JPH03120849A - Semiconductor device - Google Patents

Abstract

PURPOSE:To manufacture a CER-DIP type semiconductor device capable of facilitating the acceleration and optimization by a method wherein recessions are formed on a glass-welded surface of a ceramic substrate so as to form cavity parts when a leadframe is glass-welded onto the ceramic substrate. CONSTITUTION:In a CER-DIP type semiconductor device wherein a leadframe 12 is glass-welded onto a ceramic substrate 10 to be cap-sealed after a semiconductor chip 18 is mounted, recessions 20 are formed on the glass-welded surface of the ceramic substrate 10 so that the cavity parts 20 may be formed when the leadframe 12 is glass-welded onto the ceramic substrate 10. For example, groove type recessions 20 are provided in a frame shape on the halfway part of the glass-welded part on the ceramic substrate 10 while the peripheral part of a cap 14 is formed in a protrusion shape in specific width so as to glass-weld the leadframe 12. Through these procedures, the halfway part of the leadframe 12 will not be glass-welded so that the effect of dielectric constant by the glass- weld may be averted thereby enabling the signal propagation to be accelerated.

Description

[Detailed description of the invention] (Industrial application field) The present invention relates to a cerdip type semiconductor device.

(Prior Art) A cerdip type semiconductor device is sealed by glass-welding a lead frame to a ceramic base, mounting a semiconductor chip thereon, and then glass-welding a cap.

FIG. 4 shows a conventional cerdip type semiconductor device. In the figure, 10 is a ceramic substrate, 12 is a lead frame,
14 is a cap. 16 is a glass that joins the ceramic base 10 and the lead frame 12. Usually, low melting point glass is used as the welding glass. After mounting the semiconductor chip 18, the cap 14 and lead frame 12
The glass 16 is also welded between the two. This results in
Semiconductor chip 18 is completely encapsulated within the package.

(Problem to be Solved by the Invention) Recently, there has been a strong demand for higher speed semiconductor devices, but in the above-mentioned cerdip type semiconductor devices, glass is used for the sealing part. However, since glass has a high dielectric constant, there is a problem in that it is disadvantageous for increasing the speed of the device.

Therefore, the present invention has been made to solve the above problems, and its objectives are to speed up signal propagation,
It is an object of the present invention to provide a cerdip type semiconductor device which can be easily optimized.

(Means for solving problems) The present invention has the following configuration to achieve the above object.

That is, in a cerdip type semiconductor device in which a lead frame is glass-welded to a ceramic base and sealed with a cap after mounting a semiconductor chip, a recess is formed on the glass-welded surface of the ceramic base to connect the lead frame and the ceramic base. A feature is that when the glass is welded, a cavity is formed by the recess. Further, a conductive layer having a ground potential is provided on the inner surface of the ceramic base and the cap including the glass welding surface, and the glass is welded.

(Function) By forming a recess on the glass welding surface of the ceramic base, the lead frame is prevented from being entirely glass welded when glass is welded.

This reduces the negative influence of the fused glass on increasing the speed of signal propagation. A conductive layer is provided on the ceramic base and the inner surface of the cap including the glass welding surface, and by setting the conductive layer to ground potential, the transmission signal is protected from noise and the like.

(Example) A preferred embodiment of the present invention will be described in detail below.

FIG. 1 is a sectional view showing an embodiment of a semiconductor device according to the present invention.

In the figure, 10 is a ceramic base on which a semiconductor chip is mounted, and 12 is a lead frame welded to the ceramic base 10 with glass 16.

Reference numeral 14 denotes a cap for sealing the semiconductor chip 18. After the semiconductor chip 18 is bonded to the ceramic base 10 and wire bonded, the cap 14 is glass-welded to the lead frame 12. In the semiconductor chip mounting portion, a storage space for storing a semiconductor chip 18 and bonding wires 19 is formed by the ceramic base 10 and the cap 14 .

Reference numeral 20 denotes a groove-shaped recess provided in the middle of the glass welded portion on the ceramic substrate 10. In the embodiment, the recess 20 is provided in a frame shape. The recess 20 prevents the lead frame 12 from being welded to the ceramic base 10 and forms a cavity when glass welding the lead frame 12 to the ceramic base 10.

A recess 22 for accommodating the semiconductor chip 18 is provided in the center of the cap 14, and the peripheral edge of the cap 14 is formed into a projecting edge shape with a predetermined width for glass-welding the lead frame 12.

