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For cavity pressure measurements, injecting the polymer on top of the multilayer causes immediate, permanent pale red color changes on the pressure- indicating film. These color variations can be compa- red to a color calibration chart to determine their psi and kg/cm2

equivalents.

Digital scanning with software processing is also available to convert the differing intensities of red on the film to a spectrum of colors corresponding to the local pressures. The digitally processed film (2b) shows a uniform cavity pressure distribution between 120-140 bar. Only areas distant from the gate show pressures below 100 bar.

For mold wall to substrate pressure measurement, Pressurex film placed on the upper or lower surface of the PCB measures the contact pressure between

the upper or lower mold walls and the PCB. Frictio- nal movements between the top mold wall and the PCB leave red markings directly on the PCB surface. These verify the complete uniform contact needed to prevent the EMC from flowing out upon the sub- strate, causing what is referred to as “mold flash.”

Although no polymer is injected below the PCB, con- trolled pressure is required there to avoid damage to the solder pads. Figure 3 shows that no solder pads rise above the solder resist surface. As the measured pressure is lowest at the top of the pads, the mold tool is not contacting the pads, only the solder resist between the pads.