JPS60120544A - Lead frame for semiconductor device - Google Patents

Abstract

PURPOSE:To make it possible to perform a rapid supersonic bonding in package assembling and mounting steps by forming lead frames for high class IC with a composite strip formed by coating an aluminum alloy foil on a Fe or Fe-Ni alloy substrate by a roll cladding method. CONSTITUTION:A lead frame formed by punching a composite strip formed by coating an aluminum alloy foil of 4-15mum thick formed by adding at least one of Cu, Mn, Si of 10% or lower or at least one or Mg, Zr, Be of 6% or lower to aluminum on a Fe or Fe-Ni alloy substrate by a roll cladding method has good productivity, and is adapted for high speed bonding at the package assembling and mounting step time.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Technical Field The present invention relates to a lead frame for a semiconductor device, which enables rapid ultrasonic bonding in a package assembly and mounting process.

(b) Technical background Conventionally, in individual ICs and hybrid ICs, the connection between semiconductor elements in the IC and lead frames forming external terminals is
Bonding wires such as U-line and N-line are used.

To bond these bonding wires to the lead frame, thermocompression bonding or ultrasonic thermocompression bonding is used for Au wires, and ultrasonic bonding is used for N wires.

On the other hand, the lead frame is made of negative metal if Au wire is used for the bonding wire A7, or Fe coated with N foil with a purity of 99% or more if N wire is used.
Alternatively, a composite strip made of a FeNi alloy substrate is used.

and Fe or Fe coated with the latter N foil.
M-wire bonding to a lead frame punched from a composite strip made of a Ni alloy substrate has excellent heat resistance, so it is often used in high-grade, highly reliable ICs.

However, a drawback is that the ultrasonic bonding takes more time than thermocompression bonding, and shortening the ultrasonic bonding time is an urgent need for increasing IC productivity.

However, the lead frame for ultrasonic bonding of N wires is F
A composite strip made by cladding an E or Fa Ni alloy substrate with N foil on the entire surface or in the form of a stripe is punched or etched into a predetermined lead frame shape.

The roll cladding method and the vapor deposition method are known methods for manufacturing such composite strips, but the vapor deposition method can only produce pieces of a certain length, whereas the roll cladding method can only produce long pieces in a continuous manner. It is widely used because of its productivity.

However, even when this roll cladding method is used, it is preferable that the cladding of the M foil be as thin as possible in order to prevent a failure rate (peeling) during high-speed bonding.

In addition, in a composite strip in which an Fe or Fe-Ni alloy substrate is clad with M foil in the form of a strip, when this is made into a lead frame of a predetermined shape, the N foil is attached to a predetermined part (i.e., the bonding position of the N wire). must be located,
For this purpose, the positional accuracy of the N foil at the time of roll cladding is important.

(c) Disclosure of the invention The present inventors have discovered that the above-mentioned Fe or Fe-N
Investigating from various angles the high-speed bonding performance (dependence on ultrasonic application time) with N-wire during the package assembly and mounting process, which is the most important point of lead frames made of composite strips made of i-alloy substrates clad with N-alloy foil. added.

As a result, the area as a lead frame in which stable wire bonding is possible greatly depends on the hardness of the N alloy foil in the composite strip, and this is because (1) an appropriate hardness range is required to stabilize bonding; (2) If it is too soft, it tends to cause peeling phenomenon, and if it is too soft, it tends to cause neck breakage. (3) The appropriate hardness range of N alloy foil has a close relationship with the ultrasonic application time. (4) The hardness is the hardness of the N alloy foil, and even if hardening is avoided by alloying the N alloy foil layer itself, or by reducing the thickness of the N alloy layer, That is Fe or F
e) Due to the influence of the Ni alloy substrate, similar effects can be obtained even if it is hardened; (5) When using N alloy foil, the IJ opening element added to M should be is N
Except for elements that are stronger and form a dense oxide film on the surface,
It has been observed that similar effects can be obtained with other solid solution hardening type and precipitation hardening type elements, and even when these elements are used (II).

