JP2002324880A - Heat sink - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a heat sink where heat dissipation capacity and thermal fatigue characteristics are good and the bonding strength of solder bonding is high and a plating cost is low. SOLUTION: An aluminum fin 1 processed into the shape of an accordion and a copper plate 2 are solder bonded to each other and copper plating of 1.0-20 μm in thickness or plating containing nickel of 0.5-20 μm in thickness is applied to the solder bonded surface of the aluminum fin 1. Alternatively, the aluminum fin and an aluminum plate are solder bonded to each other and copper plating of 1.0-20 μm in thickness or plating containing nickel of 0.5-20 μm in thickness is applied to the solder bonded surfaces of the aluminum fin and the aluminum plate.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat sink capable of dissipating heat generated from a heating element such as a CPU of a personal computer, and more particularly to a heat sink having excellent heat dissipation ability and thermal fatigue characteristics.

[0002]

2. Description of the Related Art Conventionally, a heat sink for a personal computer has been manufactured by an extrusion method, a die casting method, a casting method, or the like. Recent Personal Computer CP
As the processing speed of U increases, the amount of heat generated from the CPU is increasing, and a heat sink for CPU is required to have higher heat radiation ability. In order to meet such demands, development of heat sinks in which accordion-shaped aluminum fins capable of providing a large number of fins per unit area are joined to a copper plate or an aluminum plate has been promoted. An epoxy adhesive or solder is used for joining the aluminum fin and the copper plate or the aluminum plate. However, since the epoxy adhesive has a low thermal conductivity, the heat sink using the epoxy adhesive for bonding has a poor heat dissipation capability.

On the other hand, in a heat sink using solder for bonding, it is generally difficult to directly solder to aluminum because a dense and thin oxide layer is formed on the surface of aluminum. Therefore, soldering is performed after copper plating or nickel plating is performed on aluminum. However, in the conventional plated junction heat sink, the appropriate plating thickness is unknown, and the plating cost is high, so that the plating thickness has been reduced as much as possible.

[0004]

However, since the plating thickness was too thin, there were some portions where the plating was partially missing, resulting in poor soldering. In addition, plating may be dissolved by the flux used at the time of solder joining, the aluminum base may be exposed, and poor soldering may occur. As described above, the heat sink in which the soldering failure has occurred sometimes has reduced heat dissipation capability and thermal fatigue characteristics. Therefore, the product of the heat sink did not have stable performance. Also,
The joining strength of the solder joint was also low. The present invention has been made in view of the above-described problems, and has an object to improve the solderability of an aluminum fin and an aluminum plate processed into an accordion shape, and to provide a copper-plated or nickel-plated heat sink, An object of the present invention is to provide a heat sink having excellent performance and thermal fatigue characteristics, high bonding strength of solder bonding, and low plating cost.

[0005]

According to the heat sink of the present invention, an aluminum fin processed into an accordion shape and a copper plate are soldered to each other, and a surface of the aluminum fin to be soldered is formed of copper having a thickness of 1.0 μm to 20 μm. It is plated. Further, in the heat sink of the present invention, an aluminum fin processed into an accordion shape and a copper plate are solder-joined, and a nickel-containing plating having a thickness of 0.5 μm to 20 μm is applied to a surface of the aluminum fin to be solder-joined. Things. The nickel-containing plating is nickel plating applied by electrolysis or electroless, and is preferably nickel-phosphorus plating having a phosphorus concentration of 10% by weight or less.

Further, the heat sink of the present invention is characterized in that an aluminum fin processed in an accordion shape and an aluminum plate are soldered, and a thickness of 1.0 μm to 20 μm is formed on a surface of the aluminum fin and the aluminum plate which is soldered. Is plated with copper. Further, the heat sink of the present invention has an aluminum fin processed into an accordion shape and an aluminum plate soldered to each other.
The plating is nickel-containing plating of m to 20 μm. The nickel-containing plating is nickel plating performed by electrolysis or electroless, and has a phosphorus concentration of 1%.
Nickel-phosphorus plating is preferably 0% by weight or less.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of a heat sink according to the present invention will be described with reference to FIG. This heat sink has an aluminum fin 1 processed into an accordion shape, a copper plate 2, and a solder 3 for joining the aluminum fin 1 and the copper plate 2. Here, the accordion shape is formed by alternately inverting aluminum plates, and has a gap between the aluminum plates. Aluminum fin 1 in the present embodiment
Is an aluminum plate having a length of 75 mm, a width of 58 mm, a height of 30 mm and a thickness of 0.41 mm. The aluminum plate has 16 inverted parts. The copper plate 2 has a length of 89 mm, a width of 63 mm, and a thickness of 6 mm. The surface of the aluminum fin 1 to be solder-joined to the copper plate 2 by the solder 3 has a thickness of 1.0 μm to 2 μm.
0 μm copper plating is applied. If the thickness of the copper plating is less than 1.0 μm, poor soldering may occur. On the other hand, when the thickness exceeds 20 μm, the plating cost increases.

