IPC 7711A - 第281页

OUTLINE This method is used to replace a damaged edge contact with a new dry film, adhe- sive backed edge contact. The new edge contact is hot bonded to the printed wir- ing board surface. CAUTION It is essential that th…

NOTES

IPC-7721A

Number: 4.6.1

Revision:

Date: 2/98

Subject: Edge Contact Repair, Epoxy Method

Page4of4

Provided by IHS under license with IPC

Not for Resale

No reproduction or networking permitted without license from IHS

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OUTLINE

This method is used to replace a damaged edge contact with a new dry film, adhe-

sive backed edge contact. The new edge contact is hot bonded to the printed wir-

ing board surface.

CAUTION

It is essential that the board surface be smooth and flat. If the base material is dam-

aged see appropriate procedure.

NOTE

This method uses commercially available replacement edge contacts. The edge

contacts are fabricated from copper foil and have a dry film adhesive coating on the

back. They are available in hundreds of sizes and shapes and are generally supplied

nickel and gold plated. If a special size or shape is needed they can be custom fab-

ricated.

REFERENCES

2.1 Handling Electronic Assemblies

2.2 Cleaning

2.5 Baking and Preheating

2.6 Epoxy Mixing and Handling

TOOLS & MATERIALS

Bonding Iron

Bonding System

Bonding Tips

Cleaner

Epoxy

File, Finish Grade

Heat Lamp

Polyimide Tape

Knife

Liquid Flux

Microscope

Oven

Replacement Edge Contacts,

Adhesive Backed

Scraper

Solder

Soldering Iron

Tweezers

Wipes

PROCEDURE

1. Clean the area.

2. Remove the defective edge contact and a short length of the connecting con-

ductor. Heat from a soldering iron will allow the old contact to be removed more

easily.

Figure 1 Remove the defective edge

contact and solder resist.

Figure 2 Select a replacement contact

that matches.

Figure 3 Scrape off adhesive bonding

ﬁlm from solder joint area.

Figure 4 Cut out the new edge

contact.

7721A

Repair and

Modification of

Printed Boards and

Electronic Assemblies

Revision:

Date: 2/98

Edge Contact Repair,

Film Adhesive Method

Number: 4.6.2

Product Class: R, F, W, C

Skill Level: Advanced

Level of Conformance: High

Material in this manual was voluntarily established by Technical Committees of IPC. This material is advisory only and its use

or adaptation is entirely voluntary. IPC disclaims all liability of any kind as to the use, application, or adaptation of this material.

Users are also wholly responsible for protecting themselves against all claims or liabilities for patent infringement. Equipment

referenced is for the convenience of the user and does not imply endorsement by IPC.

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Provided by IHS under license with IPC

Not for Resale

No reproduction or networking permitted without license from IHS

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3. Use the knife and scrape off any epoxy residue, contamination or burned mate-

rial from the board surface.

CAUTION

Abrasion operations can generate electrostatic charges.

4. Scrape off any solder resist or coating from the connecting conductor. (See Fig-

ure 1.)

5. Clean the area.

6. Apply a small amount of liquid flux to the connection area on the board surface

and tin with solder. Clean the area. The length of the overlap solder connection

should be a minimum of 2 times the conductor width.

7. The area for the new edge contact on the board surface must be smooth and

flat. If internal fibers of the board are exposed or deep scratches exist in the

surface they should be repaired. Refer to appropriate procedure.

8. Select a new edge contact that most closely matches the edge contact to be

replaced. (See Figure 2.)

NOTE

The new replacement edge contact may be trimmed from copper sheet.

9. Before trimming out the new edge contact carefully scrape off the adhesive film

from the solder joint connection area on the back of the new edge contact. (See

Figure 3.)

CAUTION

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

dling the replacement contact, avoid touching the epoxy backing with your fin-

gers or other materials that may contaminate the surface and reduce the bond

strength.

10. Cut out and trim the new edge contact. Cut out from the plated side. Cut the

length to provide the maximum allowable joint if lap soldering. Minimum 2 times

the conductor width. Leave the new edge contact extra long. The excess mate-

rial will be trimmed after bonding. (See Figure 4.)

11. Place a piece of tape over the top surface of the new edge contact. Position the

new edge contact on the printed wiring board surface using the tape to aid in

alignment. (See Figure 5.)

NOTE

Allow the edge contact to overhang the edge of the printed wiring board. Leave

the Tape in place during the bonding cycle.

12. Select a bonding tip with a shape to match the shape of the new edge contact.

NOTE

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

surface of the new edge contact.

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

bonding tip onto the tape covering the new edge contact. Apply pressure as

recommended by the manufacturer. (See Figure 6.)

CAUTION

Excessive bonding pressure may cause measling in the printed wiring board

surface or the new conductor to slide out of position.

Figure 5 Place the new edge contact

in place using tape.

Figure 6 Bonding system.

Figure 7 File overhanging piece of the

new edge contact.

Figure 8 Completed repair.

IPC-7721A

Number: 4.6.2

Revision:

Date: 2/98

Subject: Edge Contact Repair, Film Adhesive Method

Page2of4

Provided by IHS under license with IPC

Not for Resale

No reproduction or networking permitted without license from IHS

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