JPH08306725A - Semiconductor resin sealing method - Google Patents

Abstract

PURPOSE: To provide a semiconductor resin sealing method in the bonding of a wire to a lead frame or a bonding pad is not deteriorated and the yield is not decreased because of short circuit at the time of resin sealing. CONSTITUTION: When an assembly where the electrode parts of a semiconductor chip are bonded through a connector wire with the forward end part of leads (i.e., inner lead) arranged around the semiconductor chip is subjected to resin sealing, a protective layer is provided on the surface of connector wire in the assembly and then the assembly is resin sealed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in a resin encapsulation method for a semiconductor device, and more particularly to a semiconductor resin encapsulation method capable of manufacturing a multi-pin package with high yield.

[0002]

2. Description of the Related Art A typical conventional resin-encapsulated semiconductor device has a semiconductor element fixed to a die pad portion at the center of a lead frame and is arranged around the electrode portion of the semiconductor element and the die pad portion of the lead frame. This is a resin-molded assembly of connector wires bonded to the ends of the formed leads (that is, inner leads), and is usually manufactured by transfer molding using a die and cutting unnecessary portions of the lead frame.

[0003]

However, in the above-mentioned prior art, in the transfer molding step of the resin, the wire comes into contact with another adjacent wire or inner lead due to the flow of the resin or the like, causing a short circuit defect. There is a problem that it is easy.

In particular, as the number of pins in a large-scale integrated circuit (LSI) increases, the distance between the chip and the inner lead tends to increase, so that it is necessary to increase the span length of the wire. It is easy to occur.

Therefore, it may be considered to coat the bonding wire with an insulating film in advance, for example, Japanese Patent Laid-Open No. 2-285.
It is proposed in Japanese Patent Laid-Open No. 648, etc. that a short circuit defect can be prevented by using a wire covered with an insulating polymer resin material.

However, when a wire having a polymer resin film is used, there is a drawback that the bondability between the wire and the lead frame or the bonding pad tends to deteriorate.

The present invention has been made in view of the above points, and does not have the drawback of deteriorating the bondability between the wire and the lead frame or the bonding pad, and does not cause a reduction in the yield due to a short circuit during resin sealing. An object is to provide a resin sealing method.

[0008]

Means for Solving the Problems As a result of extensive studies to achieve the above object, as a pre-stage of resin-sealing a semiconductor element, instead of using a wire having a polymer resin film for assembly, After providing a protective layer on the surface of the connector wire in advance, by resin-sealing the assembly,
It became clear that the purpose could be achieved.

That is, according to the present invention, when an electrode assembly of a semiconductor chip and a lead (that is, an inner lead) tip portion arranged around the semiconductor chip are wire-bonded with a connector wire, the assembly is resin-sealed. It is characterized in that a connector layer is preliminarily provided with a protective layer on the surface of the connector wire and then resin is sealed.

Further, the present invention is characterized in that the surface protective layer is a polymer thin film.

The present invention is also characterized in that the polymer thin film is formed by gas phase polymerization.

Next, the present invention will be described in more detail.

A semiconductor device to which the resin sealing method of the present invention is applied has a structure in which an electrode portion of a semiconductor chip and a tip of a lead (that is, an inner lead) arranged around the chip are wire-bonded with a connector wire. belongs to. Specifically, as described above, the semiconductor element is fixed to the die pad portion in the center of the lead frame, and the electrode portion of the semiconductor element and the tip portion of the lead (that is, the inner lead) arranged around the die pad portion of the lead frame, It is common for the structure to be wire-bonded with a connector wire, but if the structure is wire-bonded,
The structure is not limited to the above. The most effective resin sealing method is transfer molding, but ordinary liquid resin potting or the like can also be performed.

A polymer resin film is preferable as the protective layer for the connector wire of the assembly having the above structure. When forming the polymer resin film on the connector wire, it is not necessary to form the film only on the connector wire. That is, when the coating is formed on the connector wire, it may be formed on the surface of the semiconductor chip at the same time.

The method for forming the film is not particularly limited. For example, plasma polymerization, vapor phase polymerization, vapor phase polymerization methods such as non-catalytic polymerization using a specific ketene acetal vapor,
A method for forming a polymer film by heat treatment after immersion in a surface treatment solution such as a silane coupling agent may be mentioned. The thickness of the film is
The thicker the film, the better the insulating property, but the deposition rate is slow or it is difficult to form a thick film. Therefore, the suitable thickness is 0.01 to 1 μm, and more preferably 0.02 to 0.8 μm. If it is less than 0.01 μm, the withstand voltage is poor and it is not preferable.

In the plasma polymerization, the monomer gas to be used is not particularly limited, and if the discharge power supplied is adjusted, a network polymer in which the molecular chains are bridged is formed, and the heat resistance and chemical resistance are also improved. An excellent film can be formed.

