JPH04309253A - Semiconductor package - Google Patents

Abstract

PURPOSE:To provide a semiconductor package which is excellent in moisture resisting reliability even when the package receives a thermal shock by improving the adhesion of the interface between a lead frame and sealing resin. CONSTITUTION:This resin sealed semiconductor package has a silicon oxide film 3 formed at least on the surface of a lead frame 2 which is brought into contact with a sealing resin 6. The silicon oxide film 3 can be formed by a vacuum deposition method or sputtering method.

Description

[Detailed description of the invention]

0001

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

0001

[Background 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 as ceramic packages because of their improved moisture resistance, ease of mass production, and relatively low cost. Both quantities are growing at an overwhelming rate. In addition, electronic components are becoming smaller,
As devices become thinner, resin-sealed surface-mount packages are rapidly increasing from conventional resin-sealed pin insertion type packages.

However, when these resin-sealed surface mount semiconductor packages are left in the air, the sealing resin absorbs moisture, and the thermal shock during soldering to a printed circuit board causes the resin and lead frame to deteriorate. The interface peels off, causing problems such as impairing the functionality of semiconductor devices. In order to solve these problems, attempts have been made to modify the surface of the lead frame, use a sealing resin that does not easily absorb moisture, and use a sealing resin that has good adhesion to the lead frame.

0003

SUMMARY OF 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-57
152,157), a method of forming fine irregularities on the surface of a lead frame (Japanese Patent Application Laid-Open No. 115,551/1980, 285,662/1999), a method of coating with polyimide, etc. ing. However, even with these formulations, when a moisture-absorbed package is exposed to thermal shock, the interface between the lead frame and the resin may partially or completely peel off, making it easier for moisture and impurities to enter from the outside, and corroding the chip wiring. However, there was a problem that the moisture resistance reliability was poor. The present invention has been made in view of the above problems, and by forming a silicon nitride film on at least the surface of the lead frame in contact with the sealing resin, the present invention improves adhesion and provides resin sealing with excellent moisture resistance and reliability. Its purpose is to provide semiconductor packages.

0003

[Means for Solving the Problems] That is, the gist of the present invention is as follows. A first invention provides a semiconductor package in which a semiconductor chip is mounted on a lead frame and sealed with resin, wherein a silicon oxide film is formed on at least the surface of the lead frame that contacts the sealing resin. The second invention is a semiconductor package, and the second invention is characterized in that the silicon oxide film of the first invention is formed by either a vacuum evaporation method or a sputtering method.

[0004] The present invention will be explained in more detail below. The lead frame used in the semiconductor package of the present invention may be made of a known material such as an iron/nickel alloy such as 42 alloy or a copper alloy. It is not particularly limited, and may include an aluminum clad foil lead frame, a lead frame partially plated with silver, etc. As for the structure of the lead frame, it can be applied to any structure as long as it is a lead frame for a resin-sealed semiconductor package. Specifically, DIP (Dual In-line Pack
age, dual in-line package), SIP (
SingleIn-line Package), ZIP (Zig-Zag
In-line Package, Zigzag In-line Package), SOP (Small Outline Package)
e Package, Small Outline Package), SOJ (Small Outline J-le
Aded Package, Small Outline
J-lead package), QFP (Quad Flat
Package, quad flat package),
PLCC (Plastic Leaded Chip C)
This applies to all conventional resin-sealed semiconductor packages such as leaded chip carriers and plastic leaded chip carriers. In addition, COL (Chip on lead,
Chip on Lead) and LOC (Lead on Ch)
Semiconductor packages with IP, lead-on-chip) structures and TAB (Tape Automated Bo
Semiconductor packages manufactured from similar lead frame equivalent components including metal leads, such as bonding, tape automated bonding, etc., are also encompassed by the present invention.

