JPH09213722A - Method and apparatus for curing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent contamination of semiconductor chips due to volatile gas by applying a jet of gas to a lead frame on a heating stage containing suction grooves from above, and discharging the gas from bottom to accelerate curing of bonding resin. SOLUTION: When paste material placed between a semiconductor chip 1 and a lead frame 2 is heated, volatile gas is produced. In the title curing apparatus, produced volatile gas is arrested by hot air flowing sideways from the surface of the semiconductor chip 1, and does not go up to the surface of the semiconductor chip 1. Further, at the underside of the semiconductor chip 1 exposed at tabs, the volatile gas is taken in by hot air flowing through the suction grooves, and is sucked and discharged through an exhaust port 7 together with the hot air. The underside of the semiconductor chip 1 exposed owing to small tab structure, as well as the surface of the semiconductor chip 1, is protected against contamination due to volatile gas. This makes it possible to prevent contamination due to volatile gas produced from bonding resin during curing.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cure technique for promoting the curing of a joining resin for joining a semiconductor chip and a lead frame, and more particularly to preventing contamination of the back surface of a semiconductor chip exposed from a tab when it is cured. Related to effective technology.

[0002]

2. Description of the Related Art In a semiconductor device manufacturing process, a semiconductor chip is bonded to a tab of a lead frame through a paste material (bonding resin), and the paste material is heated and hardened by a curing device in order to strengthen the bonding force. It
Here, an epoxy-based volatile gas is generated from the paste material during heating, but if this gas adheres to the semiconductor chip and a contamination film is formed on the surface, the bondability in the wire bonding in the next step is reduced and the sealing is reduced. There is a possibility that the adhesion with the mold resin may deteriorate in the stopping step.

In order to prevent this, in the curing device, a lead frame bonded with a semiconductor chip is mounted on a heating stage to which a heater is attached, and clean hot air is blown onto the lead frame from above to blow it from below. The structure that exhausts is adopted. As a result, the volatile gas is taken into the air collected by flowing laterally on the surface of the lead frame, so that the cleanliness of the surface of the chip is secured without being attached to the semiconductor chip.

As an example in which a curing device for heating the paste material for joining the semiconductor chip and the lead frame is described in detail, for example, "Practical Course VLSI Packaging Technology (below)" issued by Nikkei BP. "
(Published May 31, 1993), P98-P100.

Here, in the past, one kind of lead frame was generally used for one kind of semiconductor chip, but in recent years, a lead frame is commonly used for many kinds of semiconductor chips. The sharing of frames is being promoted.

[0006] Such common use is intended to give versatility to the lead frame, pursue economies of scale by further mass production, and reduce costs, but the lead frame there is a tab. The so-called small tab structure has an area smaller than that of the semiconductor chip. As an example of the specific shape, a tab area is simply reduced, a tabular frame is formed, or a cross-shaped one is formed. Then, in the lead frame having the small tab structure, most of the back surface of the bonded semiconductor chip is exposed to the outside.

Therefore, in the semiconductor chip bonded to the lead frame having the small tab structure, not only the front surface but also the back surface of the semiconductor chip is required to be clean so as not to be contaminated with volatile gas.

[0008]

However, the above-mentioned curing device does not take any measure against this point, and hot air acts only on the surface of the semiconductor chip. A contaminated film will be formed. As a result, the problem that the adhesion between the semiconductor chip and the mold resin deteriorates occurs from the back surface of the chip.

Needless to say, chip contamination is not preferable even in a lead frame having a structure in which the back surface of the semiconductor chip is not exposed.

Therefore, an object of the present invention is to provide a technique capable of preventing the semiconductor chip from being contaminated by a volatile gas generated when the lead frame is heated to accelerate the hardening of the bonding resin.

The above and other objects and novel features of the present invention will become apparent from the description of the present specification and the accompanying drawings.

[0012]

SUMMARY OF THE INVENTION Among the inventions disclosed in the present application, the outline of a representative one will be briefly described.
It is as follows.

