In-Circuit Test

Bed Architecture

A dedicated test fixture holds a matrix of spring-loaded probes that align with specific test points on the board’s bottom surface. Vacuum or mechanical pressure pulls the board down to ensure reliable electrical contact across all probes. The high cost of fabricating these fixtures makes this method suitable for mature, high-volume production lines.

Guarding Technique

Hardware engineers isolate individual resistors and capacitors from parallel circuit paths by applying a neutral guard voltage to adjacent nodes. This technique ensures that the test instrument measures only the target component’s value. Without guarding, parallel paths would create false failures or mask missing components.

Pin Density

High-density circuit boards require small test pads and close pad spacing to accommodate hundreds of test probes. If the pad density exceeds the physical limit of the test fixture, some nodes cannot be accessed.