JPH073914B2 - Circuit board cooling body and circuit board cooling structure - Google Patents

Description

TECHNICAL FIELD The present invention relates to a cooling body and a cooling structure for preventing overheating of a circuit board in various OA equipments, FA equipments and the like.

“Prior Art” The demand for higher integration of elements in the above-mentioned OA equipment and FA equipment is increasing year by year, and the layout space of the circuit board inside the equipment tends to be reduced. At the same time, there is an increasing demand to increase the arrangement density of power elements that control a relatively large amount of power and generate a large amount of heat. Therefore, in order to keep the element temperature of each circuit board within an appropriate range, it is necessary to provide efficient cooling means.

Conventionally, as this type of cooling means, a heat sink such as a metal plate is integrally fixed to the back surface of the circuit board to enhance the heat dissipation of the circuit board, or the air inside the equipment is forcedly circulated by a cooling fan to cool the circuit board. Methods such as forced air cooling are adopted.

In a conventional device or the like, a large number of circuit boards are generally arranged at intervals of about 20 to 30 mm by using the above means.

[Problems to be solved by the invention] However, in the above cooling means, when the arrangement density of the circuit boards exceeds a certain level (for example, the arrangement interval is 20 mm or less), it is inevitable that the cooling effect sharply decreases, and the ambient temperature When the temperature rises, a malfunction may occur due to heating of the element, and there has been a problem that the device cannot be downsized and the density is increased.

Also, in the method of forced air cooling with a fan, the cooling capacity becomes uneven at the place where the wind hits and the place where the wind does not hit, and the heat generation and leakage magnetism of the fan itself affect the circuit board, and the environment deteriorates due to vibration and noise. I could not ignore the problem.

In view of this, the present inventors have proposed in Japanese Patent Application No. 63-104712 a structure in which a water-cooled thin plate type cooling body is arranged adjacent to each circuit board to forcibly cool the circuit board. As the cooling body, one in which a pair of metal plates are laminated and a hollow coolant passage is formed between them is used.

However, when the present inventors actually made a prototype of such a cooling body using a material such as pure copper, and conducted an experiment, they received the biasing force of the heat transfer spring interposed between the cooling body and the circuit board. The cooling body bends, the flatness is deteriorated, the gap between the circuit board and the circuit board cannot be properly maintained, and not only the cooling effect becomes uneven, but in some cases, the cooling body comes into contact with the circuit board and adversely affects it. There was a fear. Therefore, it is difficult to reduce the distance between the circuit boards to a certain extent or less.

Therefore, the present inventors made many prototypes of cooling bodies using various alloys, measured the characteristics of each, and examined the optimum material. The characteristics desired as the material of the cooling body are summarized as follows.

 High thermal conductivity Easy to mold and low cost Excellent corrosion resistance to cooling water High rigidity and flatness maintained.

When such an examination was conducted, the present inventors found that Cu-Fe
When a cooling body is formed by using a system alloy, all of the above-mentioned required characteristics are sufficiently satisfied, and new knowledge has been obtained that extremely excellent characteristics can be obtained as a cooling body for circuit boards.

"Means for Solving the Problem" The present invention has been made based on the above findings. First, the circuit board cooling body according to claim 1 is configured by laminating a pair of metal plates, and a hollow coolant between the metal plates. A passage is formed, and each of the metal plates has Fe: 0.05 to 3 wt% and P: 0.01.
It is characterized by being formed of a copper alloy having a composition of 0.15 wt% and the balance of Cu.

In addition, in the cooling body for a circuit board according to claim 2, one of the metal plates is formed of a copper alloy having a composition of Fe: 0.05 to 3 wt%, P: 0.01 to 0.15 wt%, and the balance of Cu. The other is characterized by being molded with pure copper.

The coolant passage may be formed by bulging one of the metal plates in a semicircular cross section.

Further, the thickness of the metal plate on the bulge side is 0.3 to 2.0 mm, the width of the cross section of the coolant passage is 6 to 15 mm, and the height of the cross section of the coolant passage is
0.5 ~ 3.0mm, while the thickness of the other metal plate is 0.3 ~
It is desirable that it is 5.0 mm.

On the other hand, the circuit board cooling structure of the present invention is characterized in that the above-mentioned circuit board cooling body is arranged in parallel between a plurality of circuit boards arranged in parallel at a distance from each other.

