2.6.3 Legend Marking, Stencil Method

Printed Board Type: R/F/W/C
Skill Level: Intermediate
Conformance Level: High
Revision: D
Revision Date: Jul 7, 2000

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 a brush or roller technique. A stencil is used to outline the characters.

ACCEPTABILITY REFERENCES
IPC-A-600 2.0	Externally Observable Characteristics
IPC-A-610 8.0	Marking
PROCEDURE REFERENCE
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

Damaged Legend

TOOLS & MATERIALS
Cleaner
Color Agent/Epoxy Ink
Ink Roller
Ink Plate
Microscope
Oven
Knife
Stencil
Wipes

PROCEDURE

1. Figure 1: Replace legend using a stencil.

   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 stencil or have a special stencil made up. (See Figure 1).
   
   
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. Figure 2: Completed legend repair.

   Position the stencil on thecircuit board surface and hold in place firmly
   
   
6. Roll or brush the ink onto the stencil. Do not smudge characters or apply excess ink.
   
   
7. Cure the epoxy ink per the manufacturer's instructions.

EVALUATION

1. Visual examination for proper characters, positioning and legibility.