IPC 7711A - 第260页
CAUTION Abrasion operations can generate electrostatic charges. NOTE End mills are normally single end, two or four flute high grade solid carbide. 5. Mill down into the board at the proper coordinates to cut the inner l…
OUTLINE
This method is used to sever a conductor or short. A small section of the conduc-
tor is removed forming a break. The width of the break should be at least as wide as
the minimum conductor spacing. A precision drill system is used with a carbide end
mill. This method is recommended for surface or inner layer conductor cuts. After
milling, the area is sealed with epoxy.
NOTE
This method is recommended for surface or inner layer conductor cuts.
CAUTION
Extreme care must be taken to prevent damage to adjacent or underlying inner layer
conductors. A microscope must be used during milling when extreme accuracy is
required.
REFERENCES
2.1 Handling Electronic Assemblies
2.2 Cleaning
2.6 Epoxy Mixing and Handling
TOOLS AND MATERIALS
Cleaner
Cleaner Wipes
Color Agent
Continuity Meter
End Mills, Carbide
Epoxy
Epoxy Dispensing System
Heat Lamp
Microscope
Precision Drill Press
Oven
PROCEDURE
1. Identify the conductor or short to be cut. Determine from the artwork or draw-
ings 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. If the cut is on an inner layer conductor, mark the coordinates on the printed
wiring board surface or set up a fixture to precisely locate the board in the pre-
cision drill press. (See Figure 1.)
4. Select the appropriate size end mill or ball mill and insert it into the chuck of the
precision drill press. The milling cutter should be slightly larger in diameter than
the conductor to be cut. Set speed to high.
Figure 1 Precision drill press with
base plate.
Figure 2 Mill into PC board at proper
coordinates.
Figure 3 fill the milled hole with
epoxy up to and flush with the surface.
Figure 4 Completed repair.
7721A
Repair and
Modification of
Printed Boards and
Electronic Assemblies
Revision:
Date: 2/98
Conductor Cut,
Inner layer Conductors
Number: 4.3.2
Product Class: R, F
Skill Level: Advanced
Level of Conformance: High
Material in this manual was voluntarily established by Technical Committees of IPC. This material is advisory only and its use
or adaptation is entirely voluntary. IPC disclaims all liability of any kind as to the use, application, or adaptation of this material.
Users are also wholly responsible for protecting themselves against all claims or liabilities for patent infringement. Equipment
referenced is for the convenience of the user and does not imply endorsement by IPC.
Page1of2
Copyright Association Connecting Electronics Industries
Provided by IHS under license with IPC
Not for Resale
No reproduction or networking permitted without license from IHS
--``,``,-`-`,,`,,`,`,,`---
CAUTION
Abrasion operations can generate electrostatic charges.
NOTE
End mills are normally single end, two or four flute high grade solid carbide.
5. Mill down into the board at the proper coordinates to cut the inner layer con-
ductors or to break the inner layer short. Do not mill deeper than needed. A
microscope should be used for accuracy. (See Figure 2.)
6. Blow away material with air and clean the area.
7. Check continuity to be sure that the conductor has been cut.
8. Mix epoxy. If desired, add color agent to the mixed epoxy to match the printed
wiring board color.
9. Fill the milled hole with epoxy up to and flush with the surface. An epoxy dis-
penser may be used to accurately control the application of epoxy. Remove any
excess epoxy. (See Figure 3.)
CAUTION
Examine milled hole to be sure all material is removed from the hole prior to fill-
ing the hole with epoxy.
NOTE
A slight overfill of epoxy may be desired to allow for shrinkage when epoxy
cures.
10. Cure the epoxy per the manufacturer’s instructions.
CAUTION
Some components may be sensitive to high temperatures.
EVALUATION
1. Visual examination of cuts for spacing, and unintended damage to surrounding
conductors.
2. Electrical tests as applicable.
NOTES
IPC-7721A
Number: 4.3.2
Revision:
Date: 2/98
Subject: Conductor Cut, Inner Layer Conductors
Page2of2
Copyright Association Connecting Electronics Industries
Provided by IHS under license with IPC
Not for Resale
No reproduction or networking permitted without license from IHS
--``,``,-`-`,,`,,`,`,,`---
OUTLINE
This method is used on multilayer printed wiring boards or assemblies to disconnect
an internal connection at a plated hole. A precision drill press is used with a carbide
drill, end mill or ball mill to drill out the hole. The hole may then be filled with epoxy
and redrilled to the diameter needed.
CAUTION
Extreme care must be taken to prevent damage to adjacent conductors. A micro-
scope must be used during milling when extreme accuracy is required.
REFERENCES
2.1 Handling Electronic Assemblies
2.2 Cleaning
2.5 Baking and Preheating
2.6 Epoxy Mixing and Handling
TOOLS AND MATERIALS
Cleaner
Cleaner Wipes
Color Agent
Continuity Meter
End Mills, Carbide
Epoxy
Epoxy Dispensing System
Heat Lamp
Polyimide Tape
Oven
Microscope
Pin Clamps
Precision Drill Press
PROCEDURE
1. Identify the hole that requires rework and clean the area.
2. Mark the coordinates on the board surface and pin the printed wiring board in
place on the base plate of the precision drill press. (See Figure 1.)
3. Select the appropriate size end mill, drill or ball mill and insert it into the chuck
of the precision drill press. The cutting tool should be approximately 0.50 mm
greater than the plated through hole inside diameter. Set speed to high.
CAUTION
Abrasion operations can generate electrostatic charges.
NOTE
End mills are normally single end, two or four flute high grade solid carbide.
4. Completely mill through the hole to isolate the internal connection(s). A micro-
scope should be used for accuracy. (See Figure 2.)
5. Blow away material with air and clean the area.
6. Check continuity to be sure that the internal connection has been deleted. Also
Figure 1 Precision drill press with
base plate.
Figure 2 Completely mill through the
hole.
Figure 3 Fill the hole with epoxy up to
and flush with the surface.
Figure 4 Repair complete.
7721A
Repair and
Modification of
Printed Boards and
Electronic Assemblies
Revision:
Date: 2/98
Deleting Inner Layer
Connection At A Plated
Hole, Drill Through Method
Number: 4.3.3
Product Class: R, F
Skill Level: Advanced
Level of Conformance: High
Material in this manual was voluntarily established by Technical Committees of IPC. This material is advisory only and its use
or adaptation is entirely voluntary. IPC disclaims all liability of any kind as to the use, application, or adaptation of this material.
Users are also wholly responsible for protecting themselves against all claims or liabilities for patent infringement. Equipment
referenced is for the convenience of the user and does not imply endorsement by IPC.
Page1of2
Copyright Association Connecting Electronics Industries
Provided by IHS under license with IPC
Not for Resale
No reproduction or networking permitted without license from IHS
--``,``,-`-`,,`,,`,`,,`---