Circuit Board Repair Guide > Base Board Repair > 3.4.2 How to Repair Major Damage to Key and Slot Openings

How to Repair Major Damage to Key and Slot Openings

Repair Circuit Boards | Repair SMT Pads | Repair BGA Pads | Repair Lands | Repair Edge Contacts
Repair a Conductor | Plated Hole Repair | Base Board Repair | Replace Solder Mask or Coatings

This circuit board repair procedure is used to modify or repair a key slot, or other cutout in a printed circuit board or printed circuit board assembly. A replacement piece of matching board material is epoxied into the area that needs repair. A new cut is then machined into the repaired area if necessary.

Caution
Care should be taken to limit the application of epoxy to the specific areas desired and to avoid damage to the conductive patterns, contacts and components.

IPC Acceptability References
IPC-A-600 2.0 Externally Observable Characteristics
IPC-A-610 10.0 Laminate Conditions

Related Procedure References
CTC 1.0 Foreword - Circuit Board Repair Guide
CTC 2.1 Handling Electronic Assemblies
CTC 2.2.1 How to Clean a Circuit Board
CTC 2.2.2 Cleaning Circuit Boards, Aqueous Batch Process
CTC 2.5 Baking and Preheating of Printed Circuit Boards
CTC 2.7 Epoxy Mixing and Handling
IPC7721 3.4.2 Key and Slot Repair, Transplant Method
 
Damaged key slot at outlined area in base board needs repair
Damaged Key Slot
At Outlined Area

Tools and Materials
Alcohol Swabs - Self-saturating Isopropyl alcohol swabs. Squeeze handle to release alcohol.
Circuit Bond Pack - Clear, superior strength epoxy in two-compartment plastic package.
Cleaner - General purpose cleaner for removing contamination.
Cleaning Brushes - Disposable brushes for use with solvents for cleaning and application of coatings.
End Mills - Designed for end cutting and hole boring.
High Temperature Tape Discs - High temperature polyimide tape discs, .50" diameter.
Knife with #16 Blades - A must-have tool for precise cutting, scraping and trimming.
Micro Drill System - Versatile power tool for milling, drilling, grinding, cutting and sanding circuit boards.
Milling Machine - Use for precision milling of circuit board materials.
Oven - General purpose oven for drying, baking and curing epoxies.
Precision Drill - Precision drill press for accuracy and controlled depth drilling.
Scraper - Hardened stainless steel tip for scraping solder mask and removing defects.
Wipes - Nonabrasive, low-linting wipes for cleanup.

3.4.2 Key and Slot Repair, Transplant Method

Printed Board Type: R/W  |  Skill Level: Expert  |  Conformance Level: High  |  Rev.: D  |  Rev. Date: Jul 7, 2000

Mill out damaged area

Figure 1: Mill out the damaged
area using a milling machine or Precision Drill System.


1.  Clean the area to be filled, including the edges.
 
2.  Mill out the damaged area using a milling machine or Precision Drill System and carbide end mill. (See Figure 1).
 
3.  Clean the area.
 
Cut groove into both sides of key slot

Figure 2: Cut a groove into both
sides of the key slot using a Micro
Drill System and carbide saw.


4.  Install carbide saw into the Micro Drill System. Set the speed to maximum and machine a groove in the edge of the circuit board where the new base material will be installed. The groove must be centered in the edge to ensure that the new piece will fit properly. The groove width should be approx. 1/3 of the circuit board thickness. The groove depth should be approx. double the groove width. (See Figure 2).
 
5.  Cut a piece of replacement base board material that is the same thickness and type as the circuit board. The replacement piece should be longer than the length of the slot to allow for ease of handling.
 
Machine tongue onto replacement base material

Figure 3: Machine a tongue onto
both sides of the replacement
base material.

6.  Install an end mill into the milling machine. Machine a tongue onto both sides of the replacement piece. The dimensions of the tongue should match the size of the milled groove. (See Figure 3).
 
7.  Where required apply High Temperature Tape to protect exposed parts of circuit board bordering the prepared area.
 
8.  Carefully check the fit of the replacement piece and then clean both the replacement piece and the slot. The replacement base material should fit firmly into the slot so that it will not move or fall out when epoxied in place.
 
