This method is used to repair severe damage to a hole or to modify the size, shape or location of an unsupported tooling or mounting hole. The hole may have component leads, wires, fasteners, pins, terminals or other hardware run through it. This repair method uses a dowel of matching board material and high strength epoxy to secure the dowel in place. After the new material is bonded in place a new hole can be drilled. This method can be used on single sided, double sided or multilayer circuit boards and assemblies.
Damaged inner-layer connections may require surface wire adds.
Minimum Skill Level - Expert
Recommended for technicians with advanced soldering and component rework skills and extensive experience in most 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.
General purpose oven for drying, baking and curing epoxies.
Precision drill press for accuracy and controlled depth drilling.
Hardened stainless steel tip for scraping solder mask and removing defects.
Nonabrasive, low-linting wipes for cleanup.
Images and Figures
Damaged Hole, Non Plated
Figure 1: New hole is milled to encompass entire damaged area.
Figure 2: Place replacement dowel in position and bond with epoxy.
Figure 3: Cut off excess material and re-drill holes as required.
Figure 4: Micro-Drill System.
Clean the area.
Drill out the damaged or improperly sized hole using a carbide end mill or drill. Mill the hole using a precision drill press or milling machine for accuracy. The diameter of the cutting tool should be as small as possible yet still encompass the entire damaged area. (See Figure 1)
Abrasion operations can generate electrostatic charges.
Cut a piece of replacement base material rod. Base material rod is made from FR-4 dowel stock. Cut the length approximately 12.0 mm (0.50") longer than needed.
Clean the reworked area.
Use High Temperature Tape to protect exposed parts of the circuit board bordering the rework area.
Mix the epoxy.
Coat both the dowel and the hole with epoxy and fit together. Apply additional epoxy around perimeter of new material. (See Figure 2) Remove excess epoxy.
Cure the epoxy per Procedure 2.7 Epoxy Mixing and Handling.
Some components may be sensitive to high temperatures.
Remove the tape and cut off the excess material using the razor saw. Mill or file the dowel flush with the board surface. (See Figure 3)
Complete the procedure by redrilling holes and adding circuitry as required. (See Figure 3)
Apply surface coating to match prior coating as required.
Clean the reworked area.
Visual and dimensional examination of the reworked area for conformance to drawings and specifications.