JP2525232B2 - Ceramic package and method of manufacturing the same - Google Patents

Description

TECHNICAL FIELD The present invention relates to a ceramic package suitable for high heat dissipation for mounting on a semiconductor and a method for manufacturing the same.

[Prior Art] Alumina ceramics, which have been widely used as a packaging material, have a thermal conductivity of 0.05 cal / cm · sec because the packaging density of components has increased with the high integration of ICs and LSIs.
・ Since it is as small as ℃, it has poor heat dissipation. Conventionally, 42 alloy and Kovar, which have excellent properties such as a thermal expansion coefficient close to that of Si chips and high strength, were the mainstream materials for lead frames. Has a low thermal conductivity (42 alloy has 0.03ca
l / cm ・ sec ・ ℃), not suitable for heat dissipation lead frame. Therefore, there is a demand for a package having excellent heat dissipation by a method such as brazing a heat dissipation lead frame instead of ceramic on the die attach portion.

Copper-based lead frames have come to be used as a material excellent in heat dissipation and suitable for increasing integration density and surface mounting.

[Problems to be solved by the invention] However, Ag alloys for 42 alloy and Kovar (72% Ag
With 830 ° C high temperature brazing with eutectic Ag low), the difference in coefficient of thermal expansion between the ceramic and the copper lead frame is large, so cracks occur on the ceramic side due to residual stress, and lead frame softening causes poor handling. Because of this, the excellent material could not be utilized.

The present invention provides a ceramic package in which heat dissipation is further improved by using a material having excellent heat conductivity as a heat dissipation lead frame in a die attach portion of the ceramic package having poor heat conductivity, and a method of manufacturing the ceramic package. With the goal.

[Means for Solving the Problems] In order to achieve the above object, the first invention of the present invention is to print electric wiring with a high melting point metal on the ceramic green sheet surface and through holes and stack a plurality of the wirings at the same time. A ceramic package provided with a brazing material through a Ni-plated and / or Au-plated surface provided for sintering to form a laminated product and brazing the electric wiring surface and the lead frame of the laminated product, The lead frame is a hard copper lead frame plated with Ni and / or Au, and is a ceramic package characterized by including a soft low-temperature brazing material containing lead as a main component.

The second invention is a step of printing desired electric wiring on the ceramic green sheet surface and through holes with a high melting point metal paste, laminating a plurality of these and simultaneously sintering them into a laminated product, and the electric wiring surface of the laminated product. Ni and / or Au plating step, heating and attaching a desired low temperature brazing material to the plating surface of the electrical wiring surface of the laminate, and Ni and / or Au plating lead frame on the adhesion surface with brazing In the method of manufacturing a ceramic package manufactured by the step of, the lead frame is a hard copper lead frame and is brazed at a temperature of 300 to 450 ° C.

[Operation] In the above-mentioned structure, the hard copper lead frame of the first invention has excellent thermal conductivity (42 alloy 0.03 cal / cm · sec ·
In order to take advantage of the good handling characteristics after heat treatment with brazing, by using a soft low temperature brazing material containing lead as a main component (Brinell hardness 20 or less),
The residual stress due to the difference in thermal expansion between the ceramic and the lead frame is reduced, and the residual stress is absorbed by the brazing material layer to maintain quality reliability as a ceramic package.The brazing temperature of the lead frame is lower than that of Ag low. To

[Example] An example will be described.

An organic binder, a plasticizer, and a solvent are added to a crushed mixture of alumina powder and flux to form a slurry,
Tungsten, molybdenum powder for metallizing the ceramic green sheet formed by the doctor blade method or other ceramic green sheet forming method to a desired size by making a predetermined hole to form a through hole After printing electrical wiring with a paste whose main component is a refractory metal such as
Co-sintering to obtain a ceramic laminate with electrical wiring.

