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Bonded fins technique is a conventional high power large heat sink manufacturing technique. Bonded fin heat sink may have the bad phenomenon of loose heat sink fins, especially with thick heat sink fins, which will loose or even fall off at a higher rate. LORI Thermal launched several bonding techniques via our own technical innovations and these include highly conductive thermal epoxy bonding, welding, thus, the reliability and stability of cooling are greatly improved and any potential risks are avoided. The features of bonded fin heat sinks include more fins per inch, smaller fin gap, and flexible profile height and width so that they are suitable for different sizes of application space. This kind of heat sink is small in size and light in weight, so it is an ideal choice for cooling high power equipment. Lori bonded fin heat sink wildly applied to IGBT Devices ,Welding Devices, Motor Devices, High Power Semi, Lasers System, Renewable Energy, Factory Automation, Thermoelectric Modules - TECs, Un-interruptible Power Supplies, AC Welding Switches, Power Rectification Equipment, Power Rectification Equipment, Traction Control Motor Drives.· 

In the high power applications where significant heat is generated in a small volume, Lori’s bonded fin heat sink designs can meet the packaging needs by increasing the heatsink surface area without increasing volume, reducing thermal resistance by 50% to 66%. Bonding fin heat sink removes the design limiting fin extrusion ratio found in extruded heat sink. Typical extrusion heat sink fin ratios range from 4:1 up to a maximum 16:1; while bonded fin heat sink designs allow ratios up to 44:1 or greater, providing cooling in forced convection for some high power applications. Bonded fins, fabricated from aluminum sheet through extrusion, are bonded to the  machined and grooved base with a highly conductive thermal resin.


Bonded fin heat sink features as the following:

1. Higher aspect ratio and high fin density of fins increase cooling surface area so the heat sink with high performance.

2. Lower thermal resistance for the high power device heat dissipation.

3. Aluminum fin, copper base, aluminum base can be assembled into bonded fin assemblies.

4. Fins fabricated from sheet metal or extrusion, custom designs available, the metal plate is made of fins, which can be cut to a specific size.

5. We can customize your wings according to thermal performance requirements and packaging size height restrictions. For more complex designs, we can extrude fins to specific shapes and lengths.

6. Used for high power forced convection cooling applications.

7. Bonding resin with highly thermal conductive for minimal thermal loss.

8. Dissipate more heat than the conventional heat sinks with the same footprint.

9. Reduce heat sink and overall system volume

10. Increase the aluminum cooling surface area by two to three times than traditional heat sink








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Bonded Fin heat sink Information

Bonded Fin heat sink is the technology of choice when complete design flexibility with a cost effective, high performance solution is required. The Individual fins and grooved bases are joined together by epoxying, brazing or soldering. Brazing offers greater structural integrity and the high mechanical and thermal performance. Lori employs a variety of brazing techniques including CAB, vacuum, and dip brazing. Any bonded fin heat sinks assembly that contains copper components must be soldered or brazed. 

Fins and the base can be of either aluminum or copper material, and the fins can be of any functional height, width and length, which greatly improve thermal performance due to the increased surface area. Various materials or height can be combined in one bonded solution if necessary.

The bonded fin types can be manufactured in a number of methods. Bonded Fins are either stamped from coil stock or cut from thin plate stock. Grooved bases can be extruded, die cast, or cnc machined.

General Characteristics

Bonded fin Heat sinks are produced by using an aluminium base section into separate fins are assembled. The joint between the heat sink base section and the bonded fin is made by using a special, high density epoxy resin to guarantee optimal heat flow from the heat sink base plate to the heat sink fins, or by razing or soldering. All heat sink types are available in any desired length and fin height.

Bonded fin heat sink general characteristics as the following:

1. Lower Tooling Costs in bonded fin heat sink manufacturing

  1. 2. No limit on length of airflow, available in any desired length and fin heigh
  2. 3. Higher aspect ratio and high fin density of fin improved Thermal Performance
  3. 4. Wide range of material and fabrication Option, Various materials can be combined 

Application

Bonded Fin Heat Sink for efficient air cooling of IGBTs and resitors. Lori offers high performance customized solutions for all IGBT and resistor types available on the market. Today's high power semiconductor must be efficiently cooled to take advantage of their high current capabilities. Conventionally air cooled extruded aluminum heat sinks have been an accepted cooling method used since the beginning of the semiconductor age. At present, with the continuous improvement of power density, the requirement of thermal performance for effective heat dissipation exceeds the limit of traditional extruded heat sinks. To meet the increased performance demand Lori has designed a new generation of power heat sinks - high power bonded fin heat sink.

These heat sinks are produced by using an extruded aluminium grooved base bonded into which Individual fins are assembled. The joint between the extruded grooved base and the fin is made by using a special, high density epoxy developed by lori together with a well-known producer of epoxy resin to guarantee optimal heat flow from the grooved base to the fins. The  the material is extremely high thermal conductivity in comparison to other epoxy-materials, and so enables the bonded fin heat sink to achieve a high thermal performance which exceeds all other assembly techniques.

