IPC-CM-770D-1996 - 第84页

January

1996

IPC-CM-770

A. Heights

Although low profile sockets are available,

sockets (with their device) present a higher assembly pro-

file. Wave solder holding plates are one point affected.

B. Automatic Assembly

As sockets are increasingly

unique, there may be a tendency to hand load one (or sev-

eral) which are an anomaly to the board. Designers should

be led to reassign socket placement to common boards if

possible.

C. Land Patterns

As it is wise to use a device insertion/

extraction tool, clearance real estate about sockets is

required. The increasing use of chips also necessitates use

of a great deal of device I/O patterns which also has a ten-

dency to open board space. These open land areas offer

“hand hold” and/or probe points which make the board

more susceptible to surface damage.

16.5 Manual Assembly

Sockets are normally handled

manually using special tools designed for ease of alignment

and insertion. On certain sockets a locating pin is used to

correctly orient it to the land pattern, such as pressure fit

type sockets. Manual assembly as always offers a greater

susceptibility to damage. Major points to be addressed

when using these procedures with sockets are:

A. Board Loading

Always load from component side

with lands and holes in view. Immediately clinch diagonal

terminals on solder side.

B. Handling

Socket contact springs are susceptible to fin-

ger oils, handling damage, particulate entrapments. Use of

lint free gloves when assembling is appropriate. Handling

the sockets with tools or by the insulator is also necessary.

C. Storage

Leads are extremely susceptible to displace-

ment. Remove sockets from the shipping container one at

a time and immediately load in the board. Never

accumulate/store sockets on the work bench unprotected.

D. Clipping

If

leads must be clipped, they should be

shortened after they are in the board (never in an

unmounted condition).

16.6 Automated Assembly

Although the bulk of sock-

ets, DIPS, may be automatically loaded with stick loaders,

the balance do not lend themselves to automation. High

board frequency and quantity sockets may be loaded by

pick and place type equipment; however, operation cost

must be closely assessed for value.

16.7 Handling and Storage

The handling and storage of

component sockets should be in accordance with the guide-

lines of Section

26.

16.8 Soldering

Due to the terminakontact configura-

tion, sockets have a tendency to sink more heat than other

components. As a consequence, they will require a slightly

longer dwell time and will draw more once started. Due to

inability to adequately clean terminal area, the user/

manufacturer may restrict the use of activized fluxes. In

wave soldering through-hole mounted sockets, the socket

must be mounted on the component side of the printed cir-

cuit board or carrier. Care must be taken to ensure that flux

or solder does not wick up into the receptacle area of the

socket.

Soldering techniques are outlined in Section

27.

16.9 Cleaning

Special care and attention must be given

to avoid entrapment of particulates in the socket contact

cavity which is difficult to flush. Particulates may not only

leach corrosive products, but may also hinder contact

spring actions and defeat the socket.

Sockets rarely, if ever, require aggressive cleaners or

techniques.

Non-normal cleaners and reagents should be cleared for

use with the supplier

so

that contact plating or insulators

are not affected by the process.

Cleaning agents used after soldering should not have any

harmful effects upon the socket housing material. Check

with the socket manufacturer to verify the compatibility of

any cleaning agent with the socket housing material. Any

residue left on the contact surfaces must be removed.

Ideally, sockets should be provided with standoffs and

should not have blind holes, to permit cleaning agent to

pass between the socket and printed board. Cleaning is

more thoroughly covered in Section

28.

16.1

O

Coating

Care must be exercised to prevent coating

from getting on the contact surfaces. Wicking can present

a problem, and it may be necessary to seal around the

socket with tapes or fixtures to prevent it.

17.0 INTERCONNECT COMPONENTS

This section covers those devices used for providing per-

manent connections from one point to another and includes

terminals, pins, jumpers, bus wire, bus bars, stranded and

solid wire, and test points. For further information, see

IPC-PD-335.