The silicon oxide film formed on the lead frame of the present invention is a film made of trisilicon tetranitride, disilicon trinitride, monosilicon mononitride, or a mixture thereof, and the film formation method is vacuum evaporation, There are various methods such as physical methods such as sputtering and ion plating, chemical methods such as chemical vapor deposition (CVD) and plasma CVD, and reactive sputtering. In addition to these methods of forming directly on the lead frame, a silicon oxide thin film prepared in advance may be bonded to the lead frame later. However, since the adhesion between the silicon oxide film and the lead frame is important, those formed by either vacuum deposition or sputtering exhibit particularly excellent characteristics. Note that the thickness of the silicon oxide film is not particularly limited, and may range from several hundred angstroms to several thousand angstroms, for example.

[0006] The portion of the lead frame on which the silicon oxide film is formed is not particularly limited as long as it includes the portion that forms an interface with the sealing resin, but at least the part where the silicon oxide film is formed is the part that forms the interface with the sealing resin. It is preferable that the surface of the lead that forms the interface between the back surface of the frame portion to be mounted and the resin after sealing is included. Note that when specifying this surface, the purpose can be easily achieved by using a mask or the like at the appropriate time. In addition, in order to further improve the adhesion with the sealing resin, the surface of the lead frame is subjected to physical processing such as roughening, unevenness, and dimples on the surface of the lead frame in advance or after forming a silicon oxide film. There is no problem. In addition, the modification effect can be improved by treatment with a silane coupling agent.

The sealing resin used in the semiconductor package of the present invention may be commercially available solid epoxy resins, silicone resins, bismaleimide resins, polyimide resins, phenol resins, unsaturated polyester resins, etc., which are commercially available for general transfer molding. In addition to thermosetting resins, injection molding of polyphenylene sulfide, polyetherimide, liquid crystal polymer, polyphenylene ether, polysulfone, polyarylsulfone, polyimide sulfone, polyetherketone, polyetheretherketone, polyimide, polyamide, polyamideimide, etc. Examples include possible thermoplastic resins. 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, a solid thermosetting epoxy resin encapsulant is preferred.

Specific epoxy resins include cresol novolac type epoxy resin, phenol novolac type epoxy resin, bisphenol type epoxy resin, bisphenol A type epoxy resin, 4,4'-bis(2'',3
``-epoxypropoxy)-3,3',5,5'-biphenyl and other biphenyl skeleton epoxy resins, naphthalene skeleton epoxy resins, glycidyl ester type epoxy resins, glycidylamine type epoxy resins, chain aliphatic epoxy resins, Alicyclic epoxy resins, heterocyclic epoxy resins, trifunctional epoxy resins, tetrafunctional epoxy resins, or epoxy resins in which halogens such as bromine are introduced to impart flame retardancy can also be used.In the present invention, Although not particularly limited, cresol novolac type epoxy resins, epoxy resins with a biphenyl skeleton, and epoxy resins with a naphthalene skeleton are particularly suitable.

[0009] Examples of curing agents for epoxy resins include phenols, polyphenols, acid anhydrides, amines, dicyandiamide, and polysulfides. More specifically, there are novolac-type phenols such as phenol novolak resin, cresol novolak resin, and tert-butylphenol novolac resin, resol-type phenols, and bisphenol A. Among these, novolac type phenolic resins are preferred. Examples of the acid anhydride include phthalic anhydride, hexahydrophthalic anhydride, tetrahydrophthalic anhydride, pyromellitic anhydride, dodecylsuccinic anhydride, and the like. Examples of amines include metaphenylenediamine, diaminodiphenylmethane, diaminodiphenylsulfone, diethylenetriamine, triethylenetriamine, diethylaminopropylamine, N
-aminoethylpyrelazine, metaxylene diamine, and the like.