That is, in the curing method according to the present invention, a heating stage having a plurality of suction grooves formed on the upper surface thereof is prepared, and the lead frame to which the semiconductor chip is bonded is heated with the surface of the semiconductor chip facing upward. The semiconductor is placed on the stage, and the gas is blown from above onto the lead frame on this heating stage and exhausted from below to flow the gas into the suction groove to heat the lead frame while maintaining the cleanliness of the semiconductor chip. It is characterized by accelerating the curing of the bonding resin for bonding the chip and the lead frame.

In the curing method according to the present invention, a heating stage having a plurality of suction grooves formed on its upper surface is prepared, and a lead frame to which a semiconductor chip is bonded with its back surface exposed from a tab is prepared. Place the lead frame on the heating stage with the surface facing upward, blow gas from above onto the lead frame on the heating stage, and exhaust it from below to flow gas into the suction groove to clean the semiconductor chip. It is characterized in that the lead frame is heated while maintaining the temperature to accelerate the hardening of the joining resin for joining the semiconductor chip and the lead frame.

Further, in the curing device according to the present invention, a heater for heating the lead frame is attached and a plurality of suction grooves are formed on the upper surface on which the lead frame is mounted so that the surface of the semiconductor chip faces upward. And a heating stage, and a gas ejection unit installed above the lead frame for blowing gas toward the lead frame,
It is provided below the lead frame and has an exhaust port that sucks gas from the gas ejection part and discharges it to the outside, and flows gas to the back surface of the semiconductor chip exposed from the tab to clean the semiconductor chip. It is characterized by being able to cure while keeping it.

According to the above-mentioned means, the volatile gas generated from the bonding resin is taken into the hot air flowing through the suction groove and forcedly exhausted from the exhaust port. As a result, the back surface of the semiconductor chip can be made as clean as the front surface, and the back surface of the semiconductor chip whose back surface is exposed from the lead frame by the small tab structure can be made as clean as the front surface. Contamination by the volatile gas generated from the bonding resin is prevented.

[0017]

Embodiments of the present invention will be described below in detail with reference to the drawings. In all the drawings for describing the embodiments, members having the same functions are denoted by the same reference numerals, and the repeated description thereof will be omitted.

(Embodiment 1) FIG. 1 is an explanatory view schematically showing a curing device according to an embodiment of the present invention, and FIG. 2 is an exploded perspective view showing a heating stage shown on the left side of the curing device of FIG. 3 is a perspective view showing the main part of FIG. 2, and FIG. 4 is FIG.
FIG. 5 is a perspective view showing a main part of the heating stage shown on the right side of the curing device of FIG. 1.

The curing device shown in FIG.
Is used to accelerate the curing of the paste material (bonding resin) that bonds the semiconductor chip 1 and the lead frame 2 by heating the bonded lead frame 2, and the lead frame 2 is placed on the left and right halves of the drawing. Two types of heating stages 3a and 3b for heating the same are shown. Then, the lead frame 2 is transferred by the transfer arm from the leftmost heating stage 3a to the right heating stages 3a and 3b sequentially while being heated for a predetermined time.

As shown in FIG. 2, the heating stage 3a on the left side of the drawing has a base plate 3a ₁ located at the bottom, a heat plate 3a ₂ in which a heater 4 is embedded and fixed to the base plate 3a ₁ , and this heat plate 3a ₂ The top plate 3a ₃ is fixed to the top plate 3a ₃ and the lead frame 2 has the surface of the semiconductor chip 1 facing upward.
It is designed to be placed on top of ₃ . As shown in detail in FIG. 3, the top plate 3a ₃ is formed with a plurality of suction grooves 5 having a substantially U-shaped cross-section opening upward and extending parallel to each other along the width direction. This suction groove 5
Has a depth D of about 1 mm, a width W of about 5 mm, and a thickness T of the partition wall 6 separating the suction grooves 5, that is, a width of a contact portion with the lead frame is about 0.5 mm (FIG. 4). ). This value is set in consideration of the uniformity of the heating temperature distribution of the lead frame 2 by the heater 4 and the discharge efficiency of the volatile gas described later, but the groove size is not limited to this and various values are set. It can take a value.

