JPS6239825B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a semiconductor device, and particularly to an improvement in a method for manufacturing a semiconductor device with high power consumption.

2. Description of the Related Art In recent years, semiconductor devices, especially those used in computers and the like, are required to have high calculation speeds, and semiconductor elements are becoming more highly integrated and consume more power. Along with this, the amount of heat generated by one semiconductor element has also increased,
The cases in which these devices are installed are also required to have good heat dissipation characteristics. There are two approaches to increasing the heat dissipation characteristics of the case. One is to select a material with high thermal conductivity, and the other is to have a structure that facilitates heat dissipation. Metals are cited first as materials with high thermal conductivity, but metals generally also have a high coefficient of thermal expansion, and when compatibility with other materials is taken into consideration, the range of selection is narrowed, and they end up being expensive. In addition, there are materials such as beryllia (BeO) and silicon carbide (SiC) that are electrically insulating, have high thermal conductivity, and have a low coefficient of thermal expansion, but they are currently expensive and the powder is toxic. There are problems and the scope of use is limited. On the other hand, structures that allow easy heat dissipation include heat pipes and heat dissipation fins. However, heat pipes have complicated structures and have not yet achieved sufficient reliability. Currently, the structure that is easiest and provides relatively high heat dissipation characteristics is a case with fins.

A typical example of conventional cases with heat dissipation fins is as shown in FIG. That is, external lead pins 2 are arranged on the lower surface of a ceramic substrate 1, and heat dissipation fins 3 are attached to the opposite surface. Generally, the heat dissipation fins are attached to the side opposite to the surface on which the external lead pins are planted. This is to facilitate heat dissipation from the fins by blowing air when the semiconductor device is mounted on a printed circuit board. However, this type of conventional structure has a drawback that is extremely disadvantageous in terms of heat dissipation. That's the second
As shown in the cross-sectional view in the figure, the heat generated from the semiconductor element 4 is transmitted to the ceramic substrate 1 to which the semiconductor element is fixed, and then is conducted to the fins 3 where the heat is dissipated. The problem is that the path becomes longer and the thermal resistance increases. Therefore, in order to improve heat dissipation, as shown in Figure 3,
It is necessary to fix the semiconductor element 4 to a surface surrounded by the external lead pins 2, and to sandwich the ceramic substrate from the fixed surface to release heat directly to the fins. However, in order to obtain this package structure, it is necessary to improve the sealing method of semiconductor devices. Conventional sealing methods for ceramic cases range from simple methods such as gluing a ceramic cap with epoxy resin or pouring silicone or epoxy resin, to applying glass powder to a ceramic cap and melting it. There are frit seals that bond metal plates together, solder seals that bond metal plates with solder, Au/Sn seals that bond metal plates with Au/Sn alloy, and the most commonly used seam weld.

All methods of sealing using resin have poor moisture resistance and heat resistance, and are inappropriate as a method for sealing semiconductor devices that require high reliability. The frit seal method uses glass powder with a relatively low melting point for sealing, but it still has to be heated to 400 to 500 degrees Celsius, and there are only a limited number of semiconductor devices that do not change their characteristics at this temperature. This is not a common sealing method because the elements are highly integrated and vulnerable to high temperatures.
Solder seals are relatively cheap and easy to make, but
It has a low melting point of around 200°C and is susceptible to thermal fatigue, so it has the drawback of lacking reliability. Au/Sn seals can achieve good sealing by heating at 300 to 350℃, but since they use Au, they are expensive and
It cannot be applied to semiconductor devices in which semiconductor elements are fixed to ceramic substrates with solder. The seam welding method does not raise the temperature of the semiconductor element during sealing, is highly reliable, and can be done at low cost. As shown in FIG. 4, a metal ring 5 is provided around the outer periphery of the semiconductor element 4 in close contact with the ceramic substrate 1, a metal cap 6 is placed on top of the metal ring 5, and a pair of roller electrodes 7, 7' are pressed. When a current is applied while applying heat, heat is generated at the contact surface between the ring 5 and the cap 6,
Both are melted and bonded together. Since the heat generation is local and the temperature of the semiconductor element does not rise, it can also be applied to elements that are sensitive to high temperatures and semiconductor devices in which semiconductor elements are fixed to ceramic substrates with solder. Also,
The ring and cap are made of Fe/Ni alloy, etc.
Since it is sealed with the melted version of this, solder or
It has less thermal fatigue and higher reliability than low melting point brazing materials such as Au/Sn.

