Heat Countermeasure Solutions
for Si Power Semiconductors

The power output of power semiconductors has been increasing, and the amount of current flowing through semiconductor chips has been increasing.

Urgent tasks to maintain the performance of such power semiconductors are to efficiently dissipate the heat around semiconductor chips caused by electricity to reduce heat-related malfunctions, and to ensure insulation performance even when a large amount of current flows. Here, we suggest our heat countermeasure solutions for power semiconductors, which are based on highly-functional or composite materials for ensuring high thermal conductivity and high insulation performance, as well as addressing newly arising challenges.


Discrete

Double-sided heat dissipation power module


Case-type module

Sintered Copper Die-bonding Paste

Higher connection reliability compared to high-lead solder or sintered silver. Provides 180 180 W/(m・K) of thermal conductivity.

Die-bonding materials, which are used directly under heat generating semiconductor chips, need to quickly dissipate heat to radiating parts such as thermal interface materials (TIMs) or heat sinks for ensuring semiconductor chip performance.

Although high-lead solder is widely used in die-bonding applications for semiconductor chips, its thermal conductivity is limited to around 30W/(m・K)and the amount of thermal conduction is insufficient. Therefore, a sintered silver paste with high thermal conductivity has been introduced as a substitute. However, it requires high pressure when used in the die-bonding process, which raises problems such as the breaking of semiconductor chips during processing. For this reason, we have developed “sintered copper die-bonding paste,” which has higher thermal conductivity 180W/(m・K)than high-lead solder and allows for die-bonding without thermal compression pressure or with low thermal compression pressure.

For more details and estimation,
please click "Contact Us" at top of this page.

Our Solution

High thermal conductivity(180W/m・K)can resolve problems relating from to high-lead soldering

Conventionally, high-lead solder is widely used in power semiconductors due to its high connection reliability among solder materials. However, its thermal conductivity is lower than those of other component materials, resulting in a challenging bottleneck issue during heat dissipation. In contrast to a general high-lead solder with 30W/(m・K) of thermal conductivity, our sintered copper die-bonding paste has an increased thermal conductivity (180W/(m・K)), to be used as na ideal die-bonding material to overcome the temperature increase in power semiconductors.

Temperature distribution on sample cross-sections
(a) Sample with
sintered copper die-bonding paste
Heat is dissipated from the chip to the board, keeping the chip temperature low.
(b) Sample with
high-lead solder
Heat cannot be dissipated,
increasing the chip temperature.

(Setting items other than material properties)
Electrical power, environment temperature: measured values of samples, air properties: air at normal pressure and 30℃(other physical quantities: fixed values), density: 1.161kg/㎥, thermal conductivity: 2.610 x 10-2 W/(m•K), coefficient of molecular viscosity: 1.840 x 10-5 N•s/㎡, thermal expansion coefficient: 3.333 x 10-3 K-1, conduction, radiation, heat transfer by natural convection, buoyancy, and turbulence were taken into account.

Maintains high connection reliability even when the operating temperature is >175℃

Die-bonding with high-lead solder has the problem that the die-bonding layer suffers fatigue fractures due to the stress caused by the difference in the thermal expansion of parts, resulting in the connection of semiconductor chips not being operating adequately. During the power cycle test (Tj.max= 175℃) it has been proved that our sintered copper die-bonding paste ensures a higher number of cycles than high-lead solder and sintered silver, has good durability, and can maintain the connection reliability of semiconductor chips.

Power Cycle Test Weibull Analysis Results (Tj,max=175℃)

Product Features

High thermal conductivity(180W/(m・K))

The product has a high thermal conductivity 180 W/(m・K), which is five or more times that of high-lead solder 30 W/(m・K) and is most suitable as a die-bonding material for semiconductor chips that are subject to the highest thermal load among power semiconductors.

Two types are available: non-pressure or pressure bonding type

Our lineup of sintered copper die-bonding paste consists of two types: a “non-pressure bonding type” that does not require thermal compression pressure (required gas atmosphere: hydrogen) and a “pressure bonding type” that allows for bonding with 2 MPa or less of thermal compression pressure. Compared to sintered silver paste, which is a die-bonding material also having high thermal conductivity and a thermal compression pressure of 20 MPa, our product allow for bonding with one-tenth of that pressure. Therefore, a contribution to the improvement in the yield rate during semiconductor chip mounting is expected.

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Thermal Conductive Sheet Containing Vertically Oriented Graphite

Heat dissipation ability and reliability that significantly exceed the performance of conventional grease thermal interface materials provide a maximum of 90 W/(m・K) thermal conductivity.

