Rework for Missing Ground Connections

Figure 1: Line of plated through holes with no ground connections.

This latest problem is a board fabricated like the picture you see in Figure 1.

It may is not clear in the photo, but plated holes A through V in Row 1 should have been connected to ground in order to properly perform their function. They were not connected to each other, or to ground. 

It would seem easy enough to find a ground point and connect the pins using a wire once the board was populated, but a surface wire was unacceptable. 

A connection was needed at the bare board level. This new connection needed to be reliable without impacting the plated through holes.

Figure 2: Conductor was soldered to row of plated holes and buried below the circuit board surface by running within a machined groove.

The full row of plated holes needed to be connected to ground on layer 3.

Here Is The Solution

Using a precision milling system, we milled a groove directly adjacent the row of pads. Under high magnification, we cleared a small space under the edge of each plated hole pad to provide a connection point. See Figure 2.

That's was nifty piece of work and required a patient, steady hand. Additionally, at the end of this row of plated through holes we milled down to layer 3 to expose the ground plane for the new buss connection. See Figure 3.

Figure 3: Final connection was made to buried ground layer.

A tinned copper circuit was laid in the machined groove and carefully soldered to the underside of the pad for each plated through hole. Once that was complete, the circuit was connected to ground.

That rework was visually inspected and electrically tested. Finally the entire rework area was protected by covering it with high strength thermoset epoxy.

So there it is, good stuff, done right and done quick. One more fire quenched!

Several members of the Circuit Technology Center team contributed to this feature story.