JPH08186223A - Resin composition for formation of tie bar - Google Patents

Abstract

PURPOSE: To improve the tie bar formation property to a lead frame, low out gas property, and flow stop property of mold resin by making specified diacrylate, a photosensitizer, and a thixotropic agent the mandatory components, and containing specified diacrylate by specified wt.% or over in all acrylate. CONSTITUTION: Diacrylate, a photosensitizer, and a thixotropic agent expressed by the formula are made mandatory components, and diacrylate expressed by the formula is contained by 30wt.% or over within all acrylate. Here, X is H, CH3 , or C2 H5 , and I, m, n, p, and q are all integers of one or over. Hereby, this is excellent in tie bar formation property to a lead frame, low out gas property, and the flow stop property of mold resin, so there is no compression or deformation of a lead wire to the clamping of a mold, and the curving processing of an outer lead can be performed without any hindrance.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a resin composition for a mold resin flow stop tie bar of a lead frame used in a resin-sealed semiconductor element.

[0002]

2. Description of the Related Art Generally, a resin-encapsulated semiconductor element is formed by adhering a semiconductor chip to a lead frame, wire bonding, and then encapsulating with a molding resin. Usually, the lead frame is provided with a tie bar on the outer side of a portion of the lead frame, which is a molded product, in order to prevent the mold resin from leaking between the leads.

The operation of the tie bar will be described with reference to the drawings. FIG. 1 is a schematic view showing two sides of the lead frame 1. The lead frame 1 is provided with a tie bar 2 for preventing the flow of the mold resin leaking from between the leads outside the portion of the lead frame 1 which is a molded product. FIG. 2 shows a schematic diagram in which the mold resin is filled. The mold resin 5 is filled as burrs from the mold line 4 and further between the tie bar leads. FIG. 3 is a schematic view showing a state after the mold resin 4 filled between the mold line 4 and the tie bar 2 in FIG. 2 is punched and removed together with the tie bar 2 by a die press.

With the recent increase in the size and density of semiconductor elements and the increase in the number of leads, the spacing between lead wires is becoming narrower, and the punching method using a die press is reaching its limit. That is, it becomes difficult to process the punching die, wear of the die is increased, and the life of the expensive die is shortened, which leads to a cost increase of the entire package.
Therefore, a method of forming a lead frame without a tie bar in advance and forming a tie bar made of an insulating organic material on the lead frame (for example, Japanese Patent Laid-Open No. 1-2418)
No. 50, Japanese Patent Laid-Open No. 2-122660) have been proposed. There are two methods for forming the tie bar on the lead frame by using an insulating organic material. First, as in the conventional method, a tie bar is formed on the outside of the part to be a molded product using an insulating organic material, and it is removed in a later step. This is a method of forming a tie bar using an organic material and integrating it with a mold resin.

In the former case, the following characteristics are required for the tie bar organic material. 1) Capable of filling the gaps between the leads without gaps 2) No deformation or outgas at the temperature of bonding the semiconductor element to the lead frame and wire bonding 3) Molding resin molding temperature, molding pressure and mold pressure To withstand the flow of mold resin 4) No deformation or compression deformation of the leads due to mold clamping pressure 5) Easy removal after molding 1) The characteristics of the latter are: 1) Fill the gaps between the leads without gaps. 2), 3) Same as above 4) Tie bar can be formed at accurate position 5) Excellent adhesion to mold resin and no leakage current between leads when absorbing moisture Further, in consideration of productivity in addition to the above characteristics, an organic material for a tie bar is disclosed in JP-A-3-218032. Photocurable resin, JP-A-62-15
A heat resistant tape represented by the Teflon tape disclosed in Japanese Patent No. 8351 can be used. As the photocurable resin, an ultraviolet curable resin is generally used. However, in the above publication, no specific resin is exemplified and the characteristics are not clear. As a result of various studies on the ultraviolet curable resin, the present inventors have found out the following. UV curable resins are generally brittle when cured, or even soft and flexible after UV curing, but become brittle due to the heat applied during semiconductor chip bonding and wire bonding. The tie bar contacting the mold was cracked, and the molding resin sometimes extruded, resulting in a decrease in molding yield.

