JPH06151618A - Package for enclosing semiconductor devices - Google Patents

Abstract

PURPOSE:To maintain the hermeticity and bonding strength of the bonding part between the circuit substrate and the cap part by preventing tin in the solder from reaching the boundary surface between the nickel plating layer and the base metal. CONSTITUTION:The package for enclosing a semiconductor chip is provided with a ceramic substrate 8 for mounting the semiconductor chip and a cap part that is bonded to the ceramic substrate 8 via solder so as to hermetically seal the semiconductor chip inside. The ceramic substrate 8 has a sealing metallization layer 7 at the cap bonding surface. The sealing metallization layer 7 consists of a copper base metal layer 16 on which is formed a barrier layer 17 made of a nickel-chromium alloy, and a nickel plating layer 18 formed on top of the barrier layer 17.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor element housing package, and more particularly to a semiconductor element housing package in which a lid is joined to a circuit board via solder.

[0002]

2. Description of the Related Art Generally, a package for housing a semiconductor element mainly comprises a circuit board on which a semiconductor element is mounted and a lid joined to the circuit board. The lid is bonded to the sealing metal layer provided on the circuit board via solder, thereby hermetically sealing the semiconductor element inside.

FIG. 4 shows a sealing metal layer of a conventional semiconductor element housing package. Circuit board 29 made of an insulator
The sealing metal layer 27 formed on the circuit board 29 includes an adhesion layer 25 (thickness: 0.
6 μm), the underlying metal layer 26 made of copper (thickness 3.0 μm
m), nickel plating layer 2 made of nickel containing phosphorus
8 (thickness 0.8 μm) and gold plating layer 29 (thickness 0.2
μm) are laminated in this order.
The lid 23 is made of Kovar alloy and has a nickel plating layer 30 formed on the lower side surface. A solder layer 26 is provided between the lid 23 and the sealing metal layer 27 to join them.

[0004]

In the conventional package for accommodating a semiconductor element, when the heat generated in the semiconductor element heats the solder layer 26 for a long period of time, tin in the solder causes the tin in the solder to fall into the gold plating layer 29 and the nickel plating layer 28. Diffuse in. As the diffusion proceeds, tin reaches the interface between the nickel plating layer 28 and the base metal layer 26, and the thin and fragile compound layer 31
To form. As a result, when an external force or thermal stress due to heat generated by the semiconductor element is applied, peeling occurs at the interface between the base metal layer 26 made of copper and the nickel plating layer 28. Therefore, the airtight state of the package for housing the semiconductor element cannot be maintained, and if the peeling progresses, the lid may come off from the circuit board.

An object of the present invention is to prevent solder tin from reaching the interface between the nickel plating layer and the underlying metal layer, and maintain the airtightness and the joint strength of the joint portion between the circuit board and the lid. It is in.

[0006]

According to a first aspect of the present invention, there is provided a package for housing a semiconductor element, which is joined to a circuit board on which a semiconductor element is mounted by soldering to the circuit board so that the semiconductor element is hermetically sealed inside. And a lid body. The circuit board has a sealing metal layer including a base metal made of copper, a barrier layer made of a nickel-chromium alloy formed on the base metal, and a nickel plating layer formed on the barrier layer. It has on the joint surface with.

A semiconductor element housing package according to a second aspect of the present invention includes a circuit board on which a semiconductor element is mounted and a lid body joined to the circuit board via solder so as to hermetically seal the semiconductor element inside. I have it. The circuit board has a base metal made of copper and a thickness of 0.5 to 5 formed on the base metal.
It has a sealing metal layer including a nickel plating layer of 4.5 μm on the joint surface with the lid.

[0008]

In the package for accommodating a semiconductor element according to the first aspect of the present invention, a nickel-plating layer is provided between the base metal and the nickel plating layer.
A barrier layer made of a chromium alloy is formed. Therefore, even if tin diffuses from the solder layer into the nickel plating layer at a high temperature, the diffusion is stopped at the barrier layer and it is difficult to reach the underlying metal layer. Therefore, the airtightness and the joint strength of the joint between the circuit board and the lid are maintained.

