IPC 7711A.pdf - 第287页

PREPARATION − Remove Poor Plating or Surface Defects 1. Clean the rework area. 2. Apply plating tape to the printed wiring board surface surrounding the area to be reworked. The plating tape will protect adjacent compone…

TOOLS & MATERIALS

Abrasive Pad

Board Support

Burnisher

Cleaner

Cleaner Wipes

Connector Edge

Plating System

Conductive Pen

Desoldering Braid or

Desoldering System

Eraser Stick

Gloves, Antistatic

Polyimide Tape

Knife

Liquid Flux

Peel Testing Tape

Pin Fixtures

Plating Anodes

Plating Cables

Plating Probe

Plating Solution, Gold

Plating Solution, Nickel

Plating Solution, Electroclean

Plating Solution, Solder Strip

Plating Tape

Power Supply

Probe Clip

Rinse Bottle

Rinse Tray

Safety Glasses

Solder

Solder Iron

Solution Cups

Solution Tray

Swab

Thickness Measuring System,

Gold and Nickel

Water/Air Sprayer

Wire, Buss, 30 AWG

Work Sink

PREPARATION − Remove Solder Contamination

CAUTION

Safety glasses and safety gloves should always be worn when handling hazardous

chemicals. Do not work within a small enclosed room without supplemental ventila-

tion. If ventilation is not adequate, use a fan to move fumes away from the operator.

1. Clean the rework area.

2. Apply plating tape to the printed wiring board surface surrounding the area to

be reworked. (See Figure 1.) The plating tape will protect adjacent components

and the printed wiring board surface from unwanted exposure to stripping and

plating solutions.

3. Flow solder over the entire area of any contacts that have contamination using

a soldering iron. This provides a more even surface when plating. Remove the

bulk of the solder contamination using desoldering tools or desoldering braid.

(See Figure 2.)

4. Clean the area.

5. Place the printed wiring board on the board support so that the leading edge

overhangs the rinse tray.

6. Swab the solder stripping solution over the solder contamination using a swab.

Swab the surface until all remaining solder has been stripped off. (See Figure 3.)

7. Thoroughly rinse the entire area with water. (See Figure 4.)

8. Mildly buff the contacts using abrasive pad. Mild buffing will prepare the surface

for plating and remove any remaining solder contamination.

9. Thoroughly rinse with water to remove any residue.

Figure 5 Solder a wire to the edge of

the contacts needing plating.

Figure 6 Apply conductive paint to

the edge of the contacts.

Figure 7 Sample plating anodes

shown with fabric wrapping.

Figure 8 Brush the surface with the

saturated plating probe.

IPC-7721A

Number: 4.6.3

Revision:

Date: 2/98

Subject: Edge Contact Repair, Plating Method

Page2of6

Provided by IHS under license with IPC

Not for Resale

No reproduction or networking permitted without license from IHS

--``,``,-`-`,,`,,`,`,,`---

PREPARATION − Remove Poor Plating or Surface Defects

1. Clean the rework area.

2. Apply plating tape to the printed wiring board surface surrounding the area to

be reworked. The plating tape will protect adjacent components and the printed

wiring board surface from unwanted exposure to stripping and plating solutions.

3. Clean the area.

4. Buff the contacts using an abrasive pad. Buff the contacts until all defective or

poor plating is removed.

5. Burnish small scratches. Use the tip of the burnisher to work the copper mate-

rial into the scratch and smooth out the area. Finish by mildly buffing the area to

remove any minor burnishing marks. If there are large scratches the contact

may need replacement. See Procedure Number 4.6.1 or 4.6.2.

6. Thoroughly rinse the entire area with water to remove any residue.

BUSSING

A conductive buss must be made to all the contacts that need plating. There are 4

basic connection options.

NOTE

Making a reliable buss connection is the most important step in plating. All sorts of

problems will be eliminated by taking the time to make a reliable buss connection.

