ISO 16525-2-2014 pdf free download.Adhesives – Test methods for isotropic electrically conductive adhesives – Part 2: Determination of electrical characteristics for use in electronic assemblies.
4 Principle
The test circuit board consists of two or more terminals that are connected using an isotropic electrically conductive adhesive. The measurement of a potential difference, when a current is applied to one of the terminals, can be used for the calculation of electrically volume resistivity and interfacial contact resistivity.
NOTE This test uses the electrical characteristics of isotropic electrically conductive adhesives, which are used for connection of electronic circuits. This part of ISO 16525 describes electrically volume resistivity, which shows the electric characteristic of the Isotropic electrically conductive adhesive, and interfacial resistance, which is specific to the isotropic electrically conductive adhesive.
On the contact surface of the isotropic electrically conductive adhesives, a resistance component is present, which can be regarded as interfacial resistance. This might be so high that it cannot be neglected when compared with electrically volume resistivity of the isotropic electrically conductive adhesive. This test provides a measurement, which measures this component only. This test is characterized by calculation of resistivity from a current passing through the test circuit and voltage.
5 Apparatus
5.1 Test apparatus, consisting of a current source and a voltage meter, both as specified in IEC 60468. The potential difference is measured at the voltage terminals by applying a current to the printed circuit board using the current source from the current terminals in a specific direction. Eigurei. and Figi.ire.2 show examples of configuration of the apparatus. A digital ohmmeter, which combines all these devices, may be used as an alternative.
It is preferable to use a dry circuit-type apparatus because it does not affect the irreversibility of conductivity of the interface of the isotropic electrically conductive adhesive. For measurement of interfacial resistance, it is preferable to use a multichannel ohmmeter because it is necessary to switch from one pair of terminals to the other and the lengths of the wires differs.
Resistance is obtained from the voltage drop when a constant current is applied. Therefore, set a current value so that voltage resolution can be sufficiently small compared to the measured voltage. In the unlikely event that the specimen generates heat because an excessively high current occurs, reduce the current value and shorten the period for each measurement session. Usually, a maximum current is recommended to he approximately 10 mA.ISO 16525-2 pdf download.