Tactile Pressure-Indicating Sensor Film Helps Capacitor Manufacturer Hold Tighter Product Tolerances

Many of SB Electronics’ radial lead products are designed to take up the minimum amount of space on printed circuit boards. This is done by flattening the round capacitor profile in a pressing operation between aluminum plates.

“Histograms indicated that some of our tighter tolerance parts (±1% capacitance) were going out of spec,” says Bryan. “After making some initial dimensional measurements, I needed to visually determine the tactile surface pressure.”

Bryan inserted the Pressurex, which he had ordered in Super Low pressure range of 70--350 PSI (5--25kg/cm2), between the press plates during a product run and saw the uneven distribution of pressure between the capacitors. “As a result, I could prove the press plates weren’t flat and were causing uneven pressure distribution,” said Bryan. “This was of great value to us.”

Bryan continues to use standard tools which measure overall press results, such as gauges and calipers, but he is asking that Pressurex be included as an on-going ISO quality control protocol to analyze surface pressure magnitude and distribution.

Pressurex is available in seven different ranges that measure pressure from 2 – 43,000 PSI (0.14 – 3,000 kg/cm2). It allows for rapid and easy determination of compression magnitude and distribution. When placed between two contacting or mating surfaces, it instantly and permanently changes different shades of red, with the color change directly proportional to the actual pressure applied. Precise pressure magnitude is easily determined by comparing the resultant color intensity to a color correlation chart (conceptually similar to interpreting Litmus paper).

The film has many uses on a multi-layer printed circuit board assembly, including analyzing contact uniformity, verifying flatness (planarity) between semiconductor wafers, and revealing problems such as overloading of connector contacts, standoffs and component solder joints. It is ideal for dozens of electrical and ndustrial applications, such as assessing surface contact inconsistencies in clamps, connectors, heat sinks and heat sealing elements.

“In the past, I had used Pressurex film to evaluate bolted flange designs for custom fittings in vacuum systems,” said Bryan. “Using the pressure-indicating film I could see flaws in the pressure distribution so that we could fine-tune our product design.”