JPH09296238A - 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 on a metallic substrate with thermosetting resin. SOLUTION: This material has a compsn. contg. 0.8 to 4% Sn and 0.01 to 0.4% P, contg., at need, 0.05 to 1% Ni and/or 0.01 to 0.4% Zn, T, Zr, Cr, Mg, Mn, Fe, Co, Al, Be, Si and/or B by 0.01 to 1%, and the balance Cu with inevitable impurities.

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. This example will be described below.

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, Cu After adjusting the composition of the —Sn—P-based alloy, Ni and / or Zn may be added if necessary, and Ti, Zr, Cr, M may be added as necessary.
It has been found that the inclusion of g, Mn, Fe, Co, Al, Be, Si and / or B can provide a material suitable for a metal substrate material for resin-sealed packaging.

The present invention has been completed on the basis of the above-mentioned findings, and contains 0.8 to 4% Sn and 0.01 to 0.4% P in a copper alloy, and 0 if necessary. .05
1 to 2% of Ni or 0.01 to 3% Zn, and if necessary, Ti, Zr,
0.01 to 1% in total of one or more of Cr, Mg, Mn, Fe, Co, Al, Be, Si or B,
The present invention relates to a copper alloy which has sufficient thermal conductivity and strength as a base material for semiconductor packaging by adjusting the balance to be Cu and its unavoidable impurities.

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.

Sn Sn has the function of ensuring the strength of the alloy, but if its content is less than 0.8%, the desired strength cannot be obtained even with the combined addition of other components. If Sn is contained in a proportion of more than 4%, the thermal conductivity decreases, so
Was determined to be 0.8% or more and 4% or less. Preferably, the Sn content is 1.0 to 2.5%.

P P has the function of ensuring the strength and heat resistance of the alloy, but if the content of P P is less than 0.01%, the desired strength and heat resistance improving effect of P containing cannot be obtained, while P containing When the content is 0.4% or more, the thermal conductivity is significantly lowered regardless of the Sn content, so the P content is 0.0
It was set to 1% or more and 0.4% or less. A preferable P content is 0.02 to 0.2%.

Ni Ni secures the strength of the Sn—P-based copper alloy, and
It has the effect of improving the heat-resistant peeling property of the plating, and also has the effect of refining the crystal grain size during recrystallization annealing, but if its content is less than 0.05%, the desired strength due to the Ni content, plating The effects of improving the heat-resistant peeling property and refining the crystal grains cannot be obtained. On the other hand, when the Ni content exceeds 1%, the thermal conductivity is remarkably reduced regardless of the Sn content. It was defined as 0.05 or more and 1% or less. The preferable Ni content is 0.1 to 0.5%.

Zn Zn has a function of securing the strength of the Sn—P-based copper alloy and improving the heat-resistant peeling property of the plating like Ni, but if the content thereof is less than 0.01%, it is desirable due to the Zn content. The effect of improving the strength and the plating heat resistance cannot be obtained, and when the Zn content exceeds 3%, the thermal conductivity is remarkably reduced. Therefore, the Zn content is set to 0.01 or more and less than 3%. The preferable Zn content is 0.05 to 1.0%.

Ti, Zr, Cr, Mg, Mn, Fe, C
o, Al, Be, Si or B Ti, Zr, Cr, Mg, Mn, Fe, Co, Al, B
Since e, Si, and B have an effect of improving the strength of the Sn-P-based copper alloy and the like, one or more kinds of them are added if necessary. However, the total content is 0.0
If it is less than 1%, the effect of improving strength cannot be obtained, while if the total content exceeds 1%, the conductivity is remarkably reduced. Therefore, the total content is defined as 0.01 or more and 1% or less. It was

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. These can be evaluated by the magnitude of strength. And the preferable tensile strength is 500 N / mm ² or more. On the other hand, the conductivity, which is an index of thermal conductivity, is 20% I.
It is preferably CAS or more. The grain size is related to bending workability, but is preferably 15 μm or less. Next, the tempering state of the material needs to be an annealed state, but the final finishing state may be any of cold rolling finish, recrystallization annealing finish, and strain relief annealing finish. Hereinafter, the present invention will be described in more detail with reference to examples.

