be noted that the material composed of the bonded parts is different, and the type and size of the shear strength specimen are also different. For metal-to-metal dead joints, please refer to the standard provisions of "Bonded Specimens"; Plastic and rigid non-metallic materials, plastic and metal materials, rigid non-metallic materials and rigid non-metallic materials and other bonding parts.