Circuit Board Repair Guide > Conductor Repair Procedures > 4.3.1 How to Cut Surface Circuits or Conductors

How to Cut Surface Circuits or Conductors

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This repair procedure 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. A Surgical Knife or Micro Drill System is used. After cutting, the area is sealed with epoxy.

Note
This procedure is recommended for surface circuit cuts only.

 
Surface circuit needs to be cut
Circuit Cut, Surface Circuit
IPC Acceptability References
IPC-A-600 2.0 Externally Observable Characteristics
IPC-A-610 10.0 Laminate Conditions

Related Procedure References
CTC 1.0 Foreword - Circuit Board Repair Guide
CTC 2.1 Handling Electronic Assemblies
CTC 2.2.1 How to Clean a Circuit Board
CTC 2.2.2 Cleaning Circuit Boards, Aqueous Batch Process
CTC 2.7 Epoxy Mixing and Handling
IPC7721 4.3.1 Conductor Cut, Surface Conductors

Tools and Materials
Ball Mills
Cleaner
Color Agents
Continuity Meter
Circuit Bond Kit
Knife
Micro Drill System
Microscope
Oven
Wipes

4.3.1 Circuit Cut, Surface Circuits

Printed Board Type: R/F/W  |  Skill Level: Advanced  |  Conformance Level: High  |  Rev.: E  |  Rev. Date: Jul 7, 2000

Remove short section of circuit

Figure 1: Option A - Make two
small cuts with the knife and
remove a short section of circuit.


1. 
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.
   
2.  Clean the area.
   
3. 
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.
Micro Drill System used for milling, drilling, grinding, cutting and sanding circuit boards

Figure 2: A high quality, Micro
Drill System is recommended
for this delicate operation.


4. 
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.
Cut circuit as needed

Figure 3: Make 1 or 2 cuts as
needed to cut circuit.


5.  Carefully make 1 or 2 cuts as needed. (See Figure 3).
   
  Caution
Exercise care to avoid damage to adjoining circuits
   
6.  Check continuity to be sure that the circuit has been cut.
   
7.  Clean the area.
   
8. 
Mix circuit epoxy. If desired, add color agent to the mixed epoxy to match the circuit board color.
   
9. 
Coat the area with epoxy if needed. An epoxy dispenser may be used to control the application of epoxy. Remove any excess.
   
10. Cure the epoxy per Procedure 2.7 Epoxy Mixing and Handling.
   
Circuit repair completed

Figure 4: Completed repair.
Evaluation
   
1. 
Visual examination of cuts for spacing, and unintended damage to surrounding circuits.
   
2.  Electrical tests as applicable.




Links to Related Products


Circuit board epoxy for ciruit repair  
Circuit Bond Kit 115-1322: Liquid circuit board epoxy
Circuit Bond Kit contains 10 packages of clear, low viscosity, superior strength epoxy ideal for circuit board use. The epoxy is precisely measured out into two-compartment plastic packages. This adhesive is easy to use and there's no measuring.

Color Agents for Circuit Boards
Matching epoxy to the color of the circuit board being repaired is easy when you use a color agent. Color agents may also be applied directly to the circuit board surface for color matching.


Micro Drill System used for drilling, grinding, cutting circuit boards  
Micro Drill System 110-4105
The Micro Drill System is a repair technician's dream and is ideal for milling, drilling, grinding, cutting and sanding circuit boards. It removes coating, cuts circuits, cuts leads, drills holes, cuts slots, shapes FR4 and performs many other procedures using various interchangeable bits. Unlike most hand-held tools, the Micro Drill has a tiny, high speed DC motor in the hand piece, eliminating cumbersome drive cables and giving you better control. A separate power supply keeps the hand piece lightweight and reduces operator fatigue. Base unit has controls for forward/reverse and speed up to 45,000 RPM.



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