17.1 Part Type Description

17.1.1 Terminals

Terminals is a name applied to a broad

range of devices used in or on a printed board. These

devices are usually chosen for their optimum electrical val-

ues or physical characteristics via systems testing; for

quick repair or replacement of compatible components or

devices; for their ability to be automatically inserted; to

connect printed boards to each other; or to connect the

printed wiring to other parts of the system external to the

4-15

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

printed boards. To provide mechanical strength to the ter- minal serves as the feed through device through the glass

minal and the resultant connection, most terminals are seal. See Figure

17-3.

designed for through-the-board mounting, either with

crimping, rolling, or flaring on the back side of the board,

or by an interference fit or “press fit” into the board.

Solder-only mounting may be used when the terminals are

only used as test points.

D.

Cup Terminals

cup terminals are not normally

attached to printed boards, but are often used as part of a

connection technique which does interface with a printed

board. Cup terminals are designed for either soldering (see

Figure

17-4)

or crimping (see Figure

17-5).

Terminals can be generally categorized as follows:

A.

Turret Terminals

This type of terminal has guide slots

to assist in retaining the attaching wires, and is available

with mounting bases designed for funnel flange or roll

flange retention, or for press-fit installation. See Figure

17.1.2 Solderless (Wire) Wrap PinslPosts

Pins are

available in single and double ended types, with and with-

out solder carrying characteristics; single pin end with a

socket on the other end, with and without self solder carry-

ing characteristics; rectangular and square varieties. Vari-

17-1.

I

guide

slot

dase

clearance

IPC-I-O0251

Figure 17-1 Typical Turret Terminals

B. Bifurcated Terminals

This type of terminal contains ous self retaining features for securing to the printed board

two posts for lead or wire attachment. Bifurcated terminals are also available, as are plating and base material. There

are normally available only with their bases designed for are those that require soldering to the printed board and

funnel flange or roll flange retention. See Figure

17-2.

those that do not. Compliant pins depend on an expanded

lnsulatlon

clearance

Polnt

o1

entry

IS

same for

upper conductor

IPC-I-O0252

Figure 17-2 Typical Bifurcated Terminals

C. Pin Terminals

These terminals are designed for use section of the pin for retention in the printed board. Other

where space is limited, and are normally used only in the types require the insertion machine to crimp the pin on

“press-fit’’ style. One variation of the pin terminal is the both sides of the printed board for retention.

A

third type is

hook terminal. This type of terminal is usually found on held in place completely by the solder. The choice depends

relays and other hermetic seal devices, where the hook ter- on consideration such as the type of tooling available, the

4-16

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

IPC-1-00253

Figure 17-3 Typical Pin Terminals

board hole tolerance, and the number of pins to be inserted.

In general, the hole and plating tolerances for compliant

pins are wider than for non-compliant pins. Most all thick-

nesses of printed boards can be accommodated. Typical

mating interface), four sharp edges (for solderless wrap-

ping), and a uniform cross section. The finished loose pins

are usually put on a continuous secondary carrier to facili-

tate machine insertion and handling. See Figure 17-6. This

carrier strip is normally an expendable item and is not used

as part of the final product. There are other square pin sizes

manufactured with drawn wire as well as rectangular ver-

sions. These pins are designed to be used with mating con-

nectors as well as solderless wrapping.

B.

Stamped PinslPosts Square and Rectangular

These

pins, in 0.64 mm square as well as other square and rect-

angular sizes are manufactured from flat stock in a continu-

ous strip (see Figure 17-7).

The connection of stamped pins is designed to be near or

in the area of the minted board. where raw comnleted

pins are described as follows:

-Insulation

'

clearance

Conductors shall

bottom in cup

Conductor shall

be in line contact

with inner wall

of

terminal

Top route conductor

shall bottom against

bottom route conductor

L

IPC-1-00254

Figure 17-4 Typical Solder Cup Terminal

Insulation

clearance

Inspection hole

conductor visible

Insulation

IPC-I-

Figure 17-5 Typical Crimp Terminal

A.

Drawn Wire PinslPosts Square or Rectangular

A

most edges will be covered by solder or at the very ends, where

popular size in the industry is the 0.64 mm square variety. raw edges are of little consequence.

The pins are manufactured from a drawn wire. This method

of manufacture offers four smoothly finished surfaces (for

4-17

COPYRIGHT Association Connecting Electronics Industries

Licensed by Information Handling Services

COPYRIGHT Association Connecting Electronics Industries

Licensed by Information Handling Services