IPC-CM-770D-1996 - 第39页

January 1996 IPC-CM-770 Figure 8-7 Straight-through Lead, Unclinched Can IPC-1-00161 Figure 8-8 Offset Lead Can Mounting IPC-I-O0152 I L Figure 8-9 Transistor Mounting (Unsupported Holes) Where spacers or spreaders are u…

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.

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January

1996

IPC-CM-770

Figure 8-7 Straight-through Lead, Unclinched Can

IPC-1-00161

Figure 8-8 Offset Lead Can Mounting

IPC-I-O0152

Figure 8-9 Transistor Mounting (Unsupported Holes)

Where spacers or spreaders are used, they should deter-

mine the height of the component above the board. The

feet of the spacer should be against the board.

When using spacers, the spacer should be installed in inti-

mate contact to both component and printed board mount-

ing surfaces

as to preclude any axial play between the

component body, spacer and the board. Spacers with pro-

trusions on one side should be mounted with the protru-

sions against the board.

typical method for mounting of a “TO” component with

a spacer is shown in Figure 8-10. The effect of spacers on

the leadcan seal and on lead forming should be evaluated

before their use is determined.

Spacer

IPC-1-00162

Figure 8-10 Transistor Mounting (with Spacer)

The use of multiple lead can spreaders, Figure 8-11, serve

a similar function for offset can mounting as do spacers for

straight-thru can mounting. Leads may be terminated in the

straight-thru method or the clinched lead method.

SPREADER

IPC-1-00164

Figure 8-11 Can Mounting Spreader

In installations where flux must be removed, a clearance of

0.38 to 3.2 mm should be allowed between the board and

the base of the component. The base of the component

should be parallel to the board.

Suitable fixturing should be provided to help assure that the

component is retained in proper position throughout the

soldering operation. Where no spacer is used, a temporary

spacer may be required until the component has been sol-

dered. Tab or index locations must be closely observed to

assure proper orientation in mounted position.

8.2.4.2 Horizontal Mounting

When transistors in TO

style cans are mounted horizontally, mounting clips should

be used.

typical method of mounting a transistor of this

type is shown in Figure 8-12.

Plastic power transistors are designed such that the mount-

ing hardware may also be a part of the active circuit.

typical mounting of such a device is shown in Figure 8-13.

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IPC-CM-770

Januaty

1996

Lead bend radius requirements should also be followed

when mounting these devices.

8.2.4.3 Electrical Insulators and Thermal Conductors

When electrical insulators are also thermal conductors, the

device mounted on thermal conductors should have a maxi-

mum space of

0.05

mm between the transistor and thermal

conductor, and between the thermal conductor and the

board. However, the transistor should be in contact with the

electrical insulator/thermal conductor and the electrical

insulator/thermal conductor should be in contact with the

board at some point.

SIDE VIEW

END VIEW

IPC-1-00153

OPTIONAL SPACER

Figure 8-14 Mechanically Secured Transistor

Allow for adequate cleaning after soldering.

Minimize possibility of solder shorts to the component

case.

Minimize thermal expansion induced stresses on the sol-

der joints.

8.3 Surface Mounting

General surface mount consider-

ations that apply to multiple-lead components and assem-

blies are discussed in Section

22.

8.4 Mixed Technology

The general techniques and

sequences for mixed assembly are discussed in Section

25.

Figure 8-1 2 Horizontal “TO” Mounting

8.5 Manual Assembly

Special tools and equipment are

not normally needed or used for manual insertion of mul-

tilead radial components. General manual assembly tech-

niques are discussed in Part

U U

IPC-1-00166

8.6 Automated Assembly

There are few standards for

automatic insertion of “TO” can type components because

very few are inserted automatically. There are two general

methods for automatic insertion of transistors: axial where

the part is handled by the leads, and radial where the part

is handled by the body.

8.6.1 Design Considerations

Figure 8-1 3 Transistor Can Horizontal Mounting

8.2.4.4 Mechanical Securing

Transistors which are to

be mechanically secured should have proper stress relief in

their mounting procedures.

A method for mounting of a transistor which must be

mechanically secured to the surface of the board is shown

in Figure

8-14.

In this configuration it is essential to:

8.6.1.1 Hole Diameter

A factor to be considered with

the radial insertion is the uncertainty of lead position,

caused by the fact that leads cannot be guided directly into

the board holes. Generally, the component hole diameter

must be increased at least an additional

0.25

mm to allow

for lead position variation.

8.6.1.2 Location Considerations

Both axial and radial

insertion require tooling clearances. Above the board clear-

ances similar to Figure

8-15

must be used in the axial

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