When glass welding the lead frame 12 to the ceramic base 10, a low melting point glass layer is formed only at the portion of the ceramic base 10 where the lead frame 12 is to be glass welded.

When sealing the cap, the peripheral edge of the cap 14 is sealed by glass welding. In this way, as shown in FIG. 1, a semiconductor device is obtained in which the glass welding surface is sealed by glass welding except for the recess 20.

In the obtained semiconductor device, the middle portion of the lead frame 12 is not glass-welded, so that the influence of the dielectric constant due to the glass-welded portion can be reduced, and signal propagation can be made faster.

Incidentally, a plurality of recesses 20 may be provided in the ceramic base 10, and the recesses 20 may be provided at any suitable location within the range that can be sealed by glass welding.

FIG. 2 shows an embodiment that is a further improvement of the above example, and is characterized in that the entire welding surfaces of the ceramic base 10 and the cap 14, including the inner surface of the recess 20 and the glass welding surface, are entirely covered with a conductive layer 24. . The conductive layer 24 can be formed by applying a conductive paste, plating, vapor deposition, or the like.

When the conductive layer 24 is provided in this way, the above-mentioned recess 20
In addition to the effect of reducing the influence of the glass welded portion, by setting the conductive layer 24 to the ground potential, the transmission signal to the signal line of the lead frame 12 can be protected from noise and the like.

FIGS. 3(a), 3(b), and 3(C) show examples for bringing the conductive layer 24 to the ground potential.

FIG. 3(a) shows an example in which the ground line of the lead frame 12 and the conductive layer 24 are connected by a bonding wire 26 to have a ground potential.

FIG. 3(b) shows the lead frame 12 at the recess 20 position.
Stand up the pressure welding piece 28 to be connected to the ground line of the
8 is brought into pressure contact with the conductive layer 24, and the conductive layer 24 is brought to the ground potential.

In FIG. 3(c), the ground line of the lead frame 12 and the conductive layer 24 are soldered to the outer wall surface of the package, so that the conductive layer 24 is brought to the ground potential. 30
is a soldered piece formed on the ground line of the lead frame 12.

By bringing the conductive layer 24 to the ground potential in this manner, various effects such as being able to protect transmission signals from noise etc. can be achieved.

Note that the cap 14 may be made of metal other than ceramic, but in this case as well, the recess 20 is formed in the ceramic base 10.
A similar effect can be obtained by forming . In this case, the cap 14 and the ground line of the lead frame 12 may be connected in the same manner without forming the conductive layer 24 serving as a ground line on the cap 14.

The present invention has been variously explained above using preferred embodiments, but the present invention is not limited to these embodiments.
Of course, many modifications can be made without departing from the spirit of the invention.

(Effects of the Invention) As described above, according to the semiconductor device of the present invention, in a cerdip type semiconductor device, the influence of the welded glass on the signal line can be reduced, and the welded glass can reduce the influence of the welded glass on the signal line. This enables high-speed signal propagation by reducing adverse effects on the signal. Furthermore, by providing a conductive layer at ground potential on the glass welding surface, significant effects such as being able to reduce the effects of noise and the like on transmission signals can be achieved.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing one embodiment of a semiconductor device according to the present invention, and FIG. 2 is a sectional view showing another embodiment. FIG. 3 is an explanatory view showing an embodiment in which a conductive layer is set at ground potential, and FIG. 4 is a cross-sectional view showing a conventional example of a semiconductor device. DESCRIPTION OF SYMBOLS 10... Ceramic base, 12... Lead frame, 14... Cap, 16... Glass, 18...
Semiconductor chip, 20.22... Storage recess, 24...
Conductive layer, 26... Bonding wire, 28... Pressure contact piece, 30... Soldering piece.

Claims (1)

[Claims] 1. In a cerdip type semiconductor device in which a lead frame is glass-welded to a ceramic base and sealed with a cap after mounting a semiconductor chip, a recess is formed in the glass-welded surface of the ceramic base, and the lead frame is sealed with a cap after mounting a semiconductor chip. 1. A semiconductor device, wherein a cavity is formed by the recess when glass welding is performed between the semiconductor device and the ceramic substrate. 2. The semiconductor device according to claim 1, wherein a conductive layer having a ground potential is provided on the inner surface of the ceramic substrate and the cap, including the glass welding surface, and the glass is welded thereto.