IPC 7711A.pdf - 第276页

NOTES IPC-7721A Number: 4.5.2 Revision: Date: 2/98 Subject: Land Repair , Film Adhesive Method P a g e4o f4 Copyright Association Connecting Electronics Industries Provided by IHS under license with IPC Not for Resale No…

CAUTION

Excessive bonding pressure may cause measling in the printed wiring board

surface or the new conductor to slide out of position.

14. After the bonding cycle remove the tape used for alignment. The land is fully

cured. Carefully clean the area and inspect the new land for proper alignment.

15. If the new land has a connecting conductor apply a small amount of liquid flux

to the lap solder joint connection area and solder the conductor from the new

land to the conductor on the printed wiring board surface. Use minimal flux and

solder to ensure a reliable connection. Tape may be placed over the top of the

new land to prevent excess solder overflow.

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.

16. Remove tape and clean the area.

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

manufacturers instructions.

NOTE

Additional epoxy can be applied around the perimeter of the new pad to pro-

vide additional bond strength.

CAUTION

Some components may be sensitive to high temperature.

18. Carefully remove any excess bonding film inside the plated hole using ball mill

or drill bit. Turn the ball mill or drill bit by hand to prevent damage to the wall of

the plated through hole.

19. Install the proper component and solder in place.

NOTE

This method is used to replace a damaged or missing land, but the new land

will not have an intermetallic connection to the remaining plated hole. The sol-

der joint of the replaced component will restore the integrity of the electrical

connection or an eyelet or buss wire may be used. See Plated Hole Repair Pro-

cedures.

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

EVALUATION

1. Visual examination.

2. Measurement of new pad width and spacing.

3. Electrical continuity measurement.

IPC-7721A

Number: 4.5.2

Revision:

Date: 2/98

Subject: Land Repair, 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: 4.5.2

Revision:

Date: 2/98

Subject: Land Repair, Film Adhesive Method

Page4of4

Provided by IHS under license with IPC

Not for Resale

No reproduction or networking permitted without license from IHS

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

OUTLINE

This method is used to replace a damaged edge contact with a new edge contact.

The new edge contact is bonded to the printed wiring board surface using liquid

epoxy.

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. They are available in hundreds of sizes and

shapes and are generally supplied either plain copper, solder plated or nickel and

gold plated. If a special size or shape is needed they can be custom fabricated.

REFERENCES

2.1 Handling Electronic Assemblies

2.2 Cleaning

2.5 Baking And Preheating

2.6 Epoxy Mixing and Handling

TOOLS & MATERIALS

Cleaner

Epoxy

File, Finish Grade

Heat Lamp

Polyimide Tape

Knife

Liquid Flux

Microscope

Oven

Replacement Edge Contacts

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.

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.

Figure 1 Remove the defective edge

contact and solder resist.

Figure 2 Select a replacement contact

that matches.

Figure 3 Cut out the new edge

contact.

Figure 4 Place the new edge contact

in place using tape.

7721A

Repair and

Modification of

Printed Boards and

Electronic Assemblies

Revision:

Date: 2/98

Edge Contact Repair,

Epoxy Method

Number: 4.6.1

Product Class: R, F, W, C

Skill Level: Advanced

Level of Conformance: Medium

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.

Page1of4

Provided by IHS under license with IPC

Not for Resale

No reproduction or networking permitted without license from IHS

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