However, the disadvantage of seam welding is that it requires a large space in which the metal roller can rotate, and it is difficult to seam weld in an area surrounded by external lead pins, as shown in FIG.

The present invention solves the conventional problems by using an improved method when sealing a semiconductor element surrounded by external lead pins as described above, and achieves high reliability and low thermal resistance. This was done to realize a package. A metal ring is provided on a ceramic substrate at a position surrounding the semiconductor element, and a metal cap of a size that covers the semiconductor element and overlaps the metal ring is placed on top of the other. Then, the area where the two overlap is It is characterized by sealing by irradiation with a laser beam.

Laser beams have good directivity and hardly spread even when irradiated from a distance, so they are suitable for micro-machining, and in mechanical machining in particular, they can be easily processed from a distance even in areas where jigs and tools do not bend. It has the feature that it can be used to The present invention utilizes this feature of a laser beam to manufacture a package having a low thermal resistance structure of a semiconductor device, that is, a semiconductor device having a structure in which a semiconductor element is fixed to a surface surrounded by external lead pins as shown in FIG. It was used.

Embodiments of the present invention will be described in detail below with reference to the drawings.

Semiconductor equipment is TAB (Tape Automated)
FIG. 5 shows an example in which the present invention is applied when assembling by the bonding method. The TAB method is shown in Figure 5a.
A through hole 9 is formed in the center of the insulating film 8 as shown in FIG.
is opened, and the lead 10 is placed on the support frame 11 over this through hole.
It is supported by and made to protrude. On the other hand, the electrodes of the semiconductor element 4 are formed in the shape of a protrusion, and the tips of the leads 4 are aligned to match the positions of the protruding electrodes. All the leads can be connected at the same time by aligning and overlapping the leads and the protruding electrodes, and then applying heat and pressure using a jig that is approximately the same size as the semiconductor element. FIG. 5a shows the state in which the devices are connected as described above. A pad 12 is provided at the end of the lead 4, and by pressing an electrode terminal thereon, it is possible to operate the semiconductor element and check whether or not it exhibits a predetermined performance. As a result of the check, a normal semiconductor element is separated from the insulating film leaving the support frame 11 as shown in FIG. 5b, and for example, as shown in FIG.
It is incorporated into PIP (PIug-in-Package) 13 as shown in . The semiconductor element 4 is fixed (=mounted) at the bottom of a recess 14 formed in the center of PlP. The semiconductor element has a fifth
Since the lead 10 is connected as shown in Figure b,
It is difficult to grip the semiconductor element with tweezers or the like and rub it against the bottom of the recess 14, making it difficult to use a normal Au/Si mount or Au/Sn mount. When assembled by the TAB method, the mount is made by vapor-depositing Au etc. on the back surface of the semiconductor element, and the bottom of the recess 14 of the PlP is
It is best to metalize Au, Sn, etc. and then solder. It is of course possible to mount with silver paste or the like, but this increases the thermal resistance, which is disadvantageous in the case of semiconductor elements with high power consumption. After mounting the semiconductor element as described above, the ends of the leads 10 are connected to the external terminals 15 of the PIP. Both include, for example, the lead 10 and the external terminal 15.
By plating with Au or Sn and applying heat and pressure, all leads can be connected at the same time. The external terminals 15 are each electrically connected to an external lead pin. In Figure c, the external lead pins in the front are omitted to avoid clutter. A metal ring 5 is provided around the outer periphery of a recess (=cavity) 16 that accommodates the semiconductor element 4 and the leads 10 connected thereto, and a metal cap 6 is placed over this as shown in FIG. 3, and a laser beam is irradiated onto the metal ring 5. Both metals are melted and welded. 100 with Kovar on the metal ring and Ni plating with a thickness of 2 to 3 μm on the metal cap.
When using a μm-thick Kovar plate, the output required for welding is 100 ~
200W, speed 15mm/sec. If the semiconductor device sealed in this way is metallized with Au or the like on the side opposite to the side on which the external lead pins are planted, it will be possible to Accordingly, it is possible to provide heat dissipation fins 3 as shown in FIG. Assuming that the maximum junction temperature Tj (max) of the semiconductor element is 125℃, the outside air temperature Ta is 70℃, and the power consumption P is 5W.
The required thermal resistance RΘ is RΘ=Tj-Ta/P=125-70/5=11℃/W or less, which is impossible to achieve with the conventional structure shown in Figure 2, and the configuration shown in Figure 3 is Therefore, an airtight seal using the seam weld method cannot be achieved. Moreover, in the TAB method, as mentioned above, solder is generally used for the mount, so the temperature cannot be raised for encapsulation as with frit seals or An/Sn seals. According to the present invention, the above-mentioned difficulties can be solved and a highly reliable semiconductor device having low thermal resistance and high airtightness can be manufactured.

