IPC 7711A.pdf - 第194页

NOTES IPC-771 1A Number: 6.1.4 Revision: Date: 2/98 Subject: Removing Shorts Between Gull Wing P a g e2o f2 Copyright Association Connecting Electronics Industries Provided by IHS under license with IPC Not for Resale No…

EQUIPMENT REQUIRED

Soldering system

Soldering iron

Cup of flat faced tip

MATERIALS

Flux

PROCEDURE

1. Install appropriate tip.

2. Start with the coolest tip temperature possible (approximately 315°C) and change

as necessary. The surface attraction of the solder to the tip must overcome that

of the leads.

3. Clean tip using a damp sponge.

4. Apply flux to the bridged leads. (See Figure 1.)

5. Hold the tip so the toe of the hoof runs parallel to the row of leads, that is, the

side of the tip toward the side of the component. The angle between the side of

the tip and the side of the component would ideally be zero for maximized heat

transfer, but can be up to 30° depending on operator preference. (See Figure 2.)

6. Bring the tip face down flat onto the bridge and pause for reflow. Draw the tip,

and the liquid bridge with it, down the row of leads, respreading the solder across

the rest of the leads. (See Figure 3.)

7. Clean, as required, and inspect.

Figure 1 Apply Flux

Figure 2 Hold Tip Parallel

30 degree

maximum

Figure 3 Draw Tip Down Row

7711A

Rework of

Electronic Assemblies

Revision:

Date: 2/98

Removing Shorts Between Gull Wing

Respread Method

Number: 6.1.4

Product Class: R, F, W, C

Skill Level: Intermediate

Level of Conformance: High

Material in this manual, IPC-7711 Rework of Electronic Assemblies, 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

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NOTES

IPC-7711A

Number: 6.1.4

Revision:

Date: 2/98

Subject: Removing Shorts Between Gull Wing

Page2of2

Provided by IHS under license with IPC

Not for Resale

No reproduction or networking permitted without license from IHS

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

8.1 Splicing

1. THE PROCESS OF WIRE SPLICING IS USED IN TWO

CASES:

a. When a self-lead component (inductor, transformer,

choke, etc.) is installed (either during assembly or

as a replacement for a failed component) and,

b. In the process of repairing a damaged wire when

removal and replacement of the entire wire length

is not feasible.

2. THE FOUR MOST COMMON SPLICES USED ARE:

• Mesh Splices Mesh splices require the least wire

length in order to complete the splice and result in a

splice diameter only slightly larger than the diameter

of the wire used.

• Wrap Splices Wrap splices require a longer wire

length in order to complete the splice and have a

splice diameter equal to three times the diameter of the

wire used.

• Hook Splices Hook Splices require the most wire

length in order to complete the splice and have a

splice diameter equal to three times the diameter of the

wire used.

• Lap Splices Lap splices, like mesh splices, require a

minimal amount of original wire length and may be

used to perform repair of a damaged wire when:

a. Sufficient slack is available in the wire to achieve

the necessary overlap, and

b. The repaired wire will not be subjected to longitu-

dinal stress after repair.

3. WIRE SPLICING

Locating/Isolating Damage Locate the damaged

wire. If the wire is broken, determine if both sections

are available. Isolate the damaged area by using point-

to-point resistance measurements.

Note: If the wire was broken (separated) by a cutting

action, the cut ends can be spliced at the point of

breakage/separation. If the wire was broken (separated)

by a pulling action, e.g., stretching or pulling until sepa-

ration, then the wire strands on both sides of the break

will have suffered hidden mechanical damage in the

form of stretching, elongation and reduction of indi-

vidual strand diameter. In such cases, where separation

was caused by a pulling action, it is desirable to remove

(cut-out) wire which could have been damaged by

stretching and installing a longer splice than would nor-

mally be used.

4. FEASIBILITY OF REPAIR

Prior to repairing damaged wires, the following consid-

erations must be made:

• Should damaged wires be replaced in their entirety

• Should wires be repaired using solder sleeves

• If complete replacement is not feasible, determine if

one section of wire may be replaced thereby limiting

the number of splices to one

• If no section of the damaged wire can be replaced,

splice in a replacement section of wire with two

splices

5. INSULATED CONDUCTOR STRIPPING

Insulated conductors should be stripped a distance

longer than required for the solder connection. This

allows for easier forming of the conductor. The excess

conductor shall be trimmed off prior to soldering. The

following stripping methods are recommended.

a. Thermal wire strippers are to be used on insula-

tions that will melt upon application of heat. This

method is preferred because it minimizes the pos-

sibility of conductor damage.

Caution: Do not use mechanical strippers on wire

smaller than AWG-20, as the strippers may stretch the

wire.

b. Mechanical strippers are to be used on insulations

that cannot be thermally stripped. This method

does not apply to enamel insulation.

c. Chemical stripper is used on conductors that have

an enamel/varnish coating for insulation.

1) Follow the manufacturer’s instructions on the

length of time for the chemical reaction to take

place.

2) The stripper may have to be neutralized. Follow

the manufacturer’s safety precautions on both

equipment and personnel.

Warning: Chemical strippers contain ingredients

harmful to both skin and eyes. Prescribed protective

clothing, including industrial goggles/spectacles, shall

be worn when opening the container and during use. If

stripper gets on skin, wash immediately with fresh

water and soap and rinse freely. If stripper gets into

eyes, ﬂood with large quantity of fresh water. Do not

apply ointments or salve, obtain medical aid at once.

Follow manufacturer’s safety instructions.

October 2003 IPC-7711A

Provided by IHS under license with IPC

Not for Resale

No reproduction or networking permitted without license from IHS

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