Exhaust ports 7 are formed at two locations on both ends of each suction groove 5. Exhaust port 7 opened in suction groove 5
Is connected from the top plate 3a ₃ heat plate 3a ₂ are formed so as to extend to the base plate 3a ₁ through the, collectively to one at the base plate 3a ₁ to the exhaust motor 8 (see FIG. 1). It should be noted that the suction groove 5 is preferably formed in the width direction as in the present embodiment because the groove length is shortened and the discharge efficiency of the volatile gas is also increased, including the case of the heating stage 3b described later. However, you may form so that it may extend in a length direction. Further, the exhaust ports 7 can be formed in the required number for one suction groove 5.

For such a heating stage 3a, as shown in FIG.
As shown in FIG. 3, although the suction groove 5 is formed on the surface of the top plate 3b ₃ which is the upper surface of the heating stage 3b on the right side of the drawing, the exhaust port 7 is opened to the floor on which the heating stage 3b is installed. The heating stage 3a is different in that it is formed. Therefore, the suction is performed immediately below the lead frame 2 on the heating stage 3a, but is performed at a position far below and farther on the heating stage 3b. However, in consideration of the suction efficiency, it is preferable that the exhaust ports 7 are formed on both sides of the heating stage 3b, and the suction groove 5 is formed so as to extend in the direction of the exhaust port 7. Note that all of the curing devices may have a structure having the exhaust port 7. Further, the suction groove 5 may be formed only in the heating stage 3a, and the upper surface of the heating stage 3b may be flat.

Corresponding to each heating stage 3a, 3b, a gas ejection portion 9 having an ejection port 9a is provided above the heating stage 3a, 3b (FIG. 1). A heater 10 and a filter 11 are provided in each of the gas ejection parts 9, and clean hot air (gas) A is blown onto the lead frame 2 mounted on the heating stages 3a and 3b.

A plurality of jet ports 9a are provided in the gas jet portion 9 corresponding to the heating stage 3a in which the exhaust port 7 is directly formed.
However, the gas ejection portion 9 corresponding to the heating stage 3b having the exhaust port 7 formed on the floor is formed with the ejection ports 9a in the number corresponding to the heating stage 3b. Therefore, as shown in FIG. 1, the hot air A from the gas ejecting portion 9 on the left side of the drawing becomes like a shower like the lead frame 2.
, And a negative pressure is sucked from an exhaust port 7 formed in the heating stage 3a, while hot air A from a gas ejection part 9 on the right side of the drawing is blown so as to hit the bonded semiconductor chip 1 and the exhaust port on the floor surface is exhausted. Negative pressure is sucked from 7.

With such a curing device, the hardening of the paste material is promoted as follows. The curing device of the present embodiment can be used for heat treatment of various lead frames 2, but is particularly suitable for curing the lead frame 2 having a small tab structure in which the back surface of the semiconductor chip 1 is exposed. . Therefore, in the following description, the processing target is the lead frame 2 having the small tab structure.

First, the lead frame 2 to which the semiconductor chip 1 is bonded is placed on the heating stage 3a on the left side of FIG. 1 with the surface of the semiconductor chip 1 facing upward, while the heater 4 heats the paste material. The hot air A is blown toward the lead frame 2. Then, the entire lead frame 2 is uniformly heated under an appropriate temperature due to the contact area between the heating stage 3a and the lead frame 2 due to the above-mentioned groove size, particularly the thickness T of the partition wall 6, and the hot air A on the heating stage 3a. It is sprayed almost perpendicularly to the surface of the semiconductor chip 1 bonded to the lead frame 2, changes its direction laterally from here, and flows into the suction groove 5, and as shown in FIG. 3, flows along the suction groove 5 and exhausts. It is discharged from the mouth 7 to the outside.

As described above, when the paste material between the semiconductor chip 1 and the lead frame 2 is heated, a volatile gas is generated, which deteriorates bondability due to a contaminated film formed on the semiconductor chip 1. Semiconductor chip 1
And the adhesiveness between the resin and the mold resin deteriorate.

