3.3.2 Hole Repair, Transplant Method

Outline

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. A new hole can be drilled after the new material is bonded in place. This method can be used on single-sided, double-sided, or multilayer circuit boards and assemblies. 

Caution: Damaged inner-layer connections may require surface wire adds.

Minimum Skill Level - Expert

Conformance Level - High

Tools and Materials

Ball Mills, Abrasives, Cutting Tools Ball mills, abrasives and cutting tools for working on circuit boards.

Circuit Bond Epoxy Clear, superior strength epoxy in two-compartment plastic packages.

Cleaner General purpose cleaner for removing contamination.

Cleaning Brushes Disposable brushes for solvent cleaning and application of coatings.

End Mills Designed for end cutting and hole boring.

File High carbon steel needle file perfect for all kinds of detail work.

Flex-Rack PCB Holder Sturdy rack for PCBs used for rework and positioning.

High Temp Tape Discs High temperature polyimide tape discs, .50" diameter.

Knife with #16 Blades A must-have tool for precise cutting, scraping and trimming.

Micro Drill System Versatile power tool for milling, drilling, grinding, cutting and sanding.

Microscope Precision microscope with stand and lighting for work and inspection.

Oven General purpose oven for drying, baking and curing epoxies.

Precision Drill Precision drill press for accuracy and controlled depth drilling.

Precision Tool Set Nine precision-crafted tools for detailed circuit board work.

Scraper, Curved Tip Hardened stainless steel tip for scraping solder mask and removing defects.

Wipes Nonabrasive, low-linting wipes for cleanup.

Procedure

1. Clean the area.
2. 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)
   Note: Abrasion operations can generate electrostatic charges.
3. Cut a piece of replacement base material rod. The base material rod is made from FR-4 dowel stock. Cut the length approximately 12.0 mm (0.50") longer than needed.
4. Clean the reworked area.
5. Use High-Temperature Tape to protect exposed parts of the circuit board bordering the rework area.
6. Mix the epoxy.
7. Coat both the dowel and the hole with epoxy and fit together. Apply additional epoxy around the perimeter of the new material. (See Figure 2) Remove excess epoxy.
8. Cure the epoxy per Procedure 2.7 Epoxy Mixing and Handling.
   Caution: Some components may be sensitive to high temperatures.
9. 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)
10. Complete the procedure by redrilling holes and adding circuitry as required. (See Figure 3)
    Note: Apply surface coating to match prior coating as required.
11. Clean the reworked area.

Evaluation

1. Visual and dimensional examination of the reworked area for conformance to drawings and specifications.

Images

Hole Repair, Transplant Method

A damaged non-plated hole.

New hole is milled to encompass entire damaged area.

Place replacement dowel in position and bond with epoxy.

Cut off excess material and re-drill holes as required.