JPH09296237A - Metallic substrate material for semiconductor packaging - Google Patents

Abstract

PROBLEM TO BE SOLVED: To increase the strength and thermal conductivity of a metallic substrate for a plastic package prepared by sealing semiconductor chips adhered to a metallic substrate with thermosetting resin. SOLUTION: This material has a composition consisting of 0.05-3.5% Fe, 0.01-0.4%, P, and the balance Cu with inevitable impurities and containing, if necessary, (a) 0.01-2.0% Zn and/or 0.05-3.0% Sn and (b) 0.01-2.0%, in total, of Mg, Co, Pb, Zr, Cr, Mn, Al, Ni, Si, In and/or B.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a metal substrate material for semiconductor packaging, which is made of a copper alloy. More specifically, the package is a metal substrate to which a semiconductor chip is adhered and a heat for sealing the semiconductor chip. The present invention relates to an improvement of a metal substrate material of a package which is composed of a curable resin and which requires strength and heat dissipation of the metal substrate.

[0002]

2. Description of the Related Art As a structure of a semiconductor plastic package, a DIP which is a lead insertion mounting device was used before.
(Dual inline package) was the mainstream,
Due to the demand for higher packaging density, the S
OP (Small Outline Package), QFP (Quad Flat Package), etc. are gradually becoming the mainstream, and especially QFP which can cope with an increase in input / output signals is widely used. A lead frame is usually used in these packages, and the chip is often adhered onto the die pad and sealed with a resin.

On the other hand, recently, surface mount type area packages such as BGA (ball grid array) have been developed and adopted for microprocessors or high-speed logic semiconductors, and their applications will grow rapidly in the future. Is expected. In the area package, in addition to the case where a semiconductor chip is bonded to a printed circuit board, the case where a TAB (tape automated bonding) method is used, and the like, the chip is bonded onto a metal substrate from the viewpoint of heat dissipation. There is. Hereinafter, an example will be described.

1 and 2 show an example of a plastic package for a microprocessor, which is a schematic view of a cross section of the package. Figure 1 shows P using wire bonding
GA (pin grid array) and BGA, as shown in FIG.
Is a BGA using flip chip connection. A semiconductor chip 2 is adhered to a metal substrate 1 which is called a heat spreader (Nikkei Microdevice, 19
(Quoted from the April 1996 issue, pp. 90-96). In the figure, 3 is a sealing resin, 4 is a printed circuit board, 5 is a pin, 6 is a bump, 7
Is the bonding wire and the arrow is the heat flow. The metal substrate 1 shown in FIGS. 1 and 2 has a semiconductor chip support and a heat dissipation function. The metal substrate 1 is incorporated in the plastic package by utilizing the fact that the heat dissipation characteristic is superior to that of the usual ceramics for substrates.

On the other hand, in a conventional package, the chip may be adhered to a metal substrate having a shape different from that of the lead frame from the viewpoint of heat dissipation. Thus, unlike conventional packages, several packages have been proposed and put into practical use in which a chip is bonded and sealed on a metal substrate that is not a so-called lead frame.

[0006]

DISCLOSURE OF THE INVENTION The inventor of the present invention has considered the demands to be imposed on this type of package in the following manner. First, it is required to sufficiently dissipate the heat generated from the above-mentioned semiconductor chip, but there is the background that the above package has been put into practical use due to the improved heat dissipation of the resin package material. There is an aspect that a considerable heat dissipation property is achieved by using a metal having excellent properties as a heat dissipation medium. However, it is expected that the amount of heat generated from the semiconductor chip will increase due to the higher integration and miniaturization of the semiconductor chip. Therefore, it is necessary to efficiently dissipate the heat radiated from the entire back surface of the semiconductor chip. It is thought that the thermal management from will be important. In order to dissipate heat from the semiconductor chip, it is necessary that the adhered metal substrate has sufficient thermal conductivity and the semiconductor chip and the substrate are sufficiently bonded. If these are missing, the temperature of the chip will rise. Significantly, the function may be impaired.

On the other hand, the metal substrate exposed to a temperature rise during the packaging process or during operation has a different coefficient of thermal expansion from the resin or sealing resin for joining the semiconductor chips, and as a result, stress is generated inside the metal substrate. However, the metal substrate may be subtly deformed, and the reliability of the package may be impaired. Further, if the material strength of the metal substrate is weak during the assembly process, the metal substrate loses the flatness, so that the adhesive surface with the resin becomes incomplete and the heat dissipation and adhesive strength may deteriorate. For this reason, the metal substrate material is also required to have sufficient strength.

The present invention has been made in response to the above demands, and an object thereof is to provide a semiconductor package using a Cu alloy which is advantageous in heat dissipation of the package and has sufficient strength. There is.

