JPH0821799B2 - Bonding method for outer leads - Google Patents

Description

TECHNICAL FIELD The present invention relates to an outer lead bonding method for thermocompression bonding an outer lead of a semiconductor chip to an electrode portion of a substrate.

(Prior Art) Mounting a semiconductor on a film carrier made of a synthetic resin film and punching the film carrier to manufacture a semiconductor chip is known as a TAB method.

The semiconductor chip manufactured in this manner has outer leads formed by punching the film carrier as described above, and bonding the outer leads to the electrode portion formed on the substrate is Generally called outer lead bonding.

(Problems to be Solved by the Invention) The outer lead is bonded to the substrate by landing the outer lead on the electrode portion formed on the upper surface of the substrate and pressing the thermocompressor against the outer lead to heat and melt the electrode portion. It is done by However, the solder used as the material of the electrode part has a temperature characteristic of melting and hardening, and although there are differences depending on the type of solder, it is generally heated gradually to 160 to 180 ° C and then heated to 220 ° C or more all at once. Therefore, it is desirable to melt and then to gradually cool and cure. Further, since the outer lead is extremely thin and thin and is made of a synthetic resin such as polyimide, it is not preferable that the material is deteriorated when it is suddenly heated to a high temperature. Therefore, it is preferable to gradually heat the outer lead.

Therefore, an object of the present invention is to provide a bonding means that can satisfy such temperature characteristics of solder and outer leads.

(Means for Solving the Problem) For this purpose, the present invention lowers the nozzle shaft,
The first step of mounting the semiconductor chip adsorbed on the adsorption portion at the lower end of the nozzle shaft on the substrate, and lowering the thermocompressor preheated by the heat treatment to weaken the outer leads of the semiconductor chip to the substrate. Second step of pressing the thermo-compressor against the electrode section of the substrate, then the third step of increasing the temperature of the thermocompressor and pressing the outer lead against the electrode section of the substrate with a stronger force, and then applying cool air to the thermocompressor. The outer lead bonding method includes a fourth step of lowering the temperature of the thermocompressor by spraying to press the outer lead against the electrode portion of the substrate, and a fifth step of raising the thermocompressor to release the pressed state. Configured.

Further, desirably, in the second step, the outer leads of the semiconductor chip are pressed against the electrode portions of the substrate by a weak force of the thermocompression bonding element due to the spring force of the spring material. Further, in the third step, the outer lead is pressed against the electrode portion of the substrate with a stronger force by pressing the heat block as the heating means against the thermocompressor from above. Further, in the fourth step, cold air is blown from the lower portion of the upright tube in which the nozzle shaft is fitted and is blown onto the thermocompressor.

(Operation) According to the above configuration, the thermocompressor is first pressed against the outer lead with a weak force, then the temperature of the thermocompressor is increased and pressed with a strong force, and then the temperature of the thermocompressor is lowered, thereby removing the outer lead. It can be surely bonded to the electrode portion of the substrate.

(Example) Next, the Example of this invention is described, referring drawings.

FIG. 1 is a perspective view of a bonding head, and FIG. 2 is a partially cutaway perspective view. Reference numeral 1 is a plate-shaped support frame, and an upright tube 2 is attached to the central portion thereof. A nozzle shaft 3 is vertically slidably fitted into the upright tube 2, and a suction portion 4 for a semiconductor chip P is provided at a lower end portion thereof. This semiconductor chip P is manufactured by the TAB method. As shown in FIG. 3, the ultra-thin and ultra-thin outer leads L punched out from the film carrier are formed in four directions from four sides of the semiconductor chip C. It is extended. Note that there are some semiconductor leads in which the outer leads L extend in two directions from two sides, and the means according to the present invention can also be applied to such a semiconductor chip.

Reference numeral 5 denotes a heat block as a heating means provided on the lower surface of the support frame 1, and the upright tube 2 penetrates the heat block 5. In FIG. 2, reference numeral 12 is a feeder line. On the lower surface of the heat block 5, a tapered heat transfer portion 6 is integrally provided so as to extend downward. Reference numeral 7 denotes a thermocompressor provided on the side of the suction portion 4 so that the suction portion 4 can be pressed against the outer leads L extending in four directions.
It has a rectangular frame shape surrounding and has an enlarged portion 7a and a small pressing portion 7b in cross section. As will be described later in detail, the pressing portion 7b is pressed against the outer lead L,
This is thermocompression-bonded to the electrode portion made of solder formed on the substrate, and the expanded portion 7a is a heat storage portion. The thermocompression-bonding element 7 may be formed integrally with the heat block 5, but in the present embodiment, the thermocompression-bonding element 7 is separated from the heat block 5 to change the type of semiconductor chip. Is designed so that only the thermocompressor 7 can be replaced. In this case, in the case where the outer leads L extend in two directions, the thermocompression bonding element does not need to be formed in a rectangular frame shape, but has a shape corresponding to the outer leads L in these two directions.

