IPC 7711A.pdf - 第211页

OUTLINE This method is used to repair mechanical or thermal blisters or delaminations in printed wiring board laminated base materials. The blister is sealed by injecting a low viscosity epoxy into the blister/delaminati…

NOTES

IPC-7721A

Number: 2.7.3

Revision:

Date: 2/98

Subject: Legend/Marking, Stencil Method

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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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OUTLINE

This method is used to repair mechanical or thermal blisters or delaminations in

printed wiring board laminated base materials. The blister is sealed by injecting a low

viscosity epoxy into the blister/delamination void.

CAUTION

This method can only be used when the laminate base material has separated suf-

ficiently to allow the epoxy to flow throughout the void area.

REFERENCES

2.1 Handling Electronic Assemblies

2.2 Cleaning

2.5 Baking and Preheating

2.6 Epoxy Mixing and Handling

TOOLS & MATERIALS

Ball Mill, #1/2

Cleaner

Cleaning Wipes

Epoxy

Epoxy Cartridge with Tip

Epoxy Injection System, Optional

Hand Held Drill

Heat Lamp

Oven

Scraper

Vacuum Source, Optional

PROCEDURE

1. Clean the area.

2. Drill into delamination blister with the dental style drill and ball mill. Drill in an area

clear of circuitry or components. Drill at least two holes opposite each other

around the perimeter of the delamination. (See Figure 1.) Brush away all loose

material.

CAUTION

Be careful not to drill too deep exposing internal conductors or planes.

CAUTION

Abrasion operations can generate electrostatic charges.

3. Bake the printed wiring board to remove any entrapped moisture. Do not allow

the printed wiring board to cool prior to injecting the epoxy.

CAUTION

Some components may be sensitive to high temperature.

4. Mix the epoxy. See manufacturers instructions on how to mix epoxy without

bubbles.

Figure 1 Drill into the delamination

blister

Figure 2 Inject epoxy into the

delamination blister.

Figure 3 Completed Repair.

7721A

Repair and

Modification of

Printed Boards and

Electronic Assemblies

Revision:

Date: 2/98

Delamination/Blister

Repair, Injection Method

Number: 3.1

Product Class: R

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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CAUTION

Exercise care to prevent bubbles in the epoxy mixture.

5. Pour the epoxy into the epoxy cartridge.

6. Inject the epoxy into one of the holes in the delamination. (See Figure 2.) The heat

retained in the printed wiring board will improve the flow characteristics of the

epoxy and will draw the epoxy into the void area filling it completely.

7. If the void does not fill completely, the following procedures may be used:

A. Apply light local pressure on the board surface starting at the fill hole, slowly

proceeding to the vent hole.

B. Apply vacuum to the vent hole to draw the epoxy through the void.

8. Cure the epoxy per the manufacturers recommendation.

9. Scrape away any excess epoxy using a knife or scraper.

NOTE

If needed, apply additional thin coating to seal any scrapped areas.

EVALUATION

1. Visual examination for texture and color match.

2. Electrical tests to conductors around the repaired area as applicable.

NOTES

IPC-7721A

Number: 3.1

Revision:

Date: 2/98

Subject: Delamination/Blister Repair, Injection Method

Page2of2

Provided by IHS under license with IPC

Not for Resale

No reproduction or networking permitted without license from IHS

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