9.  Apply High Temperature Tape to the surface of the circuit board adjacent to the slot. The tape should protect any adjacent contacts or components.
 
10. Mix the epoxy.
 
11. Apply a small amount of liquid circuit board epoxy to the edges of the replacement piece and to the inside edges of the slot.
 
Insert replacement piece into slot

Figure 4: Insert the replacement
piece into the slot.


12. Insert the replacement piece into the slot. Check alignment. Remove excess epoxy. (See Figure 4).
 
13. If needed, apply additional epoxy to the edges of the slot. A mixing stick sharpened at the end may be used to apply the epoxy.
 
14. Cure the epoxy per Procedure 2.7 Epoxy Mixing and Handling.
 
  Caution
Some components may be sensitive to high temperature.
 
15. After the epoxy has cured remove the tape.
 
16. If needed use a knife or scraper and scrape off any excess epoxy.
 
  Note
If needed, apply additional thin coating to seal any scraped areas.
 
Cut off excess material

Figure 5: Cut off excess material
and file to match edge.


17. Cut off excess length of replacement material and file to match contour of existing edge. (See Figure 5).
 
18. If a new slot is needed, machine using milling machine and appropriate milling cutter. Use great care to correctly relocate the slot.
 
19. Clean the area.
 
Micro Drill System used for milling, drilling, grinding, cutting and sanding circuit boards

Figure 6: Micro Drill System.
Evaluation
 
1.  Visual examination and measurement of key slot location and dimension.


Special Order. Usually ships within 3 business days from Haverhill, MA, USA. For customer service call 1-519-651-3060.

How to purchase.                                                           View cart Minimum order $50 + shipping
Image Description Part No., Price and Quantity
Alcohol Swab Alcohol Swabs (package of 50), 235-1000-50

Self-saturating foam swabs filled with 99% Isopropyl alcohol. Ideal for removing flux residue and cleaning surfaces prior to soldering, coating and application of epoxy. Overall Length: 4.125". Squeeze handle until it "pops" releasing alcohol into the tip.

Enlarge
235-1000-50

$39.00 pkg/50

 
Liquid circuit board epoxy Circuit Bond Pack  MSDS, 115-3302

Clear, low viscosity, superior strength epoxy, precisely measured out into a two-compartment plastic package so it's easy to use and there's no measuring (2 gram). Shelf life: 6 months minimum.

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115-3302

$12.95 each

 
Cleaning Brush Cleaning Brushes (package of 100), 235-2106-100

Disposable brushes for use with solvents for cleaning and application of coatings.



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235-2106-100

$29.95 pkg/100

 
High Temperature Tape Discs 235-3050 High Temp. Tape Discs, .50" Diameter, 235-3050

High temperature tape discs are made of polyimide film with 1.5 mil of silicone adhesive that will not leave any residue. They can withstand temperatures of up to 500°F (260°C).
235-3050

US $5.95 pkg/60

 
Knife 355-0614 Knife with #16 Blades, 355-0614

A must-have tool for precise cutting, scraping and trimming. Includes five #16 blades.


Enlarge
355-0614

$9.95 each

 
Scraper 335-3197 Scraper, 335-3197

Hardened stainless steel tip for scraping solder mask and removing defects.



Enlarge
335-3197

$9.95 each

 

Products above ship direct from manufacturer and are special order/non-returnable. Will ship within 3 business days.



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Links to Related Products


Base Board Repair Kit used to repair damage to base board material   Base Board Repair Kit 201-3110
Most types of damage to base board material can be repaired with this versatile base board repair kit. The kit is industry approved and meets IPC guidelines. The kit includes epoxies and color agents. The high strength, high temperature epoxy withstands demanding physical environments.


Micro Drill System used for drilling, grinding, cutting circuit boards   Micro Drill System 110-4105
The Micro Drill System is a repair technician's dream and is ideal for milling, drilling, grinding, cutting and sanding circuit boards. It removes coating, cuts circuits, cuts leads, drills holes, cuts slots, shapes FR4 and performs many other procedures using various interchangeable bits. Unlike most hand-held tools, the Micro Drill has a tiny, high speed DC motor in the hand piece, eliminating cumbersome drive cables and giving you better control. A separate power supply keeps the hand piece lightweight and reduces operator fatigue. Base unit has controls for forward/reverse and speed up to 45,000 RPM.



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