JP2824383B2 - Wire bonding method and semiconductor device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wire bonding method for manufacturing a semiconductor device by connecting a semiconductor element and a lead with a thin metal wire, and a semiconductor device manufactured by the wire bonding method.

[0002]

2. Description of the Related Art FIG. 10 is a partial sectional view of a semiconductor device showing a conventional wire bonding method. In the figure, 1
Is a semiconductor element having a bonding pad 1a formed thereon, 2 is a die pad of a lead frame for mounting the semiconductor element 1, 3 is an inner lead (hereinafter referred to as a lead) of the lead frame, and 4 is a pad 1a of the semiconductor element 1 at one end. (Hereinafter referred to as pad center) A 1, and the other end is a predetermined stitch bond point H of the lead 3.
1 is a loop wire that is stitch-bonded to 1 and electrically connects the pad 1a and the lead 3.

The loop wire 4 is composed of a rising portion 4a from the pad 1a and an inclined lowering portion 4b extending from the upper end of the rising portion 4a toward the lead 3. The loop wire 4 has a pad 1a of the semiconductor element 1, a lead 3 and Are connected in a so-called triangular loop shape. In this case, the loop wire 4 is formed of, for example, a thin metal wire (gold wire) W having a diameter of 30 μm. Reference numeral 10 denotes a capillary which moves while feeding out the thin metal wire W from the lower end and moves even when the relative movement with respect to the thin metal wire W is lost. L2 denotes a horizontal distance from the pad center A1 to the stitch bond point H1 (hereinafter referred to as a loop length). ).

In the semiconductor device, a semiconductor element 1 mounted on a die pad 2 and a lead 3 are connected to a loop wire 4.
After the connection, the periphery of the semiconductor element 1 is sealed with a resin,
Finally, the lead 3 is formed by cutting and bending.

Next, a wire bonding method for connecting the semiconductor element 1 and the lead 3 with the loop wire 4 will be described. In the state where a ball is formed at one end of the thin metal wire W hanging from the tip of the capillary 10,
The tip of the capillary 10 is connected to the pad 1 of the semiconductor element 1.
a. Then, the ball portion of the thin metal wire W is pressed against the pad center A1 of the pad 1a, and the ball portion is ball-bonded to the pad 1a by an ultrasonic thermocompression bonding method. Next, the tip of the capillary 10 is raised vertically from the center A1 of the pad to a point B1 above by a predetermined distance while the thin metal wire W is fed from the capillary 10, and then the capillary 10 is moved to a point C1 on the opposite side of the lead 3. Move horizontally for a predetermined distance. Further, the tip of the capillary 10 is vertically raised from the point C1 to the point F1 at a predetermined height while the thin metal wire W is paid out from the capillary 10.

Next, the tip of the capillary 10 is lowered in an arc to the stitch bond point H1 of the lead 3 in a state where the relative movement between the capillary 10 and the fine metal wire W is eliminated by clamping the fine metal wire W. The other end of W is stitch-bonded to lead 3.

Here, when the tip of the capillary 10 moves from the center A1 of the pad to the point F1 through the points B1 and C1, the thin metal wire W moves obliquely from the center A1 of the pad C1.
After extending the lead 3 side at the point C1, the upper side from the point C1 extends vertically to the point F1. In this state, the capillary 10 is moved to F1.
When the metal wire W is moved downward from the point to the stitch bond point H1 in an arc shape, the tension acting on the metal wire W near the pad center A1 and the tension of the metal wire W acting on the tip of the capillary 10 are balanced, and the point between the point C1 and the point F1. The loop wire 4 is formed with almost no deformation of the thin metal wire W.

The length from the pad center A1 to the point B1 is A1B1, and the length from the point B1 to the point C1 is B1.
1C1, tan ⁻¹ (B1C1 / A1B1) = θ,
Assuming that (A1B1) 2+ (B1C1) 2 = R2, the reverse angle .theta. Becomes substantially 0 when the loop wire 4 is formed, and the reverse length R is the rising amount (loop height) of the loop wire 4 from the upper surface of the pad 1a. Corresponding to Note that a combination of the vertical ascent and horizontal movement of the capillary 10 is called a reverse motion.

