Circuit Board Repair and Rework Guide > 3.0 Base Board Procedures > 3.5.2 Base Material Repair, Area Transplant Method

3.5.2 Base Material Repair, Area Transplant Method

Printed Board Type: R/W | Skill Level: Expert | Conformance Level: High | Rev.: D | Rev. Date: Jul 7, 2000

Outline

This procedure is used to repair mechanical or thermal damage to circuit board base material. This method is used when extended areas of base material must be completely replaced. This method may be used on single sided, double sided or multilayer circuit boards or assemblies.

Caution
Surface circuits may need to be replaced in the damaged area. Be sure that the appropriate circuit diagrams, or photographs reflecting the original circuits are available so that they may be replaced after repairing the base board material. Damage to internal circuits or planes may have to be restored using surface wires.

Damaged Base Material

Acceptability References
IPC-A-600	2.0	Externally Observable Characteristics
IPC-A-610	10.0	Laminate Conditions
Procedure References
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
IPC7721	3.5.2	Base Material Repair, Area Transplant Method
Tools and Materials
Ball Mills Base Board Repair Kit Base Board Material Cleaner Color Agents End Mills Epoxy Knife		Micro-Drill System Microscope Oven Precision Drill System Scraper Surgical Saw Tape, Kapton Wipes

Procedure

Mill away damaged base material using Micro-Drill System and ball mill.

Figure 1: Mill away the damaged
base material using the Micro-Drill System and ball mill.

1.	Clean the area.

2.	Mill away the damaged board material using the Micro-Drill System and ball mill. Remove all evidence of the damaged material. No fibers of laminate material should be exposed. At the surface file the edges to ensure that the opening is rectangular or uniform in shape. (See Figure 1).

	Caution Abrasion operations can generate electrostatic charges.

3.	Clean the area.

Figure 2: Bevel edge using the
Micro-Drill System or file.

4.	Bevel the edge using the Micro-Drill System and ball mill or using a file. (See Figure 2).

Or

Figure 3: Mill a step into the edge
of the circuit board.

	Install an end mill into the chuck of a Precision Drill System. Set the speed to maximum and machine a step or lap joint in the edge of the circuit board where the new base material will be installed. The depth and width of the step should be approximately 1/2 of the circuit board thickness. (See Figure 3).

	Caution Exercise care to avoid damage to any internal conductors. If any internal conductors are damaged, surface wires may be required.

5.	Cut or machine a piece of replacement base board material that is the same thickness and type as the piece removed. The replacement piece must be precisely the same size and shape of the opening including the step joint.

Figure 4: Mill a step onto the edge
of the replacement base material.

6.	Install an end mill into the chuck of a Precision Drill Press. Machine a step onto the entire mating edge of the replacement base material. The dimensions of the step should match the size of the step in the circuit board milled groove. (See Figure 4).

7.	Where required apply Kapton tape to protect exposed parts of circuit board bordering the prepared area.

8.	Check the fit to be sure the new base material properly mates with the step in the circuit board.

9.	Mix the epoxy.

Figure 5: Bond replacement piece in place.

10.	Coat both the tongue and groove surfaces with epoxy and fit together. (See Figure 5). Remove excess epoxy.

11.	Cure the epoxy per Procedure 2.7 Epoxy Mixing and Handling.

12.	After the epoxy has cured remove the High Temperature Tape.

13.	If needed scrape off any excess epoxy using a knife or scraper.

	Note If needed, apply additional thin coating to seal any scraped areas.

Figure 6: Completed repair.

14.	Clean the area.

15.	Complete by drilling holes, slots, etc. or adding circuitry as required.