IPC-CM-770D-1996 - 第89页

IPC-CM-770

Januaty

1996

or circuit. Such assess is required for main- tenance and

adjustment of circuitry. Use of a test point is preferable to

probing the printed board, since probing a printed board

can be a shock hazard, and can cause short

Test points consist of an insulator surrounding a contact for

electrical connection. The electrical contact is equivalent to

a single socket connector.

I

IPC-1-00263

I

Figure 17-11 Horizontally Mounted Bus Bars

Test points are designed for mounting on one side of the

printed board, as illustrated in Figure 17-13 and 17-14.

IPC-1-00274

Figure 17-12 Under-DIP Mounted Bus Bars

17.1.6 Insulating Tubing

Insulating tubing is available

in both heat shrinkable and non-heat shrinkable styles, and

in a variety of materials including polyvinyl chloride and

polytetrafluoroethylene.

Typical specifications for insula-

tion tubing include MIL-1-7444, ASTM D-3295, and MIL-

1-23053. Insulation tubing is used to insulate bare wires

and component leads, to insulate metal case components,

as supplementary insulation over wire bundles, and to insu-

late and protect connection terminations.

17.2 Through-Hole Mounting

17.2.1 Component Preparation

A.

Terminals

Terminals must be clean and suitable for the

subsequent operations. Terminals to be soldered in place or

which will be soldered to subsequently must be verified

solderable prior to installation. Solderability should beveri-

fied in accordance with J-STD-002.

B. Pins

Pins to be used as connectors or for subsequent

wire wrapping should be precious metal plated, clean, and

meet applicable plating thickness and porosity specifica-

tions. There are a number of plating options available to

optimize pin solderability in areas of the pin that should be

soldered to a printed board. These options include solder

coatings, gold flashes, and alternatives such as palladium

nickel with and without gold flashes.

C. Wires

Wires to be soldered should be verified solder-

able in accordance with J-STD-002. Insulated wires should

have the insulation removed using thermal, chemical, or

precision cutting-type insulation strippers. Cutting-type

insulation strippers may be automated or manual, but

should not be operator adjustable.

-The lay of the wire strands should be restored if dis-

turbed by the insulation removal process.

-

Insulation may be removed from many types of magnet

wire by the use of chemical stripping agents in accor-

dance with the stripping agent manufacturer's recom-

mendations. Particular care should be exercised when

handling chemical stripping agents, and stripped wires

should be thoroughly cleaned.

-

Polyurethane or similar heat strippable coatings may be

removed by dipping the insulated wire to the required

depth into a pot containing the appropriate solder alloy

at the temperature recommended by the wire manufac-

turer. The dipping action will have the double effect of

removing the insulation and tinning the wire. Solder

purity should be controlled in accordance with J-STD-

001.

-

Thermal stripping is preferred for AWG 22 and smaller

conductor wire sizes. Fraying should be minimized.

Insulation discoloration resulting from thermal stripping

is permissible, but charring or burning should not be

allowed. The lay of the wire strands should be restored

if disturbed by the insulation removal process.

D. Bus Bars

Bus bars must be clean and suitable for the

subsequent operations. Portions of the bus bars to be sol-

dered should be verified solderable in accordance with

J-STD-002.

E.

Test Points

Test points must be clean and suitable for

the subsequent operations. Portions of the test points to be

soldered should be verified solderable in accordance withJ-

STD-002. The section which will mate with external test

equipment should be gold plated or protected with another

plating system which will provide suitable electrical con-

tact and minimize corrosion.

F. Insulating Tubing

Insulation tubing, when specified by

design or required for insulation purposes, should be

installed prior to soldering.

17.2.2 Land Patterns

A.

Terminals

Terminals are suitable for installation in a

variety of configurations which affect land pattern. Those

installations where the terminals is intended to be soldered

to the printed board require land patterns as follows:

4-20

COPYRIGHT Association Connecting Electronics Industries

Licensed by Information Handling Services

COPYRIGHT Association Connecting Electronics Industries

Licensed by Information Handling Services

January

1996

IPC-CM-770

Hardware Mount

Solder Mount

IPC-1-00265

Figure 17-13 One-terminal Printed Board Test Point

IPC-1-00266

Figure 17-1

4

Two-terminal Printed Board Test Point

Single Sided Board, Soldered on Shoulder Side.

