Document Number: 50053

www.vishay.com

Revision: 27-Oct-10

65

LPS 600

Power Resistor for Mounting onto a Heatsink

Thick Film Technology

Vishay Sfernice

RECOMMENDATIONS FOR MOUNTING ONTO A HEATSINK

• Surfaces in contact must be carefully cleaned.

• The heatsink must have an acceptable flatness: From 0.05 mm to 0.1 mm/100 mm.

• Roughness of the heatsink must be around 6.3 µm. In order to improve thermal conductivity, surfaces in contact (alumina,

heatsink) should be coated with a silicone grease (type SI 340 from Rhône-Poulenc or Dow 340 from Dow Corning) or a thermal

film (type Q Pad II) easier and faster to install than the grease.

• The fastening of the resistor to the heatsink is under pressure control of two screws tightened at 2 Nm for full power availability.

• The following accessories are supplied with each product: 2 screws CHC M4 x 25 class 8.8 and 2 M4 contact lock washers for

heatsink mounting,

2 screws TH M4 x 6/6 and 2 M4 contact lock washers for

connections.

CHOICE OF THE HEATSINK

The user must choose the heatsink according to the working conditions of the component (power, room temperature). Maximum

working temperature must not exceed 155 °C. The dissipated power is simply calculated by the following ratio:

P:

Expressed in W

ΔT:

Difference between maximum working temperature and room temperature

Thermal resistance value measured between resistive layer and outer side of the resistor. It is the thermal

resistance of the component: (see specifications environmental paragraph).

Thermal resistance value measured between outer side of the resistor and room temperature. It is the thermal

resistance of the thermal interface, the heatsink (type, shape) and the quality of the fastening device.

Example:

ΔT ≤ 155 °C - 50 °C = 105 °C

=

= 0.58 °C/W

PERFORMANCE

TESTS

CONDITIONS

REQUIREMENTS

Momentary Overload

IEC 60115-1

2 x

± (0.25 % + 0.05

Ω)

Rapid Temperature Change

IEC 60115-1/IEC 60068-2-14 Test Na

50 cycles

- 55 °C to + 155 °C

± (0.5 % + 0.05

Ω)

Load Life

IEC 60115-1

1000 h (90/30)

± (0.5 % + 0.05

Ω)

Humidity (Steady State)

IEC 60115-1

56 days RH 95 %/40 °C

± (0.5 % + 0.05

Ω)

Vibration

MIL STD 202 Method 204 Cond. D

(10

g; 5/500 Hz)

± (0.25 % + 0.05

Ω)

Climatic Sequence

IEC 60115-1

(55/155/56)

± (1 % + 0.05

Ω)

Tightening Torque on Heatsink

LPS 300

2 Nm

P

ΔT

R

TH (j - c)

R

TH (c - a)

+

[]

----------------------------------------------------------

=

ΔT

P

-------

105

180

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