JPH0356057Y2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION This invention relates to a semiconductor device, and more particularly to a cover for a hermetically sealed semiconductor device package.

(Prior Art) Semiconductor devices such as transistors and ICs are sealed to protect the semiconductor elements from external forces, changes in the surrounding environment, etc., and to operate the elements in a stable state over a long period of time. Microparallel seam bonding, which is an application of resistance welding, is used for semiconductor devices that require high reliability. As shown in FIG. 3, in this bonding method, a metal cover 4 is placed on a metal frame 3 called a seal frame, which is soldered to a ceramic substrate 2 on which a semiconductor element 1 is attached. A pair of tapered roller electrodes 5 and 6 are brought into contact with each other as shown in the figure, and the roller electrodes 5 and 6 and the cover 4 are brought into contact with each other under a constant pressure.
A current is passed from one roller electrode 5 or 6 to the other roller electrode 6 or 5 while moving them relative to each other, and the seal frame 3 and cover 4 are seamed and hermetically sealed by the generated heat.

Normally, the seal frame 3 and the cover 4 are fitted, and the seam joint is formed by a melted layer 7 of the plating at the interface between the seal frame 3 and the cover 4, and a mating layer 7 at the outer periphery of the cover, as shown in Fig. 4. It is formed from a fillet 8 formed by melting the base material of the cover 4 and the seal frame 3 together without melting. Therefore, the quality of the seam joint is most influenced by the state of formation of the fillet 8, and is greatly influenced by the plating of the cover 4, which forms most of the fillet 8.

Generally, the cover 4 is made by etching or pressing to form a single body 9 from a thin plate of Fe-Ni-Co alloy, which has a coefficient of thermal expansion close to that of the ceramic substrate 2, as shown in FIG. Nickel plating 10, which has good adhesion to the Co alloy and good corrosion resistance, is applied to the entire surface of the single body 9 with the nickel plating 2 necessary for seam joining.
It is applied to a thickness of ~3 μm. Since the plating of such a single cover 4 is done by electrolytic plating, it is not possible to accurately control the plating thickness of the peripheral end 11 of the cover 4, and the thickness of the plating on the peripheral end 11 of the cover 4 is 2. ~3 times as thick. For this reason, the welding current flows to the plating side during seam joining, and the generation of Joule heat becomes unstable, and the desired airtightness may not be obtained.
Therefore, in order to eliminate such problems, after applying nickel plating 10 of 6 to 10μ on both sides of the thin metal plate, the sixth
As shown in the figure, a cover 13 without plating on the peripheral end 12 was devised.

(Problem to be solved by the invention) In such seam joining using the cover 13 which is nickel plated on both sides except for the peripheral edge 12, the melting point of the nickel plating applied to the cover 13 is The temperature is 1455℃, which is almost the same as the melting point of the Fe-Ni-Co alloy that is the base material, and as mentioned above, this cover base material does not melt during seam joining, so the flow of the molten nickel plating is poor and a sufficient fillet cannot be formed. Not formed. For this reason, in the case of highly reliable semiconductors, rust and discoloration occur on the peripheral edge 12 of the seam-jointed cover 13 during environmental tests such as constant temperature and humidity tests and salt spray tests. It often progresses and impairs airtightness.

(Means for Solving the Problems) In order to solve these problems, the cover of the present invention has a nickel plating base on both sides except for the peripheral edges, and gold plating on both sides. Each layer was applied so that the sum was 3 to 10 μm.

(Function) As is clear from the equilibrium diagram, the nickel-gold plating applied to the cover forms a total solid solution with a minimum at 950°C, so it has a higher melting point than nickel, which has a melting point of 1455°C, and gold, which has a melting point of 1063°C. Melts at low temperatures.
Therefore, compared to conventional nickel plating, the molten nickel-gold plating on the top surface of the cover has better fluidity, and due to the pressure of the roller electrode, it flows sufficiently into the peripheral edge of the cover to form a good fillet. .

