Outline
This method is used to rebond a lifted land. Liquid epoxy is inserted under and around the land to bond it back down to the circuit board surface.
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 - Medium
This procedure may have some variance with the physical character of the original and most likely varies with some of the functional, environmental and serviceability factors.
Scraper, Curved Tip
Hardened stainless steel tip for scraping solder mask and removing defects.
Additional Items and Supplies
Cleaner
General purpose cleaner for removing contamination.
Oven
General purpose oven for drying, baking and curing epoxies.
Wipes
Nonabrasive, low-linting wipes for cleanup.
Circuit Bond Epoxy
Circuit Bond is a clear, low viscosity, superior strength epoxy precisely measured out into two-compartment plastic packages, so it's easy to use, and there's no measuring. For over a decade, this high-strength epoxy has been qualified and used by thousands of high-rel electronics manufacturers across the globe.
1.
Circuit Bond has a working pot life of 30 minutes. It should not be mixed until ready to use.
2.
To use Circuit Bond, remove the plastic clip separating the resin and hardener. Squeeze back and forth from one half of the package to the other to mix the contents.
3.
Cut a corner off the package and squeeze all the contents into a Plastic Cup. Stir the contents to ensure it is thoroughly mixed.
4.
Circuit Bond may contain bubbles from the mixing process. If needed, use a vacuum system to remove bubbles.
5.
Color Agent can be mixed in with Circuit Bond to match surface colors if desired.
6.
Apply using a Foam Swab, Micro Probe, or Mixing Stick as required.
7.
Cure Circuit Bond for 24 hours at room temperature or 4 hours at 65°C (150°F).
Specifications
Packaging
2 gram pre-measured packages
Mix ratio
4 parts resin to 1 part hardener
Mix Ratio by Weight (R/H)
100/25
Color
Clear, transparent
Pot life
30 minutes
Cure cycle
24 hours at room temp (25 °C) or 4 hours @ 65°C
Thixotropic Index
1
Specific Gravity
1.20
Percent Solids
100%
Viscosity (after mixing)
2000 cps
Operating temperature range
-55°C to 135°C
Hardness
88 Shore D
Lap Shear, Alum to Alum
1100 psi
Glass Transition Temperature, Ultimate
92°C
Coefficient of Expansion, cm/cm/°C
6 E-05
Dielectric strength
400 volts/mil
Dielectric Constant, 1KHz@25°C
4
Shelf Life
6 months minimum
Images and Figures
Lifted Land.
Figure 1: Carefully apply a small amount of epoxy under the entire length of the lifted land.
Figure 2: Place high temperature tape over the lifted land.
Figure 3: Completed repair.
Procedure
Clean the area.
Remove any obstructions that prevent the lifted land from making contact with the baseboard surface.
Caution: Be careful while cleaning and removing all obstructions, as not to stretch or damage the lifted land.
Mix the epoxy.
Carefully apply a small amount of epoxy under the entire length of the lifted land. The tip of the knife or scraper may be used to apply the epoxy. (See Figure 1)
Place a piece of High-Temperature Tape over the lifted land and press the land down into the epoxy and into contact with the base board material. (See Figure 2)
Apply additional epoxy to the surface of the lifted land and to all sides as needed.
Cure the epoxy per Procedure 2.7 Epoxy Mixing and Handling.
Caution: Some components may be sensitive to high temperatures.
Note: Double sided and multilayer circuit Boards, may require an eyelet to restore the through connection. Refer to section 5.0 Plated Hole Procedures.
Carefully remove any excess epoxy inside the plated hole using a ball mill or drill bit. Turn the ball mill or drill bit by hand to prevent damage to the wall of the plated through hole.
Install the proper component and solder in place.
Note: This method is used to repair lifted lands, but the repaired lands may not have an intermetallic connection to the remaining plated hole. The solder joint of the replaced component will restore the integrity of the electrical connection, or an eyelet or buss wire may be used. See Plated Hole Repair Procedures.
Replace surface coating to match prior coating as required.
Evaluation
Visual examination and tape test per IPC-TM-650 test method 2.4.1. (ANSI/IPC-FC-250A)
