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2.6.1 Legend/Marking, Stamping Method

 
Since 1983 the experienced technicians at Circuit Technology Center have used this simple method to repair and update circuit boards for customers around the world.

For more information visit: Coating and Marking Rework.
 
Outline
This method can be used to add, change or replace legend and markings on printed boards or printed board assemblies. This method uses epoxy ink and an ink stamp to place the legends on the printed board surface in much the same manner as taking a "fingerprint".

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.

Acceptability References
IPC-A-600 2.0 Externally Observable Characteristics
IPC-A-610 8.0 Marking
Procedure References
1.0 Foreword
2.1 Handling Electronic Assemblies
2.2 Cleaning
2.5 Baking And Preheating
2.7 Epoxy Mixing and Handling
IPC7721 2.6.1 Legend/Marking, Stamping Method
Kits and Systems
201-3110
Base Board Repair Kit
Kit to repair base board and laminate damage on circuit boards.
201-7100
Precision Tool Set
Nine precision-crafted tools for detailed circuit board work.
Tools and Materials
235-2106-5
Cleaning Brushes
Disposable brushes for solvent cleaning and application of coatings.
Coatings
Color Agents
Use to tint the color of epoxy used for solder mask repair or circuit base board repair.
115-3302
Circuit Bond Epoxy
Clear, superior strength epoxy in two-compartment plastic packages.
355-0614
Knife with #16 Blades
A must-have tool for precise cutting, scraping and trimming.
Additional Items and Supplies
Cleaner
Cleaner
General purpose cleaner for removing contamination.
Microscope
Microscope
Precision microscope with stand and lighting for work and inspection.
Oven
Oven
General purpose oven for drying, baking and curing epoxies.
Peg Stamps
Peg Stamps
Peg stamps for application of inks to replace text and markings.
Wipes
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
Packaging2 gram pre-measured packages
Mix ratio4 parts resin to 1 part hardener
Mix Ratio by Weight (R/H)100/25
ColorClear, transparent
Pot life30 minutes
Cure cycle24 hours at room temp (25 °C) or 4 hours @ 65°C
Thixotropic Index1
Specific Gravity1.20
Percent Solids100%
Viscosity (after mixing)2000 cps
Operating temperature range-55°C to 135°C
Hardness88 Shore D
Lap Shear, Alum to Alum1100 psi
Glass Transition Temperature, Ultimate92°C
Coefficient of Expansion, cm/cm/°C6 E-05
Dielectric strength400 volts/mil
Dielectric Constant, 1KHz@25°C4
Shelf Life6 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.
Part No. Description
115-9102 115-9102 Color Agent, Yellow
115-9185 115-9185 Color Agent, Red
115-9293 115-9293 Color Agent, Blue
115-9348 115-9348 Color Agent, Green
115-9358 115-9358 Color Agent, Light Green
115-9376 115-9376 Color Agent, Medium Green
115-9424 115-9424 Color Agent, Dark Gray
115-9457 115-9457 Color Agent, Light Brown
115-9560 115-9560 Color Agent, Dark Green
115-9561 115-9561 Color Agent, Green
115-9995 115-9995 Color Agent, Black
115-9996 115-9996 Color Agent - White
Images and Figures
2.6.1  Legend/Marking, Stamping Method
Damaged Legend
2.6.1  Legend/Marking, Stamping Method
Figure 1: Apply legend using a peg stamp.
2.6.1  Legend/Marking, Stamping Method
Figure 2: Completed legend repair.

Procedure
  1. Clean the area.
  2. Scrape off any remaining character or legend with a knife and clean the area.
    Caution: Abrasion operations can generate electrostatic charges.
  3. Select the appropriate characters from the peg stamp set or have a special stamp made up.
  4. Mix the epoxy ink. White is the most common color. Spread a thin, even coating of the epoxy ink on the ink plate or on a smooth surface.
  5. Gently press the peg stamp into the epoxy coating to coat the character surface.
  6. Gently press the peg stamp onto the desired location on the circuit board surface. (See Figure 1)
  7. Cure the epoxy ink per the manufacturer's instructions.
Evaluation
  1. Visual examination for proper characters, positioning and legibility.
Procedure for reference only.