In the sealing metal layer of the package for housing a semiconductor element according to the second invention, the thickness of the nickel plating layer is set in the range of 0.5 to 4.5 μm. Therefore, even if tin of the solder layer diffuses into the nickel plating layer at high temperature, the tin does not easily reach the interface between the nickel plating layer and the base metal layer. As a result, peeling at the interface is less likely to occur, and the airtightness and the joint strength of the joint between the circuit board and the lid are maintained.

[0010]

EXAMPLES First Embodiment FIG. 1 shows a package for housing semiconductor chip 1 to which an embodiment of the present invention is employed. The semiconductor element housing package 1 is mainly composed of a multilayer circuit board 2 and a lid 3. The semiconductor element 4 is mounted in the package 1 via the solder bumps 5. The semiconductor element 4
Is a bump mounting portion 1 arranged on the upper surface of the multilayer circuit board 2.
Connected to 2. The lid 3 is made of a Kovar alloy on which a nickel plating layer is formed. The lid 3 is
One of them is a box-shaped member having an opening, and is joined to the sealing metal layer 7 formed on the outer periphery of the upper surface of the multilayer circuit board 2 via the solder layer 6. The solder layer 6 and the sealing metal layer 7 hermetically seal the inside of the package 1.

The multilayer circuit board 2 includes a ceramic board 8 and
Thin film wiring part 9 formed in the central part on the ceramic substrate 8
And a sealing metal layer 7 formed on the outer peripheral portion of the ceramic substrate 8. Inside the ceramic substrate 8, a thick film wiring conductor 13 made of molybdenum, tungsten or the like is formed which is vertically communicated with each other by a through hole. The lower portion of the thick film wiring conductor 13 is an input / output terminal portion 13a exposed on the lower surface of the ceramic substrate 8, and an input / output pad 14 made of a nickel plating layer or the like is formed thereon.

The thin film wiring portion 9 is provided with three resin insulating layers 10 made of polyimide, and a thin film wiring layer 11 made of copper formed on both sides of each resin insulating layer 10. On the thin film wiring layer formed on the upper surface of the thin film wiring portion 9, a bump mounting portion 12 plated with nickel / gold is provided. Thin film wiring layer 1 formed on the upper surface of the ceramic substrate 8
1 is connected to the upper surface of the thick film wiring conductor 13. Further, the thin film wiring layers 11 are electrically connected to each other through through holes provided in the resin insulating layer 10.

The sealing metal layer 7 shown in FIG. 2 is an adhesion layer 1 made of chromium, which is sequentially arranged on the ceramic substrate 8.
5, a base metal layer 16 made of copper, a barrier layer 17 made of a chromium-nickel alloy, a nickel plating layer 18 containing phosphorus, and a gold plating layer 19. The adhesion layer 15 is for increasing the bonding strength between the base metal layer 16 made of copper and the ceramic substrate 8. The nickel plating layer 18 and the gold plating layer 19 are formed to strengthen the connection between the sealing metal layer 7 and the solder layer 6 (FIG. 1). The barrier layer 17 is formed to prevent the tin from reaching the base metal layer 16 when tin diffuses from the solder layer 6 (FIG. 1) into the nickel plating layer 18.

Next, a method of manufacturing the semiconductor element housing package 1 will be described. The ceramic substrate 8 is formed of a plurality of ceramic green sheets. The ceramic green sheet is subjected to an appropriate punching process, and then a metal paste made of a refractory metal powder such as tungsten and molybdenum is applied by a screen printing method. Next, a plurality of ceramic green sheets are laminated to form a ceramic green sheet laminate, which is fired at an appropriate temperature to form the ceramic substrate 8 including the thick film wiring conductor 13 therein.

Next, a copper layer is formed on the upper surface of the ceramic substrate 8 by vapor deposition, sputtering or the like. Subsequently, a photosensitive resist is applied, developed, and etched to form the first-layer thin-film wiring conductor 11 having a desired pattern. Next, a photosensitive polyimide paste is applied onto the ceramic substrate 8 by a spin coating method, and a series of treatments including baking, exposure, development and baking are continuously performed, and firing is performed in a furnace at about 400 ° C. in a nitrogen atmosphere. Then, the first resin insulating layer 10 is formed. Next, appropriate through holes are formed in the resin insulating layer 10. The second and third resin insulation layers 10 are 1
It is formed by the same method as that of the resin insulation layer. The second to fourth thin film wiring layers 11 are also formed by the same method as the first thin film wiring layer 11.