On the other hand, up to a loop length L2 of 3 mm, the connection between the pad 1a of the semiconductor element 1 and the lead 3 can be made by the above-mentioned triangular loop-shaped loop wire 4.
Exceeds 3 mm, it is difficult to form a proper loop wire 4. That is, the loop length L2 is 3 mm
Is exceeded, the loop wire 4 sags or bends due to the weight of the loop wire 4 or the bend or twist of the thin metal wire W. As shown in FIG.
11 is likely to be short-circuited with the semiconductor element 1 or the lead 3, or as shown in FIG.
There is a problem that short circuits are likely to occur.

Therefore, when the loop length L2 exceeds 3 mm, it is conceivable to connect the pad 1a of the semiconductor element 1 and the lead 3 with a so-called trapezoidal loop wire 5 as shown in FIG. . This loop wire 5
Is composed of a thin metal wire W like the loop wire 4, and includes a rising portion 5a rising upward from the pad center A1, a horizontal portion 5b extending horizontally from the upper end of the rising portion 5a toward the lead 3, and a horizontal portion. 5b extending from the end of the lead 5b to the stitch bond point H1 of the lead 3. Since the loop wire 5 has a bending point J at the connecting portion between the horizontal portion 5b and the inclined descending portion 5c, even if the loop length L2 exceeds 3 mm, the loop wire 5 is unlikely to be deformed. Conceivable.

[0011]

However, although it is conceivable to connect the pad 1a of the semiconductor element 1 and the lead 3 with the trapezoidal loop wire 5, the wire bonding uses the capillary 10 or the like. However, it is not clear how to form the loop wire 5. There is also a problem that an appropriate loop wire 5 cannot be formed depending on how the loop wire 5 is formed.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and a wire bonding method and a wire bonding method capable of properly connecting a pad and a lead of a semiconductor element with a trapezoidal loop-shaped thin metal wire. It is an object of the present invention to provide a high-quality semiconductor device which is wire-bonded by the method described above.

[0013]

According to a first aspect of the present invention, there is provided a wire bonding method, wherein an arc tangent of a horizontal movement amount with respect to a first vertical rise amount of a capillary is θ1.
(Unit degree), the arc tangent of the horizontal movement amount to the second vertical rise amount of the capillary is θ2 (unit degree), and the second horizontal movement of the capillary tip from the point after the first horizontal movement of the capillary tip The distance to the point after the movement is R2,
Let L1 be the horizontal distance from the bonding point to the pad to the starting point of the inclination of the trapezoidal loop-shaped thin metal wire toward the lead.
When the horizontal distance from the bonding point to the pad to the bonding point to the lead is L2, the height of the rising portion of the trapezoidal loop-shaped thin metal wire is h1, and the step distance between the surface of the pad and the lead is h2, K = (h1 + h2) / (L2-L
1) Assuming that 0.5 ≦ L2 ≦ 12 (unit mm), 5 ≦ θ1 ≦ 50, tan ⁻¹ K ≦ θ2 ≦ (7/2)
× tan ⁻¹ K, θ2 ≦ 60, (2/15) × L2 ≦ R
To move the capillary so as to satisfy the condition of 2 ≦ (8/15) × L2.

According to a second aspect of the present invention, there is provided a semiconductor device comprising: a rising portion of a semiconductor element from a pad; a horizontal portion from the rising portion to a lead side; and a slope from the horizontal portion to a lead. In a semiconductor device in which a pad and a lead of a semiconductor element are connected by a trapezoidal loop-shaped thin metal wire having a descending portion, the slope of the trapezoidal loop-shaped thin metal wire starts to descend from the bonding point to the pad toward the lead side. L1 is the horizontal distance to the point, L2 is the horizontal distance from the bonding point to the pad to the bonding point to the lead, h1 is the height of the rising portion of the trapezoidal loop-shaped thin metal wire, and the step between the surface of the pad and the lead. When the distance is h2 and the angle on the semiconductor element side is α (unit degree) among the angles formed by the horizontal portion and the inclined descending portion of the trapezoidal loop-shaped thin metal wire, K = (h1 + h2) /
If (L2−L1), then (2/15) × L2 ≦ L1 ≦
(8/15) × L2, 0.5 ≦ L2 ≦ 12 (unit: m
m), 180− (7/2) × tan ⁻¹ K ≦ α ≦ 180−
A trapezoidal loop-shaped thin metal wire is formed so as to satisfy the conditions of tan ⁻¹ K and 120 ≦ α ≦ 180.

