This procedure covers the repair of a damaged hole that has no inner layer connection. An eyelet is used to repair the damage to the hole and the eyelet flange replaces the lands on the circuit board surface.
This procedure is used only to restore the integrity of a through connection in a double sided board or a multilayer board where there is no inner layer connection. If there is an inner layer connection see appropriate procedure.
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Minimum Skill Level - Intermediate
Recommended for technicians with skills in basic soldering and component rework, but may be inexperienced in general repair/rework procedures.
Conformance Level - High
This procedure most closely duplicates the physical characteristics of the original, and most probably complies with all 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
Figure 1: Drill out the hole using a Micro-Drill System and ball mill.
Figure 2: The eyelet flange can be used to secure a new circuit in place.
Figure 3: Set the eyelet using an Eyelet Press.
Figure 4: Flare the eyelet barrel using the flare end of the setting tool.
Figure 5: Flatten the eyelet barrel using the flat end of the setting tool.
Figure 6: 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.
Select an eyelet using the Eyelet Selection Criteria. Use a pin gauge and caliper to measure the existing plated hole dimensions.
Insert the appropriate ball mill into the Micro-Drill System. Drill out the hole removing all the plating. The drilled hole should be .025 - .125 mm (.001" - .005") larger than the eyelet O.D. (See Figure 1)
This procedure may isolate internal connections on multilayer circuit boards.
Clean the area.
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 drilled hole and the flange of the eyelet will secure the new circuit in place. (See Figure 2)
Select the proper setting tools and insert them into an eyelet press system. (See Figure 3)
Turn the circuit board over and rest the eyelet flange on the lower setting tool. (See Figure 4)
Apply firm even pressure to flare the eyelet barrel. (See Figure 4)
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 5)
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 6)
Visual examination, dimensional requirement of land diameter and inside diameter.