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SEMI G30-88 © SEMI 198 6, 1988 1 SEMI G30-88 TEST METHOD FOR JUNCTION-TO-CASE THERM A L RESI STANCE MEASUREMENTS OF CERA MI C PA CKAGES 1 Purpose The purpose of this test is to deter mine the thermal resistance of cerami…

SEMI G26-1296

6.6.2 Instrument Conditions

Typical operating conditions are:

Excitation source 27 MHz plasma

Carrier gas 99.999% Argon

Sample flow 1 ml/min

Power output 1000 watts

Plasma temperature 8000° K

Slit width of Spectrometer 30 µ m

6.6.3 Measurement of Sodium, Potassium, and Antimony — A standard solution of ten (10) ppm of sodium,

potassium, and antimony should be prepared and cycled through the ICP instrument. The blank extract sample and

the unknown molding compound extracts are then run through the ICP. The values obtained for sample are corrected

by subtracting values obtained for the blank. With the ICP, sodium, potassium, and antimony can be analyzed with

sensitivities to the ten (10) PPB levels. Any additional elements present may be obtained on the same cycle with no

additional preparation.

Table 1 Preparation of Standard Solutions for Instrument Calibration

Standard Solution

Anion

ml of Stock Soln. Diluted

to 1000 ml

Anion Conc. mg/1

Standard Solution II

Standard Solution III

Chloride (Cl) 5 5 1 0.2

Phosphate (HPO

) 25 25 5 1.0

Bromide (Br

) 10 10 2 0.4

Nitrate (NO

30 30 6 1.2

Sulfate (SO

) 25 25 5 1.0

Cation

Sodium (NA

) 5 5 1 0.2

Ammonium (NH

) 5 5 1 0.2

Potassium (K

) 10 10 2 0.4

NOTICE: SEMI makes no warranties or representations as to the suitability of the standards set forth herein for

any particular application. The determination of the suitability of the standard is solely the responsibility of the user.

Users are cautioned to refer to manufacturer’s instructions, product labels, product data sheets, and other relevant

literature respecting any materials mentioned herein. These standards are subject to change without notice.

The user’s attention is called to the possibility that compliance with this standard may require use of copyrighted

material or of an invention covered by patent rights. By publication of this standard, SEMI takes no position

respecting the validity of any patent rights or copyrights asserted in connection with any item mentioned in this

standard. Users of this standard are expressly advised that determination of any such patent rights or copyrights, and

the risk of infringement of such rights, are entirely their own responsibility.

International), 3081 Zanker Road, San Jose, CA 95134. Reproduction o

the contents in whole or in part is forbidden without express written

consent of SEMI.

SEMI G30-88 © SEMI 1986, 19881

SEMI G30-88

TEST METHOD FOR JUNCTION-TO-CASE THERMAL RESISTANCE

MEASUREMENTS OF CERAMIC PACKAGES

1 Purpose

The purpose of this test is to determine the thermal

resistance of ceramic packages using thermal test chips.

This test method deals only with junction-to-case or

mounting surface measurements of thermal resistance

and limits itself to heat sink and fluid bath testing

environments. Following the guidelines outlined in this

test method, junction-to-case thermal resistance

measurements of ceramic packages using the heat sink

and fluid bath methods should give the same results

only under certain limited conditions (i.e., under

conditions that approximate unidirectional heat flow

through the chip and substrate to the preferred heat

removal surface). If discrepancies occur, the heat sink

mounting technique shall be considered as the referee

test method. The heat sink mounting method for

measuring junction-to-case thermal resistance will be a

conservative measure of the package’s ability to

transfer heat to the ambient environment because heat

sinking is provided only on one side of the package,

whereas the fluid bath mounting method has the

potential for equally cooling both sides of the package.

1.1 Definitions — The following d efinitions and

symbols shall apply for the purpose of this test:

a. case temperature, T

, in degrees Celsius. The case

temperature is the temperature at a specified

accessible reference point on the package in which

the microelectronic chip is mounted.

b. mounting surface temperature, T

, in degrees

Celsius. The mounting surface temperature is the

temperature of a specified point at the device-heat

sink mounting interface (or primary heat removal

surface).

c. junction temperature, T

, in degrees Celsius. The

term is used to denote the temperature of the

semiconductor junction in the microcircuit in which

the major part of the heat is generated. For purposes

of this test, the measured junction temperature is

only indicative of the temperature in the immediate

vicinity of the element used to sense the

temperature.

d. power dissipation, P

, in watts, is the heating power

applied to the device causing a junction-to-reference

point temperature difference.

e. thermal resistance, junction-to-specified reference

point, R

ΘJR

, in degrees Celsius/watt. The thermal

resistance of the microcircuit is the temperature

difference from the junction to some reference point

on the package divided by the power dissipation P

f. temperature-sensitive parameter, TSP, is the

temperature-dependent electrical characteristic of

the junction under test which can be calibrated with

respect to temperature and subsequently used to

detect the junction temperature of interest.

2 Apparatus

2.1 The apparatus required for the se tests shall include

the following as applicable to the specified test

procedures.

a. Thermocouple material shall be copper-constantan

(type T) or equivalent, for the temperature range

-100 to +300°C. The wire size shall be no larger

than AWG size 30. The junction of the

thermocouple shall be welded to form a bead rather

than soldered or twisted. The accuracy of the

thermocouple and associated measuring system

shall be ± 0.5°C.

b. Suitable electrical equipment as required to provide

controlled levels of conditioning power and to make

the specified measurements. The instrument used to

electrically measure the temperature-sensitive

parameter shall be capable of resolving a voltage

change of 0.5 mV.

c. Controlled temperature chamber, fluid bath, or heat

sink capable of maintaining the specified reference

point temperature to within ± 0.5°C of the preset

(measured) value. Typical temperature-controlled

heat sink and fluid bath assemblies are presented for

illustrative purposes only.

