JPH0461259A - Cooling method and structure for semiconductor integrated circuit devices - Google Patents

Abstract

PURPOSE:To improve the cooling efficiency of a semiconductor integrated circuit device by blasting finely divided liquid or solid refrigerant over the surface of a semiconductor chip or a package where the semiconductor chip is hermetically sealed. CONSTITUTION:When an integrated circuit formed on a chip 5 starts its operation, the heat generated from the chip 5 is transmitted to a cap 6 or a package base 2 so that a whole chip carrier may be heated. Then, refrigerant fine particles are blasted to virtually the whole area of the rear side of the cap 6 of each chip carrier 1 from the tip of a nozzle 17 connected with a jacket 13 for refrigerant supply service. The refrigerant fine particles which have arrived at the rear side of the cap 6 are heated and boiled so that the heat may be robbed of the rear side of the cap 6 by heat of vaporization, thereby cooling the chip carriers.

Description

DETAILED DESCRIPTION OF THE INVENTION =Field of Industrial Application: The present invention relates to cooling technology for semiconductor integrated circuit devices.

2. Conventional technology] In recent years, the power consumption per semiconductor chip has increased significantly due to higher integration and higher speed, and
When mounting a chip on a substrate, how efficiently the heat generated from the chip during operation can be released to the outside is an important measure to ensure the operational reliability of the chip. In particular, when a chip is surface-mounted on a board (face-down bonding), the chip and the board are connected via small-diameter bump electrodes (solder bumps), so the heat from the chip is not efficiently transferred to the outside. , the chip may become overheated, which may result in malfunction of the circuit or shorten the life of the chip.

By the way, Nikkei BP (1987, July 13)
Nikkei Electronics JP167 to P176 describe a cooling method in which a chip (or a package in which the chip is sealed) is directly immersed in an inert liquid refrigerant. The above-mentioned immersion cooling method is a cooling method that uses heat transfer when the refrigerant rises on the surface of the chip (or package) by bringing the refrigerant into direct contact with the chip (or package). Compared to cooling methods (such as conduction cooling methods), it has the advantage of making the thermal resistance between the coolant and the chip much smaller.

[Problem to be solved by the invention]

However, in the immersion cooling method described above, when the amount of heat generated by the chip is relatively small, the chip (or package)
Cooling progresses efficiently by boiling (nucleate boiling) that is centered on scratches or irregularities on the surface of the chip, but as the amount of heat generated by the chip increases, the bubbles generated on the surface of the chip (or package) gradually As a result, a so-called film boiling state occurs in which the entire surface is covered with bubbles, which causes the surface to be insulated by a film of steam, resulting in a drastic reduction in cooling efficiency. As a countermeasure to this problem, the previous document '1 proposes to increase the temperature of the refrigerant below its boiling point (subcool 4
! 11) This prevents the occurrence of film boiling, but in this case, a heat exchanger is required to cool the refrigerant 4, which has the disadvantage of making the device complex.

The present invention has been made in view of the above problems, and its purpose is to provide a cooling technique that can improve the cooling efficiency of semiconductor integrated circuit devices.

The above and other objects and novel features of the present invention will become apparent from the written description and accompanying drawings.

Means for Solving the 3 Problems] Among the inventions disclosed in this application, a brief overview of typical inventions is as follows.

One invention of the present application is a method in which a liquid or solid refrigerant is atomized and sprayed onto the surface of a semiconductor chip or a package in which the semiconductor chip is hermetically sealed, and cooling is performed using the heat of vaporization.

Effect] According to the above-mentioned means, by atomizing the refrigerant and spraying it on the surface of the chip (or package), the refrigerant can be brought to 111 in a state close to nucleate boiling point 1, so the cooling efficiency due to the film 4 is improved. can be avoided.

The main departure station will be described in detail below using examples.

〔Example).

The single conductor integrated circuit device of this embodiment is a chip carrier as shown in FIG.

The chip carrier 1 is a package in which a semiconductor chip 5 is face-down bonded via a solder bump 4 onto an electrode 3 on the main surface of a package substrate 2 made of a ceramic material such as mullite, and the chip 5 is hermetically sealed with a cap 6. It has a structure.

The cap 6 is made of a highly thermally conductive ceramic such as aluminum nitride (IN), and is bonded to the main surface of the package substrate 2 with a sealing solder 7. A metallized layer 8 is provided on the outer periphery of the main surface of the package substrate 2 and on the lower surface of the legs of the cap 6 to improve the wettability of the sealing solder 7.
]゛Composite gold rR in which 11N1 and Au are sequentially laminated
Consists of a membrane. The back surface (upper surface) of the chip 5 sealed within the cap G is joined to the lower surface of the cap 6 by heat transfer solder 9. This is to transfer the heat generated from the chip 5 to the cap 6 through the heat transfer solder 9. In order to improve the wettability of the heat transfer solder 9, a metallized layer 8 is provided on the lower surface of the cap 6.