[0010] As the filler, powders such as fused silica, crystalline silica, titanium oxide, silica titania, talc, alumina, zirconia, beryllia, calcium sulfate, calcium carbonate, barium carbonate, silicon nitride, aluminum nitride, fibers, whiskers, etc. can be mentioned. The type, particle size, blending amount, etc. of these fillers are determined depending on the use and are not particularly limited. In addition, the average particle size is 10
The diameter is preferably 20 μm or less, and the shape can be selected by appropriately combining a spherical shape, a crushed shape, a notched corner shape, or the like. In addition, it is preferable to appropriately use ordinary curing accelerators such as imidazoles, organic phosphines, and boron salts, and coupling agents such as silane coupling agents. In reality, a small amount of a stress reducing agent, a mold release agent, a coloring agent, a flame retardant, etc. are further blended and melted and kneaded to form an epoxy resin encapsulant.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Examples of the present invention will now be described in detail with reference to the accompanying drawings. (Example 1) FIGS. 1(a) and 1(b) are cross-sectional views showing an example of a semiconductor package of the present invention, and FIG. 1(C) is a schematic diagram of the back side of a lead frame constituting the present invention. show. The lead frame 1 and the lead frame stage 2 made of iron/nickel alloy (42 alloy) were ultrasonically cleaned with Tri-Clene, rinsed with acetone, and after drying these solvents, they were coated with a vacuum evaporator using an electron beam heating source to a thickness of approximately A 1,000 angstrom silicon dioxide film was formed. A silicon chip 4 for evaluation with opposing comb-shaped aluminum wiring is bonded to this lead frame on a stage, a bonding wire 5 is further bonded, and an epoxy sealing resin having the composition shown in Table 1 is transferred and sealed.
An OP type semiconductor package was manufactured. Table 2 shows the results of evaluation using the following evaluation methods regarding (1) adhesion and (2) moisture resistance reliability between the lead frame and the resin of the fabricated semiconductor package. All results were good.

0012

[Table 1]

[0013]

[Table 2]

(Examples 2 to 4) Using an iron/nickel alloy (42 alloy) or copper lead frame on which a silicon dioxide film or silicon oxide film was formed by vacuum evaporation or sputtering as shown in Table 1, Example 1 was prepared. The evaluation chip was mounted and resin-sealed in the same manner as above. The evaluation results are shown in Table 2. Adhesion and moisture resistance reliability were both excellent.

(Comparative Examples 1 and 2) Comparative Example 1 is a semiconductor package using a conventional iron/nickel alloy (42 alloy) lead frame without a silicon oxide film;
This is the case of a conventional semiconductor package using a copper-based lead frame without a silicon oxide film. Evaluations were made in the same manner as in Examples, and the results are summarized in Table 2.

(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. We used an ultrasonic imaging device to observe the adhesion between the encapsulating resin of the removed semiconductor package and the back side of the lead frame stage.
A comparative evaluation was made 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 ■ Moisture resistance reliability After curing the semiconductor package sealed with epoxy resin in the same way, it was immersed in a solder bath at 260°C for 10 seconds, and biased in a saturated pressurized steam atmosphere at 125°C while applying a bias voltage of 20 volts. It was subjected to a pressure cooker test. Semiconductor packages each mounted with 20 silicon chips for evaluation were evaluated based on the number of packages that became open defects due to corrosion of the aluminum wiring after 80 hours and 200 hours.

[0015]

As described above, the semiconductor package of the present invention, in which a semiconductor chip is mounted on a lead frame on which a silicon oxide film is formed on at least the surface in contact with the sealing resin and sealed with the resin, has the following advantages: Good adhesion and excellent moisture resistance reliability.

[Brief explanation of the drawing]

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

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

[Explanation of symbols]

1; Lead frame
4; Semiconductor chip 2; Lead frame stage
5; Bonding wire 3; Part where silicon oxide film is formed
6; Sealing resin

Claims (2)

[Claims] 1. A semiconductor package in which a semiconductor chip is mounted on a lead frame and sealed with resin, characterized in that a silicon oxide film is formed on at least the surface of the lead frame that contacts the sealing resin. semiconductor package. 2. Claim 1, wherein the silicon oxide film is formed by a vacuum evaporation method or a sputtering method.
resin-sealed semiconductor package.