2.2 Heat Sink Assembly — A typical heat sink

assembly for mounting the microelectronic device

under test is shown in Figure 1. The primary heat sink

is water cooled using a temperature-controlled fluid

circulator bath. An adapter socket/heat sink is fastened

to the heat removal surface of the primary heat sink,

and has a special geometry to handle specific size

packages (e.g., flat packs, dual-in-line packages, chip

carriers). This adapter provides a repeatable and

SEMI G30-88 © SEMI 1986, 1988 2

efficient interface between the package and the primary

heat sink. The mounting surface temperature is

determined with a thermocouple attached from the side

or bottom of the adapter with a thermal conducting

adhesive or grease at or near the interface between the

adapter and the package. It is at this point that the

device-under-test temperature is specified and

controlled. The adapter also contains the socket or other

electrical interconnection scheme. A thin coating (about

25 – 50 mm thick) of a thermal heat-sinking compound,

such as zinc-oxide-loaded silicone thermal grease, is

used at the interface to provide a reliable thermal

contact.

2.3 Fluid Bath Assembly — A typical temperature-

controlled fluid bath for thermally characterizing the

microelectronic device under test is shown in Figure 2.

In this figure, the package is mounted in a fluid bath

separate from the fluid circulator, although it can be

immersed directly in an integrated fluid circulator/bath

unit. The fluid in the bath should be continuously

stirred or agitated to ensure the required temperature

stability. Since this working fluid is being used as an

infinite heat sink, the case-to-fluid (ambient)

temperature difference at the case temperature reference

point of interest should be minimized, i.e., less than or

equal to 20°C. For case-to-fluid temperature differences

greater than 20°C, accuracy and repeatability

difficulties may occur due to a large variable

temperature gradient in the fluid film boundary layer at

the package-fluid interface. The case-to-fluid

temperature difference can be minimized by increasing

the fluid velocity and by decreasing the power density

seen by the fluid. The device under test should be

mounted such that heat transfer to the fluid is not

impeded. For leaded devices, the leads should be

oriented in such a manner so as not to interfere with the

heat transfer to the fluid and provide freedom to any

thermal currents caused by the power dissipation within

the package. The case temperature of the device under

test should be measured with a thermocouple that is

attached to the package and should not be assumed to

be at the fluid temperature. Care should be taken to

minimize exposure of the thermocouple bead to the

high temperature gradient in the fluid film boundary

layer at the package-fluid interface. The working fluid

should have a thermal conductivity at 25°C of at least

0.0006 W/cm°C. Working fluids such as inert

fluorocarbon liquids and silicone oils are suitable as a

cooling media.

3 Procedure

3.1 Direct Measurement of Refere nce Point

Temperature — T

. For the purpose of measuring a

microelectronic device thermal resistance, the reference

point temperature shall be measured at the package

location of highest temperature which is accessible

outside the package. This reference point location is

determined with the device operating in free air and

with no external heat-sinking. In general, this reference

point is found to be on the outside surface of the

package substrate directly underneath the chip in the

major path of heat flow from the chip to the heat sink or

ambient. Examples of the reference point location for

both cavity-up and cavity-down ceramic packages are

depicted in Figure 3. The package surface may be

altered to facilitate this measurement, provided that

such alteration does not affect the original heat transfer

paths and, hence, the thermal resistance, within the

package by more than a few percent. For packages with

an integral heat dissipater attached to the outside

surface of the package substrate, the case temperature

reference point shall be on the surface of the heat

dissipater at a point opposite the backside of the chip as

indicated in Figure 4.

3.1.1 Case temperature, T

. The microelectronic

device under test shall be mounted under specified

conditions so that the case temperature can be held at

the specified value. A thermocouple shall be attached

on the surface of the device package directly under the

chip. A conducting epoxy may be used for this purpose.

The thermocouple bead should be in direct mechanical

contact with the case of the microelectronic device

under test. For devices which, in their normal

application, are intimately connected (by pressure

contact, adhesive, soldering, or other means) to an

external heat sink, the mounting surface temperature, as

measured directly below the primary heat removal

surface of the case, may be used as the equivalent case

temperature.

If it is found that attaching the thermocouple directly to

the case is impractical, an alternate approach utilizing a

thermocouple welded to one side of a thin metal disk

should be used. This can be accomplished by parallel

gap welding the crossed thermocouple wires to one side

of a 0.25 cm (0.094 in) diameter, 0.02 cm (0.008 in)

thick beryllium-copper disk and then, with a thin layer

of adhesive, bonding the other side of the disk to the

case at the point of interest.

3.1.1.1 Mounting surface temperature , T

. The

mounting surface temperature is measured directly

below the primary heat removal surface of the case. It is

measured with a thermocouple at or near the mounting

surface of the heat sink. A typical mounting

arrangement is shown in Figure 5. The surface of the

copper mounting base shall be nickel plated and free of

oxides.

The thermocouple hole shall be drilled into the

mounting base such that the thermocouple lead is

directly below the area on the case of interest. It is