According to a third aspect of the present invention, in the wire bonding method, after bonding one end of the fine metal wire drawn out from the tip of the capillary to the pad of the semiconductor element, the thin metal wire is drawn out from the capillary. After performing the vertical ascending of the capillary and the horizontal movement to the opposite side of the lead twice, the vertical ascending of the capillary is further performed to a predetermined height, and then the relative movement between the capillary and the fine metal wire. After the capillary is horizontally moved by a predetermined amount to the lead side in a state where the wire is removed, the capillary is moved in an arc shape to the lead side, and the other end side of the fine metal wire is bonded to the lead, and the pad of the semiconductor element is And a lead, a rising portion from the pad, a horizontal portion from the rising portion to the lead side,
A wire bonding method for connecting with a trapezoidal loop-shaped thin metal wire having an inclined descending portion from a horizontal portion onto a lead, wherein an axial direction in which the thin metal wire of the capillary is fed out, and movement of the capillary during horizontal movement If the angle with the direction is obtuse, the amount of movement of the capillary moving while feeding out the thin metal wire is increased from the set value.If the angle is acute, the amount of movement of the capillary moving while feeding out the thin metal wire is the set value. It is to reduce more.

In the wire bonding method according to a fourth aspect of the present invention, after bonding one end of a fine metal wire drawn from a tip of a capillary to a pad of a semiconductor element, the wire is fed from the capillary while the fine metal wire is fed out. After performing the vertical ascending of the capillary and the horizontal movement to the opposite side of the lead twice, the vertical ascending of the capillary is further performed to a predetermined height, and then the relative movement between the capillary and the fine metal wire. After the capillary is horizontally moved by a predetermined amount to the lead side in a state where the wire is removed, the capillary is moved in an arc shape to the lead side, and the other end side of the fine metal wire is bonded to the lead, and the pad of the semiconductor element is And a lead, a rising portion from the pad, a horizontal portion from the rising portion to the lead side,
A wire bonding method for connecting with a trapezoidal loop-shaped thin metal wire having an inclined descending portion from a horizontal portion onto a lead, comprising: a horizontal moving direction of a bonding head for moving a capillary toward a semiconductor element side; The loop angle between the line connecting the pad and the lead of the semiconductor element above is ψ (unit radian), and the horizontal distance of the trapezoidal loop-shaped thin metal wire from the bonding point to the pad to the bonding point to the lead is L2 ( P2 = ｛N where P1 is the amount of metal wire drawn out of the capillary and N is the proportionality constant, which is set to connect the pad and the lead with the trapezoidal loop-shaped metal wire. × (L
The moving amount of the capillary at the time of feeding out the thin metal wire is adjusted so that the thin metal wire is fed out by the corrected feeding amount P2 calculated by (2-3) × (ψ−π / 2) +1｝ × P1. It is to determine.

[0017]

According to the first aspect of the present invention, the moving state of the capillary moving while feeding out the thin metal wire is represented by θ1,
Analysis is performed using variables such as θ2 and R2, and the ranges of θ1, θ2, and R2 are determined so that a trapezoidal loop-shaped thin metal wire can be appropriately formed. It can be connected with a trapezoidal loop-shaped thin metal wire.

According to the second aspect of the present invention, the trapezoidal loop-shaped thin metal wires for connecting the pads and the leads of the semiconductor element are formed by the wire bonding method according to the first aspect of the present invention. An appropriate trapezoidal loop-shaped thin metal wire can be formed between the leads, and a high-quality semiconductor device can be formed.

According to a third aspect of the present invention, a first aspect is provided.
In the case of the invention, the amount of movement of the capillary moving while feeding out the thin metal wire is increased or decreased by the magnitude of the angle between the axial direction of the capillary and the direction of the horizontal movement of the capillary. Regardless of the magnitude of the dispensing resistance, the required amount of fine metal wire is dispensed from the capillary. Therefore,
A pad and a lead of the semiconductor element can be connected by a trapezoidal loop-shaped thin metal wire having a uniform loop height.