An internal wiring 10 made of, for example, W (tungsten) is formed in the inner layer of the package substrate 2.
The electrode 3 on the main surface side of the package substrate 2 and the electrode 3 on the lower surface side are electrically connected through the package substrate 2 . Solder bumps 11, which serve as external terminals when the chip carrier 1 is mounted on a module substrate to be described later, are bonded to the electrode 3 on the lower surface side.

To assemble the chip carrier 1, the solder bumps 4 formed on the main surface of the sweet potato chip 5 are positioned on the electrodes 3 on the main surface of the package substrate 2, and then the package substrate 2 is placed in an inert gas atmosphere glue flow. The chips 5 are transferred face-down to the main surface of the package substrate 2 by being transferred to a furnace and heating and remelting the solder bumps 4 therein. Next, the package substrate 2 is sealed using the sealing solder 7.
At the same time, the cap 6 is bonded to the main surface of the heat transfer solder 9.
The back surface of the chip 5 is bonded to the bottom surface of the cap 6 using a . To solder the cap 6 to the main surface of the package board 2, please refer to the package board. After applying the sealing solder 7 to the main surfaces of the package substrate 2 and the legs of the cap 6, the cap 6 is placed on the main surface of the package substrate 2, and then the sealing solder 7 is heated and melted in a reflow oven. At this time, in order to improve the wettability and spreadability of the sealing solder 7, a weight of appropriate weight is placed on the cap 6 to apply a load.

The sealing solder 7 and the heat transfer solder 9 are connected to the solder bump 4.
It is made of solder that has a lower melting temperature than the solder that makes up the solder.

Otherwise, when the sealing solder 7 and the heat transfer solder 9 are heated and melted in a reflow oven, the solder bumps 4 will be remelted.
Could the solder bump 4 be crushed by the load applied to the cap 6? l>, adjacent solder bumps 4 and 7 will be short-circuited. For this reason, Il.
■ The bump 4 is made of, for example, a Pb/Sn alloy containing Sn with a culmability of 3 to 4% (melting temperature 7320 to 330%).
The sealing solder, solder 7 and heat transfer solder 9 are made of a Pb/Sn alloy (melting temperature 21) containing about 10% by weight of Sn (melting temperature 21) from 0 to 310°C.
Consists of low melting point solder such as

In this embodiment, a predetermined number of chip carriers 1 having the above structure are mounted on the main surface of a module substrate 12 shown in FIG. 1 via solder bumps 11.

The modicoll board 12 is made of ceramic, for example,
A multilayer wiring (not shown) is formed inside it. To mount the chip carrier 1 on the main surface of the module board 12, the solder bump 11 connected to the electrode 3 on the lower surface of the package board 2 is accurately positioned over the electrode (not shown) on the main surface of the module board 12. This module board 12
The solder bumps 11 are transferred to a flow furnace in an inert gas atmosphere, and the solder bumps 11 are heated and remelted therein. At this time, in order to prevent the sealing solder 7 and the heat transfer solder 9 of the chip carrier 1 from remelting, the t1 solder bump 11 has a lower melting point than the sealing solder 7 and the heat transfer solder 9. Solder, e.g. 30% by weight
It is made of a Pb/Sn alloy containing a certain amount of Sn (molten I!l! temperature of about -250 to 269°C).

Above the module substrate 12 on which the chip carrier 1 is mounted, a coolant supply jacket 13 and a coolant discharge jacket 14 are arranged, respectively. Inside the refrigerant supply jacket 13, there is a supply port 1 provided at one end thereof.
A liquid refrigerant (for example, perfluorocarbon) is press-fitted through the hole 5. On the other hand, a discharge port 16 is provided at one end of the refrigerant discharge jacket 14 for discharging refrigerant vapor to the outside. In the middle of the discharge port 16,
A pump (not shown) for forcibly exhausting refrigerant vapor within the refrigerant discharge jacket 14 is connected. The other end of the discharge port 16 is connected to a refrigerant supply source (not shown), and the cooled and liquefied refrigerant is again press-fitted into the refrigerant supply jacket 13 through the supply port 15 .

Above each chip carrier 1 mounted on the main surface of the module substrate 12, a nozzle 17 whose upper end is opened into the coolant supply jacket 13 is arranged.

The tip (lower end) of the nozzle 17 is arranged near the back surface of the cap 6 of each chip carrier 1, so that fine particles of the refrigerant are sprayed over almost the entire back surface of the cap 6. Also, each chip carrier 1
A refrigerant discharge jacket 14 is located on the cap 6 at the upper end.
A cylindrical cooling block 18 with holes formed inside is mounted. The lower end of the cooling block 18 is connected to the outer circumference of the cap 6 via a brazing material 19. A bellows 20 is formed on a part of the side wall of the cooling block 18.