[0009]

Means for Solving the Problems Accordingly, the present inventors have:
As a result of repeated research to develop a copper alloy suitable for a metal substrate of a package (hereinafter referred to as “resin-encapsulated package”) including a metal substrate to which a semiconductor chip is bonded and a thermosetting resin that seals these, After adjusting the composition of the —Fe—P-based alloy, Zn and / or Sn may be added if necessary, and Mg, Co, Pb, Z may be added as necessary.
It has been found that by containing r, Cr, Mn, Al, Ni, Si, In and / or B, a material suitable for a metal substrate material for resin-sealed packaging can be provided.

The present invention has been completed based on the above findings, and 0.05 to 3.5% by weight of Fe in a copper alloy (the percentages below refer to% by weight unless otherwise specified).
And P in an amount of 0.01 to 0.4%, and optionally 0.05 to 5% of Zn or 0.05 to 3% of Sn, and 1 or 2 of them, and further, if necessary. Mg,
Co, Pb, Zr, Cr, Mn, Al, Ni, Si, I
Sufficient thermal conductivity as a base material for semiconductor packaging by containing 0.01 to 2% of n or B in a total amount and adjusting the balance to Cu and its unavoidable impurities. The present invention relates to a copper alloy characterized by having both strength and strength.

Since the thermal conductivity, which is one of the performances of the substrate, has a direct proportional relationship with the electrical conductivity according to Wiedemann-Franz's law, it is possible to predict the heat dissipation characteristic of the copper substrate from many electrical conductivity data. . An additional element may be added in order to increase strength, which is another performance of the substrate, but in this case, the electric conductivity decreases. The alloy composition of the present invention was selected after careful investigation to achieve a high level of both properties in which one property is improved and the other is decreased.

Next, the reason why the component composition of the copper alloy is limited as described above in the present invention will be explained together with its action.

Fe Fe has an action of improving the strength and heat resistance of the alloy by forming an intermetallic compound with P alone or P, but if the content is less than 0.05%, a desired high strength can be obtained. However, if Fe is contained in a proportion exceeding 3.5%, the workability is lowered and the conductivity is remarkably lowered.
The Fe content was set to 0.05% or more and 3.5% or less.

P P forms an intermetallic compound with Fe to improve the strength without lowering the conductivity, but if it is less than 0.01%, there is no effect, and if it exceeds 0.4%, the workability is remarkable. The P content is 0.0
It was set to 1 or more and 0.4% or less.

Zn Zn acts as a deoxidizing agent at the time of melt casting and has an effect of improving the heat-resistant peeling property of plating, but if the content is less than 0.05%, the effect is not remarkable.
When the content exceeds 5%, the conductivity is remarkably lowered, and stress corrosion cracking is likely to occur. Therefore, the Zn content is set to 0.05% or more and 5% or less.

Sn Sn has the function of ensuring the strength of the alloy, but if the content of Sn is less than 0.05%, the strength is not sufficiently improved, while if the Sn content exceeds 3%, the conductivity decreases. And the hot workability of the alloy are deteriorated.
The n content was determined to be 0.05% or more and 3% or less.

Mg, Co, Pb, Zr, Cr, Mn, A
1, Ni, Si, In or B Mg, Co, Pb, Zr, Cr, Mn, Al, Ni, S
Since i, In or B has the same effect as improving the strength of the copper alloy, one or more kinds of them are added if necessary. However, the total content is 0.01
If the total content is less than 2%, the effect of improving the strength cannot be obtained, while if the total content exceeds 2%, the conductivity is significantly reduced.
The total content of these is set to 0.01 to 2%.

The strength required for the metal substrate according to the present invention is, in addition to the deformation resistance described in (a) Paragraph No. 0007, (b) the performance for realizing the thinning of the substrate and the like. These can be evaluated by the magnitude of strength. The preferred tensile strength is 450 N / mm ² or more. On the other hand, the conductivity, which is an index of thermal conductivity, is 45% I.
It is preferably ACS or more. Furthermore, it is preferable that the crystal grain size after solution treatment that affects the bendability is 15 μm or less. Next, the tempering state of the material needs to be an aging treatment state, but the final finishing state may be any of cold rolling finish, aging finish, and strain relief annealing finish. Hereinafter, the present invention will be described in more detail with reference to examples.

[0019]

Example A copper alloy having various component compositions shown in FIG. 3 (Table 1) was melted in a high frequency melting furnace and cast into an ingot having a thickness of 20 mm. The melt casting was performed in the atmosphere. next,
This ingot was hot-rolled at 800 to 950 ° C. to a plate thickness of 8 mm, chamfered to remove scale on the surface, and then cold-rolled to form a plate having a thickness of 2 mm. Then 3
After annealing at a temperature of 50 to 900 ° C. for 1 hour to adjust the crystal grain size to about 5 to 10 μm, cold rolling was performed to 0.5 mm. After further aging at a temperature of 350 to 600 ° C. for 5 hours, it was cold-rolled into a plate of 0.25 mm.