In FIG. 2, reference numeral 8 denotes a frame-shaped bracket arranged so as to surround the heat block 5,
Is connected to this bracket 8 via a shaft 9. Reference numeral 10 is a coil spring for urging the thermocompressor 7 downward, and 11 is a bearer portion for guiding the shaft 9 up and down.

2 and 4 (a), 14 is a contacting / separating means for moving the thermocompressor 7 up and down to bring it into contact with and separate from the heat transfer portion 6, and is attached to the mounting plate 22 on the lower surface of the support frame 1. , And has an arm 15 rotatably mounted around a pin 16. A roller 17 that comes into contact with the lower surface of the bracket 8 is pivotally attached to the tip of the arm 15. Reference numeral 18 denotes a spring member that urges the roller 17 downward, that is, in a direction of separating the thermocompression-bonding member 7 downward from the heat transfer section 6. Reference numeral 19 is a rod suspended from the frame 21 (see FIG. 1), and the lower end of the rod is an arm.
The roller 17 is pressed against the roller 20 axially attached to the other end of the roller 15, and the roller 17 is pressed against the lower surface of the bracket 8 against the spring force of the spring member 18. As will be described later in detail, the heat transfer from the heat transfer section 6 to the thermocompressor 7 is cut off by connecting the thermocompressor 7 to the heat transfer section 6 to control the temperature of the thermocompressor 7. I have to. In the joined state in which the thermocompression-bonding element 7 is in the raised position,
A small interval t is secured between both 6 and 7 (Fig. 4 (a)).
(Refer to a partially enlarged view) By securing the interval t in this way, the thermocompression-bonding element 7 is prevented from being excessively heated by the heat transfer section 6.

In FIG. 4 (a), a shaft 23 is provided upright on the upper surface side portion of the support frame 1. Reference numeral 24 is a multi-stage cylinder provided above the shaft 23, and its rod 25 is grounded to the upper surface of the shaft 23. 26 is a second cylinder, the rod 27 of which is connected to the upper surface of the support frame 1. The second cylinder 26 supports the load of the support frame 1, the heat block 5 and the like by its retreat force F2 (see FIG. 7C). This cylinder 24
It is a pressing means for strongly pressing the pressing element 7 against the outer lead L, and is an elevating means for moving the thermocompression bonding element 7 up and down independently of the adsorption section 4.

In FIG. 4 (a), 40 is a pulse motor for raising and lowering the nozzle shaft 3, which rotates a screw rod 41 and raises and lowers a nut body 42 screwed thereto. A block 43 is attached to the upper end of the nozzle shaft 3,
The nozzle shaft 3 is biased downward by the coil spring 44. 45 is a shaft the upper end of which is pressed by the nut body 42, and a roller 46 which is pressed against the lower surface of the block 43 is attached to the lower end of the shaft. 47 is a shaft
Reference numeral 45 is a lifting guide block, and 48 is a coil spring that biases the shaft 45 upward. In each drawing, the urging direction of the spring is indicated by an arrow.

Therefore, when the pulse motor 40 operates and the nut body 42 descends, the shaft 45 descends against the spring force of the coil spring 48, the roller 46 also descends, and the nozzle shaft 3 descends by the spring force of the coil spring 44. To do. When the nut body 42 rises, the shaft 45 rises due to the spring force of the coil spring 48, and the nozzle shaft 3 is pushed up by the roller 46 and rises.

In FIG. 1, 50 is a motor for rotating the nozzle shaft 3 about its axis, 51 is a cam, 52 is a cam follower, 53 is a rotator to which the cam follower 52 is attached, and 54 is a rotator 53. Shaft 55 hung vertically on the nozzle shaft 55
A roller that is mounted on the tip of a rod 56 extending from the side and presses against the shaft 54. These means horizontally rotate the semiconductor chip P adsorbed to the adsorbing portion 4 and correct the position and the position in the θ direction, but since they are not directly related to the present invention, a detailed description thereof will be given. Omit it.

