Vishay Mounting Power Semiconductors Application Information

Powerex, Inc., 200 Hillis Street, Youngwood, Pennsylvania 15697-1800 [phone]
Powerex, Europe, S.A. 428 Avenue

G.

Durand, BP107, 72003

Le

Mans, France (43) 41.14.14

Mounting Power Semiconductors

D.

I. Mounting Surface Preparation

in

the

A. Surface flatness

mounting
.001
commercial
require
rough
machining
surface

B.

Surface finish

mounting
equivalent
semiconductor
microinches
microinches
finishes
no

performance.

C.

Care

devices

as
scratches,

the

minor
one

flatness is

surface

thermal

interface

inch

per

inch.

extruded

spot

facing

plates,

etc.

to

meet

flatness

interface

to that of the

maximum
maximum

add

undue

improvement

should

be

as

well

to

minimize

and

mounting

interface

scratches,

should

realize

much

finish

in

interface.

requirements.

in

device

taken

as
voids,
other

achieving

in

etc.
more

device

area

should

Generally,

heat

sinks

and

cast

sinks;

require

additional

the

required

the

device

area

should

or

32

for

disc

and

for

stud.

cost with little or

thermal

in

handling

the

heat

sinks

nicks,

deep

imperfections

area.

While

are

not

desirable,

that

surface

critical

than

a good

be

be

Finer

so

63

in

Treated heat sink finishes

be

removed
interface
on

heat

the

mounting
chromate
removed
optimum
tin-plated
even

where

E.

Mounting

free
and films.

stored
immediately
cleaning
satisfactory
lightly
3M

Scotch
steel
Semiconductor

As

freshly

oxide

from

the

device

area.

Black

anodizing

sinks

must

be

area.

Also,

acid

dip

finishes

from

the

mounting

performance.

finishes

desirable

corrosion

interface

of

all foreign material, oxides,

and

operation

polish

wool,

in

many

could

Since

most

are

not

after

machining,

cleaning

the

mounting

Britst

pad

followed

are

areas

assembled
is

recommended.

technique

by

Cleaning

bared

aluminum

layer

in

a matter

Alcoa :# 2 electrical joint

may

be

used

to

clean

should

mounting

or paint

removed

irridite

or

must

area

Nickel

and

acceptable

applications

be a problem.

should

heat

sinks

a

is

area

with

or

No.

000

a

Solvent

forms

of

seconds,

compound

aluminum

from

be

for
and

be

are

to
fine

wipe.

an

heat

sink

mounting
Semiconductor
Surface
cleaning.
lint-free
After

cleaning,
interface
immediately
semiconductor
thereafter to
compound
metal

particles.

F.

Powerex recommends the use.
thermal Interface compound
power semiconductors.

proper

A

interface
scratches

a

device/heat
twenty-fold
case-to-sink
possible.
for

high

surfaces,

Cleaning

should

not

Parts

may

surface

an

compound

applied

device

prevent

from

application

compound

and

imperfections

sink

improvement

thermal

This

is

power

semiconductors.

followed

Solvent

be

touched

be

placed

until

final

appropriate thermal .

should

and

after

on

assembly.

be

the

attached

the

thermal

collecting dust

and

for

With

the

of a

thermal

to

fill

the

voids,

in

the

mounting

especially

area,

in

device

resistance

important

a

is

by

a

wipe.

a

of

all

a

General Purpose Thermal Interface Compound Comparison Chart

Maximum
Continuous
Heat Sink

DC340Q)

Temperature

1500C

Advantages

Disadvantage

-Difficult

-Contains filler particles
which

can

surfaces

Alcoa

#2®

95°C

-Removes

-Temperature

-Mildly

toxic

oxides

DC

2OOQ)

150°C

-Easy

to

apply

-Migrates

-Good control of
film

thickness

<D

Product of

Dow

® Product of

@)

Check

Coming Corporation.

Aluminum

to

see

that

Company of America.

no

cotton threads

are

left

on

the mounting interface

surfaces.

1-34

to

apply

indent

slightly

mounting

limited

Stud

OK

OK

OK

Disc

OK

-Preferred

~ealuminum

heat
surface

for

sink

OK

Suggested
Appllcator(s)

-Rubber
squeegee

-Q-Tip@

-Rubber

squeegee

-Q-Tip@

-Rubber

squeegee

Powerex, Inc., 200 Hillis Street, Youngwood, Pennsylvania 15697-1800 [phone]
Powerex, Europe, S.A. 428 Avenue

G.

Durand, BP107, 72003 Le Mans, France (43) 41.14.14

II. Mounting TIps
A.

Mount studs

for

Stud Devices

to

a heat sink

through a clearance hole

of

(1)

hex

nut

and

a lockwasher or

nut or

(2)

hex

nut-belleville washer

hex

tenz

combination or

B.

