OUTLINE

This procedure covers the repair of a damaged hole that has no inner layer connection. An eyelet is used to repair the damage to the hole and the eyelet flanges replace the lands on the circuit board surface.

CAUTION
This procedure is used only to restore the integrity of a through connection in a double sided board or a multilayer board where there is no inner layer connection. If there is an inner layer connection see appropriate procedure. 
  

ACCEPTABILITY REFERENCES
IPC-A-600	2.0	Externally Observable Characteristics
IPC-A-600	3.0	Internally Observable Characteristics
PROCEDURE REFERENCE
CTC 7721	1.0	Foreword
CTC 7721	2.1	Handling Electronic Assemblies
CTC 7721	2.2	Cleaning
IPC 7721	5.1	Plated Hole Repair, No Inner Layer Connection

TOOLS & MATERIALS
Ball Mills
Caliper Gauges
Cleaner
Eyelet Press
Eyelets, Various Sizes
Flux, Liquid
Knife
Micro-Drill System
Microscope
Pin Gauges
Plated Hole Repair Kit
Setting Form Tool, Various Sizes
Setting Anvil, Various Sizes
Solder Iron
Solder
Wipes

EYELET SELECTION CRITERIA

ID - Inside Diameter
The eyelet inside diameter should be a .075 - .500 mm (.003"-.020") greater than the component lead diameter.

LUF - Length Under Flange
The length of the eyelet barrel under the flange should be .630 - .890 mm (.025" - 035") greater than the thickness of the circuit board. This added length allows for proper protrusion when setting the eyelet.

FD - Flange Diameter
The eyelet flange diameter should be small enough to prevent interference with adjacent lands or circuits.

OD - Outside Diameter
The clearance hole drilled through the circuit board should allow the eyelet to be inserted without force but should not exceed .125 mm (.005") greater than the eyelet outside diameter.

NOTE
Be sure to select an eyelet meeting the proper criteria. An eyelet with an oversize flange may interfere with adjacent circuits. An eyelet that is too short will not protrude through the circuit board for proper setting.

PROCEDURE

1. Clean the area.



2. Select an eyelet using the Eyelet Selection Criteria. Use a pin gauge and caliper to measure the existing plated hole dimensions.



3. Insert the appropriate ball mill into the Micro-Drill System. Drill out the hole removing all the plating. The drilled hole should be .025 - .125 mm (.001" - .005") larger than the eyelet O.D. (See Figure 1).

   CAUTION
   This procedure may isolate internal connections on multilayer circuit boards.
   
   

4. Clean the area.



5. Apply a small amount of liquid flux to the land or circuit on the circuit board surface, if any, and tin with solder using a soldering iron and solder. Clean the area.



6. Insert the eyelet into the hole. If a new circuit is required, the new circuit may extend into the drilled hole and the flange of the eyelet will secure the new circuit in place. (See Figure 2).



7. Select the proper setting tools and insert them into an eyelet press system. (See Figure 3).



8. Turn the circuit board over and rest the eyelet flange on the lower setting tool.



9. Apply firm even pressure to form the eyelet barrel.

   NOTE
   Inspect the eyelet flange for evidence of damage. Refer to IPC-A-610 Acceptability of Electronic Assemblies.
   
   

10. Apply a small amount of liquid flux and solder the eyelet flanges to the lands on the circuit board surface if necessary. Clean the area. Inspect for good solder flow and wetting around the eyelet flanges and lands.

EVALUATION

1. Visual examination, dimensional requirement of land diameter and inside diameter.



2. Electrical continuity measurement.