IPC-CM-770D-1996 - 第92页

January

1996

IPC-CM-770

wrap. The maximum wire wrap should not overlap (see

Figure 17-21).

I I

W

Hook-up

Figure 17-20 Double-ended Terminal

(a)

Mlnlmum

Wrap

I

Blfurcated

(SPllt)

lug

Turret

lug

I

(b)

Maxlmum Wrap

Hook

lug

\

IPC

-1-00095

L

Figure 17-21 Terminal Wrap Prior to Soldering

E.

Jumper Wires

Component leads should not be used for

the purpose of jumper wires, bus wires or for interfacial

connections on printed boards. Jumper wires should be as

direct and as short as possible, without being taut, and

should not be routed over or under other components.

Where continuity between the two sides of a printed board

is desired, a short piece of unsleeved bus wire is used

either in a “C” or “Z” shape to conform to pattern

restrictions.

F. Point to Point Connections

The following rules should

be adhered to in selecting point to point jumper wires.

Bus wire over

1

inch long should be sleeved, and secured

to the board at one- inch intervals.

Bus wire crossing conductors should be sleeved.

Bend radii will conform to normal component bend

requirements.

The shortest route will be used unless design consider-

ations dictate otherwise.

Sleeving will be of sufficient length that slippage to either

end will not result in a gap between the insulation and

solder joint or bend of more than 3.2 mm. Sleeving

should not show damage caused by the soldering opera-

tion. (See Figure 17-22.)

3.2 mm 1.5 mm

-

,

[0.125”] max.

,

[0.060”] min

-

(al

Supported

Holes

-~

PTH

or

Eyelet

1.5 mm[0.060”] min.

r3i; mm [0.125”] max

Terrnlnal

post

i-

v///////a///A

(b)

Termlnals

IPC-1-00272

Figure 17-22 Methods

of

Mounting Jumpers

G. Jumper Wires or Leads Crossing Conductors

All

jumper wires crossing printed wiring conductor or conduc-

tors should be insulated with insulation sleeving. Compo-

nent leads should be insulated if they are within 1.27 mm

of the conductor surface, or over 9.52 mm in length from

the component body to bend radius. Large, supported, or

anchored components may not fall in this category.

H.

Insulation Clearance

The clearance between the end of

the insulation and the solder of the connection should be as

follows:

Minimum Clearance

The insulation should not be

embedded in the solder connection or touch the terminal.

The contour of the conductor should not be obscured at

the termination end of the insulation.

Maximum Clearance

Clearance should be less than two

wire diameters including insulation, or

0.15

mm, which-

ever is larger, but should not permit shorting to adjacent

conductors or terminals.

1.

Wire Bending Tools

Wire bending tools should be used

to form component lead and wires when preforming is

required. Round nose or protected long nose pliers may be

used as a bending tool. Bending tools, manual or auto-

matic, should not nick the wire. Other deformation should

not reduce the wire cross sectional area more than ten

percent.

17.2.3.2 Solderless (Wire) Wrap Assemblies

A. Wire Wrapping Guidelines

The following material is

provided to explain various types of solderless wrapped

connections. Figure 17-23 shows the common terminology

of this type of interconnection.

Conventional solderless wrapped connection consists of a

helix of continuous, solid, uninsulated wire tightly

wrapped around a suitable wrapost to produce a mechani-

cally and electrically stable connection (see Figure

4-23

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Licensed by Information Handling Services

COPYRIGHT Association Connecting Electronics Industries

Licensed by Information Handling Services

IPC-CM-770 Januaty 1996

17-24). The number of turns required will depend on the

gauge of the wire used.

Wrapost

Apex

Wrapost

2

3

Level

Wrapper Turn

Insulated Wire

2

Level

-

2

1

Level

IPC-1-00273

Figure 17-23 “Wrapping Terminology”

Modified solderless wrapped connection is shown in Fig-

ure 17-25. In addition to the length of uninsulated wire

wrapped around the wrapost as defined for the conven-

tional solderless wrapped connection, an additional mini-

mum wrap of insulated wire in intimate contact with three

comers of the wrapost should be wrapped around the

wrapost to help insure better vibration characteristics.

Turn Requirement. (Table 17-3.) Each connection should

have the minimum number of complete turns given in

Table 17-3 in order to be acceptable.

Wire Size. (Table 17-4.) Unless otherwise specified, the

wire size in Table 17-4 will be used for all wire wrapping.

Wire wrapping tools may be manual, pneumatic, battery,

or electrically operated. To assure consistent results, only

pneumatic or electrically powered wire wrapping tools

should be used on Class 3 equipment.

