JPH0724294B2 - Semiconductor mounted cooling structure - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to a cooling structure for mounting a semiconductor element, and more particularly to a semiconductor element and a multilayer laminated board via a flexible printed circuit for micro soldering as a beam heat source. The present invention relates to a semiconductor-mounted cooling structure that efficiently cools the semiconductor element.

[Conventional technology]

As for the method of connecting the external connection pad of the semiconductor element to the outside, as is generally known, the wire bonding method using a thin metal wire, the printed circuit board and the external connection pad of the semiconductor element are faced to each other and fine soldering is performed. As a control collapse method for directly joining by means of a method using a flexible printed circuit, for example, Japanese Patent Laid-Open No. 62-465.
There is a tape automated bonding method as described in Japanese Patent No. 37.

Further, the connection between the semiconductor element and the multilayer laminated board is disclosed in JP-A-61-203.
As described in Japanese Patent No. 648, there is a method in which the control collapse method described above is used to absorb thermal strain and prevent the solder pole from being broken, thereby connecting the solder pole. FIG. 2 shows a control collapse method as a conventional example in which semiconductor elements are mounted at high density. That is, FIG. 2 is a vertical cross-sectional view of a conventional embodiment of the invention. Reference numeral 1 is a semiconductor element, 2 is a bonding layer, 10 is a multilayer wiring, 11 is a multilayer laminated plate, 12 is a radiator, and 13 is a solder bump. means. The semiconductor element 1 is arranged in a face-down manner and is soldered to the multilayer wiring 10 in the multilayer laminate 11 via solder bumps 13. Therefore, the radiator 12 is bonded to the back surface of the semiconductor element via the bonding layer 2.

[Problems to be solved by the invention]

As shown in the above-mentioned prior art, in order to connect the semiconductor element terminals and the multilayer laminated board at high density, the semiconductor elements are arranged in the face-down, and the semiconductor element terminals and the multilayer laminated board are opposed to each other by the control collapse method directly. Soldering is more advantageous.

However, when the shape of the semiconductor element becomes large, stress is generated due to the difference in coefficient of thermal expansion between the semiconductor element and the multilayer laminated plate,
Even with the above conventional method, the stress cannot be reduced, and the solder bump is broken. To solve this, it is more advantageous to use a flexible printed circuit.

Furthermore, if the semiconductor elements are arranged in a phase-down manner, it is necessary to remove the heat generated by the semiconductor elements from above, and the stress due to the weight and strain of the cooling body will be applied directly to the solder bumps at the connection parts, destroying the solder bumps. There is a risk of Therefore, a structure in which the stress from the cooling body does not directly act on the solder bumps is preferable.

An object of the present invention is to provide a semiconductor mounted cooling structure that reduces stress applied to terminals of a semiconductor element and effectively removes heat generated by the semiconductor.

[Means for solving problems]

Briefly describing the present invention, the present invention relates to a semiconductor mounting cooling structure, which is a cooling structure for mounting a semiconductor element that requires heat and indirectly requires cooling, in which a pad forming surface for external connection of the semiconductor element is provided. And the lower surface of the semiconductor element is joined to a metal cooling body whose inside is cooled by a cooling medium, the pad is joined by a flexible printed circuit, and the external terminal of the flexible printed circuit is It is characterized in that it is joined to the multilayer laminate through the through holes of the metal cooling body.

The purpose is to arrange the external connection pad forming surface of the semiconductor element upward, and the pad and the flexible printed circuit are soldered from above with a beam heat source, and the lower surface of the semiconductor element is joined to a cooling body to heat the surface. It is solved by absorption by the cooling body.

Since the external connection pad of the semiconductor element is on the top surface, the alignment with the flexible printed circuit can be performed accurately from the top by optical means such as TV, and the soldering can be done by laser, infrared, xenon, etc. This can be easily done by directly heating the heat source to melt the solder. Also,
Inspection and repair after joining can be easily performed because the joint is exposed at the top. Further, since the flexible printed circuit is used, the stress applied to the solder joint portion of the semiconductor element is small and the reliability during use is greatly improved.