In addition, Lori bonded fin heat sinks are also widely applied in many fields, like The Thermoelectric module, Uninterruptable power supply (UPS), Variable speed motor control, AC welding switch, Power rectifier, Laser power supply, Traction drives.

Custom Designs

Lori is always developing new bonded fin heat sink to meet our customer's requirements. If a custom solution is required, we will support your thermal modeling and assist you to design a new heat sink that meets your mechanical and thermal requirements. Lori offers a variety of bonded fin heat sink assemblies. Bonded fins can be made in a different way to meet your needs. You can choose from either natural or forced convection.

Lori Options for Custom Solutions

  • Material: Aluminum or Copper base and Aluminum and copper fins
  • Brazed, soldered ,High thermal conductivity epoxy to attach fins to base
  • Fin heights: .020 to 2.75 inches
  • Fin widths: up to 24.0 inches
  • Fin Densities:100+ fins per inch
  • Fin material thickness: .008 to .032 (fin height and densities depend on thickness)
  • Epoxy bonded fin heat sink FAQS

1.  Can bonded fin heat sinks be black anodized?

Yes, it is possible to black anodize bonded fin heat sinks, but the black finish would not contribute significantly to heat removal in forced convection also it would increase costs substantially. Economical gold chromate is available as a finish to help protect against corrosion.

2. Will the bonded fins fall out?

Proper materials, surface preparation, strict process control, and exceptional quality standards ensure error-free products. Lori solutions has refined the bonded fin-to-base attachment process to the point that failures do not occur. Thousands of defect-free parts per year attest to the success of this process.

 

3. Does the epoxy joint limit heat flow into the bonded fin?

The joint design is combined with the conductivity of the epoxy resin to control the overall temperature rise at an unmeasurable level. (Average >1.0 °C rise at 25 watt heat per fin)

 

4. Why not dip-braze the assembly instead of using epoxy bond?

Cost — fixturing and processing a dip-brazed heat sink would add substantially to cost while adding very little to heat sink performance.

5.Do the tops of the long thin fins really increase the bonded fin heat sink's heat dissipation ability?

Yes, in many cases, the overall fin efficiency for bonded fin heat sink is between 60% and 75%. While fin efficiency of conventional extrusions may be high as 85%, bonded fin heat sink increased two to three times surface area than compensates for lower fin efficiency.

6. How closely can the bonded fins be spaced?

This depends on the width of the heat sink base. Typically, on bases up to 8.0" wide, 0.032" thick bonded fins can be spaced 0.125" on center. For heat sink bases between 8.0" and 16.0", 0.050" thick fins can be spaced 0.20" center to center. Base widths above 16.0" must be examined on an individual basis.

 

7. Can the heat sink be made of copper for increased conductivity?

Yes, Lori solutions has successfully epoxy bonded copper fin into aluminum bases – both extruded and machined. In some applications copper fins are assembled in combination with aluminum fins to save cost and increase thermal performance. For certain applications requiring very high thermal performance - both the fins and base must be made of Copper. For these applications, the heat sink will be brazed or soldered, not epoxy bonded. The cost of a copper bonded heat sink is typically three times that of the comparable bonded fin heat sink in aluminum.

8. What materials are typically used for bonded fin heat sink?

At Lori solutions – the bonded fin heat sink base material is typically made from extruded 6063-T5 aluminum alloy and the fins made of roll stock aluminum alloy 1100- H14. This aluminum fin material is 15% more conductive than the fin material of conventional extruded aluminum heat sinks, increasing the fin efficiency – off setting any minor conductivity loss from the epoxy joint – resulting in overall thermal performance of the bonded fin heat sink being essentially equal to an extruded heat sink of similar fin geometry.

9. The Bonded Fin Advantage

Bonded fin heat sink offers thermal design engineers many benefits over conventional extruded aluminum heat sink. The increased fin count of bonded fin heat sink is the result of a tightly controlled assembly techniques, allowing fin manufacture as a process independent from heat sink base .

The bonded fin process removes the conventional fin extrusion ratio limitation dictated by the strength of the steel in extrusion dies. Extrusion Ratios greater that 6:1 (fin height above the base as compared to the narrowest open space between fins) are common place, but ratios of 8:1 and 10:1 can only be done on a limited basis and have been found to be very application specific.

Bonded fin heat sinks offer fin ratios as high as is practical. Increasing the fins'number increases the surface area exposed to cooling air, and greater exposed surface area means more heat transferred away from the electronics device. In most typical air cooled applications - heat sinks are convection limited, and the overall thermal performance of an air cooled heat sink can often be improved significantly if more surface area can be exposed to the air stream. Lori solution’s high performance bonded fin heat sink utilize thermally conductive metal-filled epoxy to bond planar fins onto a grooved extrusion or machined base plate. This bonded fin process allows for a much greater fin height-to-gap aspect ratio of 20 to 40, greatly increasing the cooling abillity without increasing volume requirements.

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