Grease thermal interface materials (TIMs), which are widely used as thermal conductive materials between power semiconductors and heat sinks, do not provide enough thermal conduction to radiating parts such as heat sinks, raising the problem of ensuring semiconductor chip performance. The thermal conductive sheet containing vertically oriented graphite, a thermal interface material we have developed, has a maximum of 90W/(m・K) thermal conductivity and can quickly dissipate heat to reduce temperature increase in semiconductors.

For more details and estimation,
please click "Contact Us" at top of this page.

Our Solution

Degradation in semiconductor chip performance due to heat is reduced by high thermal conductivity (max. 90W/(m・K))

A maximum of 90W/(m・K)thermal conductivity is achieved by orienting high thermal conductive graphite filler in the vertical direction. The thermal conductivity of this product, which is about 18 times that (5W/(m・K)) of grease thermal interface materials (TIMs), allows for quick heat dissipation to radiating parts such as heat sinks, reducing temperature increase in semiconductors and contributing to ensure semiconductor chip performance.

Use Example of Thermal Conductive Sheets

Pump-out due to thermal deformation does not occur and endurance reliability is secured

The use of grease thermal interface materials (TIMs) raises the problem that grease is forced out due to the thermal deformation of power semiconductors and voids generate in the grease (pump-out), thereby increasing thermal resistance and resulting in insufficient heat dissipation. The use of a sheet of thermal interface material (TIM) can avoid the occurrence of pump-out and increase endurance reliability.

Product Features

A maximum of 90W/(m・K) of excellent thermal conductivity

Forming vertically oriented graphite filler in sheets results in excellent thermal conductivity in the vertical direction. A maximum of 90 W/(m・K) is achieved when the product is in bulk form, and a maximum of 45 W/(m・K) is achieved when it is in practical use.

Graphite particle
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High Heat-resistant Coating Material “HIMAL”

A high heat-resistant coating material that prevents delamination between compounds and semiconductor chips/boards/bonding materials/other components, and can add insulation performance (>230V/μm).

Delamination between compounds and boards due to difference in thermal stress between power semiconductor component materials, which is newly caused by an increase in the operating temperature of power semiconductors, is a serious problem. The high heat-resistant coating material “HIMAL” has a good heat resistance (glass-transition temperature (Tg) of 220℃ and thermal decomposition temperature (Td5) of 410℃). Therefore, even in severe temperature environments, delamination between compounds and boards is prevented by the high adhesiveness and flexibility, increasing the reliability of power semiconductors. As the high heat resistance and adhesiveness of the product are held in high regard, it is being used for power modules in hybrid vehicles.

For more details and estimation,
please click "Contact Us" at top of this page.

Our Solution

Prevents delamination of semiconductor package even in severe temperature environments

Delamination between compounds and boards due to the difference in thermal stress between power semiconductor component materials is a problem. “HIMAL” <HL-1210G2>which has a linear expansion coefficient of about 60 ppm and an elastic modulus of 2.6 GPa, is more flexible compared to compounds, semiconductor chips and lead frame metals, and can mitigate the stress caused during temperature increase or processing. This results in delamination prevention in semiconductor packages, contributing to an increase in their reliability.

Enhances insulation in semiconductor packages and saves space

The sizes of semiconductor packages such as power semiconductors that handle 1700 V or more of high voltage have been increasing to ensure insulation performance. “HIMAL” has a high break down voltage of 230V/μm or more, that achieves in partial insulation performance without upsizing packages.

Product Features

High reliability of semiconductor packages due to stress reduction and high adhesion in PKG

Even in severe temperature environments, HIMAL, which has both high heat resistance and adhesiveness, can mitigate the stress caused between component materials, preventing delamination. Therefore, the temperature of the thermal cycle test (TCT), which is conventionally carried out between -40℃ and 125℃can be increased up to 175℃. Furthermore, the power cycle test (PCT) indicated that the power cycle lifetime is nearly doubled*.

HIMAL Application Power Cycle Lifetime* SAT Observation Results
12,000 times

Delamination between compound
and Ni-plated board

22,000 times

No delamination between compound
and Ni-plated board (adhered condition)

Power Cycle Lifetime Improvement Results

Experiment conditions: Operating temperature:180℃, Subjects of comparison:①Ni-plated board + compound,  ②Ni-plated board + HIMAL + compound
* Our study Set as 10% increase of the power cycle lifetime j,max

10 times or more insulation performance of compounds reduces leak current

HIMAL provides about 10 times insulation performance (>230V/μm)of general compounds. Leak current can be reduced by applying it to areas in packages where leak current is likely to occur.

Dielectric breakdown voltage of general compounds
15-20 V/μm
Dielectric breakdown voltage of HIMAL
>230 V/μm
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