FIG. 3 shows a cooling means, and 13 is an inner tube fitted between the nozzle shaft 3 and the upright tube 2,
Cold air is sent between the upright tube 2 and the inner tube 13 through a pipe 28, and this cold air is blown from the lower end of the upright tube 2 toward the pressing portion 7b of the thermocompression-bonding element 7 that presses the outer lead L at any time. (See dashed arrow). The pipe 28 is connected to the upper portion of the upright pipe 2, and the blown cold air descends between the upright pipe 2 and the inner pipe 13. Therefore, the nozzle shaft 3
The nozzle block 3 is prevented from being excessively heated by the heat block 5 to be thermally deformed, thereby causing an error in bonding accuracy. The temperature of this cold air is, for example, normal temperature. There is also a gap between the nozzle shaft 3 and the inner pipe 13, and this gap insulates the heat of the heat block 5 from being transferred to the nozzle shaft 3. As described above, if cold air is blown out from the lower end portion of the upright tube 2 through which the nozzle shaft 3 is inserted, the cool air is blown out in all directions and is evenly distributed over the pressing portion 7b positioned so as to surround the adsorption portion 4. Although there is an advantage that cold air can be blown, the cool air blowing means is provided separately from the upright tube 2 and the heat block 5, and the cool air is blown toward the pressing portion 7b of the pressing member 7 from obliquely above the thermocompressor 7. It may be sprayed, and the specific configuration of the cooling means is not limited to this embodiment.

This bonding head has the above-mentioned structure. Next, the bonding method will be described with reference to FIGS. 4 (a) to 4 (f).

The bonding head that has sucked the semiconductor chip P onto the lower end of the suction portion 4 reaches above the substrate S (FIG. 4A). Next, when the motor 40 is driven, the suction portion 4 is lowered, the semiconductor chip P is mounted on the substrate S, and the outer lead L is landed on the electrode portion 30 made of solder formed on the upper surface of the substrate S (same as above). Figure (b)).

Then, the cylinder 24 is actuated to lower the support frame 1. The roller 20 then separates from the rod 19,
The arm 15 is rotated by the spring force of the spring material 18 to rotate the thermocompressor 7.
Moves down, and its pressing portion 7b presses the outer lead L and presses it against the electrode portion 30 (FIG. 7 (c)). In this case, if the pressing portion 7b is suddenly pressed against the outer lead L with a strong force, the outer lead L and the electrode portion 30 are likely to be adversely affected. Therefore, this means is the rod of the multi-stage cylinder 24.
25 is first projected with a weak force to lower the thermocompressor 7, and the arm 15 is rotated with the spring force of the spring material 18, whereby the pressing portion 7b is pressed against the outer lead L with a weak force first (fourth). Figure (c)). Next, if the heat transfer part 6 lands on the thermocompression-bonding element 7, the thrust output of the rod 25 of the multistage cylinder 24
By increasing F1, the pressing portion 7b is moved to the outer lead L
Press firmly against ((d) in the figure).

Then, the rod 25 of the cylinder 24 is retracted upward to raise the heat block 5 ((e) in the figure). In this state, the thermocompression-bonding element 7 is separated from the heat transfer section 6, and the spring force of the spring member 18 keeps the outer lead L pressed. Then, the rod 27 further rises, the thermocompression-bonding element 7 separates from the outer lead L, and the bonding operation is completed ((f) in the figure).

By the way, the solder, which is a material of the electrode portion 30, has a temperature characteristic of melt hardening. That is, in general, 160 ° to 180 ° C
After heating to a certain degree, it is desirable that the material be melted by heating at 220 ° C. or more at once, and then gradually cooled to be hardened. Therefore, the present apparatus controls the heating temperature of the electrode section 30 as follows.

The temperature of the heat block 5 is constant at 220 to 230 ° C. at all times, but in FIGS. 4 (a) and 4 (b), the thermocompressor 7 has a small gap t with the heat transfer part 6, so 160-180 ° C
It has been preheated to a degree. Next, as shown in FIG. 7C, the thermocompression-bonding member 7 descends and lands on the outer lead L,
The electrode portion 30 is gradually heated while pressing the outer lead L.

Next, as shown in FIG. 7D, the heat transfer part 6 lands on the thermocompression-bonding element 7, and the temperature of the thermocompression-bonding element 7 is raised at a stretch to 220 to 230 ° C. to completely heat and melt the electrode part 30. Then, in that state, the outer lead L is strongly pressed against the electrode portion 30 by the protrusion output F1 of the rod 25 of the cylinder 24, and the outer lead L is thermocompression-bonded to the electrode portion 30.

