IPC-CM-770D-1996 - 第37页

January 1996 IPC-CM-770 Part Three Multiple Leaded Components 8.0 MULTIPLE-RADIAL-LEAD COMPONENTS The packaging technology is well established for transis- tors in metal “TO” cans. This configuration was used for early m…

IPC-CM-770

Januaty

1996

reflowed. Automated board handling facilitates precise and

rapid movement of assemblies through the process.

7.7

Handling and Storage

The handling and storage

chip components should be in accordance with the guide-

lines of Section

26.

7.8

Soldering

General soldering techniques applying to

all types of components are described in Section

27.

7.9

Cleaning

General techniques for cleaning applying

to all types of components are described in Section

28.

7.10

Conformal Coating

General techniques for confor-

mal coating for all types of assemblies are described in

Section

29.

2-12

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January

1996

IPC-CM-770

Part Three

Multiple Leaded Components

8.0 MULTIPLE-RADIAL-LEAD COMPONENTS

The packaging technology is well established for transis-

tors in metal “TO” cans. This configuration was used for

early multiple lead components and is still popular today.

Multiple-lead component cans are also available in many

sizes and shapes. The following general considerations

should be taken into account when designing printed board

assemblies with multiple- lead components:

Land size, lead forming and lead clinching.

The physical dimensions of the multiple lead component.

Automatic, semi-automatic, and manual component inser-

tion tolerances and restraints.

Component dimensions and tolerances.

Mechanical securing such as clips, clamps, brackets,

sockets, etc.

8.1 Part Type Description

8.1.1 Multiple-Lead Variable Resistors

Figure 8-1 is an

illustration of one type of multiple leaded variable resistor.

IPC-1-00193

Figure 8-1 Multiple-lead Variable Resistor

8.1.2 Transistor Outline “TO” Cans

This type of com-

ponent consists of a hermetically sealed can with up to

twelve round leads exiting from the bottom of the device

(usually in a circular pattern). Dimensions of standard and

registered “TO” devices are included in JEDEC 95-83.

Available tooling, hermetic sealing, and a rugged consmc-

tion made the can with

or 12 leads a natural first inte-

grated circuit (IC) package. It requires special punching

dies, drilling templates or off-grid numerically-controlled

(NC) drill programming for the 5.84 mm diameter pin

circle.

8.2 Through-Hole Mounting

Multiple-lead cans are used

in many printed board applications. However, the wide

variety of multiple-lead can sizes and number of leads

make it impossible to standardize on a mounting method

for such devices. The following text describes the more

commonly used multiple-lead can mounting techniques.

8.2.1 Lead Forming

Leads exiting from multilead radial

type components may be formed to standard grid spacings

and out away from under the body of the component. This

technique is used to provide inspection of solder joints,

stress relieving component leads, enhanced cleaning, etc.,

as shown in Figure 8-2.

0.75

yN--

0.5

[0.020]

(one lead diameter)

IPC-1-00154

Figure 8-2 “TO” Can Lead Forming

8.2.1.1 Component Retention

The dimple in Figure 8-3

increases the retention to the board and gives better contact

to the board circuitry. The main disadvantages are the die

sets required to form the leads and the hole size to dimple

height requirements. With the variation of lead sizes on the

board, this becomes the main concern.

IPC-1-00194

Figure 8-3 Dimple Preformed Leads

8.2.1.2 Preparation for Automatic Insertion

When the

radial method of automatic insertion of the TO-5, TO-18,

and similar families of devices is used, the leads must gen-

erally be prepped prior to the insertion operation, i.e.,

straightened and cut.

8.2.2 Land Patterns

Land Patterns for multilead radial

packages are a function of the dimensions and number of

leads as they exit the body of the component to be

3-1

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IPC-CM-770

Januaty

1996

mounted. Pattern configuration will also vary depending

upon the lead forming requirements as with spreader

mounting or reform into alternate patterns. Additional

information for hole/land requirements can be found in

Section 21.

In Figure 8-4, the leads of a TO-100 are formed to a stan-

dard 6.4 x 9.5 mm pattern, leaving space for two via or

plated holes available for internal plane connections or for

conductor routing. Lead forming provides a standoff and

protective coating is specified for the carrier surface to

insulate the printed wiring.

A typical printed board mounting pattern for 10-lead

multiple- lead cans with a 5.84 mm lead circle, such as

TO-96, TO-97, and TO-100, is shown in Figure 8-5.

ow0

O000

0000

Two Conductors

Per Channel

Lead Centers

3.18 [0.125]

All Conductors

0.33 [0.013]

All Spacing

0.25 [0.01 O]

Lands 1.65 [0.065]

Plated Hole 1

[0.040]

Component Centers

12.7 [0.500]

Component Area

11.2 [0.400] dia.

IPC-1-00156

Figure 8-4 Typical TO-100 Can Layout (Inches Only)

The small lead circle dimensions require accurately located

lands, of a small diameter, with minimum annular rings.

8.2.3 Lead Configuration After Assembly

The basic

multiple- lead can mounting techniques can be grouped as

follows:

Straight-thru lead, unclinched

Straight-thru lead, clinched

Straight-thru lead, with spacer (clinched, unclinched or

swaged)

Preformed lead, unclinched

Preformed lead, clinched

Preformed lead, with spacer (clinched, unclinched, or

swaged)

1.5

[0.060]

IPC-1-00157

Figure 8-5 Typical Mounting Pattern for 10-lead Cans

With Clinched Leads

Additional information for lead extension/forming require-

ments can be found in Section 21.

A mounting pattern for 12-lead multiple-lead cans with

radially offset and clinched component leads, such as

TO-73 and TO-101, is shown in Figure 8-6.

8.2.4 Mounted Component Configurations

Radial-lead

components such as transistors may be mounted vertically

or horizontally.

8.2.4.1 Vertical Mounting

In this method, Figure 8-7,

the component leads are simply inserted in the proper rein-

forced hole in the printed board and joined to the land by

conventional soldering techniques.

IPC-1-00159

Figure 8-6 Typical Mounting Pattern for 12-lead Cans

with Clinched Leads Mounting

A typical method for vertical mounting of a transistor with-

out a spacer is shown in Figures 8-8 and 8-9.

3-2

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