[0006]

DISCLOSURE OF INVENTION Problems to be Solved by the Invention The present invention has been made as a result of the examination of resins applied to a method of removing after molding.
Formability of tie bar on lead frame, low outgassing,
It is intended to provide a resin composition for a tie bar which has an excellent flow-proof property of a mold resin and which can be easily removed by applying pressurized water after molding the mold resin.

[0007]

The present invention comprises a diacrylate represented by the formula (1), a photosensitizer and a thixotropic agent as essential components, and the diacrylate represented by the formula (1) in all acrylates. A resin composition for forming a tie bar containing 30% by weight or more.

[0008]

Embedded image (X is H, CH ₃ , C ₂ H ₅ , l, m, n, p and q are each an integer of 1 or more)

The weight average molecular weight of the diacrylate of the formula (1) is not particularly limited, but is 500 or more to 10,000.
The following is preferred. If it is less than 500, the cured product of the resin is too hard and the tie bar contacting the mold is cracked due to the pressure of the mold during molding, which is not preferable. If it exceeds 10,000, the cured product of the resin will be too soft and the moldability will be poor. The weight average molecular weight is measured by gel permeation chromatography.
If the diacrylate represented by the formula (1) is less than 30% by weight in all the acrylates, the flexibility and the removability are poor, which is not preferable. The diacrylate of formula (1) is easily available on the market, for example, trade name Aronix M-61.
00, M-6200, M-6250, M-6400, M
-6500 (Toagosei Chemical Industry Co., Ltd.), Viscoat 37
00 (Osaka Organic Chemical Industry). When used together for the purpose of decreasing viscosity, improving heat resistance, improving curability, etc., as acrylates, phenol ethylene oxide modified acrylate, nonylphenol ethylene oxide modified acrylate, nonylphenol propylene oxide modified acrylate, bisphenol A ethylene oxide modified acrylate, isocyanuric Acid ethylene oxide modified diacrylate, isocyanuric acid ethylene oxide modified triacrylate, 1,6-hexanediol diacrylate, neopentyl glycol diacrylate, polypropylene glycol diacrylate, polyethylene glycol diacrylate, trimethylolpropane triacrylate, dipentaerythritol hexa Acrylate, pentaerythritol triacrylate Tetramethylolmethane tetraacrylate and the like, but not limited thereto.

Examples of the photosensitizer used in the present invention include, but are not limited to, Michler's ketone compounds, thioxanthone compounds, benzophenone compounds, benzoin ether compounds and the like. The thixotropic agent used in the present invention is
For example, an ultrafine filler having a submicron particle diameter such as Aerosil (trade name) is added to impart thixotropic properties.
This makes it possible to form tie bars on the lead frame by dispensing, screen printing, or the like. Further, a small amount of a thiol compound or an amine compound can be added to enhance the curability. Further, a filler such as silica may be added to improve the strength of the tie bar. The filler used at that time is preferably a spherical filler having an average particle diameter of 10 μm or less in order to prevent the lead frame from being compressed and deformed. Further, considering the curability of the composition, the addition amount thereof is preferably 75% by weight or less based on the entire composition. If it exceeds 75% by weight, the viscosity of the resin composition increases,
It becomes difficult to form the lead frame by printing or the like.

[0011]

The UV-curable resin composition of the present invention acts as a flow stop for the mold resin, and the cured product has an appropriate softness depending on the molding temperature.
Since there is no compression deformation of the lead wire, the outer lead can be bent without any trouble. Further, since the structure is flexible, the tie bar can be easily removed by pressurized water such as a water jet after molding. The resin composition of the present invention contains a diacrylate represented by the formula (1), a photosensitizer and a thixotropic agent as essential components, and if necessary, a curing accelerator, a filler, a silicone oil, a liquid rubber, or the like. An additive such as a stress-reducing agent and an antifoaming agent can be premixed and kneaded using a three-roll mill to produce.