In vapor deposition polymerization, generally, two or more kinds of polycondensable monomers are vapor-deposited separately, and then heated to cause polycondensation, whereby aromatic polyamide, polyurea, polyurethane and the like can be polymerized. As an example, terephthalic acid chloride and 4,
When an aromatic polyamide is polymerized with 4'-diaminodiphenyl ether, polycondensation proceeds by dehydrochlorination under vacuum at about 100 ° C.

On the other hand, the non-catalytic polymerization using a cyclic ketene acetal having no substituent, which is generally represented by Chemical Formula 1, is
When a 5- or 6-membered cyclic ketene acetal, that is, 2-methylene-1,3-dioxolane, 2-methylene-1,3-dioxane is used, a polymer film having good polymerizability on the metal surface and excellent solvent resistance is formed. Has been reported.

[0019]

Embedded image As a method of forming the polymerized layer of the silane coupling agent, the connect wire portion or the assembly is immersed in a solution of about 0.5 to 5% of the silane coupling agent and then heat-treated. If it is less than 0.5%, the treatment effect is insufficient. On the other hand, if it is more than 5%, not only does the treatment effect not increase, but rather a uniform film is formed due to aggregation of the silane coupling agent itself. I can't get it. Further, the cost is increased, which is not preferable. As the solvent to be used, water or an organic solvent can be used, but if water is disliked,
A relatively volatile hydrophobic solvent, specifically hexane,
It is preferable to use cyclohexane or the like.

The gas phase polymerization method, which is advantageous for forming a uniform film, is suitable.

[0021]

As described above, when resin-sealing the assembly in which the electrode portion of the semiconductor chip and the tip of the lead (that is, the inner lead) arranged around the semiconductor chip are wire-bonded with the connector wire, By providing a protective layer in advance on the connector wire surface of the assembled product and then resin-sealing, there is no defect that reduces the bondability between the wire and the lead frame or the bonding pad, and the yield due to short-circuit defects during resin sealing Does not cause a drop.

[0022]

Embodiments of the present invention will be described below. Note that the present invention is not limited to these examples. (Example 1) The die pad part (8 m
A semiconductor element (7 mm square, 60-pin QFP) is fixed to the m-square), and the tip of the lead (that is, inner lead) arranged around the electrode portion of the semiconductor element and the die pad portion of the lead frame is connector wire bonded. (Wire length 3 mm). After covering a predetermined lead portion of the assembly with a cover film, the cover film is set in a plasma polymerization apparatus and the pressure in the chamber is reduced. Ethane as a monomer gas, gas flow rate 50 STPml / min, gas pressure 20
Introduced into the chamber at 0 Pa, 13.56 MHz, 8
It discharges continuously at 0 Watts. At this time, a plasma polymerized film is also formed on the surface of the connect wire. At this time, the film thickness is approximately 0.1 μm. After completion of the polymerization, the sample is taken out and the cover film is removed.

Next, the above sample was set in a transfer molding machine, and a cresol novolac type epoxy resin was sealed at 180 ° C., followed by full curing at 175 ° C. for 6 hours.

No electrical defects such as wire shorts were found in the obtained package. (Example 2) The assembly of the semiconductor element and the lead used in Example 1 was set in a reduced pressure vaporizer, and 6-membered 2-methylene-1,3-dioxane was used as a vapor in the device.
Contact was performed for 30 minutes in an atmosphere of 0 ° C. and 300 mmHg. At this time, the inner wall of the reduced pressure vaporizer is treated with 3-aminopropyltrimethoxysilane in order to prevent vapor ketene acetal from contacting and polymerizing. At this time, a predetermined portion of the lead is covered as in the first embodiment. Polymeric films preferentially form on the connector wires and exposed lead portions. At this time, the film thickness is 0.07 μm.

The sample with the cover removed was sealed by transfer molding in the same manner as in Example 1.

In the obtained package, no electrical short circuit failure due to contact between connector wires was observed. (Comparative Example 1) A package was formed by using the same steps and materials as in Example 1 and Example 2 except that the polymerization treatment was not performed.

In the obtained package, an electrical short circuit failure was recognized due to the contact between the connector wires.

[0028]

As described above, according to the present invention, an assembly in which the electrode portion of the semiconductor chip and the tip of the lead (ie, inner lead) arranged around the semiconductor chip are wire-bonded with a connector wire. When the resin is sealed with a resin, there is no drawback that the bondability between the wire and the lead frame or the bonding pad is deteriorated by providing a protective layer on the surface of the connector wire of the assembly in advance and then sealing the resin. It is possible to suppress a decrease in yield due to a short circuit defect during sealing.

Claims (3)

[Claims] 1. When resin-sealing an assembly in which an electrode portion of a semiconductor chip and a lead tip portion arranged around the semiconductor chip are wire-bonded with a connector wire, the surface of the connector wire of the assembly is previously sealed. A method for encapsulating a semiconductor resin, which comprises encapsulating with a resin after providing a protective layer. 2. The method for encapsulating a semiconductor resin according to claim 1, wherein the surface protective layer is a polymer thin film. 3. The method for encapsulating a semiconductor resin according to claim 2, wherein the polymer thin film is formed by gas phase polymerization.