[0019]

[Examples] Figures 3 and 4 in a high-frequency melting furnace (Tables 1-1 and 2)
Copper alloys having various component compositions shown in Table 1 were melted and cast into an ingot having a thickness of 20 mm. This ingot was homogenized and annealed at 700 ° C. for 4 hours, then faced, and cold-rolled to a thickness of 2 mm. After that, recrystallization annealing was performed at a temperature of 450 to 650 ° C. for 1 hour to adjust the crystal grain size to 10 to 20 μm, and then cold rolling was performed to 0.5 mm. And then 3
After performing recrystallization annealing at a temperature of 50 to 600 ° C. for 1 hour to adjust the crystal grain size to 5 to 10 μm, cold rolling is performed to 0.2.
It was a 5 mm plate.

Various properties of each plate material thus obtained were evaluated. For the measurement of tensile strength and elongation, J
A tensile test in the rolling parallel direction was performed using IS13 tensile test pieces. Thermal conductivity is to be evaluated by the value of conductivity,
The specific resistance is measured by the 4-terminal method, and the conductivity (%
IACS) was determined. The heat-resistant peeling resistance determined for reference is 10 mm wide for the test material after copper undercoating of 0.5 to 0.8 μm, electroplating of tin of 1 to 1.5 μm, and then heat reflow treatment. , Length 100 mm
After cutting, it is heated at 150 ° C for a predetermined time (every 100 hours), and one side is bent 90 ° at a bending radius of 0.25 mm (= plate thickness) once. Was observed to confirm the presence or absence of peeling of the plating. The heat resistance was evaluated by heating for 5 minutes at various temperatures and determining the temperature at which the Vickers hardness became 1/2 that before heating as the semi-softening temperature.

As can be seen from Tables 1-1 and 2, the alloys of the present invention have excellent strength and electrical conductivity, and those containing Ni or Zn are also excellent in the heat resistant peeling resistance of the plating. On the other hand, the comparative alloy No. 1 to No. Four
Is the No. of the alloy of the present invention. Although some of the component compositions are different from those of No. 1, alloy No. 1 of the present invention. Compared with No. 1, comparative alloy No. No. 1 has a low Sn content and thus has poor strength. Comparative alloy N
o. Since No. 2 does not contain P, it has poor heat resistance and strength. Comparative alloy No. No. 3 has a high Sn content and therefore has a poor electrical conductivity. Comparative alloy No. In No. 4, since P is high, the conductivity is poor. Comparative alloy No. No. 5 has an inferior electric conductivity because it contains subcomponents exceeding the concentration range of the present invention. Comparative alloy No. 6 and N
o. No. 7 has a high conductivity because Ni and Zn are high, respectively.

[0022]

As described above, the copper alloy of the present invention is
It has excellent thermal conductivity and strength as well as excellent plating heat resistance peeling property, and is suitable as a metal substrate material for resin-sealed 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 chart showing the alloy composition and properties of the present invention (Table 1-
1).

FIG. 4 is a chart showing the alloy composition and characteristics of a comparative example (Table 1-
2).

[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, in a weight ratio of Sn: 0.8 to.
4%, P: 0.01 to 0.4%, the balance consisting of Cu and its unavoidable impurities, and a copper alloy excellent in thermal conductivity and strength, for semiconductor packaging. Substrate material. 2. The material of the metal substrate of a plastic package obtained by sealing a semiconductor chip bonded on a metal substrate with a thermosetting resin is Sn: 0.8-
4%, P: 0.01 to 0.4%, further 0.0
5% to 1% Ni or 0.01% to 3% Zn
A metal substrate material for semiconductor packaging, characterized by containing one or two kinds, the balance being Cu and inevitable impurities thereof, and being made of a copper alloy excellent in thermal conductivity and strength. 3. The material of the metal substrate of a plastic package obtained by sealing a semiconductor chip adhered on a metal substrate with a thermosetting resin is Sn: 0.8-
4%, P: 0.01 to 0.4%, Ti,
Zr, Cr, Mg, Mn, Fe, Co, Al, Be, S
i or B is contained in a total amount of 0.01 to 1%, and the balance is Cu and its unavoidable impurities.
A metal substrate material for semiconductor packaging, comprising a copper alloy having excellent thermal conductivity and strength. 4. A plastic package obtained by encapsulating a semiconductor chip adhered on a metal substrate with a thermosetting resin, the substrate material being Sn: 0.8 by weight ratio.
.About.4%, P: 0.01 to 0.4%, and further,
It contains one or two of 05 to 1% Ni or 0.01 to 3% Zn, and contains Ti, Zr, and C.
It contains 0.01 to 1% of one or more of r, Mg, Mn, Fe, Co, Al, Be, Si or B in a total amount, the balance being Cu and its unavoidable impurities, and A metal substrate material for semiconductor packaging, which is made of a copper alloy having excellent strength.