The land

pattern should be a minimum of

0.5

mm larger in diam-

eter than the diameter of the terminal shoulder. The clear-

ance between the terminal shank and the hole should be

0.13

mm maximum. See Figure

17-15.

Single Sided Board, Soldered on Flange Side.

The land

pattern should be a minimum of

0.5

mm larger in diam-

eter than the projection of the flared flange. The difference

idiameter between the terminal shank and the hole should

be

0.13

mm maximum. See Figure

17-16.

Double Sided Board without Plated-Through-Hole

Termi-

nals are not recommended for installation where the ter-

minal would act as an interfacial connection.

Double Sided Board with Plated-Through-Hole

The land

pattern on the shoulder side of the board should be

0.5

mm larger in diameter that the solder of the terminal. The

land pattern on the flange side of the board should be

0.5

mm larger in diameter that the projection of the flared

I

IPC-1-00267

Figure 17-15 Terminal Installation, Single-Sided Board,

Soldered on Shoulder Side

flange. The difference in diameter between the hole and

the terminal shank should be between

0.25

and

0.5

mm.

To assure proper filling of the hole with solder, the termi-

nal should be installed with an elliptical swage as illus-

trated in Figure

17-17

and

17-18.

4-21

COPYRIGHT Association Connecting Electronics Industries

Licensed by Information Handling Services

COPYRIGHT Association Connecting Electronics Industries

Licensed by Information Handling Services

IPC-CM-770

Januaty

1996

I

IPC-1-00268

I

Figure 17-1

6

Terminal Installation, Single-Sided Board,

Soldered on Flared Flange Side

IPC-1-00269

I

L

Figure 17-17 Installation of Terminal in Plated-through

Hole

r-""

30"160"

swaging

tool

r--

-

"1

I

\

\"",I

on swagmg

tool

Grind or.mlll flats

I

Plated-thru

hole

IPC-I-O0270

L

Figure 17-1

8

Elliptical Swaging

B. Pins

Pins should be soldered in plated-through-holes,

and the standard requirements for minimum annular ring

(0.13

mm minimum) apply.

C. Wires

Wires, when soldered to printed boards, utilize

the same land configurations as through-the-board mounted

components.

D. Bus Bars

Bus bars utilize the same land configurations

as through-the-board mounted components.

E. Test Points

Test points utilize the same land configu-

ration as through-the-board mounted components.

17.2.3 Lead Configuration After Assembly

17.2.3.1 Soldered Assemblies

A. Placement of Heat Sensitive Components

Where a

number of different types of components are mounted on a

turret terminal, the most heat sensitive components should

be placed at the top (see Figure 17-19). The sequence of

installation from top to bottom should be as follows:

Semiconductors and diodes

Resistors

Relays

Capacitors

Coils

Hookup wires

Jumpers

B. Component Lead and Wire Attachment to Terminals

There should be no more than the three leads or wires

attached to a terminal, lug or any section of a multisection

turret terminal. However, each lead or wire must be in inti-

mate contact with the terminal and they should be

mechanically secure prior to soldering (see Figure 17-19).

C. Lead and Wire Placement on Double-Ended Terminals.

(See Figure 17-20.) The component lead should be attached

to the terminal on one side of the board and the bus and

jumper wire should be placed on the same side. Hookup

wires should only be connected to the terminal opposite the

component's side of the board.

V

IPC-I-O0271

Figure 17-19 Placement of Terminal-Mounted

Components

D. Terminal Wire Wrapping Prior to Soldering

The wrap

of the wire or component lead before soldering should be

sufficient to hold the wire in place without movement dur-

ing the solder operation. Minimum requirements to assure

mechanical security should be one half or

180

of wire

4-22

COPYRIGHT Association Connecting Electronics Industries

Licensed by Information Handling Services

COPYRIGHT Association Connecting Electronics Industries

Licensed by Information Handling Services