IPC TM-650 2.5.17.2

Abstract

This test method covers the two-wire resistance test for the determination of the volume resistivity of polymerbased conductive pastes and other conductive materials used in HDI. This test is valid for conductive materials with volume resistivity on the order of 10-5 W-cm or higher. For measuring resistivity on highly conductive materials or any material that cannot be patterned into a circuit pattern, a four-wire (Kelvin Probe) test method, such as IPC-TM-650, Method 2.5.14, is recommended. 1.1 Definition Volume resistivity is a material property that can be utilized to calculate the resistance in a circuit design. For materials with high resistivity, a two-wire resistance test may be used to measure the volume resistivity. The resistance in any sample (R in units of W) is related to the dimensions of the test circuit and the volume resistivity (r) inherent in the material (see Figure 1). R = r ( L tW) L, W, and t are the length, width, and thickness respectively of the test circuit (in cm). The quantity L/W is called a square, ([). The volume resistivity can then be expressed as: r = Rt (L W)= Rt [ with units of ohms-cm (W-cm).