Diameter

of

the mounting

clearance hole

the diameter of

1/64"

and

perpendicular to the

C.

Remove proJections from

the

should

nut.

should

not exceed

stud

by

be

accurately drilled

mounting

mounting clearance hole.

and drilled holes

deburred.
be

deburred

exceeding

D.

Avoid

drilling

stud

devices.
tends to
hole
degree perpendicularity tolerance
necessary
mounting

E.

Apply appropriate thermal

unscrew

can

Interface compound

film

to the

as

device
surface
stud
compound
threads of the
be

alter

torque

stud device.

F.

Always use a torque wrench

mounting
individual

correct

quality torque

specified

used.
applied

the semiconductor

of the heat

device

lubricated as

the

recommended

and

torque to

range,

The

on

should

The

edge

with

a chamfer not

.01

"

radius.

and

tapping holes for

Thermal

the

occur,

and

between

surface

mounting

well

on

and

cause

stud

device

torque

the

the hole

is

as

to the mounting

sink.

the heat sink to

to seat the device.

stud

and

this

undue

devices.

data

be

wrench,

should

should

hex

nut while holding

stationary.

be

of the hole

ratcheting

stud

the 1/10 of a

difficult to

in

a very thin

area

only of the

Rotate the

nut

will

drastically

mounting

stress on the

Refer

sheet for the

used.

accurate

always

always

by

more

surface.

Punched

carefully

from

and

achieve.

must

to the

A

good

in

be

means

pal

than

may

which

the

spread

The

not

when

the

be

G.

Do

not

exceed maximum

recommended torque limits.

Application of excessive torque
major

cause

of

stud

device
problems.
mechanically
torque or thermally
little.

III. Mounting Tips
A.

Machine

Semiconductors

damaged

or

spot face the heat

by

damaged

for

Disc Devices

can

too

sink mounting surface areas
diameter larger than that

to

disc pole face

Keep

spot

face
interference
disc

package.

B.

Use locating pins (or alternative
method)

optimum
Preassemble
hammer
each
useful
Improperly
using

wrong
device
of
causes
problems.

C.

Apply appropriate thermal

to

load

into center

heat

sink. A gauge

to prevent excessive

mounting

a locating

diameter,

seating

the silicon

of disc device mounting

Interface compound

film

to

the

mounting
device,
surfaces of the heat
disc to
seat the

D.

Check the polarity

prior to assembly to
is
Also
prior to

E.

Follow Clamping TIps

1.

2.

as

well

spread

devices.

installed

Use
clamp
even
Select the proper
aware
temperature limitation (less than

130°C for most

in

position

assembly.

a self-leveling type mounting

to

assure

distribution of

of

clamp

be mounted.

shallow to prevent

with

other parts of the

center the disc for

distribution.

roll

pins

with

a light

dowel

hole

block

disc off center or

pin

too

long

resulting

and

element,

as

the compound and to

the

desired

SCR

in

possible fracturing

are

major

in

a very thin

surfaces of the

to the

mounting

sinks.

Rotate the

of

the deVIce

insure

the device

direction.

gate

leads,

parallelism

pressure.

size

clamp;

insulation

clamps).

is

a

mounting

be

much

by

too

to

of

the

in

is

pin

length.

andlor

improper

/

etc.

and

be

3.

Coat

clamp

threads for

discs

with

Never-Seez®
equivalent
to prevent nut
binding
are

4.

Take
to prevent bodily
forces
resulting

a

becoming a flying

5.

Prestressing
force prior to actual
application
springs
clamps.

6.

Preset
assembly
deflection type indicators.

7.

Apply
evenly,
disc.

8.

Advance
equal
tightening

9.

Apply the
on
too
clamp,
down to correct force - start
clamping

a.

b.

type

and

when

high

being

applied.

necessary

can

result

in

the

broken

the

can

and

to

screen

indicators to

on

clamps that

clamping

and

perpendicularly to the

nuts onto clamp bolts

length

and

with

a

correct

the device data

much

force be

do

not

attempt to

procedure allover
Manual
appropriate
advance
until
gauge
or the
turns
on
HydrauliC
apply

the assembly

a
torque each nut
alternately to
Release

method -

nuts

either the

reads

required

are

applied,

type of

press method -

the calibrated force to

good

quality torque

press.

large

area

or

compound,

clamp

clamping

safety

harm
in

clamp breakage

projectile.

clamp

help

force

finger tight before

wrench.

force as described

sheet.

applied

wrench,

1/4

the

clamp

with

10ft.

in

order

thread

forces

precautions
as

high

bolt

to its

rated

use

in

the

to seat clamp

out defective

zero

before

have

smoothly,

Should

to the

back

again.

using

an

alternately

tum each

clamp

indicator

desired

force

number of

depending

used.

press.

Using

wrench,

1/4

tum

Ibs.

torque.

load

1-35