(Example) An example of the present invention will be described below with reference to FIGS. 1 and 2. In FIGS. 1a and 1b, the semiconductor device package cover 14 to be seam-bonded is made by, for example, half-etching a Fe-Ni-Co alloy thin plate to make a recess in the part 15 that contacts the seal frame, and then A nickel underplating 16 of 5 .mu.m, preferably 3 .mu.m, and then a gold plating 17 of 1 to 5 .mu.m, preferably 3 .mu.m, is formed into a single piece using a press working method. Therefore, the peripheral end 12 (sheared surface) of the cover 14 is not plated. If the plating thickness is 10 μm or less, press working can be performed without any problem.
FIG. 2 is a view showing the seam-joined state of the cover 14 thus obtained, and 3 is a conventional seal frame to which nickel plating 18 has been applied.
Cover 1 according to the present invention is placed on this seal frame 3.
A pair of tapered roller electrodes 5 and 6 (not shown) are brought into contact with the peripheral edge of the cover 14 while holding the axes of the roller electrodes 5 and 6 parallel to the surface of the cover 14. The roller electrodes 5, 6 and the cover 14 are seam-joined while being moved relative to each other under a constant pressure. The seam joint includes a nickel-gold interdiffusion layer 19 made of plating material at the interface between the seal frame 3 and the cover 14, and a
It is formed from a nickel-gold fillet 20 due to the melting of the plating at the periphery of the nickel plating 16, and since nickel-gold forms a total solid solution with a minimum at 950°C, the melting point of the nickel plating 16 is 1455°C or the gold plating. It melts at a temperature lower than the melting point of 17, 1063°C, and has good fluidity. Therefore, the roller electrodes 5, 6
As a result of the compression, the water flows sufficiently into the peripheral end 12 of the cover 14 to form a good fillet 20. In addition, since it melts at a lower temperature than conventional nickel plating, it can be seamed with less seam welding current, suppressing the temperature rise of the semiconductor device package,
Damage to semiconductor elements can be reduced.

(Effect of the invention) The hermetically sealed semiconductor device package cover according to the invention has a nickel plating base on both sides except for the peripheral edge, and gold plating on top of the nickel plating with a total thickness of 3 to 10 μm. Since it is applied to the seam, it forms a total solid solution with a minimum at 950°C, which has better fluidity than conventional nickel plating, and the molten nickel on the top surface of the cover - The gold plating flows well into the circumferential edge of the cover to form a good fillet. Therefore, rust and discoloration do not occur in the seam joints in environmental tests such as constant temperature and humidity tests and salt spray tests, making it possible to provide a highly reliable semiconductor device with no deterioration in airtightness.

Further, since the cover according to the present invention has no plating on the peripheral edge of the cover, the plating thickness can be made uniform, and a cover with good seam bonding properties can be easily manufactured.

Furthermore, since it melts at a lower temperature than conventional nickel plating, it is possible to suppress the rise in temperature of the semiconductor device package, reduce damage to the semiconductor element, and save power consumption.

[Brief explanation of the drawing]

Fig. 1 shows a hermetically sealed semiconductor device package cover according to the present invention, Fig. a is a plan view thereof, and Fig. b
The figure is a sectional view taken along the line b-b of figure a, Figure 2 is a diagram of the seam joining state of the cover according to the present invention, Figure 3 is a schematic diagram for explaining the seam joining method, and Figure 4 is the seam of the cover. FIG. 5 is a sectional view of a conventional cover, and FIG. 6 is a sectional view of another conventional cover. 3...Seal frame, 12...Peripheral end, 14
...Cover, 16, 18...Nitsukerumetsuki, 1
7...Gold plating, 19...Interdiffusion layer, 20...
Fillet.

Claims (1)

[Scope of utility model registration request] In a hermetically sealed semiconductor device package in which a metal cover is placed on a seal frame provided at the open end of a ceramic container and the seal frame and cover are brought into contact with each other through a parallel gap seam, the peripheral edge of the cover is The base layer is nickel plating on both sides except for gold plating on top of which the sum of both is 3 to 10 μm.
A cover for a hermetically sealed semiconductor device package, which is characterized in that each cover is made to have the following characteristics.