IPC 7711A.pdf - 第239页

EVALUATION 1. Visual examination 2. Measurement of new pad width and spacing. 3. Electrical continuity measurement. IPC-7721A Number: 4.2.2 Revision: Date: 2/98 Subject: Conductor Repair , Foil Jumper , Film Adhesive Met…

7. Select a replacement conductor with film adhesive backing that most closely

matches the size of the conductor to be replaced. If a special size or shape is

needed they can be custom fabricated. (See Figure 2.)

NOTE

New conductors are fabricated from copper foil. The foil is plated on the top

side with solder and an epoxy bonding film is applied to the bottom side.

8. Before trimming out the new conductor carefully scrape off the adhesive epoxy

film from the solder joint connection area on the back of the new conductor.

(See Figure 3.)

CAUTION

Scrape off the epoxy backing only from the joint connection area. When han-

dling the new conductor avoid touching the epoxy backing with your fingers or

other materials that may contaminate the surface and reduce the bond strength.

9. Cut out and trim the new conductor. Cut out from the plated side. Cut the

length to provide the maximum allowable conductor overlap for soldering. Mini-

mum 2 times the conductor width. (See Figure 4.)

NOTE

If the configuration permits, the overlap solder joint connection should be a

minimum of 3.00 mm from the related termination. This gap will minimize the

possibility of simultaneous reflow during soldering operations.

10. Place a piece of tape over the top surface of the new conductor. Place the new

conductor into position on the printed wiring board surface using tape to help in

alignment. Leave the tape in place during the bonding cycle. (See Figure 5.)

11. Select a bonding tip with a shape to match the shape of the new conductor.

NOTE

The bonding tip should be as small as possible but should completely cover the

entire width of the new conductor.

12. Position the printed wiring board so that it is flat and stable. Gently place the hot

bonding tip onto the tape covering the new pad. Apply pressure as recom-

mended in the manual of the repair system or repair kit. (See Figure 6.)

13. After the bonding cycle lift the bonding iron and remove the tape used for align-

ment. The new conductor is fully cured. Carefully clean the area and inspect the

new conductor for proper alignment.

14. Apply a small amount of liquid flux to the lap solder joint connection area and

solder the conductor from the new conductor to the conductor on the printed

wiring board surface. Use minimal flux and solder to ensure a reliable connec-

tion. Tape may be placed over the top of the new conductor to prevent excess

solder overflow. Clean the area.

15 Mix epoxy and coat the lap solder joint connections. Cure the epoxy per the

manufacturer’s instructions.

CAUTION

Some components may be sensitive to high temperature.

16. Apply surface coating to match prior coating as required.

Figure 5 Place the new conductor in

place using tape.

Figure 6 Repair system.

Figure 7 Completed repair.

IPC-7721A

Number: 4.2.2

Revision:

Date: 2/98

Subject: Conductor Repair, Foil Jumper, Film Adhesive Method

Page2of4

Provided by IHS under license with IPC

Not for Resale

No reproduction or networking permitted without license from IHS

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

EVALUATION

1. Visual examination

2. Measurement of new pad width and spacing.

3. Electrical continuity measurement.

IPC-7721A

Number: 4.2.2

Revision:

Date: 2/98

Subject: Conductor Repair, Foil Jumper, Film Adhesive Method

Page3of4

Provided by IHS under license with IPC

Not for Resale

No reproduction or networking permitted without license from IHS

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

NOTES

IPC-7721A

Number: 4.2.2

Revision:

Date: 2/98

Subject: Conductor Repair, Foil Jumper, Film Adhesive Method

Page4of4

Provided by IHS under license with IPC

Not for Resale

No reproduction or networking permitted without license from IHS

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