In the heat sink according to the first embodiment, the aluminum fin 1 processed in accordion shape has a thickness of 1.0 μm to 20 μm
Since the copper plating is performed, the solder wettability of the surface to be soldered is good and the solderability is good.
Therefore, the heat dissipation capability and thermal fatigue characteristics of the heat sink can be increased. Also, the joining strength of the solder joint can be increased. Further, since the copper plating thickness is within the above range, the plating thickness can be easily controlled, and
Plating cost can be reduced.

Next, a second embodiment of the heat sink of the present invention will be described. The heat sink of the present embodiment is
In the heat sink according to the first embodiment described above, the surface of the aluminum fin 1 to be solder-bonded has a thickness of 0.5 μm.
The nickel-containing plating of m to 20 μm is applied. If the thickness of the nickel-containing plating is less than 0.5 μm, poor soldering may occur. In addition, 20μ
If it exceeds m, the plating time will be long. Further, the nickel-containing plating is nickel plating performed by electrolysis or electroless, and is preferably nickel-phosphorus plating having a phosphorus concentration of 10% by weight or less.

In the heat sink according to the second embodiment, since the nickel-containing plating having a thickness of 0.5 μm to 20 μm is applied to the surface of the accordion-shaped aluminum fin to be soldered, the soldering is performed. The surface to be soldered has good solder wettability and good solderability. Therefore, the heat dissipation capability and thermal fatigue characteristics of the heat sink can be increased. Also, the joining strength of the solder joint can be increased. When the nickel-containing plating thickness is in the above range, the plating thickness can be easily controlled and the plating cost can be reduced. The nickel-containing plating is nickel plating applied by electrolysis or electroless, and has a phosphorus concentration of 1%.
By using nickel-phosphorus plating of 0% by weight or less, the bonding strength of the solder bonding surface can be increased.

Next, a heat sink according to a third embodiment of the present invention will be described. The heat sink of the present embodiment is
In the heat sink of the first embodiment described above, an aluminum plate is used in place of the copper plate 2, and a copper plate having a thickness of 1.0 μm to 20 μm is applied to a surface of the aluminum fin and the aluminum plate to be soldered. . If the thickness of the copper plating is less than 1.0 μm, poor soldering may occur. Also, if it exceeds 20 μm,
Plating cost increases.

In the heat sink of the third embodiment, since the surfaces of the aluminum fins and the aluminum plate processed into the accordion and to which the aluminum plate is soldered are plated with copper having a thickness of 1.0 μm to 20 μm,
Good solder wettability on the surface to be soldered, and good solderability. Therefore, the heat dissipation capability and thermal fatigue characteristics of the heat sink can be increased. Also,
The joining strength of the solder joint can be increased. Also,
When the copper plating thickness is within the above range, the plating thickness can be easily controlled and the plating cost can be reduced.

Next, a heat sink according to a fourth embodiment of the present invention will be described. The heat sink of the present embodiment is
In the heat sink of the first embodiment described above, an aluminum plate is used in place of the copper plate 2, and a thickness of 0.5
The plating is performed with a nickel-containing plating of μm to 20 μm. If the thickness of the nickel-containing plating is less than 0.5 μm, poor soldering may occur. Also, 20
If it exceeds μm, the plating time will be long. Further, the nickel-containing plating is nickel plating applied by electrolysis or electroless, and is preferably nickel-phosphorus plating having a phosphorus concentration of 10% by weight or less.

In the heat sink according to the fourth embodiment, the nickel-containing plating having a thickness of 0.5 μm to 20 μm is applied to the surfaces of the aluminum fin and the aluminum plate which are processed into an accordion shape and which are to be soldered. The solder wettability of the surface to be soldered is good, and the solderability is good. Therefore, the heat dissipation capability and thermal fatigue characteristics of the heat sink can be increased. Also, the joining strength of the solder joint can be increased. When the nickel-containing plating thickness is in the above range, the plating thickness can be easily controlled and the plating cost can be reduced. Further, the nickel-containing plating is nickel plating applied by electrolysis or electroless, and the nickel-phosphorus plating having a phosphorus concentration of 10% by weight or less can increase the bonding strength of the solder bonding surface. it can.

