This procedure covers the use of an eyelet for the repair of a damaged land on a plated hole that has an inner layer connection.
This method is used to restore the integrity of a through connection on a multilayer circuit board, having an inner layer connect, but ONLY if the full barrel of the plated through hole remains intact. If there is barrel damage see appropriate procedure.
This method will reduce the inside diameter of the hole. The minimum hole size requirement must be checked for acceptance.
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Minimum Skill Level - Advanced
Recommended for technicians with soldering and component rework skills and exposure to most repair/rework procedures, but lacking extensive experience.
Conformance Level - Medium
This procedure may have some variance with the physical character of the original and most likely varies with some of the functional, environmental and serviceability factors.
Precision microscope with stand and lighting for work and inspection.
Micro Drill System
Versatile power tool for milling, drilling, grinding, cutting and sanding circuit boards.
Use to provide accurate measurements for thickness and hole diameters.
Properly maintained soldering iron and properly sized soldering iron tips.
Nonabrasive, low-linting wipes for cleanup.
Images and Figures
Damaged Plated Hole with Inner Layer Connection.
Figure 1: Insert the eyelet into the hole.
Figure 2: Set the eyelet using an Eyelet Press.
Figure 3: Flare the eyelet barrel using the flare end of the setting tool.
Figure 4: Flatten the eyelet barrel using the flat end of the setting tool.
Figure 5: Completed repair.
Eyelet Selection Criteria
ID - Inside Diameter
The eyelet inside diameter should be a .075 - .500 mm (.003"-.020") greater than the component lead diameter.
LUF - Length Under Flange
The length of the eyelet barrel under the flange should be .630 - .890 mm (.025" - 035") greater than the thickness of the circuit board. This added length allows for proper protrusion when setting the eyelet.
FD - Flange Diameter
The eyelet flange diameter should be small enough to prevent interference with adjacent lands or circuits.
OD - Outside Diameter
The clearance hole drilled through the circuit board should allow the eyelet to be inserted without force but should not exceed .125 mm (.005") greater than the eyelet outside diameter.
Be sure to select an eyelet meeting the proper criteria. An eyelet with an oversize flange may interfere with adjacent circuits. An eyelet that is too short will not protrude through the circuit board for proper setting.
Clean the area.
Examine the hole to ensure that there is no damage to the wall of the hole. Check continuity to establish the integrity of the connection.
Select an eyelet using the Eyelet Selection Criteria. Use a pin gauge and caliper to measure the existing plated hole dimensions. The eyelet must have an inside diameter sufficient to receive the component lead and an outside diameter that will allow the eyelet to be inserted into the hole without force.
Remove oxides from the surface lands where the eyelet is to be installed using a buffer and clean.
Apply a small amount of liquid flux to the land or circuit on the circuit board surface, if any, and tin with solder using a soldering Iron and solder. Clean the area.
Insert the eyelet into the hole. If a new circuit is required, the new circuit may extend into the hole and the flange of the eyelet will secure the new circuit in place. (See Figure 1)
Select the proper setting tools and insert them into the eyelet press. (See Figure 2)
Turn the circuit board over and rest the eyelet flange on the lower setting tool. (See Figure 3)
Apply firm even pressure to flare the eyelet barrel. (See Figure 3)
Change the upper setting tool from a flare tool to a flat end tool. Apply firm even pressure to flatten the eyelet barrel. (See Figure 4)
Inspect the eyelet for evidence of damage. Refer to IPC-A-610 Acceptability of Electronic Assemblies.
Apply a small amount of liquid flux and solder the eyelet flanges to the lands on the circuit board surface if necessary. Clean the area. Inspect for good solder flow and wetting around the eyelet flanges and lands. (See Figure 5)
Clean the area.
Install the component lead and solder, if required.
Visual examination, dimensional requirement of land diameter and inside diameter.