Next, the formation of the sealing metal layer 7 will be described. First, an adhesion layer made of chromium, a base metal layer made of copper, and a barrier layer made of a chromium-nickel alloy are sequentially formed on the ceramic substrate 8 by sputtering. Then, the adhesive layer 1 having a desired pattern is formed by applying a photosensitive resist, developing, and etching.
5, the underlying metal layer 16 and the barrier layer 17 are formed.

Subsequently, a nickel plating layer 18 containing phosphorus and a gold plating layer 19 containing phosphorus are formed by electroplating on the portion where the resist pattern is not formed. At this time, simultaneously, a nickel plating layer and a gold plating layer are formed on the input / output terminal portion 13a of the metallized wiring 13, and the input / output pad 14 is formed. When the resist layer is removed, the sealing metal layer 7 as shown in FIG. 2 is completed, and at the same time, the multilayer circuit board 2 is completed.

Next, the semiconductor element 4 having the solder bumps 5 formed thereon is mounted on the bump mounting portion. The semiconductor element 4 is fixed on the multilayer circuit board 2 by melting the solder bumps. Then, the lid 3 having the nickel plating layer is mounted on the sealing metal layer 7 via solder. In this state, the solder is melted by passing through a reflow furnace, and the lid 3 is fixed onto the multilayer circuit board 2. As a result, the semiconductor element 4 is hermetically sealed in the semiconductor element housing package 1.

Use of the obtained product has the following effects. When the semiconductor element 4 continues to operate, the heat generated there heats the solder layer 6. Then, tin in the solder layer 6 begins to diffuse into the gold plating layer 19 and the nickel plating layer 18. However, the diffused tin is blocked by the barrier layer 17 and hardly reaches the underlying metal layer 16. As a result, a compound layer is less likely to be formed between the nickel plating layer 18 and the underlying metal layer 16, and therefore the airtightness and the bonding strength of the sealing metal layer 7 are maintained well.

The thickness of the barrier layer 17 is 0.1 to 0.1.
It is preferably in the range of 1.0 μm in order to prevent tin diffusion. When the thickness is less than 0.1 μm, tin diffuses into the interface between the nickel plating layer 18 and the base metal layer 16. When the thickness is further reduced, a compound layer is formed at the interface and peeling occurs at the interface. On the other hand, barrier layer 1
If the thickness of No. 7 exceeds 1.0 μm, the internal stress increases and the adhesion strength decreases.

The barrier layer 17 and the nickel plating layer 1
The adhesion strength with 8 is improved by nickel in the barrier layer 17. Next, an experimental example will be described. The first
In the multilayer circuit boards used in the examples, the thickness of the barrier layer was changed, and the peeling of the interface between the underlying metal layer and the nickel plating layer, the diffusion of tin to the interface and the state of adhesion strength were investigated. Here, what was left high temperature at 175 ° C. for 1000 hours was examined. The results are shown in Table 1 below.

[0022]

[Table 1]

When the thickness of the barrier layer was in the range of 0.1 to 1.0 μm, peeling of the interface and diffusion of tin to the interface did not occur, and the adhesion strength was sufficient. When the thickness was 0.05 μm, diffusion of tin to the interface was observed. Thickness 0.03 μm
Then, a compound layer was formed by tin at the interface, and peeling of the interface was observed. On the other hand, if the thickness exceeds 1.0 μm,
The adhesion strength was significantly reduced due to the increase in internal stress. Second Embodiment FIG. 3 shows a sealing metal layer 7 formed on a ceramic substrate similarly to the above-mentioned embodiment. This sealing metal layer 7
Is mainly composed of an adhesion layer 15 made of chromium, a base metal layer 16 made of copper, a nickel plating layer 18 containing phosphorus, and a gold plating layer 19 which are sequentially formed on the upper surface of the ceramic substrate 8. Each of these layers is formed by a method similar to the method described in the above embodiment. Here, the nickel plating layer 18 is formed in the range of 0.5 to 4.5 μm. Since the thickness of the nickel plating layer 18 is 0.5 μm or more, even if tin penetrates into the nickel plating layer 18 from the solder layer as described in the above-mentioned embodiment, the tin does not penetrate the nickel plating layer 18 and the base metal. Compounds are unlikely to form at the interface with the layer 16. Therefore, in the same manner as in the above-mentioned embodiment, the sealing metal layer 7 maintains good airtightness and adhesion.