Therefore, the inventors of the present invention conducted research in order to adopt the above-mentioned points in the production of lead frames for high-grade ICs, and arrived at the present invention.

That is, this invention provides N on a Fe or FeNi alloy substrate.
This is a lead frame made of a composite strip coated with alloy foil using a roll cladding method, and this coating includes coating both sides or one side of a substrate over the entire surface or partially in the form of stripes. The coating thickness must be c4 to 15μ after clad rolling, and the coating film must have a hardness of 40 to 60 (Vickers hardness) after heating in the package assembly and mounting process using this composite strip as a lead frame. This is a requirement.

Furthermore, when making N alloy foil, the addition element to N is 1
A solid solution hardening type containing at least one of 0% or less of 1, Zr or SL, or a precipitation hardening type of N containing at least 6% of 1, Zr or SL. Therefore, it is possible to select these and use them as a ternary or quaternary N alloy.

With the above-mentioned configuration, the A3 allows the coating thickness of the N alloy foil cladding on the substrate to be as thin as possible, enables high-speed bonding, and has a hardness of 40 Vickers hardness after heating during the package assembly and mounting process as a lead frame.
As a result of various studies on composite strips that can maintain a value of ~60, we found: In the molded lead frame, the hardness of the N film showed a value of 40 to Go even when heated at 400 to 450° C. for 10 to 30 minutes in the package assembly and mounting process F (7), indicating extremely stable bonding properties.

The same results were obtained when N alloy foil was used instead of N with a purity of 99.8%. However, the disadvantage of this steam name method is that it is expensive.

■ Lead frames made of composite strips obtained using the existing roll cladding method had unstable bonding properties.

This is because the Mm on the board is equivalent to conductive N with a purity of 99.3% or higher, so this N foil is softened by heating at 400-450°C for 10-30 minutes during the package assembly and mounting process. This is because the hardness of the N film after this step is 25 to 35, which is too soft.

■ N so that the apparent hardness remains 40 to 60 on Vickers hardness after the above heating in the package assembly and mounting process.
When a composite strip with a film thickness of 2 to 4 μm was prepared by the roll cladding method, the lead frame made of this composite strip showed extremely stable bonding properties.

However, since the thickness of the N film is thin, it is difficult to apply rearward tension during pressure contact, and as a result, the positional accuracy of N is poor and the production yield of lead frames is extremely poor.

■ Lead frames made from composite strips using N alloy foil with a film thickness of 15μ or more and a hardness of 40 to 60 after heating during the package assembly and mounting process had excellent bonding properties, but N alloy foil Since the metal was too large, the molding yield into lead frames was extremely poor due to flood distortion.

■ Use N alloy foil, film thickness 4-15μ, and hardness 40
Lead frames made from composite strips of .about.60 had excellent high-speed bonding properties and productivity.

The following considerations were obtained.

From the above, it was found that N containing at least one of 1, Mn, SL, etc., or 6% or less of 1, Zy, -, etc., was added to the Fe or Fo-NL alloy substrate. Lead frames made by coating alloy foil with a thickness of 4 to 15 μm using the 1-ruclad method and punching from composite strips have good productivity and are suitable for extremely high-speed bonding during package assembly and mounting. , it has been recognized that it has a positive effect on people.

The performance of the lead frame obtained according to the present invention and each lead frame compared with each other was compared, and the results shown in Table 1 were obtained.

Table 1: iq- ni 1 2 3 4 4 6 shi-8 ]] Ensemble 12 Giant Notes (1)... EC/V is 99.3% conductivity M.

(2)...N hardness is 1 straight according to Vickers order 11.

The appropriate composition of the N alloy used in the product of the present invention shown in the above table is N
-(1-6%) Mg-based, #-(0,001-0.1%)
1 series, M-(0.7~3.0%> Mn series, N-(1,
5-5%) SL system, Nl (0.1-0.5%) Z
Among these alloys, M-1, M-Zr, and M-Cm alloys are the most suitable composites for lead frames, especially in terms of high-speed bonding in one culm of package assembly and hardness after heating. It was recognized that it is an article.

