4.1.2 Lifted Conductor Repair, Film Adhesive Method
Outline
This method is used to repair damaged and lifted conductors. Dry film epoxy is used to rebond the lifted conductor.
Caution: This method should not be used to rebond a conductor 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.
$5.00 Pkg/5
Scraper, Curved Tip Hardened stainless steel tip for scraping solder mask and removing defects.
$10.00 Each
Additional Items and Supplies
Cleaner General purpose cleaner for removing contamination.
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Microscope Precision microscope with stand and lighting for work and inspection.
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Tweezers Multiple sizes and tip configurations of tweezers for various small parts handling needs.
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Wipes Nonabrasive, low-linting wipes for cleanup.
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Bonding Iron Tips
Bonding Iron Tips fit into the handheld Bonding Iron. The bottom surface of each Bonding Tip is used to apply heat and pressure to bond adhesive-backed replacement lands, pads, and edge contacts to a circuit board surface. The pressure/force listed is the recommended load in pounds to apply to the top surface of the replacement adhesive-backed pads, lands, and conductors. The load is based on the Bonding Tip surface area to meet the recommended load for Circuit Frames at 200 - 400 psi.
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
Circuit Frames
Circuit Frames have a dry-film adhesive backing that is heat-cured in 30 seconds. Use Circuit Frames to repair and replace damaged surface mount pads, lands and conductors without the mess of liquid epoxy, with a bond strength equal to the original, in just a few minutes. The dry-film adhesive backing makes this delicate repair procedure easy, fast, and highly reliable. Circuit Frames are available with a bright tin, tin/lead and nickel/gold plating finishes. This reliable IPC recommended procedure meets the highest conformance level for this type of repair. For over 30 years Circuit Frames have been used by thousands of commercial, medical and military manufacturers around the globe. Below are examples for some Circuit Frame patterns.
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: Cut out a piece of dry film epoxy and place it under the lifted conductor.
Figure 2: Place Kapton tape over the lifted conductor.
Figure 3: Bond the lifted conductor using a Bonding Iron.
Figure 4: Completed repair.
Procedure
Clean the area.
Remove any obstructions that prevent the lifted conductor 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.
Cut out a piece of dry film epoxy that closely matches the size of the lifted conductor. Be careful not to contaminate the dry film epoxy with materials that could reduce the bond strength. (See Figure 1)
Note:Dry film epoxy thickness should be selected to meet the requirements of the circuit Board.
Place the dry film epoxy under the lifted conductor. (See Figure 1)
Select a bonding tip with a shape to match the shape of the lifted conductor.
Note: The bonding tip should be as small as possible but should completely cover the entire surface of the conductor.
Place a piece of High-Temperature Tape over the lifted conductor. (See Figure 2)
Position the circuit board so that it is flat and stable. Gently place the hot bonding tip onto the tape covering the new conductor. Apply pressure as recommended in the manual of the repair system or repair kit for 5 seconds to tack the conductor in place. Carefully peel off the tape.
Gently place the bonding tip directly onto the new conductor. Apply pressure as recommended in the manual of the repair system or repair kit for an additional 30 seconds to fully bond the conductor. The conductor is fully cured. Carefully clean the area and inspect the new conductor.
Replace surface coating to match prior coating as required.
Evaluation
Visual examination and tape test per IPC-TM-650 (ANCI/IPC-FC-250A) test method 2.4.1.