Implementation of the invention is not limited to the above example. For example, as shown in Figure 6, DIP (DuAl-in-line)
Package) can also be applied. normal
In a DIP, a semiconductor element is mounted on the side (back side) opposite to the direction of the external lead pins 2, and is encapsulated mainly by the seam welding method. Seam welding is difficult when semiconductor elements are mounted on the front surface (bottom surface) and heat dissipation fins or heat dissipation studs (not shown) are provided on the back surface to improve heat dissipation. In this example as well, a low thermal resistance package can be realized by sealing with a laser beam.

The present invention can also be applied to a case where a plurality of semiconductor elements are mounted on the bottom surface of a multilayer ceramic substrate 1 and each semiconductor element is enclosed in a box-shaped cap 6 as shown in FIG. In this example, a heat dissipation fin 3 is attached to the back surface of the ceramic substrate, so that the entire substrate can be cooled. The external lead pins are attached to the side surface of the board 1 so that they can be mounted on a printed board or the like.

As described in detail above, according to the present invention, semiconductor devices that need to be assembled in a low thermal resistance ceramic case, such as semiconductor devices with high power consumption or semiconductor devices with a low maximum allowable junction temperature, can be attached to external lead pins. The enclosed surface, i.e.
When mounted as a semiconductor device on a printed circuit board, etc., it can be mounted and sealed on the surface facing the printed circuit board, etc., so a heat sink such as a heat dissipation fin or a heat dissipation stud can be attached to the surface opposite to this surface. Therefore, a high performance and highly reliable semiconductor device can be manufactured.

[Brief explanation of the drawing]

1 and 2 are a perspective view and a sectional view of a conventional semiconductor device, FIG. 3 is a sectional view of a semiconductor device according to the present invention, FIG. 4 is a sectional view explaining the seam weld method, and FIG. 5 is a sectional view of a conventional semiconductor device. FIG. 6 is a perspective view illustrating a case where the present invention is applied to a PIP, FIG. 6 is a perspective view when the present invention is applied to a DIP, and FIG. 7 is a perspective view when the present invention is applied to a hybrid board. In the figure, 1... Ceramic substrate, 2... External lead pin, 3... Heat dissipation fin, 4... Semiconductor element, 5... Metal ring, 6... Metal cap,
7, 7'... Roller electrode, 8... Insulating film, 9... Through hole, 10... Lead, 11... Support frame, 12... Pad, 13... PIP, 14...
Recessed portion, 15... external terminal, 16... cavity.

Claims (1)

[Claims] 1. A semiconductor element is mounted on the side from which the external lead pins are led out of a ceramic substrate on which external lead pins are arranged, a metal ring is provided around the outer periphery of the semiconductor element in close contact with the ceramic substrate, and the semiconductor element is covered. In addition, a metal cap of a size that overlaps the metal ring is stacked, and a laser beam is irradiated to the overlapped portion of the metal ring and the metal cap to bond them together, and a surface opposite to the surface on which the semiconductor element is mounted is bonded. A method of manufacturing a semiconductor device, comprising: attaching a heat dissipating member on the ceramic substrate.