JPH04320055A - Lead frame and semiconductor package - Google Patents

Abstract

PURPOSE:To increase adhesive properties with sealing resin and to improve crack resistance and moisture resistance reliability of a resin-sealed semiconductor package by covering a surface of a lead frame with special polysilazane. CONSTITUTION:A material of a lead frame is formed of materials such as Fe-Ni alloy such as 42 alloy, a Cu-based alloy, etc., Polysilazane covering the frame is represented by a formula, where its average molecular weight is desirably 100-100000. The polysilazane is used by diluting with inactive solvent such as benzene, toluene, etc., but 100% polysilazane may be used. After the frame is covered with the polysilazane, the polysilazane is crosslinked or condensed by baking to form a stable film. A silicon chip 4 is wire bonded on a stage 2 in the frame 1 in which the polysilazane 3 is baked, and then sealed with epoxy-based sealing resin 6 after wire bonding 5 to manufacture a semiconductor package.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lead frame on which a semiconductor chip is mounted and a semiconductor package sealed with resin using this lead frame.

0002

[Prior Art] In recent years, semiconductor packages in which a semiconductor chip is mounted on a lead frame and then sealed with epoxy resin, etc., have been developed using ceramics, which have improved moisture resistance and reliability, are easy to mass produce, and are relatively low cost. It has been put into practical use and is increasing in both quantity and overwhelming the other packages. but,
When these resin-sealed semiconductor packages are left in the air, the sealing resin absorbs moisture, and the interface between the resin and lead frame peels off due to thermal shock when soldering to a printed circuit board, causing cracks in the resin. There have been problems such as generation of problems and damage to the functions of semiconductor devices. In order to solve this phenomenon, attempts have been made to reduce the moisture absorption of the epoxy sealing resin, improve crack resistance, and improve adhesion to the lead frame, as well as improve the lead frame.

0003

[Problems to be Solved by the Invention] In order to improve the adhesion between the lead frame and the sealing resin, various measures have been considered from the lead frame side. For example, a method of treating the surface of a lead frame with a silane coupling agent (JP-A-56-164,564, JP-A-5
7-152,157), a method of forming fine irregularities on the surface of a lead frame (Japanese Patent Application Laid-Open No. 115-1988)
51, Japanese Unexamined Patent Publication No. 2-285,662) and a method of coating with polyimide have been proposed. However, even with these methods, problems remain, such as when a moisture-absorbed package is exposed to thermal shock, the interface between the lead frame and the resin partially peels off, causing cracks and impairing moisture-resistance reliability. The present invention has been made in view of these problems, and an object of the present invention is to provide a lead frame and a semiconductor package that have excellent adhesion, crack resistance, and moisture resistance reliability.

0004

[Means for Solving the Problems] As a result of intensive studies to solve the above-mentioned problems, the present inventors have developed a lead frame whose surface is coated with a specific polysilazane, which is compatible with a sealing resin. We have discovered that a semiconductor package with excellent adhesion, in which a semiconductor chip is mounted on this lead frame and sealed with resin, has extremely good crack resistance and moisture resistance reliability, and has thus arrived at the present invention. That is, the gist of the present invention is as follows.

The first invention is a lead frame whose surface is coated with polysilazane having a repeating unit represented by the following formula [Formula 2].

[0006]

[Formula 2] (In the formula, R1, R2 and R3 are each a hydrogen atom, an alkyl group, an alkenyl group, a cycloalkenyl group, an amino group, an alkylamino group, an alkylsilyl group, or a group other than these groups that represents silicon in the main chain and There is a group in which the group directly bonded to nitrogen is carbon. However, at least one of R1, R2 and R3 is a hydrogen atom.)

A second invention is a resin-sealed semiconductor package characterized in that a semiconductor chip is mounted on the lead frame of the first invention and sealed with resin.

The present invention will be explained in more detail below. As the material of the lead frame of the present invention, a known lead frame material such as an iron/nickel alloy such as 42 alloy or a copper alloy is used. The structure of the lead frame is not particularly limited as long as it is a lead frame for a resin-sealed semiconductor package. DIP (Dual In-
linePackage, dual in-line package), SIP (Single In-line Pa
ckage, single inline package), ZI
P (Zig-Zag In-line Package
, zigzag in-line package), SOP (Sm
all Outline Package, SOJ (Small
Outline J-lead Package,
Small Outline J- Lead Package)
, QFP (Quad Flat Package,
quad flat package) or PLCC (P
Lastic Leaded Chip Carrier
This applies to all ordinary resin-sealed semiconductor packages such as plastic leaded chip carriers. In addition, TAB (Tape Automated Bon
ding, tape automated bonding)
, COL (Chip on lead) or LOC (Lead on Chip)
, lead-on-chip) and similar components including metal leads and their semiconductor packages are also included in the present invention.