[0015]

(Example 1) Accordion-shaped aluminum fins were formed on aluminum fins with a thickness of 0.5 μm, 0.8 μm,
1.0 μm, 3.0 μm, 5.0 μm, 10.0 μm,
Copper plating of 20.0 μm and 30.0 μm was performed, and this was solder-bonded to a copper plate, thereby manufacturing 20 heat sinks each having the same thickness as that shown in FIG. Solder joining was performed using a flux in a reflow furnace in a nitrogen atmosphere.
A heat cycle test was performed on these heat sinks. Heat cycle conditions are -65 ° C to 125 ° C,
One cycle was 1 hour, and was 100 cycles. Then, before and after the heat cycle test, the heat dissipation capability of the heat sink and the bonding strength between the heat sink and the copper plate were measured.

The bonding strength was determined as in the example shown in FIG. That is, the heat sink is cut to a width of 25 mm, an elongated plate-shaped hook 22 is passed through the inverted portion 21 of the aluminum fin of the heat sink, and both ends of the hook 22 are held and raised, and the copper plate 23 is held and lowered. And its tensile strength was measured. This tensile strength was defined as the joining strength. The heat dissipation ability was evaluated by measuring the heat resistance value. As the thermal resistance value, an example of a thermal resistance value measuring device shown in FIG. 3 was used. This thermal resistance measuring device measures the temperature of the interface between the wind tunnel 31, a fan 32 for generating wind, a heating element 33, a thermocouple 34 for measuring the temperature of wind entering the wind tunnel, and a heat sink for measuring the heating element. And a thermocouple 35 to be measured. A heat sink is set in this thermal resistance measuring apparatus, and the wind temperature T1 entering the wind tunnel and the interface temperature T2 between the heat generating element and the heat sink are determined under the conditions of a wind speed of 2.5 m / s and a heating value of the heating element of 75 W. It was measured. The thermal resistance value was calculated from the following equation (1). Thermal resistance value (° C./W)=(T2−T1)/Wattage of heating element (1) The thermal fatigue characteristics were evaluated by the thermal resistance values before and after the heat cycle. Table 1 shows the bonding strength and the thermal resistance measured in this manner.

[0017]

[Table 1]

A heat sink having a copper plating thickness of 0.8 μm or less had a higher thermal resistance value and lower bonding strength than a heat sink having a copper plating thickness of 1.0 μm or more. In particular, after the heat cycle test, the thermal resistance was large and the bonding strength was small. Observation of the cross section of the solder joint surface of the heat sink with such a large thermal resistance value and low joint strength revealed that copper plating had disappeared when the copper plating thickness was 0.8 μm or less, resulting in poor solder wetting. Many were seen. From these results, when the copper plating thickness was from 1.0 μm to 30 μm, good heat dissipation and thermal fatigue characteristics were obtained. However,
As the thickness of the copper plating increases, the cost of the copper plating increases. Therefore, a heat sink having a copper plating thickness of 30 μm or more is not practical. Therefore, the plating thickness of the copper plating is set to 1.
A heat sink provided with a thickness of 0 μm to 20 μm can increase the heat dissipation capability and improve the thermal fatigue characteristics. Also, the joining strength of the solder joint can be increased. Further, the plating thickness can be easily controlled, and the plating cost can be reduced.

Example 2 An aluminum fin and an aluminum plate processed into an accordion shape have a thickness of 0.1 mm.
5 μm, 0.8 μm, 1.0 μm, 3.0 μm, 5.0
μm, 10.0 μm, 20.0 μm, 30.0 μm copper plating, aluminum fins and aluminum plate and copper plate are soldered together, and 20 heat sinks similar to those shown in FIG. did. Solder joining was performed using a flux in a reflow furnace in a nitrogen atmosphere. The bonding strength and thermal resistance of these heat sinks were measured in the same manner as in Example 1. Table 2 shows the results.

[0020]

[Table 2]

A heat sink having a copper plating thickness of 0.8 μm or less had a higher thermal resistance value and lower bonding strength than a heat sink having a copper plating thickness of 1.0 μm or more.
In particular, after the heat cycle test, the thermal resistance was large and the bonding strength was small. From these results, when the copper plating thickness was from 1.0 μm to 30 μm, good heat dissipation and thermal fatigue characteristics were obtained. However, as the thickness of the copper plating increases, the cost of the copper plating increases. Therefore, a heat sink having a copper plating thickness of 30 μm or more is not practical. Therefore, a heat sink provided with a copper plating thickness of 1.0 μm to 20 μm can have a high heat dissipation capability and good thermal fatigue characteristics. Also, the joining strength of the solder joint can be increased. Further, the plating thickness can be easily controlled, and the plating cost can be reduced.

