Outline
This coating removal method uses various grinding and scraping tools, depending on the composition of the coating material. A knife or dental-style scraper is normally used when a scraping method is desired. A handheld drill is normally used when a grinding technique is desired. A wide variety of rotary abrasive materials, including ball mills, may be required.
To determine the appropriate coating removal procedure, the coating must first be identified. Refer to procedure number 2.3.1.
Caution: Abrasion operations can generate electrostatic charges.
Minimum Skill Level - Expert
Recommended for technicians with advanced soldering and component rework skills and extensive experience in most 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.
Scraper, Curved Tip
Hardened stainless steel tip for scraping solder mask and removing defects.
Additional Items and Supplies
Cleaner
General purpose cleaner for removing contamination.
Microscope
Precision microscope with stand and lighting for work and inspection.
Wipes
Nonabrasive, low-linting wipes for cleanup.
Images and Figures
Coating Removal Required At Outlined Area
Figure 1: Scrape away damaged or unwanted coating with a knife or scraper.
Figure 2: Rubberized abrasives are best used to remove thin, hard coatings.
Figure 3: Rotary brushes are best used to remove soft coatings.
Figure 4: Removal complete.
Figure 5: Micro-Drill System.
Procedure - Scraping
Clean the area.
Remove the damaged or unwanted coating or solder mask using a knife or scraper. Hold the blade perpendicular to the coating and scrape from side to side until the desired material is removed. (See Figure 1)
Remove all loose material and clean the area.
Procedure - Grinding
Clean the area.
Insert an abrasive tip into the handheld drill. Abrade away the damaged or unwanted coating. Move the tool from side to side to prevent damage to the circuit board surface. (See Figure 2)
Remove all loose material and clean the area.
Note: Rubberized abrasives of the proper grade and grit are ideally suited for removing thin hard coatings from flat surfaces but not for soft coatings since these would cause the abrasive to "load up" with coating material and become ineffective.
Rotary brushes are better suited than rubberized abrasives on contoured or irregular surfaces, such as soldered connections, etc. since the bristles will conform to surface irregularities while removing hard or soft coatings. (See Figure 3)
Note: The procedure for removing thick coatings is primarily to reduce their thickness to a thin coating and then to remove the remaining thin coating by the scraping method.
Evaluation
Visual examination or UV light may be used to verify the complete removal of the coating.