In the bellows 20, when the cap 6, cooling block 18, package board 2, module board 12, etc. thermally expand due to the heat generated by the chip 5, strong stress is applied to the solder bump 11 due to the difference in the coefficient of thermal expansion of each of these members. 1:, (,)Z).

Next, the reliability and effects of the cooling structure of this embodiment described above will be explained.

The integrated circuit formed on chip 5 is Il! Start an I-meeting'4
Then, the heat generated from the chip 5 is transferred to the camp 6 and the package substrate 2, and the entire chip carrier 1 is heated. Then, fine particles of refrigerant are sprayed from the tip of the nozzle 17 connected to the refrigerant supply jacket 13 onto almost the entire back surface of the cap 6 of each chip carrier 1.
It will be done. The fine particles of the refrigerant that reach the back surface of the cap 6 are heated and rise to a temperature of 1. :The heat is removed from the back of the cap 6), and the chip carrier 1
Let it cool down. The refrigerant vaporized on the back of the cap 6 is
The coolant is discharged to the outside through the cooling block 18, the refrigerant discharge jacket 14, and the discharge port 16.

In the above-mentioned cooling system, each fine refrigerant particle reaches the back surface of the cap 6 from the tip of the nozzle 17 and boils in an extremely fine region on the back surface of the cap 6, so the refrigerant boils in a state close to nucleate boiling. do. Therefore, nozzle 17
Optimize the type of discharge ix and discharge t4, the amount of refrigerant supplied to the back of the cap, and the amount of refrigerant that boils: * mh: i is the same ( : i,",',,'
, 1'-6(, ni, nis, chip 5 operates 11,'
During the τ period, the refrigerant is always nuclear starved and the invoice is stored f2. This allows the refrigerant film S @
I: It is possible to avoid low cooling efficiency due to overheating of the chip 5, failure of the integrated circuit, etc.
It is possible to effectively prevent the life of the chip 5 from decreasing.

In the above, the invention made by the present inventor has been specifically explained based on examples, but the present invention is not limited to the above-mentioned examples, and the species and type can be changed without departing from the gist of the invention. It goes without saying that there is.

In the previous embodiments, the case where liquid refrigerant fine particles were used was described, but solid refrigerant fine particles may also be used.

In the embodiment described above, the case was explained in which the present invention was applied to a cooling technique from a chip to a chip, but the present invention can also be applied to packages of various structures in which a chip is hermetically sealed. It is also possible to directly cool the back surface of a bare chip (bare chip) by blowing fine refrigerant particles -F4 on the substrate.

=Effects of the Invention] The effects obtained by typical inventions disclosed in this application are briefly explained below.

According to a cooling method for semiconductor integrated circuit devices in which fine particles of a solid or liquid refrigerant are sprayed onto the surface of a conductor chip or a package in which a semiconductor chip is airtight, the refrigerant can boil to a state close to nucleate boiling. As a result, a decrease in cooling efficiency due to film boiling can be avoided, and the heat generated from the semiconductor chip can be efficiently released to the outside.

[Brief explanation of the drawing]

FIG. 1 is a cutaway front view of a main part showing a cooling structure of a semiconductor integrated circuit device according to an embodiment of the present invention, and FIG. 2 is a cutaway front view of a main part of a chip carrier type semiconductor integrated circuit device. 1... Chip carrier, 2... Package substrate 2.
3... Electrode, 4.11... Solder bump, 5... Single conductor chip, 6... Cap, 7... Sealing cliff, 8... Metallized layer, 9...・Solder for heat transfer, 10・
...Internal wiring, 12...Module board, 13...
Refrigerant supply jacket, 14... Refrigerant discharge jacket, 15... Supply port, 16... Discharge port, 17...
Nozzle, 18... Cooling block, 19... Brazing metal,
2G...Bellows.

Claims (1)

[Claims] 1. A method for cooling a semiconductor integrated circuit device, which comprises spraying fine particles of a solid or liquid refrigerant onto the surface of a semiconductor chip or a package in which the semiconductor chip is hermetically sealed. 2. A semiconductor chip or a package in which the semiconductor chip is hermetically sealed is mounted on the main surface of the substrate, and the semiconductor chip,
Alternatively, a cooling structure for a semiconductor integrated circuit device, characterized in that a spraying means for discharging fine particles of a solid or liquid refrigerant is arranged near the package. 3. The cooling structure for a semiconductor integrated circuit device according to claim 2, wherein the package has a chip carrier structure in which a semiconductor chip face-down bonded to the main surface of the package substrate is hermetically sealed with a cap. .