After that, the electric wiring surface is plated with Ni and optionally with Au, and then the low-temperature brazing material is selected from each of the examples and comparative examples (hard brazing material containing no lead) shown in Table 1. In a positive atmosphere (for example, an atmosphere of H ₂ 30% and N ₂ 70%), the maximum temperature was kept at 350 ° C. for 25 minutes to adhere the brazing material. After that, each of the examples and comparative examples shown in Table 2 was used as a heat dissipation lead frame material in a reducing atmosphere (for example, an atmosphere of H ₂ 20 to 40% and N ₂ 60 to 80%) at a temperature of 30.
It was kept at 0 to 450 ° C for 10 to 30 minutes, heated and brazed. However, the heating for attaching the brazing material may be omitted and the heating may be performed simultaneously with the heating of the heat dissipation lead frame material.

The examples are all hard copper lead frames, and the oxygen free copper (OFHC) of the comparative examples is a soft copper lead frame. Further, the quality of handling was judged by the Vickers hardness before and after the brazing heat treatment of the heat dissipation lead frame. That is, the hard copper lead frame of the example is slightly lower than the value of the conventional 42 alloy, but is good in handling. However, the soft copper lead frame became too soft after brazing and could not be handled.

The heat-dissipating ceramic package thus obtained is shown in (a) plan view and (b) bottom view of FIG. Also, the second
FIG. 3 shows a cross-sectional view of a main part and a cross-sectional view in which a circle portion is enlarged in detail.

Further, the airtightness and the presence or absence of cracks were examined and shown in Table 1. The examples all gave good results.
The lead-free low-temperature brazing material of Comparative Example had a high Brinell hardness and was not airtight. However, the soft copper lead frame, which had a defect in handling, had good airtightness and did not crack.

The size of each of these heat dissipation ceramic packages is a rectangle in which the length of one piece is about 5 mm or more, and if the length is less than 5 mm, no crack will be generated in the ceramic.

[Effects of the Invention] As described above, according to the present invention, a hard copper lead frame having good heat conductivity and sufficient hardness after brazing and having good handleability is provided with a soft low temperature brazing material. By doing so, it was possible to provide a ceramic package excellent in heat dissipation and a method of manufacturing the same, which satisfies the demands for high integration and increased mounting density of components.

[Brief description of drawings]

1 (a) and 1 (b) are a plan view (a) and a bottom view (b) of the ceramic package of this embodiment. FIG. 2 is a sectional view of the main part of the ceramic package of this embodiment. FIG. 3 is a detailed enlarged cross-sectional view of the circled portion in FIG. 1 ... Lead frame, 2 ... Alumina ceramic, 3
...... Low material, 4 …… metallized layer, 5 …… Ni plating and / or Au plating, 6 …… through hole part, 7 …… pad part, 8 …… wire bonding part.

Claims (2)

(57) [Claims] 1. A ceramic green sheet surface and through-holes are printed with electric wiring made of a high melting point metal, a plurality of the electric wirings are laminated and then simultaneously sintered to form a laminated product, and the electric wiring surface of the laminated product and a lead frame. Ni prepared for brazing and
In a ceramic package provided with a brazing material through a plated and / or Au-plated surface, the lead frame is a Ni-plated and / or Au-plated hard copper lead frame, and the brazing material is mainly lead. A ceramic package characterized by having a soft low-temperature brazing material as an ingredient. 2. A desired electric wiring is printed on the surface of the ceramic green sheet and the through hole with a high melting point metal paste,
A process of laminating a plurality of these and simultaneously sintering them into a laminated product, a process of plating the electric wiring surface of the laminated product with Ni and / or Au, and a desired low-temperature soldering process with the electric wiring surface of the laminated product as a plated surface. In a method of manufacturing a ceramic package, which comprises a step of heating and adhering a material and a step of brazing a lead frame having Ni and / or Au plating on the adhering surface, the lead frame is a hard copper lead frame, A method for manufacturing a ceramic package, which comprises brazing at a temperature of ~ 450 ° C.