Online Catalog

1. Read before you start

In order to properly select/design a heat sink,we need to clearly specify the operating conditions and calculate a thermal resistance target for the heat sink.

Please answer the following questions in as much detail as possible.

If you cannot answer a question, leave it blank, and we will fill in a typical value based on our experience.

After answering the questions, please push the "Request" button.We will review your responses and provide feedback ASAP.

Please fill in items 1 through 6, answering the questions as completely as possible.

If you are unsure about a question, leave it blank.

After completing all sections, press the "Request" button above to submit your information.

In order to select an appropriate heat sink, the process must be done in two steps.

Thermal Resistance

First, we need to calculate a thermal resistance target for the heat sink. This is a measure of the heat sink's performance under given conditions at a specified airflow.

Thermal Resistance = Max Temp. − Amb Temp. Power Consumption − Thermal Resistance Junction−Case.

ex.

2.1(°C/W) = 100(°C)−55(°C) 25(W) − 0.1(°C/W)

Ref:Selecting a Heat Sink

For general instructions on how to calculate a target thermal resistance, please click on the "1. Heat Source" section and access the "Help" section.

Design Factors

Once the thermal resistance target has been calculated, a heat sink can then be selected, based on the following 6 design factors below:

1. Heat Source
2. Heat Sink
3. Air Duct
4. Air Flow
5. Thermal Interface
6. Attachment

Click on each design factor and input as much information as possible. It is not necessary to input all of the requested information, if you are not sure. For any omitted information, we will use a typical value.

Heat sink performance depends on many factors, some of which may not covered in this section. We will provide the proposed solution based on our test data and experience. However, due to complex nature of the of the various factors, the final performance could not be guaranteed. Customers are responsible to verify performance in their actual operating environment.

2. Send when you are done

Please confirm your inputs and enter your contact information along with any additional relevant information. Once the request is sent, we will review and contact you by email.

Duct Size (H)
mm

Duct Size (W)
mm

Heat Sink (H)
mm

Ambient
°C

Heat Sink (W): mm
Heat Sink (L): mm

Max Case Temp: °C
Wattage: W

Air Flow:
Air Speed: m/s

Thermal Resistance: °C/W

Input Data

Heat Source :

Heat Sink :

Air Duct :

Air Flow :

Thermal Interface :

Attachment :

Contact Information

* The fields with an asterisk(*) are required.

Company Name *	Department/Division

Country *	Name *

Email *	Phone #

Additional Info

1. Heat Source

Input IC Chip (Heat Source) Specification

Target thermal performance

Power consumption(TDP) (W)

Maximum allowed case temperature (°C)

IC chip(heat source) size

A (mm)	B (mm)	C (mm)	D (mm)	E (mm)

Chip manufacturer and model number

Additional Info

Setting The Specifications For an IC/Chip in the Heat Sink Selection Process

In order to properly select/design a heat sink,we need to clearly specify the operating conditions and calculate a thermal resistance target for the heat sink.

Please answer the following questions in as much detail as possible.

If you cannot answer a question, leave it blank, and we will fill in a typical value based on our experience.

After answering the questions, please push the "Request" button.We will review your responses and provide feedback ASAP.

Please fill in items 1 through 6, answering the questions as completely as possible.

If you are unsure about a question, leave it blank.

After completing all sections, press the "Request" button above to submit your information.

Examples of published IC/Chip specifications:

Intel®G31/P31 Express Chipset Thermal and Mechanical Design Guidelines

The power dissipation and the maximum allowed case temperature are provided. The TDP(Thermal Design Power) is 15.5(W), and the Max. case temperature is 106 °C. The maximum allowed temperature increase is calculated by subtracting the Max. local ambient temperature from the Max. case or junction temperature The Max. local ambient temperature is the temperature of the air that will enter the heat sink cooling the the IC/chip. This value cannot be predetermined and will be your responsibility to specify. However, using 45-55 °C as the Max. local ambient is often used for electronics enclosures and telecommunications equipment, in our experience. If we assume 45 °C for the Max. local ambient temperature, then the maximum allowable temperature rise would be 106-45 = 61°C, in this example. The target thermal resistance can then be calculated by dividing the allowable temperature rise by the thermal design power of 15.5 Watts: (106-45)/15.5 = 3.94 °C/W

"Altera Device Packaging Specifications"

Here is an example of a package's mechanical specifications. D1 and E1 dimensions are critical in estimating the thermal performance of the heat sink and in the selection of the thermal interface material. D and E dimensions are critical in the mechanical design of the heat sink and the attachment hardware.

