2.6.3 Legend/Marking Repair, Stencil Method

Outline

This method can be used to add, change, or replace legends and markings on printed boards or printed board assemblies. It uses epoxy ink and a brush or roller technique. A stencil is used to outline the characters.

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 2.6.3	Legend/Marking, Stencil Method

Tools, Materials and Supplies

Circuit Bond Epoxy
Clear, superior strength epoxy in two-compartment plastic packages.

Flex-Rack PCB Holder
Sturdy rack for PCBs used for rework and positioning.

Cleaning Brushes
Disposable brushes for solvent cleaning and application of coatings.

Color Agents
One part, semi-paste ink used to tint the color of epoxy and for direct printing on circuit board surfaces.

Cleaner
General purpose cleaner for removing contamination.

Knife with #16 Blades
A must-have tool for precise cutting, scraping and trimming.

Microscope
Precision microscope with stand and lighting for work and inspection.

Oven
General purpose oven for drying, baking and curing epoxies.

Precision Tool Set
Nine precision-crafted tools for detailed circuit board work.

Wipes
Nonabrasive, low-linting wipes for cleanup.

Procedure

Clean the area.
Scrape off any remaining character or legend with a knife and clean the area.
Caution: Abrasion operations can generate electrostatic charges.
Select the appropriate stencil or have a special stencil made up. (See Figure 2)
Mix the epoxy ink. White is the most common color. Spread a thin, even coating of the epoxy ink on the ink plate or a smooth surface.
Position the stencil on the circuit board surface and hold it in place firmly.
Roll or brush the ink onto the stencil. Do not smudge characters or apply excess ink.
Cure the epoxy ink per the manufacturer's instructions.

Evaluation

Visual examination for proper characters, positioning, and legibility.

Images and Figures

Legend/Marking Repair, Stencil Method

Figure 1. Scrape off any remaining character or legend with a knife and clean the area.

Figure 2. Position a stencil on the circuit board surface and roll or brush the ink to replace the missing legend

Figure 3. Cure the epoxy ink per the manufacturer's instructions.

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Product Type
Assemblies Bare PCBs Other

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2.6.3 Legend/Marking Repair, Stencil Method

Procedure covers the methods for repair and replacement of legend and markings on circuit boards. Minimum Skill Level: Intermediate Conformance Level: High

Procedure covers the methods for repair and replacement of legend and markings on circuit boards.

Minimum Skill Level: Intermediate
Conformance Level: High