The circuit board cooling body may be connected to an adjacent circuit board via a heat transfer member.

Further, the distance between the circuit board and the cooling body may be 0.5 mm or less.

[Operation] In the circuit board cooling body of the present invention, the rigidity of the cooling body is remarkably higher than that of a general heat transfer material such as pure copper by limiting the material of the metal plate as described above. Therefore, it is possible to prevent the flatness of the cooling body from being deteriorated due to its own weight, the coolant pressure, the biasing force of the heat transfer member, and the like, and the distance between the adjacent circuit board and the cooling body is changed to make the cooling efficiency uneven. There is no problem that the cooling body comes into contact with the circuit board and adversely affects it.

Further, in the circuit board cooling structure of the present invention, since the cooling body is not deformed as described above, the circuit board arrangement interval can be reduced, the cooling effect of the cooling body can be improved, and the circuit board The device can be downsized by increasing the integration density.

[Embodiment] FIG. 1 shows an embodiment of a cooling structure for a circuit board according to the present invention. Reference numeral 1 denotes a circuit board arranged in parallel at a plurality of intervals inside a casing (not shown), Reference numeral 2 denotes a cooling body arranged in parallel between the circuit boards 1 with a space therebetween.

This cooling body 2 is, as shown in FIGS.
Metal plates 3A and 3B are joined together, one metal plate 3B is bulged in a continuous semicircular cross section, and a coolant passage 4 is formed therein. In the illustrated example, the coolant passage 4 is It is formed in a meandering shape having straight portions parallel to each other.

The planar shape of the coolant passage 4 should be determined in consideration of the heat distribution of the circuit board 1, the required cooling efficiency, and the type of coolant, and for example, the coolant passage may be provided around a large power element that generates a large amount of heat. It is preferable to increase the arrangement density of No. 4 and increase the cooling efficiency.

In order to form the coolant passage 4 as described above, a convex portion having the shape of the coolant passage 4 is press-formed on one metal plate 3B in advance, and then the other metal plate 3A is diffusion bonded or Brazing method and / or either metal plate
After printing a film of a pressure preventive agent such as carbon, ink or paint on 3A (3B) in the shape of the coolant passage 4, the other metal plate 3B (3A) is roll-bonded onto this, and this bonded plate is It is set in a mold (not shown) having a recess having the same shape as that of the coolant passage 4 to be formed, and expansion tube processing or the like in which pressurized air is blown from the end portion of the joint plate along the pressure-bonding preventive agent film is adopted.

Of the metal plates 3A, 3B, at least the metal plate 3A on the flat side
Is formed of a copper alloy having a composition of Fe: 0.05 to 3 wt%, P: 0.01 to 0.15 wt% and the balance of Cu. However, Zn, B, Mg, Al, S
One or more elements such as i, Pb, Mn, Co, Ni, Ag, Zr and Sn
Even when the content is 0.5 wt% or less, the performance of the cooling body 2 of the present invention is not adversely affected.

In the above composition, Fe is added to increase the strength of the metal plate and improve the spring property, and if its content is less than 0.05 wt%, a sufficient effect cannot be obtained. If it is less than 3 wt%, the thermal conductivity of the cooling body 2 is lowered.

P is used as a deoxidizing agent in the process of manufacturing the raw material, and if the content is less than 0.01 wt%, the effect cannot be obtained, and if it exceeds 0.15 wt%, the effect is saturated and the thermal conductivity is lowered.

It is also possible to form only one of the metal plates 3A from the above copper alloy, and in this case, it is desirable that the other metal plate 3B be formed from pure copper having good thermal conductivity and formability. Pure copper as used herein refers to a copper material having a Cu content of 99.9 wt% or more.
While the metal plate 3B made of pure copper can be easily processed into a swelling tube or the like, the metal plate 3A made of the Fe—Cu alloy improves the rigidity of the coolant 2 as a whole.

As shown in FIG. 3, the thickness T2 of the metal plate 3B on the bulging side is 0.3.
~ 2.0 mm, preferably 0.3-1.0 mm. If it is less than 0.3 mm, the rigidity is lowered and the flatness cannot be maintained. If it is larger than 2.0 mm, bulging becomes difficult. Thickness of the other metal plate 3A
T1 is 0.3 to 5.0 mm, preferably 0.5 to 2.0 mm. 0.3m
If it is less than m, the rigidity is lowered and the flatness cannot be maintained. Also
If it is larger than 5.0 mm, the bulging process becomes difficult.