(Example 3) Aluminum fins processed into accordion shape were provided with
m, 1.0 μm, 3.0 μm, 5.0 μm, 10.0 μm
1, 20.0 μm, and 30.0 μm electrolytic plating was performed, and aluminum fins and an aluminum plate and a copper plate were solder-joined to produce 20 heat sinks each having the same thickness as that shown in FIG. Solder joining was performed using a flux in a reflow furnace in a nitrogen atmosphere. The bonding strength and thermal resistance of these heat sinks were measured in the same manner as in Example 1. Table 3 shows the results. In addition, nickel-free phosphorous concentration of 3% by weight
Heat sinks are also made by applying phosphorus plating, electroless nickel-phosphorus plating with a phosphorus concentration of 8% by weight, electroless nickel-phosphorus plating with a phosphorus concentration of 10% by weight, and electroless nickel-phosphorus plating with a phosphorus concentration of 15% by weight. And
The bonding strength and the thermal resistance were measured in the same manner as in Example 1.
Table 3 also shows these results.

[0023]

[Table 3]

In the heat sink plated with nickel by electrolysis, no difference was observed in the bonding strength and the thermal resistance value in the measured nickel plating thickness. The solder wettability of the solder joint surfaces of these heat sinks was good. However, in practice, it is important that plating is performed reliably, and if the plating thickness is too large, the plating cost increases. Therefore, the heat sink provided with the nickel-containing plating having a plating thickness of 0.5 μm to 20 μm can increase the heat dissipation capability,
Further, the thermal fatigue characteristics can be improved. Also, the joining strength of the solder joint can be increased. Further, the plating thickness can be easily controlled, and the plating cost can be reduced.

Further, the phosphorus concentration by electroless is 15% by weight.
The nickel-phosphorus-plated heat sink is made of electrolytic nickel plating, electroless nickel-phosphorus-plated heat sink of 3% by weight, electroless nickel-phosphorus plating of 8% by weight. The heat resistance value was higher and the bonding strength was lower than that of the heat sink that had been applied, and the heat sink that had been subjected to nickel-phosphorus plating in which the phosphorus concentration by electroless was 10% by weight. In particular, after the heat cycle test, the thermal resistance was large and the bonding strength was small. Observation of the cross section of the solder joint surface of these heat sinks revealed that the higher the phosphorus concentration of the nickel-phosphorus plating, the more the solder wetting failure occurred. Therefore, when the phosphorus concentration of the nickel-phosphorus plating is 10% by weight or less, the heat dissipation capability, the thermal fatigue characteristic, and the bonding strength of the solder bonding of the heat sink can be improved.

Example 4 Aluminum fins and aluminum plates processed into an accordion shape were provided with thicknesses of 0.5 μm, 0.8 μm, 1.0 μm, 3.0 μm,
5.0 μm, 10.0 μm, 20.0 μm, 30.0 μ
m, nickel plating was performed by electrolysis, and aluminum fins and an aluminum plate and a copper plate were joined by soldering, thereby manufacturing 20 heat sinks each having the same thickness as that shown in FIG. Solder joining was performed using a flux in a reflow furnace in a nitrogen atmosphere. The bonding strength and thermal resistance of these heat sinks were measured in the same manner as in Example 1.
Table 4 shows the results. In addition, phosphorus concentration by electroless 3
Weight percent nickel-phosphorus plating, electroless nickel-phosphorus plating with a phosphorus concentration of 8% by weight, electroless nickel-phosphorus plating with a phosphorus concentration of 10% by weight, and electroless nickel-phosphorus plating with a phosphorus concentration of 15% by weight A heat sink was also manufactured, and the bonding strength and the thermal resistance value were determined in Example 1.
It measured similarly to. Table 4 also shows these results.

[0027]

[Table 4]

In the heat sink plated with nickel by electrolysis, no difference was observed in the bonding strength and the thermal resistance value in the nickel plating thickness in the measured range. The solder wettability of the solder joint surfaces of these heat sinks was good. However, in practice, it is important that plating is performed reliably, and if the plating thickness is too large, the plating cost increases. Therefore, the heat sink provided with the nickel-containing plating having a plating thickness of 0.5 μm to 20 μm can increase the heat dissipation capability,
Further, the thermal fatigue characteristics can be improved. Also, the joining strength of the solder joint can be increased. Further, the plating thickness can be easily controlled, and the plating cost can be reduced. Further, the heat sink plated with nickel-phosphorus having a phosphorus concentration of 15% by weight by electroless treatment had a large thermal resistance value and a low bonding strength. Therefore, the phosphorus concentration of the nickel-phosphorus plating is 1 unit.
When the content is 0% by weight or less, the heat dissipation capability of the heat sink, the thermal fatigue characteristics, and the joining strength of the solder joint can be improved.

