Outline
This method is used to rebond a lifted circuit. Liquid epoxy is inserted under and around the circuit to bond it back down to the circuit board surface.
Caution: This method should not be used to rebond a circuit that has been stretched or damaged.
Minimum Skill Level - Intermediate
Recommended for technicians with skills in basic soldering and component rework, but may be inexperienced in general repair/rework procedures.
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.
Micro Probes
Sharp probes for dispensing adhesive and positioning small objects.
Probe
Sharp dental-style probe for manipulating small objects and removal of debris.
Scraper, Curved Tip
Hardened stainless steel tip for scraping solder mask and removing defects.
Syringes
Polypropylene syringe barrels with stainless steel dispensing tips.
Additional Items and Supplies
Cleaner
General purpose cleaner for removing contamination.
Oven
General purpose oven for drying, baking and curing epoxies.
Tweezers
Multiple sizes and tip configurations of tweezers for various small parts handling needs.
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
Color Agents
Color Agent is a one-part, air-drying, semi-paste ink commonly used to print hard surfaces, including circuit board base materials. Color Agent can be used to tint the color of epoxy used for solder mask repair or circuit baseboard repair. To use, mix a small amount of color agent with 2 part epoxy as the epoxy is initially mixed. Add more color agents to increase the color intensity if needed.
Figure 1: Apply a small amount of epoxy under the entire length of the lifted circuit.
Figure 2: Completed repair.
Procedure
Clean the area.
Remove any obstructions that prevent the lifted circuit from making contact with the baseboard surface.
Caution: Be careful while cleaning and removing all obstructions, not to stretch or damage the lifted conductor.
Clean the area.
Mix the epoxy.
Carefully apply a small amount of epoxy under the entire length of the lifted circuit. The tip of a knife may be used to apply the epoxy. (See Figure 1)
Press the lifted circuit down into the epoxy and into contact with the base board material.
Apply additional epoxy to the surface of the lifted circuit 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.
Apply surface coating to match prior coating as required.
Evaluation
Visual examination and tape test per IPC-TM-650 (ANSI/IPC-FC-250A) test method 2.4.1.