On the other hand, when the thickness of the nickel plating layer increases, the internal stress generally increases and the adhesion strength decreases.
However, since the thickness of the nickel-plated layer 18 is set to 4.5 μm or less, the adhesion strength will be somewhat reduced and no practical problem will occur. Next, an experimental example will be described. In the second example, the thickness of the nickel plating layer was changed, and the peeling of the interface between the base metal layer and the nickel plating layer, the diffusion of tin to the interface, and the state of adhesion strength were investigated.
Here, what was left high temperature at 175 ° C. for 1000 hours was examined. The results are shown in Table 2 below.

[0025]

[Table 2]

The nickel plating layer has a thickness of 0.5 to 4.5.
Within the range of μm, there was no interfacial peeling or diffusion of tin to the interface, and sufficient adhesion strength was obtained. 0.8μ thickness
At m, tin diffusion was observed at the interface. Thickness 0.4
At μm, a compound layer of tin was formed at the interface, and interfacial peeling was observed. On the other hand, if the thickness exceeds 4.5 μm,
The adhesion strength was extremely reduced due to the increase in internal stress.

[0027]

In the semiconductor element accommodating portion package according to the first invention, the barrier layer made of nickel-chromium alloy formed between the base metal of the sealing metal layer and the nickel plating layer prevents the diffusion of tin. Blocks and suppresses reaching the underlying metal. Therefore, interfacial peeling is unlikely to occur, and the airtightness and bonding strength of the sealing metal layer are maintained.

In the sealing metal layer of the package for housing a semiconductor element according to the second invention, the thickness of the nickel plating layer is set in the range of 0.5 to 4.5 μm. Therefore, it becomes difficult for tin to form a compound at the interface between the nickel plating layer and the base metal at high temperature. As a result, interfacial peeling is unlikely to occur, and the airtightness and bonding strength of the sealing metal layer are maintained.

[Brief description of drawings]

FIG. 1 is a partial vertical cross-sectional view of a semiconductor element housing package according to an embodiment of the present invention.

FIG. 2 is an enlarged partial view of FIG.

FIG. 3 is a diagram corresponding to FIG. 2 of another embodiment.

FIG. 4 is a diagram corresponding to FIG. 2 of a conventional example.

[Explanation of symbols]

 1 Package for Semiconductor Element Storage 2 Multilayer Circuit Board 3 Lid 4 Semiconductor Element 6 Solder Layer 7 Sealing Metal Layer 16 Base Metal Layer 17 Barrier Layer 18 Nickel Plating Layer

Claims (2)

[Claims] 1. A package for storing a semiconductor element, comprising: a circuit board on which a semiconductor element is mounted; and a lid body joined to the circuit board via solder so as to hermetically seal the semiconductor element inside, The circuit board has a sealing metal layer including a base metal made of copper, a barrier layer made of a nickel-chromium alloy formed on the base metal, and a nickel plating layer formed on the barrier layer. A package for housing a semiconductor element, characterized in that the package is provided on a joint surface with the lid. 2. A package for storing a semiconductor element, comprising: a circuit board on which a semiconductor element is mounted; and a lid body joined to the circuit board via solder so as to hermetically seal the semiconductor element inside, The circuit board has a sealing metal layer including a base metal made of copper and a nickel plating layer formed on the base metal and having a thickness of 0.5 to 4.5 μm on a joint surface with the lid. A package for housing a semiconductor element, which is characterized in that