JPS6232620B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a circuit package on which a semiconductor integrated circuit element or the like is mounted, and more particularly to a circuit package that dissipates heat generated in the element to the outside by thermal conduction.

As semiconductor devices become more highly integrated, the number of connection points with the outside of the device has increased. On the other hand, there is a strong demand for smaller and faster electronic devices using semiconductor elements.
It is necessary to package semiconductor elements with higher density.
The flip-chip method is known as an effective means for increasing the number of external terminals of a semiconductor device and for high-density mounting on a wiring board.

However, in the flip-chip method, the connection between the semiconductor element and the wiring board is limited to the solder bump area, so the disadvantage is that heat dissipation is poor compared to a method in which the entire back surface of the semiconductor element is directly attached to the board using gold-silicon eutectic alloy, etc. There is.

Due to the above drawbacks, it is not possible to mount semiconductor elements that generate a large amount of heat on a board using the flip-chip method.
It was not possible to package high-speed devices with high density.

As a means to compensate for the above drawbacks and ensure good heat dissipation, there is a method disclosed in Japanese Patent Application Laid-Open No. 53-31968. In the above method, a metal block is metallurgically bonded to one surface of a heat generating element or a heat conductive cap and pressed against the other surface to form a heat conduction path. This method requires that the metal block be pre-fixed to one side. Fixing the metal lump to the element side further complicates the element manufacturing process and causes a decrease in yield. Furthermore, when a large number of elements are mounted on a substrate, it is often necessary to replace defective elements or repair connections. For this reason, if a metal lump is attached to the cap side, it becomes necessary to replace the cap every time the cap is reprocessed. This is because the metal block has already been deformed, and therefore sufficient contact with the element surface cannot be guaranteed if it is reused.

SUMMARY OF THE INVENTION An object of the present invention is to provide a circuit package which has good heat dissipation properties by closely adhering a deformable and good heat conductive sheet to a heat generating element.

In order to dissipate heat to the outside from a heat generating element such as a semiconductor element mounted on a board using the flip-chip method, it is necessary to directly attach a heat conductive material to the heat generating element and guide the heat to the heat dissipating part by thermal conduction. It is valid. Pressing an integrally formed heat sink against a heat generating element at once may cause damage to the element or the solder connection due to warping of the board supporting the element and variations in the height of the solder connection that connects the element and the board. This may cause inconveniences such as causing a problem or not making contact.

In order to prevent damage to heat generating elements and solder connections and to ensure adhesion, conventional methods used methods such as pressing a piston-shaped heat sink against each element with a spring or fixing soft metal to the heat sink side. . In the above method, a large number of mechanical parts such as pistons are used, so miniaturization cannot be achieved, and a step of fixing soft metal in advance is required.

In order to improve the above disadvantages, a means including a soft and deformable thermally conductive sheet that can absorb the warpage of the board and the height variation of the connection part is inserted between the surface of the thermally conductive cap on the heat sink side and the surface of the heat generating element. By pressing the cap and the substrate relative to each other, the cap and the substrate are brought into close contact with both surfaces without damaging the element or the connecting portion, thereby forming a good heat conduction path.

An embodiment of the present invention will be described below with reference to FIG. In FIG. 1, 10 is a semiconductor element, 11 is solder 20 is a wiring board, 21 is an external connection pin, 22
30 is a flange, 30 is a thermally conductive cap, 31 is a soft metal thermally conductive sheet, 32 is a guide pin for sheet positioning, and 40 is a cooling liquid.

The semiconductor element 10 is mounted on one surface of a multilayer wiring board 20, which is usually made of ceramic, by a flip-chip method using solder 11. Connecting pins 21 are provided on the other side of the wiring board to connect this module to a higher level board. Cap 30 is attached to substrate 20 via flange 22. The cap is made of a material with good thermal conductivity, such as aluminum or copper, and the heat conducted to the cap includes a tube section inside the cap, and is dissipated to the outside by a cooling liquid flowing through the tube section. A positioning pin 32 is provided on the inner wall of the cap, and a thermally conductive sheet 31 is attached to the pin 32. sheet 31
The cap is made of a soft metal such as indium, and deforms due to the pressure when attaching the cap to the flange, so that it adheres tightly to the surface of the semiconductor element and the inner wall of the cap without damaging the semiconductor element or the solder connections, filling the gap. . As described above, by filling the gap between the semiconductor element and the cap with soft metal, a good heat conduction path is formed, and the heat generated in the semiconductor element is efficiently guided to the cap 30 by heat conduction through the sheet 31. . Further, the contact surface of the sheet with the semiconductor element is formed into a convex surface smaller than the surface of the semiconductor element. This is to prevent strain caused by the difference in thermal expansion coefficients between the board 20 and the cap 30 from being excessively applied to the solder joint 11. When a parallel flat sheet is used as shown in Figure 2, pressure is applied. The semiconductor element becomes deformed by being embedded in the sheet, and the above-mentioned strain is applied directly to the solder connection part, and there is a risk that the solder may be damaged.

According to the present invention, the thermally conductive sheet inserted between the semiconductor element and the thermally conductive cap can be brought into close contact with the surface of the element without damaging the semiconductor element or the solder connection part. The generated heat can be efficiently guided to the heat sink (thermal conductive cap) by thermal conduction.

Further, the device does not require any complicated mechanism or process, and the device can be made smaller and the work can be simplified.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of the device of the present invention in which a cap is attached to a substrate, and FIG. 2 is a partially enlarged cross-sectional view of a conventional device using parallel flat sheets. 10...Semiconductor element, 11...Solder, 20...
Wiring board, 30... Thermal conductive cap, 31...
Thermal conductive sheet, 40...Cooling liquid.

Claims (1)

[Claims] 1. A substrate supporting a plurality of heat generating elements, a heat sink, and a surface disposed between the surface of the heat sink and the surface of the plurality of heat generating elements, the surface facing the plurality of heat generating elements; A soft and deformable thermally conductive sheet in which a convex shape having a top surface having a shape smaller than the surface shape of the opposing heat generating element is formed at a position facing the surface of each of the plurality of heat generating elements. and deforming each convex raised surface of the means including the thermally conductive sheet by applying contact pressure to each of the opposing heat generating elements, and the means including the thermally conductive sheet. A circuit package in which a surface on the heat sink side of the circuit package is fixed to the heat sink so that heat generated by the heat generating element can be guided to the heat sink by thermal conduction.