When each plate thickness is set within the above range, the width W of the cross section of the coolant passage 4 is 6 to 15 mm and the height H of the cross section is 0.5 to
It is desirable to set it to 3.0 mm. If the width W of the cross section is less than 6 m, the height of the inflated tube becomes small, and if it is larger than 15 mm, the flatness of the metal plate 3A on the non-inflated side cannot be maintained.

According to the cooling body 2 having the above size, the arrangement interval between the circuit boards 1 is 20 to 30 mm in the conventional air cooling means, whereas according to the experiments by the present inventors, cooling water is circulated as the cooling material. It was found that the arrangement interval between the circuit board 1 and the cooling body 2 which can be effectively cooled when used is 0.5 mm or less. Therefore, the arrangement density of the circuit board 1 can be increased to about double.

It should be noted that only the openings at both ends of the cooling medium passage 4 of the cooling body 2 are swelled to have a circular cross section, and the connection pipes 6 made of copper or the like are inserted therein and brazed with silver brazing or the like. A tube 5 is connected to each of these connection pipes 6, and a chlorofluorocarbon gas, water, various liquids, etc. are circulated and supplied from a refrigerant supply mechanism (not shown) outside the device via these tubes 5.

The type, temperature, and flow rate of the coolant to be supplied are determined in consideration of keeping the circuit board 1 in the proper temperature range of the element and preventing condensation on the cooling body 2 and the tubes 5.

In order to prevent condensation, a condensation sensor is attached to the cooling body 2 and a flow rate control mechanism that reduces or stops the flow rate of the refrigerant when the condensation is detected is provided, or a temperature sensor is attached to the cooling body 2 to change the ambient temperature. However, a temperature control mechanism for keeping the temperature of the cooling body 2 constant may be provided.

According to the above configuration, since at least one of the metal plates constituting the cooling body 2 is made of the above composition, the spring property of the cooling body 2 as a whole does not deteriorate even after long-term use, and the rigidity is normal heat transfer such as pure copper. Since it is larger than the case where the material is used, the flatness of the cooling body 2 is less likely to deteriorate due to its own weight or the coolant pressure even after long-term use. Therefore, the distance between the circuit board 1 and the cooling body 2 changes, and the cooling efficiency becomes non-uniform.
The problem that the cooling body 2 comes into contact with the above and adversely affects is unlikely to occur, and the reliability can be improved.

Further, since the cooling body 2 is not deformed, the arrangement interval of the circuit boards 1 can be reduced, the cooling effect by the cooling body 2 can be improved, and the integration density of the circuit boards 1 can be increased to reduce the size of the device. Can be achieved.

Further, unlike a structure in which the inside of the device is cooled by a fan or the like, there is no fear of noise or magnetic influence, and by adjusting the arrangement of the cooling body 2 or the planar shape (density) of the coolant passage 4,
For example, increase the cooling efficiency near the element that generates a large amount of heat,
It is easy to take measures such as lowering the cooling efficiency in the part where the heat generation amount is small, and it is possible to reduce malfunctions due to local overheating and overcooling of the circuit board 1. It is easy to maintain a narrow fixed range, and the operational stability of the device can be greatly improved.

Although the coolant passage 4 is formed in a meandering shape in the above-described embodiment, a shape in which a plurality of flow passages 4B are formed in parallel as shown in FIG. 4 can also be implemented. In this case, since the passage distance and time of the coolant are shortened, there is an advantage that the temperature distribution of the cooling body 2 becomes more uniform.

Further, in order to improve the flowability of air, a large number of through holes may be formed in a portion other than the coolant passage 4 of the cooling body 2.
Further, a large number of small fins may be fixed to the cooling body 2 to promote heat exchange with air.

Next, FIG. 5 shows a different fixing structure of the cooling body 2. In this example, the heat sink 7 is fixed to the back surface of the circuit board 1, and the cooling body 2 is directly fixed to the heat sink 7. According to this example, the entire surface of the circuit board 1 can be directly and efficiently cooled through the heat sink 7 of the circuit board 1, and the circuit board 1 having a particularly large heat generation amount can be effectively cooled.