[0029]

According to the heat sink of the present invention, an aluminum fin processed into an accordion shape and a copper plate are soldered, and a surface of the aluminum fin to be soldered is copper-plated with a thickness of 1.0 μm to 20 μm. Is what it is. Therefore, the heat dissipation capability and the thermal fatigue characteristics can be improved, and the joining strength of the solder joining can be increased. Further, the plating thickness can be easily controlled, and the plating cost can be reduced.
Further, in the heat sink of the present invention, an aluminum fin processed into an accordion shape and a copper plate are solder-joined, and a nickel-containing plating having a thickness of 0.5 μm to 20 μm is applied to a surface of the aluminum fin to be solder-joined. Things. Therefore, the heat dissipation capability and the thermal fatigue characteristics can be improved, and the joining strength of the solder joint can be increased. Further, the plating thickness can be easily controlled, and the plating cost can be reduced.
The nickel-containing plating is nickel plating applied by electrolysis or electroless, and has a phosphorus concentration of 10% by weight.
By using the following nickel-phosphorus plating, the heat dissipation ability and the thermal fatigue property can be improved, and the joining strength of the solder joint can be increased.

Further, the heat sink of the present invention is characterized in that an aluminum fin processed into an accordion shape and an aluminum plate are soldered, and a thickness of 1.0 μm to 20 μm is formed on the surface of the aluminum fin and the aluminum plate which is to be soldered. Is plated with copper. Therefore, the heat dissipation capability and the thermal fatigue characteristics can be improved, and the joining strength of the solder joint can be increased. Further, the plating thickness can be easily controlled, and the plating cost can be reduced. Further, the heat sink of the present invention has an aluminum fin processed in an accordion shape and an aluminum plate soldered, and a surface of the aluminum fin and the aluminum plate to be soldered is nickel-containing having a thickness of 0.5 μm to 20 μm. It is plated. Therefore, the heat dissipation capability and the thermal fatigue characteristics can be improved, and the joining strength of the solder joint can be increased. Further, the plating thickness can be easily controlled, and the plating cost can be reduced. The nickel plating is
Nickel plating applied by electrolysis or electroless, and nickel-phosphorus-containing plating having a phosphorus concentration of 10% by weight or less can improve heat dissipation capability and thermal fatigue characteristics, and can be used to join solder joints. Strength can be increased.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a first embodiment of a heat sink according to the present invention.

FIG. 2 is a perspective view showing a method of measuring thermal resistance in an embodiment of the heat sink of the present invention.

FIG. 3 is a perspective view showing a method for measuring bonding strength in an embodiment of the heat sink of the present invention.

[Explanation of symbols]

1 ... aluminum fin, 2 ... copper plate, 3 ...
Solder

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 5E322 AA01 AB11 FA04 5F036 AA01 BA04 BA24 BB05 BB33 BD03

Claims (6)

[Claims] An aluminum fin processed into an accordion shape and a copper plate are soldered, and a thickness of 1.0 μm to 20 μm is formed on a surface of the aluminum fin to be soldered.
A heat sink, wherein a copper plating is applied to the heat sink. 2. An aluminum fin processed into an accordion shape and a copper plate are soldered, and a thickness of 0.5 μm to 20 μm is formed on a surface of the aluminum fin to be soldered.
A heat sink, wherein a nickel-containing plating is applied. 3. The nickel-phosphorous plating according to claim 2, wherein the nickel plating content is nickel plating applied by electrolysis or electroless and has a phosphorus concentration of 10% by weight or less. heatsink. 4. An aluminum fin processed in an accordion shape and an aluminum plate are solder-joined, and a surface of the aluminum fin and the aluminum plate to be solder-joined is plated with copper having a thickness of 1.0 μm to 20 μm. A heat sink, comprising: 5. An aluminum fin processed into an accordion shape and an aluminum plate are soldered, and a nickel-containing plating having a thickness of 0.5 μm to 20 μm is applied to a surface of the aluminum fin and the aluminum plate to be soldered. A heat sink, which is characterized in that: 6. The nickel-containing plating is nickel plating applied by electrolysis or electroless,
6. The heat sink according to claim 5, wherein the heat sink is a nickel-phosphorus plating having a phosphorus concentration of 10% by weight or less.