Proper Eylet Sizing for Throughhole Repair

Properly Sizing an Eyelet for PCB Repair

While most of today’s PCB are primarily using surface mount parts there are still plenty of boards with primarily throughhole components in “service”.

At some point in the future these boards may need to have one or more of their components removed and replaced while being serviced and in some of these cases the repairer may pull a barrel. This means that that the plated throughhole will need to be repaired by the replacement of the barrel using an eyelet. This procedure is outlined in IPC 7721 the Repair of Printed Wiring Boards in section 5.1, Plated Hole Repair (see the video below).

As well as this procedure is written and for how long it has been used going all the way back to the military standards, this section may cause even the most experienced repair technician some searching for how to select the right eyelet.

The eyelet inside diameter should be 3-20 mils greater than the component lead diameter. (That is 0.075 to 0.500 mm for others who are metric-oriented in our measurements.)

The length under the flange of the eyelet should be 25-35 mils greater than the thickness of the PCB. (That is 0.63 to 0.890 mm.

The outside diameter of the eyelet should allow the eyelet to be inserted into the drilled hole without force, but should not exceed 5 mils (0.125 mm) greater than the eyelet outside diameter.

That is how the eyelet should be sized.