The present invention will be described below with reference to examples. Example 1 In the formula (1), R ₁ is O— (CH ₂ ) ₄ and R ₂ is (CH
₂ ) ₄ , 100 parts by weight of diacrylate having l = 2, 3 parts by weight of Irgacure 184 (manufactured by Ciba Geigy) as a photosensitizer, 93 parts by weight of spherical silica having an average particle diameter of 1 μm as a filler, and a thixotropic agent As Aerosil R-805
10 parts by weight (manufactured by Nippon Aerosil Co., Ltd.) were kneaded to prepare a resin composition for tie bar. This resin composition has a thickness of 12
5 μm, 0.3 mm pitch, QFP copper frame with 344 leads, thickness 30 μm outside the mold line,
Print through a screen in a line shape with a line width of 0.3 mm,
A high pressure mercury lamp of 80 W / cm ₂ was irradiated from a height of 15 cm for 1 minute to cure. Next, a semiconductor element was mounted on the die pad using silver paste, wire bonding was performed, and then resin sealing was performed using an epoxy mold resin. The mold resin was completely stopped at the tie bar. Finally, the tie bar could be completely removed by honing with high pressure water. After the tie bar was removed, the lead wire had no compression deformation or other deformation. Example 2 In formula (1), R ₁ is (O—CH ₂ —CH ₂ ) ₂ , R ₂
Except that a diacrylate having (CH ₂ ) ₄ , 1 = 5 was used, a resin composition was prepared in the same manner as in Example 1, and the same moldability and removability were examined and the same result was obtained. Example 3 In formula (1),

[0013]

Embedded image (L = 3)

A resin composition was prepared in the same manner as in Example 1 except that the resin was used, and the same moldability and removability were examined, and the same result was obtained.

Comparative Example 1 A resin composition was prepared and evaluated in the same manner as in Example 1 except that 25 parts by weight of diacrylate and 75 parts by weight of pentaerythritol triacrylate used in Example 1 were used. A crack was generated in the tie bar resin when the mold resin was sealed, and the mold resin leaked. Comparative Example 2 A resin composition for tie bars was prepared and evaluated in the same manner as in Example 1 except that 100 parts by weight of tetrapropylene glycol diacrylate was used instead of 100 parts by weight of diacrylate in Example 1. As a result, a crack was generated in the tie bar resin when the mold resin was sealed, and the mold resin leaked. Comparative Example 3 A resin composition for tie bar was prepared and evaluated in the same manner as in Example 1 except that 100 parts by weight of diacrylate of Example 1 was used and 100 parts by weight of trimethylolpropane triacrylate was used. As a result, a crack was generated in the tie bar resin when the mold resin was sealed, and the mold resin leaked.

[0016]

According to the present invention, a resin tie bar for performing inexpensive molding resin molding can be formed on a multi-pin lead frame with high productivity.

[Brief description of drawings]

FIG. 1 is a schematic view of two sides of a lead frame.

FIG. 2 shows a schematic diagram in which a mold resin is filled.

FIG. 3 is a schematic diagram showing a state after the mold resin filled between the mold line and the tie bar is punched and removed by a die press together with the tie bar.

Claims (2)

[Claims] 1. A diacrylate represented by the formula (1), a photosensitizer and a thixotropic agent as essential components, and the diacrylate represented by the formula (1) is contained in an amount of 30% by weight or more in all acrylates. A characteristic tie bar forming resin composition. Embedded image (X is H, CH ₃ , C ₂ H ₅ , l, m, n, p and q are each an integer of 1 or more) 2. The weight average molecular weight of the formula (1) is 500 to 1.
The resin composition for forming a tie bar according to claim 1, which is 10,000.