BUSSING − Wire Soldered to Edge (Option 1)

CAUTION

When finished, this method will leave a small unplated line along the inner tip of each

contact.

1. Apply Polyimide tape to all the contacts to be plated. The tape should cover the

entire contact except for a small line along the inboard edge. The tape will pre-

vent further solder contamination.

2. Solder a wire directly to the inboard tip or connecting conductor of each con-

tact to be plated. The smallest amount of solder should be used to prevent fur-

ther contamination. (See Figure 5.)

BUSSING − Conductive Paint Applied to Edge (Option 2)

CAUTION

When finished, this method will leave a small unplated line along the inner tip of each

contact.

1. Apply Polyimide tape to all the contacts to be plated. The tape should cover the

entire contact except for a small line along the inboard edge. The tape will pre-

vent the conductive paint from contaminating the contact surface.

2. Apply a thin coating of conductive paint directly to the inboard tip of each con-

tact to be plated. The conductive paint should extend out to one edge so that

a clip can be applied to make electrical connection. (See Figure 6.)

IPC-7721A

Number: 4.6.3

Revision:

Date: 2/98

Subject: Edge Contact Repair, Plating Method

Page3of6

Provided by IHS under license with IPC

Not for Resale

No reproduction or networking permitted without license from IHS

--``,``,-`-`,,`,,`,`,,`---

BUSSING − Mechanical Probe, Individual Contacts (Option 3)

1. Each contact needing plating can be individually probed using the plating probe.

Touch the tip of the plating probe to the inboard edge of each contact or to the

connecting conductor as each solution is applied during the plating process.

BUSSING − Pin Fixture, Multiple Contacts (Option 4)

1. Make a mechanical connection to each contact using a pin fixture. The pin fix-

ture has spring loaded contact pins on centers matching the spacing of the

edge contacts to be plated. The contact pins make direct mechanical connec-

tion to the inboard tip of each contact, the connecting conductor trace or a

connecting plated through hole.

PROCEDURE − Plating Process

1. Place the printed wiring board on the board support so that the leading edge

overhangs the rinse tray.

2. Make the cathode connection (-) to the printed wiring board by using a plating

probe or probe clip. Connect the probe clip directly to the wire buss connection

or to the edge where conductive paint has been applied. The cable should be

connected to the (-) or black jack on the power supply.

3. Connect the plating probe to the power supply (+) or red jack. (See Figure 7.)

4. Set the output current on the power supply to setting recommended by the

equipment manufacturer.

5. Dip the plating probe into the electroclean plating solution. Wait a few seconds

for the solution to saturate the absorbent wrapping.

6. Swab the entire surface to be plated by brushing the surface with the saturated

plating probe. The plating probe should be moved back and forth briskly to pre-

vent burning and to provide even coverage. (See Figure 8.) Swab the area for

the time recommended by the equipment manufacturer.

7. Thoroughly rinse the entire area with water. Any burning or darkening of the

contacts may be removed with an abrasive pad. Saturate the abrasive pad and

the printed wiring board surface with water and lightly buff the contacts until all

evidence of the burning or discoloring is removed. Rinse the entire area with

water.

CAUTION

Do not allow the rework area to dry out between steps. The water coating pre-

vents oxidation.

8. Connect the nickel plating probe to the power supply (+) or red jack.

9. Dip the plating probe into the nickel plating solution. Wait a few seconds for the

solution to saturate the absorbent wrapping.

10. Swab the entire surface to be plated by brushing the surface with the saturated

plating probe. The plating probe should be moved back and forth briskly to pre-

vent burning and to provide even coverage. Swab the area for the time recom-

mended by the equipment manufacturer. Before rinsing, lightly buff the contacts

with an abrasive pad.

IPC-7721A

Number: 4.6.3

Revision:

Date: 2/98

Subject: Edge Contact Repair, Plating Method

Page4of6

Provided by IHS under license with IPC

Not for Resale

No reproduction or networking permitted without license from IHS

--``,``,-`-`,,`,,`,`,,`---