In this curing device, the generated volatile gas is blocked by the hot air A flowing laterally from the surface of the semiconductor chip 1 and does not reach the surface of the semiconductor chip 1. Further, on the back surface of the semiconductor chip 1 exposed from the tab, the volatile gas is taken into the hot air A flowing through the suction groove 5 and is sucked and exhausted from the exhaust port 7 together with the hot air A. Therefore, not only the front surface of the semiconductor chip 1 but also the back surface exposed by the small tab structure is prevented from being contaminated by the volatile gas.

After performing such heat treatment for about 5 seconds on the heating stage 3a, the lead frame 2 is moved to the next heating stage 3a and the same treatment is performed for about 5 seconds. The heating time and the number of times of heating are not limited to this, and the heating can be performed for the required time and number of times.

After the heat treatment is performed twice, the volatile gas from the paste material is hardly generated, and then the lead frame 2 is heated by the heating stage 3b. Then, when the heat treatment is performed on the heating stage 3b three times, for example, for a total of about 15 seconds, the curing step is completed. Even in this heating stage, the back surface of the semiconductor chip 1 is prevented from being contaminated by the volatile gas slightly generated by the hot air A flowing in the suction groove 5.

After that, the lead frame 2 is resin-molded to protect the semiconductor chip 1 from the external atmosphere, and lead cutting and predetermined inspection are performed to complete the semiconductor device.

As described above, according to the curing technique according to the present embodiment, the semiconductor chip bonded to the lead frame 2 is formed by forming the suction groove 5 on the upper surfaces of the top plates 3a ₃ and 3b _{3 of} the heating stages 3a and 3b. Since hot air A is blown from above onto the surface of No. 1 and is exhausted from the exhaust port 7 below, the volatile gas is taken into the hot air A flowing through the suction groove 5 and forcedly exhausted from the exhaust port 7. As a result, the back surface of the semiconductor chip 1 can be made as clean as the front surface, and contamination of volatile gas during curing of the back surface of the semiconductor chip 1 whose back surface is exposed from the lead frame 2 due to the small tab structure is prevented. It

Since the partition 6 secures a certain amount of contact area between the lead frame 2 and the heating stage 3a, even if the suction groove 5 is formed, processing can be performed at an appropriate heating temperature.

(Embodiment 2) FIG. 6 is a perspective view showing a top plate in a heating stage according to another embodiment of the present invention.

In the present embodiment, the cross-sectional shape of the suction groove 15 in the width direction is substantially V-shaped. The groove shape in the case of the first embodiment is a substantially U-shape, and one suction groove 5
A total of three cuts of two side portions and one bottom portion are required to form the. On the other hand, by making the groove shape substantially V-shaped, it is sufficient to cut twice to form the two side surface portions, so that the cost for forming the suction groove 15 can be reduced.

As in the case of the heating stage 3a described above, even in the suction groove 15 having the main shape, an exhaust port opening to the suction groove 15 may be formed.

Although the invention made by the inventor has been specifically described based on the embodiment, the invention is not limited to the embodiment, and various modifications may be made without departing from the gist of the invention. It goes without saying that it is possible.

For example, in the present embodiment, hot air A is used to heat the lead frame 2, but this is not intended to limit the scope of application of the present invention, and may contaminate the semiconductor chip. A gas other than the hot air A such as an inert gas such as nitrogen gas may be used.

Further, although the present embodiment describes the case where the present invention is applied to a lead frame having a small tab structure in which the back surface of a semiconductor chip is exposed, a lead having a normal structure in which the back surface of the chip is not exposed is described. It can also be applied to frames.

[0040]

The effects obtained by typical ones of the inventions disclosed in the present application will be briefly described as follows.

(1) That is, according to the curing technique of the present invention, even a semiconductor chip whose back surface is exposed from the lead frame due to the small tab structure can have the back surface of the same degree of cleanliness as the front surface, Contamination due to volatile gas from the bonding resin generated during curing is prevented.

(2) As a result, the adhesiveness between the resin and the lead frame in the mold sealing step, which is the next step, can be improved, and the effect of improving the reflow resistance can be obtained. It is possible to improve yield by improving quality such as reduction of cracks.

