IPC 7711A - 第225页
OUTLINE This procedure is used to repair mechanical or thermal damage to printed wiring board base material. This method is used when extended areas of base material must be completely replaced. This method may be used o…
CAUTION
Abrasion operations can generate electrostatic charges.
2A. Mill away the damaged board base material using dental style drill and ball
mill. All damaged base board material and solder resist must be removed.
(See Figure 2.)
NOTE
An undercut to enhance mechanical strength may be desired for class 3
product. (See Figure 3.)
3. Remove all loose material and clean the area.
4. Where needed, apply tape to protect exposed parts of printed wiring board.
NOTE
The printed wiring board may be preheated prior to filling the area with epoxy.
A preheated printed wiring board will allow the epoxy to easily flow and level out.
Epoxy applied to an unheated printed wiring board may settle below the printed
wiring board surface as the epoxy cures.
5. Mix the epoxy. If desired, add color agent to the mixed epoxy to match the
printed wiring board color.
6. Fill the area with epoxy up to and flush with the printed wiring board surface. No
fibers of laminate material should be exposed. A wood stick sharpened at the
end may be used to apply and spread the epoxy. For large areas, apply the
epoxy with a foam swab to create a texture in the surface. (See Figures 4 and
5.)
NOTE
A slight overfill of epoxy may be desired to allow for shrinkage when epoxy
cures.
NOTE
Epoxy may be applied using a foam swab to restore the surface appearance.
7. Cure the epoxy per the manufacturer’s instructions.
CAUTION
Some components may be sensitive to high temperature.
8. After the epoxy has cured remove the tape.
9. If needed, use a knife or scraper and scrape off any excess epoxy. Scrape until
the new epoxy surface is level with the surrounding printed wiring board surface.
10. Remove all loose material. Clean the area.
NOTE
If needed, apply an additional thin coating to seal any scraped areas.
EVALUATION
1. Visual examination for texture and color match.
2. Electrical tests to conductors around the repaired area as applicable.
NOTES
Figure 5 Apply the epoxy with a foam
swab to create a texture in the surface.
IPC-7721A
Number: 3.5.1
Revision:
Date: 2/98
Subject: Base Material Repair, Epoxy Method
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 procedure is used to repair mechanical or thermal damage to printed wiring
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 printed wiring boards or assemblies.
CAUTION
Surface conductors may need to be replaced in the damaged area. Be sure that the
appropriate conductor diagrams, or photographs reflecting the original conductors
are available so that they may be replaced after repairing the base board material.
Damage to internal conductors or planes may have to be restored using surface
wires.
REFERENCES
2.1 Handling Electronic Assemblies
2.2 Cleaning
2.5 Baking and Preheating
2.6 Epoxy Mixing and Handling
TOOLS & MATERIALS
Ball Mills, Carbide
Base Board Material
Carbide Saw
Cleaner
Cleaning Wipes
Color Agent, Various Colors
End Mills, Carbide
Epoxy
Hand Held Drill
Heat Lamp
Polyimide Tape
Knife
Oven
Precision Drill Press
Razor Saw
Scraper
PROCEDURE
1. Clean the area
2. Mill away the damaged board material using a hand held drill 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.
3A. Bevel the edge using a hand held drill and ball mill or using a file. (See Fig-
ure 2.)
Figure 1 Mill away damaged base
material.
Figure 2 Bevel edge using a hand
held drill or file.
Figure 3 Mill a step into the edge of
the PC board.
Figure 4 Mill a step onto the edge of
the replacement base material.
7721A
Repair and
Modification of
Printed Boards and
Electronic Assemblies
Revision:
Date: 2/98
Base Material Repair,
Area Transplant Method
Number: 3.5.2
Product Class: R, W
Skill Level: Expert
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
Exercise care to avoid damage to any internal conductors. If any internal
conductors are damaged, surface wires may be required to restore electri-
cal connection.
3B. Install an end mill into the chuck of a precision drill press. Set the speed to
maximum and machine a step or lap joint in the edge of the printed wiring
board where the new base material will be installed. The depth and width
of the step should be approximately 1/2 of the printed wiring board thick-
ness. (See Figure 3.)
4. 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 pre-
cisely the same size and shape of the opening including the step joint.
5. 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 printed wiring boardmilled groove.
(See Figure 4.)
6. Where required apply Polyimide tape to protect exposed parts of printed wiring
board bordering the prepared area.
7. Check the fit to be sure the new base material properly mates with the step in
the printed wiring board.
8. Mix the epoxy.
9. Coat both the tongue and groove surfaces with epoxy and fit together. (See
Figure 5.) Remove excess epoxy.
10. Cure the epoxy per the manufacturers instructions.
CAUTION
Some components may be sensitive to high temperature.
11. After the epoxy has cured remove the Polyimide tape.
12. If needed scrape off any excess epoxy using a scraper or knife.
NOTE
If needed, apply additional thin coating to seal any scrapped areas.
13. Clean the area.
14. Complete by drilling holes, slots, etc. or adding circuitry as required.
15. If solder resist replacement or conformal coating is needed see appropriate pro-
cedure.
EVALUATION
1. Dimensions of area replaced should be checked to conform to specifications
required.
NOTES
Figure 5 Bond replacement piece in
place.
Figure 6 Completed repair.
IPC-7721A
Number: 3.5.2
Revision:
Date: 2/98
Subject: Base Material Repair, Area Transplant Method
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
--``,``,-`-`,,`,,`,`,,`---