Various properties of each of the plate materials thus obtained were evaluated. To measure tensile strength and elongation,
A tensile test in the rolling parallel direction was performed using a JIS No. 13 tensile test piece. The thermal conductivity was evaluated by the value of electric conductivity, and the specific resistance was measured by the four-terminal method, and the electric conductivity (% IACS) was obtained by using it. The heat resistance peeling resistance of the plating is 1 to after the copper undercoat of 0.5 to 0.8 μm is applied to the test material.
A width of 10 mm for a product that is electroplated with 60 μm Sn-40% Pb solder of 1.5 μm and then heat-reflowed.
After cutting to a length of 100 mm at 150 ° C for a predetermined time (100
Each time, heating was performed, 90 ° bending on one side was performed once reciprocally with a bending radius of 0.25 mm (= plate thickness), and the vicinity of the bent portions on the front and back surfaces was observed from a 20 times visual field to confirm the presence or absence of plating peeling.
The heat resistance was evaluated by heating at various temperatures for 5 minutes, and the temperature at which the Vickers hardness became 1/2 that before heating was determined as the semi-softening temperature.

As can be seen from Table 1, the alloys of the present invention have excellent strength, conductivity and heat resistance, and those containing Zn are also excellent in heat resistant peeling resistance. On the other hand, the comparative alloy No. 1 is F for the alloy of the present invention
Since e is high, the strength is high, but the elongation is low, and the conductivity is poor. Comparative alloy No. No. 2 is Sn, No. 3 has a high Zn content and thus has poor conductivity. Comparative alloy No. Since No. 4 does not contain P, the strength is poor. Comparative alloy No. Since No. 5 has a high P, the conductivity and the heat resistant peeling resistance of the plating are poor.

[0022]

As described above, the copper alloy of the present invention is
It has excellent thermal conductivity and strength, as well as excellent heat resistance and plating heat-resistant peeling property, and is suitable as a substrate material for semiconductor packaging.

[Brief description of drawings]

FIG. 1 is a schematic view of a cross section of a plastic sealed package.

FIG. 2 is a schematic view of a cross section of a plastic sealed package.

FIG. 3 is a table (Table 1) showing alloy compositions and properties of the present invention and comparative examples.

[Explanation of symbols]

 1 heat spreader (metal substrate) 2 semiconductor chip 3 sealing resin 4 printed circuit board 5 pins 6 solder bumps 7 bonding wire

Claims (4)

[Claims] 1. A material of the metal substrate of a plastic package obtained by sealing a semiconductor chip adhered on the metal substrate with a thermosetting resin is Fe: 0.05 in weight ratio.
To 3.5%, P: 0.01 to 0.4%, the balance being Cu and its unavoidable impurities, and a copper alloy having excellent thermal conductivity and strength. Metal substrate material for welding. 2. A material of the metal substrate of a plastic package obtained by sealing a semiconductor chip adhered on the metal substrate with a thermosetting resin is Fe: 0.05 in weight ratio.
.About.3.5%, P: 0.01 to 0.4%, and further contains one or two of 0.05 to 5% Zn or 0.05 to 3% Sn, A metal substrate material for semiconductor packaging, wherein the balance comprises Cu and its unavoidable impurities, and a copper alloy having excellent thermal conductivity and strength. 3. The weight ratio of the material of the metal substrate of the plastic package obtained by sealing a semiconductor chip adhered on the metal substrate with a thermosetting resin is Fe: 0.05.
.About.3.5%, P: 0.01 to 0.4%, and further contains Mg, Co, Pb, Zr, Cr, Mn, Al, Ni, S.
The total amount of at least one of i, In, and B is 0.01 to
A metal substrate material for semiconductor packaging, containing 2%, the balance being Cu and inevitable impurities thereof, and a copper alloy having excellent thermal conductivity and strength. 4. The metal substrate material of a plastic package obtained by sealing a semiconductor chip adhered on a metal substrate with a thermosetting resin, in a weight ratio, Fe: 0.05-.
3.5%, P: 0.01 to 0.4%, and further contains one or two of 0.05 to 5% Zn or 0.05 to 3% Sn, and Mg, Co,
0.01 to 2% of Pb, Zr, Cr, Mn, Al, Ni, Si, In or B is contained in a total amount of 0.01 to 2%,
A metal substrate material for semiconductor packaging, wherein the balance comprises Cu and its unavoidable impurities, and a copper alloy having excellent thermal conductivity and strength.