Moreover, since the back surface of the semiconductor element is bonded to the metal cooling body, the heat generated by the semiconductor element is efficiently cooled.

In the semiconductor-mounted cooling structure of the present invention, the lower surface of the semiconductor element and the metal cooling body are electrically insulated and joined by sandwiching a layer having high electrical resistance and good thermal conductivity therebetween. The structure is preferred.

The metal cooling body is made of a metal plate having good heat conduction, a passage is formed therein, a cooling medium is flown in the passage to perform cooling, and a portion where the passage is not formed has a thickness direction thereof. A through hole is formed in the through hole, and the flexible printed circuit and the multilayer laminated board are electrically connected to each other through an electric circuit in the through hole.

Further, it is preferable that the external connection pads of the semiconductor element and the terminals of the multilayer laminate are connected by soldering with a flexible printed circuit.

〔Example〕

Hereinafter, the present invention will be described in more detail with reference to Examples.
The present invention is not limited to these examples.

Embodiment 1 FIG. 1 is a vertical cross-sectional view of a semiconductor mounted cooling body of the present invention showing the entire structure. In FIG. 1, reference numeral 1 is a semiconductor element,
2 is a bonding layer, 3 is a semiconductor element terminal, 4 is a flexible printed circuit, 5 is a multilayer wiring terminal, 6 is an insulating plate, 7 is a metal cooling body, 8 is a cooling hole, 9 is a through hole, 10 is a multilayer wiring, 11 Means a multilayer laminate. The semiconductor element 1 is arranged with the external connection pad forming surface facing upward, that is, is arranged on the face-up and is electrically insulated from the metal cooling body 7 via the bonding layer 2 and is bonded so that heat conduction is good. The metal cooling body 7 is made of a metal having good heat conduction, such as steel, and the cooling hole 8 is formed therein by using a metallic joining method such as soldering, brazing, or diffusion joining. A cooling medium is caused to flow through and is cooled. The metal cooling body 7 is provided with a through hole 9 in a portion where there is no cooling hole 8. The multi-layer laminated plate 11 is installed under the metal cooling body 7, and the multi-layer wiring 10 is drawn out on the insulating plate 6 through the through hole 9. The external connection pads of the semiconductor element 1 and the multilayer wiring 10 are soldered at the semiconductor element terminal 3 and the multilayer wiring terminal 5 via the flexible printed circuit 4.

FIG. 3 is a front view showing a connection state between the flexible printed circuit 4 and the semiconductor element 1. In FIG. 3, reference numerals 1, 3 and 5 have the same meanings as in FIG. 1, 14 is an insulating film, and 15 is a stress relaxation notch. The flexible printed circuit 4 is formed by forming a copper electrode on an insulating film, for example, a polyimide film, and the electrode is soldered to the semiconductor element terminal 3 and the multilayer wiring terminal 5. Since the flexible printed circuit itself is a flexible structure, the stress applied to the joint is small, but the stress relaxation notch 15 is further formed in the corner of the insulating film 14 to reduce the stress applied to the joint, resulting in destruction of the joint. Prevent.

FIG. 4 is a horizontal cross-sectional view of the metal cooling body 7 at the horizontal center. Reference numerals 1, 5, 8 and 9 in FIG. 4 have the same meanings as in FIG. Cooling holes 8 are finely formed in the metal cooling body 7 below the semiconductor element 1, and heat generated from the semiconductor element 1 is efficiently removed by flowing a coolant, such as water, into the cooling holes 8. Through holes 9 are formed around the semiconductor element 1 for passing the multilayer wiring 10. The through hole 9 is formed at a position where the cooling hole 8 is not formed,
The inlet and outlet of the cooling medium to and from the cooling hole 8 are formed in the gap between the through holes 9. In order to form a fine and complicated cooling hole in the metal cooling body 7, a groove is formed in the pattern of the cooling hole 8 by etching or the like in the metal plate by soldering, soldering or brazing another metal plate, It becomes possible by joining by diffusion joining or the like. Further, in order to hold the multilayer wiring terminal 5 in the through hole 9, it is achieved by filling an electrical insulator between the through hole 9 and the multilayer wiring terminal 5.