Further, in the embodiment shown in FIG. 6, in order to prevent interference between the element 8 fixed to each circuit board 1 and having a relatively large protrusion amount, and the coolant passage 4 of the cooling body 2, a portion facing the element 8 is provided. The cooling medium passage 4 is formed so as to project to the opposite surface side of the cooling body 2. Such a cooling body 2 can also be easily manufactured by the manufacturing method described above.

Next, in the embodiment shown in FIG. 7, instead of directly fixing the cooling body 2 to the circuit board 1, the heat transfer plate 10 is provided on the back surface of the cooling body 2.
And the element 9 on the circuit board 1 via this heat transfer plate 10.
Is characterized by being cooled.

The heat transfer 10 has a large number of U-shaped cuts 12 formed at equal intervals by punching or laser processing, and the tongues 11 inside these cuts 12 are bent and protruded to provide heat conduction. Molded with a material with good properties.
The tip 11A of each tongue piece 11 elastically comes into surface contact with the upper surface of each element 9.

In this example, each element 9 of the circuit board 1 can be effectively cooled, and in comparison with the configuration of FIG.
It has an advantage that it can be easily attached and detached.

Needless to say, the shape and arrangement of the tongue piece 11 may be appropriately changed according to the size and arrangement of the element 9.

Next, FIG. 9 is characterized in that a flexible heat transfer sheet 13 is detachably inserted between the cooling body 2 and the circuit board 1. Silicone resin or the like can be used as the heat transfer body 13.

Next, FIG. 10 shows an element having a particularly large heat generation on the circuit board 1.
A heat radiation plate 14 is fixed to 15 and the heat radiation plate 14 is brought into contact with the back surface of the cooling body 2. According to this example, it is possible to cool the element 15 that generates a particularly large amount of heat more intensively than the other elements 9.

Next, FIG. 11 shows an example in which a long cooling body 2 is arranged in a meandering manner so as to come into contact with the back surface of each circuit board 1.

In addition, FIG. 12 shows that a plurality of ventilation holes (not shown) are formed in the cooling body 2 and a blower fan 16 for circulating air in the casing 17 is provided to blow the air cooled through the cooling body 2 into a fan. 16 shows a configuration in which the circuit board 1 is fed by 16 and is passed through the gap between the circuit boards 1. In this case as well, the amount of air blown can be smaller than that in the conventional structure in which the fan is forcibly cooled, so that noise and magnetic influence of the fan can be reduced. Furthermore, the present invention is not limited to the above embodiments, and the configuration may be changed as appropriate according to the arrangement and shape of the circuit board.

[Examples] Next, the effects of the present invention will be demonstrated with reference to experimental examples.

(Experimental Example 1) Changes in Young's modulus and conductivity in pure copper and Cu-Fe based alloys having different Fe contents were examined.

Young's modulus is measured in the direction of tensile test of metallic materials (JIS Z 2241)
It was done by. The material of the sample is pure copper: copper purity 99.9 wt% or more Cu-Fe alloy: P: 0.03 wt% Fe: The balance of the Cu sample is JIS No. 5 and the relationship between stress and elongation is measured using an extensometer. After obtaining the figure, a parallel line was drawn on the initial straight line portion, and the Young's modulus (E) was obtained from the relationship between the stress and elasticity indicated by the intersecting points. The results are shown in Table 1. Since the electrical conductivity is proportional to the thermal conductivity of the material, it is given as an evaluation value of the thermal conductivity, and the relative value when pure copper is 100% is shown.

(Example 2) A change in the amount of bending due to a change in the thickness of pure copper and a Cu-Fe alloy was measured. The pure copper was the same as that used in Experimental Example 1, and the alloy used had a composition of Fe: 0.1 wt%, P: 0.03 wt% and the balance Cu.

The size of the measurement sample was JIS No. 5 piece, and the change in the amount of bending was measured by applying a load to the center part of the span of the support beam at both ends. In addition,
The span of the beam was 100 mm and the load was 100 gf. The results are shown in Table 2.

(Experimental example 3) In order to imitate the actual use condition, pure copper and Cu-Fe alloy plate materials (100 x 135 x 1.0 mm) are used, and both ends of the plate materials in the 135 mm direction are supported, A load of 400 gf was applied to the entire surface with a uniform pressure distribution, and the amount of bending at the center was measured.
The composition of the alloy is the same as in Experimental Example 2. The results are shown in Table 3.