The polysilazane coated on the lead frame of the present invention is represented by the above formula [Formula 2], and the molecular structure and manufacturing method are not limited. For example, polysilazane obtained by reacting dihalosilane and ammonia in an ether solvent (US Pat. No. 4,397,828), polysilazane obtained by reacting dihalosilane with a base to form an adduct, and then reacting with ammonia. N-methylpolysilazane obtained by reacting dihalosilane and methylamine in an ether solvent (Japanese Patent Publication No. 64-500,0)
31 Specification), and S-methylpolysilazane obtained by reacting methyldihalosilane and ammonia in a dichloromethane solvent (U.S. Pat. No. 4,482,669).
etc. can be mentioned.

The polysilazane used has a number average molecular weight of 1
A value in the range of 00 to 1,000,000 is preferable. Polysilazane is generally used diluted with a solvent inert to polysilazane, such as benzene, toluene, xylene, etc., but 100% polysilazane can also be used. The method of coating the lead frame with polysilazane is not particularly limited, and methods such as dipping and spin coating are possible. To adjust the film thickness,
The solvent dilution concentration may be determined depending on the coating method. It may be coated repeatedly.

On the other hand, since polysilazane lacks stability as it is, it reacts with moisture in the air and deteriorates, which may cause problems in the properties of polysilazane over time. Therefore, it is necessary to perform firing as a stabilizing treatment. This baking treatment crosslinks or condenses the polysilazane to form a stable film. The firing conditions are preferably set at a temperature increase rate of 0.1 to 50°C/min, more preferably 1 to 10°C/min. The firing temperature is in the range of 100 to 500°C, more preferably 300 to 400°C. As the heat source, resistance heating or high frequency heating can be used. Note that the firing atmosphere may be air, an inert gas such as nitrogen gas, a reducing gas such as hydrogen or ammonia, or a mixed gas thereof.

The portion of the lead frame to be coated with polysilazane is not particularly limited as long as it is basically a portion that will form an interface with the sealing resin in a subsequent process. However, particularly preferred is the back surface of a frame portion called a stage on which a semiconductor chip is mounted, and the partial surface of a lead that forms an interface with the resin after sealing. Note that when specifying these surfaces to be processed, the purpose can be easily achieved by using a mask. In addition, in order to further improve the adhesion with the sealing resin, the lead frame may be subjected to physical treatment such as roughening or unevenness on the surface in advance or after coating with polysilazane. . Further, depending on the purpose, the lead frame of the present invention may be treated with a silane coupling agent or the like. The sealing resin used in the semiconductor package of the present invention includes solid epoxy resins, silicone resins, bismaleimide resins, polyimide resins, etc., which are commercially available for normal transfer molding.
In addition to thermosetting resins such as phenolic resins or unsaturated polyester resins, polyphenylene sulfide and polyetherimide, liquid crystal polymers, polyphenylene ethers, polysulfones, polyarylsulfones, polyimide sulfones, polyetherketones, polyetheretherketones, polyimides, and polyamides. and thermoplastic resins that can be injection molded, such as polyamideimide. Furthermore, a liquid material that is potted and sealed with the above-mentioned thermosetting epoxy resin or silicone resin can also be used. Among these, solid thermosetting epoxy resins are preferred.

[0013]

EXAMPLES Hereinafter, the lead frame and semiconductor package of the present invention will be specifically explained with reference to Examples and Comparative Examples. Examples 1-3, Comparative Examples 1-2. Iron/nickel alloy (4
2 alloy) or copper-based lead frames were ultrasonically cleaned with trichlene, rinsed with acetone, and after drying these solvents, polysilazane was applied and treated under each of the conditions listed in Table 1. Here, in Table 1, perhydropolysilazane refers to polysilazane in which R1, R2 and R3 are all hydrogen atoms in the formula [Chemical formula 2]. Also, N-methylpolysilazane is R1 and R2
represents a hydrogen group and R3 represents a methyl group, polysilazane.