Next, as shown in FIG. 7E, the heat transfer part 6 rises and separates from the thermocompression-bonding element 7, interrupts heat transfer to the thermocompression-bonding element 7, and blows out cool air as indicated by a dashed arrow. To cool the thermocompressor 7 and the electrode part 30 to 180 ° C or less,
The pressing state by the thermocompression-bonding element 7 is continued. In addition, the electrode part 30
After heating to 220 ° C. or higher, the thermocompressor 7 is suddenly raised together with the heat transfer section 6 to release the pressed state of the outer lead L, and the electrode section 30 is heated and is in a molten state. L jumps up and melts the electrode part 30
Easy to separate from. Therefore, as described above, even after the heat transfer part 6 is raised, the outer lead L is kept pressed by the thermocompression-bonding element 7 to cool the electrode part 30 to about 180 ° C., and the outer lead L jumps up. After the fear of the problem disappears, the thermocompression-bonding element 7 is lifted to release the pressed state. Then, as shown in (f) of the figure, when the pressing state by the thermocompression-bonding element 7 is released, the blowing of the cold air is stopped, the electrode portion 30 is gradually cooled and hardened, and the outer lead L becomes the electrode portion. Stick to 30.

As described above, the present means allows the thermocompression-bonding element 7 to come into contact with and separate from the heat block 5 which is a heating means, and also to press the pressing portion 7b and the electrode portion.
Since there is a means for blowing cold air toward 30 to cool it, the electrode portion 30 can be satisfactorily heated and melted, and the outer lead L can be reliably bonded to the electrode portion 30. 180
The above temperatures such as ℃ and 220 ℃ are examples, and these temperatures vary depending on the type of solder and the like.

(Effects of the Invention) According to the present invention, while satisfying the temperature characteristics of the electrode portion of the substrate, the electrode portion can be heated and melted to reliably bond the outer leads of the semiconductor chip. Further, in this case, in the second step, the thermocompressor is softened by pressing the outer lead of the semiconductor chip against the electrode portion of the substrate by a weak force of the spring force of the spring material, so that the outer crimp is not damaged. Can be pressed against the outer lead. In the third step, the heat block, which is a heating means, is pressed against the thermocompression-bonding member from above, so that the temperature of the thermocompression-bonding member is sharply increased and pressed against the outer lead with a stronger force to surely melt the electrode portion. The outer lead can be bonded to the electrode part. In the fourth step, cold air is blown from the lower portion of the upright tube in which the nozzle shaft is inserted and blown onto the thermocompressor, so that cold air is blown from the lower portion of the upright tube in all directions to the thermocompressor. Even if cold air is blown evenly, the thermocompression-bonding member can be uniformly cooled without spatial variation, and the molten electrode portion can be uniformly cooled and solidified.

[Brief description of drawings]

FIG. 1 shows an embodiment of the present invention. FIG. 1 is a perspective view of a bonding head, FIG. 2 is a partially cutaway perspective view, FIG. 3 is a sectional view of a cooling means, and FIG. FIG. 3 ... Nozzle shaft 4 ... Adsorption part 7 ... Thermocompressor 30 ... Electrode part P ... Semiconductor chip L ... Outer lead S ... Substrate

Claims (4)

[Claims] 1. A first step of lowering a nozzle shaft to mount a semiconductor chip adsorbed on an adsorption portion at a lower end portion of the nozzle shaft on a substrate, and a thermocompressor preheated by a heating means. The second step of pressing the outer leads of the semiconductor chip against the electrode parts of the substrate with a weak force, and the second step of raising the temperature of the thermocompressor and pressing the outer leads against the electrode parts of the substrate with a stronger force.
Step, and then the fourth step of lowering the temperature of the thermocompressor by blowing cold air to the thermocompressor to press the outer leads against the electrode part of the substrate, and raising the thermocompressor to release the pressed state The outer lead bonding method, which comprises: 2. The outer lead according to claim 1, wherein, in the second step, the outer lead of the semiconductor chip is pressed against the electrode portion of the substrate by a weak force of the thermocompressor due to the spring force of the spring material. Bonding method. 3. In the third step, the temperature of the thermocompressor is raised by pressing the heat block, which is the heating means, against the thermocompressor from above, and the outer lead is attached to the substrate with a stronger force. The outer lead bonding method according to claim 1, wherein the outer lead is pressed against the electrode portion. 4. In the fourth step, cool air is blown out from the lower portion of the upright pipe in which the nozzle shaft is fitted and inserted,
The outer lead bonding method according to claim 1, wherein the cold air is blown onto the thermocompression bonding element.