Insulated or

Uninsulated Wire

Reference Corner

I

IPC-1-00274

L

Figure 17-24 Conventional Solderless Wrapped

Connection

Insulated Wire

I’

4

Corners

of

Contact

of

Insulated Wire

t

”2

Turn or

3

Corners

of

Contact

of

Insulated Wire

(2

IPC-1-00275

Figure 17-25 Modified Solderless Wrapped Connection

Table 17-3 Turns Requirement

Wire Gage

Insulated Wire* Uninsulated Wire AWG

Minimum Turns

of

Minimum Turns

of

I

30

I

7

I

28

6 26

7

I

24

I

5

I

22

I

5

I

20

I

4

I

Sufficient

for intimate

contact

of 3 corners

of the

wrapost

*Required for Modified solderless wrapped connections only

Table 17-4 Wire Size (in inches)

Wi re Uninsulated

AWG Wire

0.D

0.0420 +.O02 0.201 +0.0006/-0.0002 24

Insulation

0.D

0.0265 +0.0015 0.159

+

0.0004/-0.002 26

I

28

I

0.0126

+

0.0004/-0.0001

I

0.230 +0.0015

I

30

I

0.010

+

0.003/-0.0001

I

0.0195 +0.001

I

17.2.4 Guidelines for Mounted Component Configura-

tion

Except as noted in Section 17.3, the devices and

materials described in this Section have been designed for

throughhole mounting, and are used for electrical as well as

mechanical purposes. Reliable assemblies are the result of

proper design for the use of these devices. Design consid-

erations include proper hole diameters to permit solder

flowthrough (in plated-through-holes), adequate land sizes

to permit filleting between the land and the component, and

suitable finishes on the printed board and the component.

All areas to be soldered should be tin or tin-lead plated and

reflowed. Areas to be wire-wrapped or probed (as in test

points) are usually gold plated.

17.3 Surface Mounting

With the exception of wires,

these devices are not suitable for surface mounting. Wires

4-24

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COPYRIGHT Association Connecting Electronics Industries

Licensed by Information Handling Services

January 1996 IPC-CM-770

may be surface mounted (lap soldered) to a printed board

trace, conductor, or land under the following conditions:

The attachment area meets the requirements defined in

Section 22. The land width should be 1-1/2 times the wire

diameter, and the length of the connection should be five

times the wire diameter.

The connection must be protected from peeling stresses,

either by external clamps, or by adhesives to attach the

wire to the board.

17.4 Mixed Technology

Mixed assembly technology has

no unique requirements for these components.

17.5 Manual Assembly

A. Terminals

Terminals are often installed manually. Ter-

minal swaging tools are available from each terminal

manufacturer to permit funnel or roll swages as required.

Elliptical swages, after suitable tool modification, can also

be performed manually.

B. Pins

Pins may be installed manually; however, it

should be noted that pressing the pins into the printed

board and achieving a uniform insertion depth manually is

difficult.

Tooling should be provided to control the depth of inser-

tion. This is a minor problem when using insertion tooling

similar to that shown in Figure 17-26. Another method of

controlling the insertion depth of the pins is to use pins

with a “board stop” which will contact the board or other-

wise indicate proper insertion.

C. Wire and Cable Preparation

Sufficient insulation shall

be stripped from the wire or leads to provide for insulation

clearances as specified. Chemical stripping agents shall be

used for solid wire only and shall be neutralized or

removed prior to soldering. After insulation removal, defor-

mation of remaining insulation shall not exceed 20% of the

insulation thickness. In stripping insulation, care should be

taken to avoid nicking or otherwise damaging the wire or

the remaining insulation. For Class

1

or 2 assemblies, the

number of damaged or severed strands in a single wire

shall not exceed the limits given in Table 17-5. For wires

used a potential of

6kV,

or greater, or for Class

3

assem-

blies, there shall be no broken strands; nicked strands shall

be per Table 17-5. Insulation discoloration resulting from

thermal stripping is permissible.

Table 17-5 Nicked or Broken Strand Limits

Maximum allowable nicked or

Number

of

Strands broken strands

Fewer than 7

O

7-1 5

37-40

4 26-36

3 19-25

2 16-1

8

1

5

41 or more 6

D.

Bus Bars

Because of the size of the bus bars, these

devices are usually installed manually. The bars are

inserted in the appropriate holes, and pins are clinched to

retain the bus bar.

E.

Test Points

Test points can be installed manually.

17.6 Automated Assembly

A. Terminals

Tooling is available to install and flare most

terminals automatically.

B. Pins

Pins are most often installed automatically. Pins

are available with carriers which feed the pins to the tool-

ing, which inserts the pins to a uniform depth.

C. Wire

Wire is usually installed manually with the

exception of jumpers and wire wrap. Wire wrap connec-

tions can be installed automatically by wire wrap machines

which can follow preplanned wire lists, install the wire

wraps, and route the wires between the connections.

D.

Bus Bars

Bus bars are not normally installed auto-

matically. The size of the bars and the tolerances involved

normally precludes automating installation of these

devices.

E.

Test Points

Test points may be installed automatically.

17.7 Handling and Storage

The handling and storage of

interconnect components should be in accordance with the

guidelines of Section 26.

17.8 Soldering

Soldering of devices in this Section fol-

low the guidelines outlined in Section 27.

17.9 Cleaning

Cleaning techniques are covered in Sec-

tion 28.

17.1

O

Conformal Coating

Conformal coating techniques

are covered in Section 29. In addition, the devices in this

Section may require masking. Care must be taken to apply

and remove the masking without contaminating the device.

4-25

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Licensed by Information Handling Services

COPYRIGHT Association Connecting Electronics Industries

Licensed by Information Handling Services