It has also been found that equivalent characteristics can be obtained with ternary alloys such as 5, M-Zr, and even quaternary M alloys.

Note that the Fa-Ni alloy substrate used in this invention is Fe
A 36-55% NL alloy is optimal.

Patent applicant Sumitomo Electric Industries Co., Ltd. Agent Patent attorney Kazu 1) Showa procedure? (Written by Hosho on his own initiative) August 31, 1980 1. Display of the case 1988 Patent Application No. 228894 2. Name of the invention Lead frame for semiconductor device 3. Person making the amendment Relationship to the case Patent applicant address 5-15 Kitahama, Higashi-ku, Osaka Name (21)
3) Sumitomo Electric Industries, Ltd. 4, Agent Address: 1-18-18-6, Nakatsu, Oyodo-ku, Osaka, Contents of Amendment 1: The scope of the claims is amended as shown in the attached sheet.

2. Specification cylinder page 5, line 19 Correct "N alloy layer" to "M layer".

3, page 9, line 17, line 9, line 6, line 14 “1
Correct "5μ" to "15μm".

4. On page 7, lines 8 to 13, ``As a result of the above...'' is corrected to ``The result of various studies based on the above structure.''

5. Page 7, lines 14 and 20 Correct "99.8%" to "99.8% or more."

6, page 7, line 15 First, I corrected "M foil" to "N film."

7, page 7, line 15 Correct "1~4μ" to "1~4μm".

8, page 8, line 13 Correct "2~4μ" to "2~4μm".

9, page 8, line 20 First, correct "15 μm or more" to "15 μm or more."

n Page 9, line 4 Correct "flood" to "crud."

Claims: (A lead frame for a semiconductor device, characterized in that it is made of a composite shape in which an 11Fe or Fe NL alloy substrate is coated with N alloy foil by a roll cladding method.

(The lead frame according to claim 1, wherein both surfaces of the 21Fe or Fe NL alloy substrate are entirely or partially covered with N alloy foil.

(The lead frame according to claim 1, characterized in that one side of the 31Fe or Fe-NL alloy substrate is entirely or partially covered with N alloy foil.

(4) The lead frame according to claim 1, wherein the coating film made of N alloy foil has a thickness of 4 to 15 μnl after cladding rolling.

(5) The coating film made of N alloy foil has a Vickers hardness of WI! of 40 to 60 after heating in the package assembly and mounting process. Claim 1 characterized in that it has a degree of
Lead frame as described in section.

(6) The lead frame according to claim 1, characterized in that the N alloy foil is of a solid solution hardening type containing 10% or less of N, 1, or at least one type of Si.

(Strength) The lead frame according to claim 1, characterized in that the N alloy foil is of a precipitation hardening type containing 6% or less of at least one of 1, Zr, or - in N.

(I volunteered to write the procedure correction) September 4, 1982 Commissioner of the Patent Office

Claims (1)

[Scope of Claims] A lead frame for a semiconductor device comprising a composite strip in which a fil Fe or Fe-Ni alloy substrate is coated with N alloy foil by a roll cladding method. (The lead frame according to claim 1, characterized in that both surfaces of a 21Fe or Fe-NL alloy substrate are entirely or partially covered with N alloy foil. The lead frame according to claim 1, wherein the lead frame is coated with N alloy foil.[The coating film made of 41A & alloy foil has a thickness of 4 to 15μ after clad rolling The lead frame according to claim 1. (5) The claim characterized in that the coating film made of N alloy foil has a Vickers hardness of 40 to 60 after heating in the package assembly and mounting process. The lead frame according to claim 1. Claim 1, characterized in that the +61 A1 alloy foil is a solid solution hardening type in which M contains 10% or less of at least one of 5, 1, or Sl. (7) A precipitation hardening type N alloy foil containing at least one of 1.7.r or i in an amount of 6% or less is used as the N alloy foil. The lead frame described in item 1.