[0014]

[Table 1]

[0015] The coating method was to mask the lead frame except for the back side of the frame portion with the above polysilazane solution diluted to 1% with xylene, and then perform a dipping treatment. After dipping, a tube furnace was used in a nitrogen and ammonia atmosphere at a heating rate of 10°C/min and a firing temperature of 4.
After being held at 00°C for 30 minutes, it was cooled to room temperature. A silicon chip for evaluation with opposing comb-shaped aluminum wiring was bonded on the stage to the lead frame treated as described above, wire bonding was further performed, and commercially available epoxy sealing resin was transfer molded for sealing. A semiconductor package was manufactured. A partial view of the back side of the lead frame of Example 1 is shown in FIG. 1(c), and a schematic cross-sectional view of a semiconductor package using this is shown in FIG. 1(a). Further, a schematic cross-sectional view of the semiconductor package of Example 3 is shown in FIG. 1(b). Table 1 summarizes the results of evaluating the lead frame and resin of the fabricated semiconductor package in terms of (1) adhesion, (2) crack resistance (number of cracks generated), and (2) moisture resistance reliability using the following evaluation methods. Note that Comparative Example 1 is a case of a conventional lead frame made of iron/nickel alloy (42 alloy), and Comparative Example 2 is a case of a conventional copper lead frame.

(Evaluation method) (1) Adhesion The resin-sealed and after-cured semiconductor package was allowed to absorb moisture for 48 hours at 85° C. and 85% relative humidity, and then immersed in a 260° C. solder bath for 10 seconds. The adhesion between the encapsulating resin of the removed semiconductor package and the back surface of the lead frame stage was observed using an ultrasonic imaging device, and compared and evaluated using the following criteria. The entire surface is in close contact
．． ．． ．． ．． ．． ．． The central part of A is adhered and the surrounding area is peeled off. ．． ．． ．． ．． ．． B The entire surface has peeled off.
．． ．． ．． ．． ．． ．． C. Crack resistance (Number of cracks generated) Similarly to ■, the number of external cracks generated among the 10 semiconductor packages dipped in solder is recorded. ■Moisture-resistance reliability A semiconductor package sealed with epoxy resin and after-cured in the same way was immersed in a solder bath at 260°C for 10 seconds, and while applying a bias voltage of 20 volts,
It was subjected to a bias pressure cooker test in a saturated pressurized steam atmosphere at ℃. 80 hours and 20 hours in a semiconductor package each equipped with 20 silicon chips for evaluation.
The evaluation was based on the number of packages that became open defects due to corrosion of the aluminum wiring after 0 hours.

[0017]

As described above, the lead frame coated with polysilazane of the present invention has good adhesion with the sealing resin, and a semiconductor package in which a semiconductor chip is mounted on the lead frame and sealed with the resin can be obtained. shows excellent crack resistance and moisture resistance reliability.

[Brief explanation of drawings]

1(a) is a cross-sectional view of a resin-sealed semiconductor package showing an example of the present invention, (b) is a cross-sectional view of a resin-sealed semiconductor package also showing an example of the present invention, and (c) is a cross-sectional view of a resin-sealed semiconductor package showing an example of the present invention. FIG. 2 is a view of a lead frame for a resin-sealed semiconductor package viewed from the opposite side of the chip mounting surface.

FIG. 2(a) is a cross-sectional view of a resin-sealed semiconductor package using a conventional lead frame, and FIG. 2(b) shows a lead frame of a conventional resin-sealed semiconductor package.

[Explanation of symbols]

1; Lead frame 2; Lead frame stage 3; Part covered with polysilazane 4; Semiconductor chip 5; Bonding wire 6; Sealing resin

Claims (2)

[Claims] 1. A lead frame, the surface of which is coated with polysilazane having a repeating unit represented by the following formula [Chemical formula 1]. [Formula 1] (In the formula, R1, R2 and R3 are each a hydrogen atom, an alkyl group, an alkenyl group, a cycloalkenyl group, an amino group, an alkylamino group, an alkylsilyl group, or other than these groups, silicon and A group in which the group directly connected to nitrogen is carbon.However, at least one of R1, R2 and R3 is a hydrogen atom.) 2. A resin-sealed semiconductor package, characterized in that a semiconductor chip is mounted on the lead frame according to claim 1 and sealed with a resin.