IPC-CM-770D-1996.pdf - 第44页

IPC-CM-770 Januaty 1996 110.16 mm1 [.400"] max 2.54 mm [. 1 OO"] max f .25 mm [.O1 O"] non accum IPC-I-O0042 Figure 10-1 16-Lead DIP IPC-1-00373 I Figure 10-2 Single In-line Component and through the print…

January

1996

IPC-CM-770

t-"I

SOT

t"i

SOT

IPC-I-

Typical SOT Packages

into a

10+5"

vee provide retention of the component. (See

Figure

10-

10.1.2 Single-lnline Packages

The single inline (SIP)

components are similar to the dual inline (DIP) compo-

nents with leads that exit the component body "in-line"

2.54

mm apart center to center, but in a single row pattern

rather that the dual row (square) pattern of the DIP (see

Figure

10-2).

Single inline (SIP) component configuration is usually

associated with resistor networks and can therefore reduce

handling, inventory, and assembly require- ments by the

use of a single component, versus a number of discrete

components. Advantageous use of the SIP type component

are applications where printed board real estate is limited.

10.2 Through-Hole Mounting

10.2.1 Component Preparation

SIP components are

ready for manual insertion without the use of special tools

or fixtures. Lead preparation is not normally required. Lead

clinching is required for component retention on board

through manufacturing operations. Standoffs are usually

built-in to the component body to accomplish proper board

spacing as shown in the typical SIP specification in Figure

10-2.

For DIP packages (whether lands are of a round,

square or ribbon across section) leads should be dressed to

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IPC-CM-770

Januaty

1996

110.16

mm1

[.400"] max

2.54

OO"]

max

.25

[.O1

O"]

non

accum

IPC-I-O0042

Figure 10-1 16-Lead DIP

IPC-1-00373

Figure 10-2 Single In-line Component

and through the printed board such that deformation does

not cause clearance spacings to be reduced beyond the

minimum. Slanting, bowing and bending of leads in any

direction should not exceed

of the lead width (or diam-

eter) nor should leads be twisted more than

15".

10.2.2 Land Patterns

DIP layouts usually follow a rect-

angular grid pattern and reasonable densities are possible,

such as that shown in Figure

10-3.

10.2.3 Lead Configuration After Assembly

The maxi-

mum clinched lead length is dependent upon the length of

lead that is available for cutting and clinching and the

thickness of the printed board.

nominal clinched lead

ength is

1.25

mm although a range from

0.75

mm mini-

mum to

2.25

mm maximum is attainable. In all cases the

land diameter should be large enough to accommodate the

clinched lead to minimize solder bridging. (See Figure

10-4.)

minimum of two

(2)

diagonally opposite leads should be

clinched for part retention as shown in Figure

10-4.

10.2.4 Mounted Configuration

The base of the device

should be parallel to the surface of the printed board to the

All

lines 0.3

[0.012]

Plated hole

1.0 [0.040]

All

line spacing 0.2 [0.010]

Lands 1.5 [0.06]

Component centers 12.5 [0.5]

22.5 [0.9]

Component area 19.6 [0.785]

8.3 [0.332]

........

9 lines 7.5 10.31

lin es^^^^^^

-5 lines 5.0 [0.2]

........*

5.0 [0.2]--1 200

IPC-1-00169

Figure 10-3 A Typical Dual In-line Layout

View

IPC-I-O0201

Figure 10-4 Lead Configuration (After Assembly)

extent that minimum lead protrusion and maximum com-

ponent body height from the board is maintained (see IPC-

A-610).

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January

1996

IPC-CM-770

Heat sinks may be required and should be properly secured

to the board

that they do not stress the subsequent sol-

der joints. A resilient spacer may be used as shown in

\\V

“Resilient spacer

IPC-I-O0203

Figure 10-5 Resilient Spacer to Heat Sink Frame

Figure

10-5.

The lead-to-body seals of mounted devices should be

undamaged. Body chipouts that extend to or into the glass

seal and chipouts that expose a normally encased area of a

lead, are unacceptable. Hairline cracks in either the seal or

the body are not acceptable.

10.3 Surface Mounting

For whatever reason the deci-

sion is made to use through-hole components in combina-

tion with surface-mount components, there must be a will-

ingness to compromise some of the advantages of a totally

surface mount assembly. Modified through-hole compo-

nents do not provide the space savings that components

intended for surface mounting provide. However lead

modification may be the only reasonable approach to sur-

face mounting, if the required components are not available

in surface mounted packages.

10.3.1 Component Preparation

One method for mount-

ing both through-hole and surface mounted components on

the same board is to modify the leads

that they can be

surface mounted and soldered.

10.3.1.1 DIPS

Where only a few DIPs are involved on an

otherwise surface mounted assembly, the leads may be

formed to resemble a SOIC package. (See Figure

10-6.)

For production, machines are available which cut and form

IC leads into a “gullwing”-type configuration. (See Figure

10-6.)

Another method of modifying DIPs for surface mounting is

the “Butt” mounting technique. This involves simply cut-

ting the DIP leads to a shorter length and placing the

device on a land pattern to be soldered along with the other

surface mounted devices.

10.3.1.2 SIPS

SIPs lead forming is shown in Figure

10-7.

Take care to assure the coplanarity of the reformed

leads, especially if the assembly is to be vapor phase

reflow soldered. Leads may be carefully formed by hand

for low volume or prototypes. For production, machines

are available which cut and form IC leads into SOIC type

configuration.

Dip, thru-hole mount

Dip, modified

“SOIC”

type mount

(gull-wing lead)

Dip, modified

“BUTT”

mount

(“I”

lead)

IPC-I-O0206

Figure 10-6 Modifying DIP for Surface Mounting

10.3.2 Land Patterns

Land patterns for DIPs and

SIPs

that are surface mounted depend on the lead shape of the

parts. The gullwing lead shape uses the same land pattern

concepts for SOICs described in Section

When using

DIPs with the “1”-lead, the land pattern should be suf-

ficient to provide a minimum of

0.25

mm on all sides of

the lead.

Figure 10-7 Gull-Wing Lead for SIP-type Component

10.3.3 Lead Configuration After Assembly

The lead

configuration for surface mounting for SIPs and DIPs

remain the same after assembly as before assembly. If

reflow soldering techniques are used, the leads must be in

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