Example 2 The mounting method of the present invention uses a thin metal cooling body, and since the terminals of the semiconductor element can be joined thinly, the overall structure is thin. In the future, it is required to reduce the impedance of the electric circuit by increasing the speed of the electric signal, but in this case, according to the present invention, the thinly mounted cooling body can be formed into a three-dimensional structure by stacking it in layers. Three-dimensional mounting with cooling becomes possible.

Example 3 The cooling structure of the present invention can be applied to a superconducting device. As a superconducting material, the Y-Ba-Cu-O-based perovskite crystal is 8
It is known to show superconductivity at 2K. Therefore, boiling point
72K liquid nitrogen is used as the refrigerant. When indirectly cooling such a superconducting device with liquid nitrogen, the superconducting device operates by flowing and cooling liquid nitrogen into the cooling body of the present invention.

〔The invention's effect〕

 The present invention has the following two effects.

The first effect is that the external connection terminals of the semiconductor element, which are fine and the most difficult to join, can be easily soldered, and moreover, since there is little stress on the joint, a joint with high reliability against breakage is provided. can get. Alignment in soldering can be done by directly observing from above from the semiconductor element because it is a face-up, and soldering is also locally observed by beam heat source such as laser, infrared ray, xenon, etc. while observing directly from above. Can be heated. Furthermore, inspections and repairs after joining can be observed from the top, which is easy.

The second effect is that the cooling efficiency of the semiconductor element is good. That is, the heat is directly transmitted from the back surface of the semiconductor element to the cooling body. The cooling body is efficiently removed to the outside by the finely formed cooling holes. When the semiconductor element and the cooling body are electrically connected to each other, they are connected via a thin insulating film.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional view of a semiconductor mounted cooling structure according to an embodiment of the present invention, FIG. 2 is a vertical cross-sectional view of a conventional embodiment, and FIG. 3 is a flexible printed circuit for joining a semiconductor element and a multilayer wiring. FIG. 4 is a cross-sectional view showing a state of forming cooling holes and through holes in a cooling body. 1: semiconductor element, 2: bonding layer, 3: semiconductor element terminal, 4: flexible printed circuit, 5: multilayer wiring terminal, 6: insulating plate, 7: metal cooling body, 8: cooling hole, 9: through hole, 10 : Multilayer wiring, 1
1: Multilayer laminated board, 12: Heat radiator, 13: Solder bump, 14: Insulating film, 15: Notch for stress relaxation

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Mitsuo Kato 4026 Kuji Town, Hitachi City, Hitachi, Ibaraki Prefecture Hitate Manufacturing Co., Ltd.Hitachi Laboratory Ltd. Hitachi Research Laboratory

Claims (4)

[Claims] 1. In a cooling structure for mounting a semiconductor element that requires heat generation and indirectly requires cooling, a pad forming surface for external connection of the semiconductor element is arranged upward, and a lower surface of the semiconductor element cools the inside. It is bonded to a metal cooling body cooled by a medium, the pad is bonded by a flexible printed circuit, and the external terminal of the flexible printed circuit is bonded to a multilayer laminate through a through hole of the metal cooling body. A semiconductor-mounted cooling structure characterized in that 2. The lower surface of the semiconductor element and the metal cooling body,
In between, sandwich a layer with high electrical resistance and good thermal conductivity,
Claim 1 wherein they are electrically insulated and joined
The semiconductor mounted cooling structure as described in the item. 3. The semiconductor mounting cooling according to claim 1 or 2, wherein the external connection pads of the semiconductor element and the terminals of the multilayer laminate are connected by soldering with a flexible printed circuit. Structure. 4. The metal cooling body is made of a metal plate having good heat conduction, a passage is formed therein, and a cooling medium is flown in the passage to cool the metal cooling body, and a portion where the passage is not formed is formed. The through-hole is formed in the plate thickness direction, and the flexible printed circuit and the multilayer laminated board are electrically connected to each other through an electric circuit in the through-hole. The semiconductor mounted cooling structure according to any one of 1.