2. Heat Sink

Input Heat Sink Size Requirements

Maximum allowed heat sink size (if any)

W:Width(mm)	L:Length(mm)	H:Height(mm)

If you only know the height limitation, simply enter this number.

Target thermal resistance (for the heat sink) (°C/W)

Additional Information

Regarding a heat sink size

A larger heat sink will typically perform better, as the surface area of the heat sink will become greater. Also, by increasing the volume of the heat sink, the amount of bypass area around the heat sink will be reduced, forcing more airflow to go through the heat sink.

Bypass Air Flow (Large)

Bypass Air Flow (Small)

However, a larger heat sink may require a more complicated and expensive attachment method. Push pins or shoulder screws versus thermal tape or epoxy. (REF:Online Catalog - Heat Sink Attachment)

If mechanical attachment hardware like push pins or shoulder screws are used, holes in the PCB must be located outside of the chip’s footprint. This will require the use of a larger heat sink or a heat sink with attachment tabs.

3. Air Duct

Input Duct Size

Duct Size

Additional Duct Information

Has a formal duct been created to prevent air from bypassing around the heat sink? In the actual environment, if no duct has been created, other components like a daughter card, memory module, PCB components, the chassis, etc..., will act like a duct and help to channel the air. The estimated size of the duct created by these components is useful. If this detailed information is not available, just having height information for the chassis itself can be very useful.

W:Width(mm)	H:Height(mm)

Additional Info

Bypass Considerations

If there is a lot of space around the heat sink, a significant amount of the air will flow around the heat sink instead of going through it. We call this bypass air flow.

Having a duct that channels the air, forcing it into the heat sink, will significantly improve the thermal performance.

Bypass Air Flow (Large)

Bypass Air Flow (Small)

The thermal resistance test data in our catalog is based on fully ducted air flow conditions. Therefore, the performance curve in our catalog is measured under ideal conditions. (Ref:Technical information - Measurement & Calculations).

In the actual environment, if no duct has been created, other components like a daughter card, memory module, PCB components, the chassis, etc..., will act like a duct and help to channel the air.

Depending on the duct size, the heat sink performance will vary. Generally, the performance of a heat sink with a denser fin pattern and higher pressure drop will be more sensitive to the duct size and the amount of bypass airflow.

Typically, the adjacent board or chassis wall will act as a duct, minimizing the amount of bypass space over the top of the heat sink. If no information is entered for the duct size height, we will assume that the duct size is equal to the heat sink size plus 2mm.

4. Air Flow

Input Air Flow Conditions

Ambient Temperature (°C)

Target Thermal Performance

Natural convection

Heat sink position Heat sink position

Unknown

Fin up

Fin side/Vertical Fin Vertical

Fin side/Horizontal Fin Horizontal

Forced air flow condition

Air speed Air speed （m/s）

Additional Info

Aiflow Condition

The air flow condition can be classified as Natural Convection or Forced convection.

Natural convection is a condition where the air flow is only generated by a a temperature differential and NOT by external means like a fan or blower.

Forced Convection is a condition where air flow IS generated by an external source like a fan or blower.

Greater air speed will result in better thermal performance.

In the actual environment, the air speed generated by a fan or blower will depend on many factors, such as where the components are located relative to the heat sinks, and fin pattern density of the heat sinks that are used.

The air speed used for simulation is ithe inlet air speed, just in front of the heat sink.

Adhesive Tape : Spec
T412 Spec	T411 Spec	8810 Spec	8815 Spec	BP105 Spec

Gap Filler : Spec
PG80B-0.5 Spec	PG80B-1 Spec	PG80B-1.5 Spec	PG80B-2 Spec	SF10-1 Spec	T-FLEX640 Spec	T-PLI210 Spec	T-PLI220 Spec

Phase Change : Spec
TPCM5125 Spec	TPCM7125 Spec

Heat sink selection

Thermal Resistance

Design Factors