IPC 7711A.pdf - 第322页

5. Inspect the proposed path for the foil jumper to ensure proper clearance. Use a milling machine to mill a shallow groove in the solder mask surface from the BGA pad area to the perimeter of the BGA site. Tight spacing…

OUTLINE

This method is used to change a circuit path at a BGA site for engineering changes

or modifications.

NOTE

This procedure requires precision milling equipment and highly trained technicians.

CAUTION

This procedure is not applicable for ‘‘via in pad’’ applications.

REFERENCES

1.0 Foreword

2.1 Handling Electronic Assemblies

2.2 Cleaning

2.5 Baking And Preheating

2.6 Epoxy Mixing and Handling

4.2.1 Conductor Repair, Foil Jumper, Epoxy Method

4.4.3 Surface Mount, BGA Pad Repair, Film Adhesive Method

6.1 Jumper Wires

TOOLS & MATERIALS

BGA Rework System

Bonding Iron

Bonding Tips

Bonding System

Buffer

Circuit Frames, BGA Pads

Cleaner

Drill System

End Mills

Epoxy

Flux, Liquid

Foil Jumpers

Heat Lamp

Microscope

Milling System

Oven

Precision Knife

Repair System or Repair Kit

Scraper

Solder

Soldering Iron

Tape, High Temperature

Tweezers

Wipes

PROCEDURE

1. Clean the area.

2. Remove the BGA component if installed, remove excess solder from the pads,

and clean and inspect the site using standard BGA rework equipment.

3. Cut the short conductor (dog bone) connecting the BGA pad to the connecting

via using a drill system or milling machine and appropriate size end mill. (See Fig-

ure 1 and 6.)

4. Remove the existing BGA pad. Apply heat from a soldering iron if needed. (See

Figure 2.)

Figure 1 Cut the connection to the via

using a drill system.

Figure 2 Remove BGA pad & mill shal-

low channel into solder mask surface.

Figure 3 Bond a new BGA pad in

place.

Figure 4 Solder a foil jumper to the

tail extending from the new BGA pad.

7721A

Repair and

Modification of

Printed Boards and

Electronic Assemblies

Revision:

Date: 11/99

Jumper Wires, BGA

Components, Foil

Jumper Method

Number: 6.2.1

Product Class: R/F

Skill Level: Expert

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.

Page1of2

Provided by IHS under license with IPC

Not for Resale

No reproduction or networking permitted without license from IHS

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

5. Inspect the proposed path for the foil jumper to ensure proper clearance. Use a

milling machine to mill a shallow groove in the solder mask surface from the

BGA pad area to the perimeter of the BGA site. Tight spacing may restrict the

width of the channel to 0.25 mm [0.010 in] or less. Use a carbide end mill

approximately 0.050 mm [0.002 in] wider than the new connecting circuit. (See

Figure 3.)

NOTE

Be sure to mill a shallow groove to prevent damage to internal conductive lay-

ers.

6. Bond a replacement BGA pad in place using a bonding system. (See Procedure

4.7.3.) The new BGA pad must have a tail that will align with the foil jumper to

be added next. (See Figure 4.)

7. Select a foil jumper to match the width and thickness of the circuit to be

replaced. Cut a length approximately as needed. The foil jumper should overlap

the BGA tail section a minimum of two times the circuit width.

8. Gently abrade the top and bottom ends of the new foil jumper with the buffer to

remove any oxidation and clean.

NOTE

If needed, the ends of the foil jumper may be tinned with solder prior to lap sol-

dering in place.

9. Position this new foil jumper along the milled groove. The foil jumper should

overlap the existing circuit a minimum of two times the circuit width. (See Figure

4.)

10. Apply a small amount of liquid flux to the overlap joint.

11. Lap solder the foil jumper to the BGA tail section using solder and a soldering

iron. Make sure the foil jumper is properly aligned.

12. Clean the area.

13. Mix epoxy. If desired, add color agent to the mixed epoxy to match the printed

wiring board color.

14. Coat the top and bottom of the foil jumper with epoxy. The epoxy bonds the

new circuit to the base board material and insulates the circuit. (See Figure 5.)

CAUTION

Some components may be sensitive to high temperature.

16. Clean the board as required.

17. Install new BGA per applicable procedures.

18. Solder one end of a fine gauge wire to the end of the extending foil jumper. (The

opposite end of the wire will be soldered later.) (See Figure 5.)

19. Route and terminate the other end of the jumper wire.

EVALUATION

1. Visual examination for alignment and overlap of new circuit.

2. Visual examination of epoxy coating for texture and color match.

3. Electrical tests as applicable.

Figure 5 Solder a wire to the foil

jumper bond with epoxy.

Figure 6 Sample of drill system used

to cut the connection from the BGA

pad to the via.

IPC-7721A

Number: 6.2.1

Revision:

Date: 11/99

Subject: Jumper Wires, BGA Components, Foil Jumper Method

Page2of2

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 add a foil jumper at a BGA site by running the foil jumper

through a hole in the board. This method is normally used for engineering changes

or modifications.

NOTE

This procedure requires precision milling equipment and highly trained technicians.

This method is used when there is a buried via, and other methods of terminating to

the opposite side are not an option.

REFERENCES

1.0 Foreword

2.1 Handling Electronic Assemblies

2.2 Cleaning

2.5 Baking and Preheating

2.7 Epoxy Mixing and Handling

6.1 Jumper Wires

TOOLS & MATERIALS

BGA Rework System

Buffer

Cleaner

End Mills

Epoxy

Flux, Liquid Foil Jumper

Heat Lamp Microscope

Milling System

Oven

Precision Drill System

Precision Knife

Scraper

Solder

Soldering Iron

Tape, High Temperature

Teflon Sleeving

Tweezers

Wipes

Wire

PROCEDURE

1. Clean the area.

2. Remove the BGA component if installed, remove excess solder from the pads.

Clean and inspect the site.

3. Remove solder mask from the via pad terminating to the subject BGA pad.

4. Mill a hole through the board at the precise coordinates using a Precision Drill

System and End Mill of the appropriate size. (See Figure 1 and 5.)

NOTE

Although both power and ground planes may be cut, inner layer signal traces

must be avoided.

5. Carefully inspect the milled hole and clean the area.

Figure 1 Mill a hole through the board

and insert a Teﬂon sleeve.

Figure 2 Insert a copper foil jumper

into the plated hole and Teﬂon sleeve.

Figure 3 Solder the foil jumper to the

plated hole connected to the BGA pad.

Figure 4 Overcoat the new connection

with epoxy.

7721A

Repair and

Modification of

Printed Boards and

Electronic Assemblies

Revision:

Date: 10/03

Jumper Wires, BGA

Components, Through

Board Method

Number: 6.2.2

Product Class: R/F

Skill Level: Expert

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.

Page1of4

Provided by IHS under license with IPC

Not for Resale

No reproduction or networking permitted without license from IHS

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