(3) Further, since a certain amount of contact area is secured between the semiconductor chip and the heating stage, even if the suction groove is formed, processing can be performed at a specified curing temperature.

(4) By forming the suction groove into a substantially V-shaped groove shape, the suction groove can be formed by cutting twice, and the cost can be reduced.

(5) Since the above effects (1) to (4) can be achieved only by forming the suction groove on the upper surface of the heating stage, cost increase can be minimized. .

[Brief description of drawings]

FIG. 1 is an explanatory view schematically showing a curing device according to a first embodiment of the present invention.

2 is an exploded perspective view showing a heating stage shown on the left side of the curing device in FIG. 1. FIG.

FIG. 3 is a perspective view showing a main part of FIG. 2;

4 is a cross-sectional view of FIG.

5 is a perspective view showing a main part of a heating stage shown on the right side of the curing device in FIG. 1. FIG.

FIG. 6 is a perspective view showing a top plate in the heating stage according to the second embodiment of the present invention.

[Explanation of symbols]

1 semiconductor chip 2 lead frame 3 total 3a heating stage 3a ₁ base plate 3a ₂ heat plate 3a ₃ top plate 3b heating stage 3b ₃ top plate 4 heater 5 suction groove 6 partition wall 7 exhaust port 8 exhaust motor 9 gas ejection section 9a ejection port 10 Heater 11 Filter 15 Suction groove A Hot air

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Issei Suzuki, 5-22-1 Kamimizuhoncho, Kodaira-shi, Tokyo Inside Hitachi Microcomputer System Co., Ltd. Address 2 Inside Hitachi Tokyo Electronics Co., Ltd.

Claims (8)

[Claims] 1. A heating stage having a plurality of suction grooves formed on an upper surface thereof is prepared, and a lead frame to which a semiconductor chip is bonded is placed on the heating stage so that a surface of the semiconductor chip faces upward. By blowing gas from above onto the lead frame on the heating stage and exhausting it from below, the gas is flowed into the suction groove to heat the lead frame while maintaining the cleanliness of the semiconductor chip. A curing method characterized by accelerating the curing of a bonding resin for bonding a chip and a lead frame. 2. A heating stage having a plurality of suction grooves formed on an upper surface thereof is prepared, and a lead frame to which a semiconductor chip is bonded is prepared with a back surface exposed from a tab, and a front surface of the semiconductor chip faces upward. The lead frame is placed on the heating stage in such a manner that the lead frame on the heating stage is blown with gas from above and exhausted from below to flow the gas into the suction groove to cause the semiconductor chip. A curing method, characterized in that the lead frame is heated while maintaining the cleanness thereof to accelerate the curing of the bonding resin for bonding the semiconductor chip and the lead frame. 3. A curing device for heating a bonding resin for bonding a semiconductor chip and a tab of a lead frame to accelerate the curing thereof, wherein a heater for heating the lead frame is attached and a surface of the semiconductor chip is A heating stage in which a plurality of suction grooves are formed on an upper surface on which the lead frame is placed so as to face upward, and a gas ejection unit which is installed above the lead frame and blows gas toward the lead frame. And an exhaust port provided below the lead frame for sucking the gas from the gas ejection portion and discharging the gas to the outside, and flowing the gas to the back surface of the semiconductor chip exposed from the tab. A curing device characterized in that the semiconductor chip can be cured while maintaining the cleanness of the semiconductor chip. 4. The curing device according to claim 3, wherein a plurality of the exhaust ports are formed so as to open in the suction groove. 5. The curing device according to claim 3, wherein the exhaust ports are provided on both sides of the heating stage, and the suction groove is formed so as to extend toward the exhaust port. . 6. The curing device according to claim 3, 4 or 5, wherein the suction groove is formed in a width direction of the heating stage. 7. The curing device according to claim 3, 4, 5 or 6, wherein the suction groove has a depth of about 1 mm, and the lead frame contact portion separating the suction grooves has a width of about 1 mm.
A curing device characterized by being 0.5 mm. 8. The curing device according to claim 3, 4, 5, 6, or 7, wherein the suction groove has a substantially V-shaped cross-sectional shape in the width direction.