First-Aid Kits for Circuit Boards
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4.3.1 Circuit Cut, Surface Circuits
Outline
This method is used to sever a circuit or short. A small section of the circuit is removed forming a break. The width of the break should be at least as wide as the minimum conductor spacing. The Surgical Knife or high speed, Micro-Drill System is used. This method is recommended for surface circuit cuts only. After cutting, the area is sealed with epoxy.
Note
This method is recommended for surface circuit cuts only.
Minimum Skill Level - Advanced
Recommended for technicians with soldering and component rework skills and exposure to most repair/rework procedures, but lacking extensive experience.
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.
| Acceptability References |
| IPC-A-600 2.0 |
Externally Observable Characteristics |
| IPC-A-610 10.0 |
Laminate Conditions |
| Tools and Materials |
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Cleaner
General purpose cleaner for removing contamination. |
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Continuity Meter
Meter and probes to test for electrical continuity. |
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Epoxy Kit
High temperature epoxy for masking and structural repairs to circuit boards. |
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Microscope
It is a challenge to undertake precision repair without a good microscope. |
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Oven
General purpose oven for drying, baking and curing epoxies. |
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Wipes
Nonabrasive, low-linting wipes for cleanup. |
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| Images and Figures |
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| Circuit Cut, Surface Circuit |
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| Figure 1: Option A - Make two small cuts with the knife and remove a short section of circuit. |
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| Figure 2: A high quality, Micro-Drill System is recommended for this delicate operation. |
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| Figure 3: Make 1 or 2 cuts as needed to cut circuit. |
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| Figure 4: Completed repair. |
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Procedure
- Identify the circuit or short to be cut. Determine from the artwork or drawings where the best location is to make the break. The width of the break should at least match the minimum required electrical spacing.
- Clean the area.
- Carefully make two small cuts with the knife and remove the short section of circuit. (See Figure 1). Or use a Micro-Drill as covered in the next step.
- Select the appropriate size ball mill and insert it into the Micro-Drill System. Set the speed to high. (See Figure 2). The ball mill should be approximately the same width as the circuit to be cut.
Note
Ball mills should be dental grade carbide steel for precision cutting and long life.
- Carefully make 1 or 2 cuts as needed. (See Figure 3).
Caution
Exercise care to avoid damage to adjoining circuits.
- Check continuity to be sure that the circuit has been cut.
- Clean the area.
- Mix epoxy. If desired, add color agent to the mixed epoxy to match the circuit board color.
- Coat the area with epoxy if needed. An epoxy dispenser may be used to control the application of epoxy. Remove any excess.
- Cure the epoxy per Procedure 2.7 Epoxy Mixing and Handling.
Evaluation
- Visual examination of cuts for spacing, and unintended damage to surrounding circuits.
- Electrical tests as applicable.
This procedure is for reference only. Refer to the Procedure References listed above, or contact Circuit Technology Center for appropriate industry approved references.
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CircuitMedic
22 Parkridge Road, Haverhill, MA 01835 USA
Phone: 978-373-1600 - Fax: 978-372-5700
Division of Circuit Technology Center, Inc.
Copyright © 2012 All rights reserved.
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ISO9000:2008 Certified
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Member Since 1986
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