"Effects of the Invention" As described above, in the circuit board cooling body according to the present invention, since at least one of the pair of metal plates constituting the cooling body is formed of Fe-Cu based alloy, ordinary heat transfer such as pure copper is performed. Compared to the case where the cooling body is formed of a material, the spring property and rigidity are remarkably high, and the flatness of the cooling body does not deteriorate even after long-term use.

Further, according to the circuit board cooling structure of the present invention, since the flatness of the circuit board cooling body is maintained high for a long period of time as described above, the distance between the circuit board and the cooling body is changed to cool the circuit board. Problems such as non-uniform efficiency and the adverse effect of the cooling body coming into contact with the circuit board are less likely to occur, and reliability can be improved.

Further, since the cooling body is not deformed, the arrangement interval of the circuit boards can be reduced, the cooling effect by the cooling body can be improved, and the density of the circuit boards can be increased to reduce the size of the device.

Furthermore, unlike the structure that cools the circuit board inside the device with a fan, there is no risk of magnetic influence on the element or noise generation, and the arrangement of the cooling body and the planar shape (density) of the coolant passages can be adjusted. As a result, it is possible to prevent local overheating and overcooling of the circuit board, easily maintain the element temperature in a narrower range, and significantly improve the operational stability of the device.

[Brief description of drawings]

1 to 3 show one embodiment of a circuit board cooling structure and a circuit board cooling body according to the present invention. FIG. 1 is a front view of the circuit board cooling structure, and FIG. 2 is a cooling body. FIG. 3 is a plan view showing the back surface, and FIG. 3 is an enlarged cross-sectional view of the coolant passage. Also, FIG. 4 is a plan view showing another embodiment of the circuit board cooling body of the present invention, FIG. 5 is a front view showing a second embodiment of the circuit board cooling structure according to the present invention, and FIG. A front view showing a third embodiment of the circuit board cooling structure, FIGS. 7 and 8 are front views and a plan view showing a third embodiment of the circuit board cooling structure, and FIGS. 9 to 12 are circuits. Fourth of substrate cooling structure
It is a front view which shows an Example thru | or 7th Example. 1 ... Circuit board, 2 ... Circuit board, 3A, 3B ... Metal plate,
4 ... Coolant passage, 5 ... Tube, 6 ... Connection pipe, 7 ... Heat sink, 8, 9, 15 ... Element, 10, 13, 14 ...
… Heat transfer member.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-63-45900 (JP, A) Actually open 59-6893 (JP, U) Actually open 51-140449 (JP, U) Actually open 2- 26289 (JP, U)

Claims (7)

[Claims] 1. A cooler for a circuit board, comprising a pair of metal plates bonded together, and a hollow coolant passage formed between the metal plates, wherein each of the metal plates is Fe: 0.05-3 wt%, P : 0.01 to 0.15
A cooling body for a circuit board, which is formed of a copper alloy having a composition of wt% and the balance of Cu. 2. A circuit board cooling body comprising a pair of metal plates bonded together and a coolant passage formed between the metal plates, wherein one of the metal plates is Fe: 0.05-3 wt%, P: 0.01. ~ 0.15wt
%, The balance being formed of a copper alloy having a composition of Cu, and the other of the metal plates is formed of pure copper. 3. The cooling body for a circuit board according to claim 1, wherein the coolant passage is formed by bulging one of the metal plates in a semicircular cross section. 4. The thickness of the metal plate on the bulging side is 0.3 to 2.0 mm,
The width of the cross section of the coolant passage is 6 to 15 mm, the height of the cross section of the coolant passage is 0.5 to 3.0 mm, and the thickness of the other metal plate is 0.3 to 5.0 mm. Claim 3
The cooling body for a circuit board described. 5. A circuit characterized in that the cooling body for a circuit board according to claim 1, 2, 3 or 4 is arranged in parallel between a plurality of circuit boards which are arranged in parallel with each other at intervals. Substrate cooling structure. 6. The circuit board cooling structure according to claim 5, wherein the circuit board cooling body is connected to an adjacent circuit board via a heat transfer member. 7. The circuit board cooling structure according to claim 5, wherein the distance between each of the circuit boards and the circuit board cooling body is 0.5 mm or less.