3.3.2 Hole Repair, Transplant Method

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 Hole, Non Plated

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

Acceptability References
IPC-A-600	2.0	Externally Observable Characteristics
IPC-A-610	10.0	Laminate Conditions

Procedure Reference
CTC	1.0	Foreword
CTC	2.1	Handling Electronic Assemblies
CTC	2.2.1	Cleaning, Local
CTC	2.2.2	Cleaning, Aqueous Batch Process
CTC	2.5	Baking and Preheating
CTC	2.7	Epoxy Mixing and Handling
IPC 7721	3.3.2	Hole Repair, Transplant Method see procedure below

Tools and Materials
Base Board Repair Kit
Base Material Rod
Cleaner
End Mills
Epoxy
Knife
Micro-Drill System
Microscope
Mixing Sticks
Oven
Precision Drill System
Razor Saw
Tape, Kapton
Wipes

Procedure 3.3.2 Hole Repair, Transplant Method

Figure 1: New hole is milled to encompass entire damaged area.

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 Figures 1 and 2).

	Note Abrasion operations can generate electrostatic charges.

Figure 2: Precision Drill System for accurate hole drilling and milling.

3.	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.

4.	Clean the reworked area.

5.	Use Kapton tape to protect exposed parts of the circuit board bordering the rework area.

6.	Mix the epoxy.

Figure 3: Place replacement dowel in position and bond with epoxy.

7.	Coat both the dowel and the hole with epoxy and fit together. Apply additional epoxy around perimeter of new material. (See Figure 3). Remove excess epoxy.

8.	Cure the epoxy per Procedure 2.7 Epoxy Mixing and Handling. Caution Some components may be sensitive to high temperatures.

Figure 4: Cut off excess material and redrill holes as required.

9.	Remove Kapton tape and cut off the excess material using the razor saw. Mill or file the dowel flush with the board surface. (See Figure 4).

10.	Complete the procedure by redrilling holes and adding circuitry as required. (See Figure 4). Note Apply surface coating to match prior coating as required.

Figure 5: Micro-Drill System

11.	Clean the reworked area.

Evaluation

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