According to the fourth aspect of the present invention, the third aspect is provided.
In the case of the invention, the positional relationship between the pad and the lead of the semiconductor element with respect to the magnitude of the extension resistance between the capillary and the fine metal wire is finely analyzed by using variables such as L2 and 、, and the metal wire is moved while being extended based on these variables. The amount of capillary movement to be performed is determined. For this reason,
Further, it becomes possible to precisely feed out a necessary amount of the fine metal wire from the capillary. Therefore, it is possible to more accurately connect the pad and the lead of the semiconductor element with a trapezoidal loop-shaped thin metal wire having a uniform loop height.

[0021]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. Embodiment 1 FIG. FIG. 1 is an explanatory diagram of a wire bonding method according to one embodiment of the present invention. The same or corresponding portions as those of the semiconductor device and the wire bonding method shown in FIGS. 10 and 12 are denoted by the same reference numerals, and description thereof will be omitted.

First, a description will be given of a semiconductor device on which wire bonding has been completed. Each pad 1a of the semiconductor element 1 mounted on the die pad 2 is connected to a lead 3 corresponding to the pad 1a by a loop wire 5 having a trapezoidal loop shape. One end of the loop wire 5 is ball-bonded to the pad center A2 of the pad 1a, and the other end is a stitch bond point H of the lead 3.
2 is stitch-bonded. The loop wire 5 rises upward from the pad center A2 and rises 5a.
A horizontal portion 5b extending horizontally from the upper end of the rising portion 5a toward the lead 3; and an inclined descending portion 5 extending downward from the end of the horizontal portion 5b to the stitch bond point H2 of the lead 3.
c, and each part is formed in an appropriate shape without dripping of the wire and unnecessary bending.

Next, a wire bonding method for connecting the pad 1a of the semiconductor element 1 and the lead 3 with the loop wire 5 as described above will be described.

With the ball portion formed at one end of the thin metal wire W hanging from the tip of the capillary 10, the tip of the capillary 10 is lowered to the pad 1a of the semiconductor element 1. Then, the ball portion of the thin metal wire W is pressed against the pad center A2 of the pad 1a, and the ball portion is bonded to the pad 1a by ultrasonic thermocompression bonding (ball bonding).
I do. Next, from the tip of the capillary 10, a fine metal wire W
Is raised vertically from the pad center A2 to a point B2 above by a predetermined distance, and then horizontally moved to a point C2 on the opposite side of the lead 3 by a predetermined distance. Further, while feeding out the fine metal wire W from the tip of the capillary 10, the tip of the capillary 10 is moved to C2.
After vertically rising from the point to a point D2 above by a predetermined distance, this is horizontally moved to a point E2 on the opposite side of the lead 3 by a predetermined distance. Thereafter, the tip of the capillary 10 is moved to E2 while the fine metal wire W is further extended from the tip of the capillary 10.
From the point to the F2 point at a predetermined height.

Subsequently, the distal end of the capillary 10 is horizontally moved from the point F2 to the point G2 substantially above the pad center A2 in a state where the thin metal wire W is clamped and the relative movement between the capillary 10 and the thin metal wire W is eliminated. This is lowered in an arc from the point G2 to the stitch bond point H2 of the lead 3. Then, the other end of the thin metal wire W is connected to a lead 3.
When stitch bonding on the upper stitch bond point H2,
The pad 1a of the semiconductor element 1 and the lead 3 are connected by the loop wire 5.

Here, when the tip of the capillary 10 moves from the pad center A2 to the points B2 and C2, the thin metal wire W extends obliquely from the pad center A2 to the point C2.
Then, when the tip of the capillary 10 moves from the point C2 to the point D2, the thin metal wire W is formed at the point C2, and the upper side of the thin metal wire W above the point C2 is bent toward the lead 3. In addition, the tip of the capillary 10 is moved from point C2 to point D.
When the metal wire W moves to the two points E2, the thin metal wire W extends obliquely from the point C2 to the point E2. And Capillary 1
When the leading end of 0 moves from the point E2 to the point F2, the thin metal wire W is given a habit at the point E2, and the upper side of the thin metal wire W above the point E2 is bent toward the lead 3. Accordingly, when the tip of the capillary 10 is at the point F2, the thin metal wire W extending from the pad center A2 has a shape that reaches the point F2 through the points C2 and E2.

In this case, the length from the pad center A2 to the point B2 is A2B2, and the length from the point B2 to the point C2 is B2.
C2, the length from the C2 point to the D2 point is C2D2, the length from the D2 point to the E2 point is D2E2, and tan ⁻¹ (B2C2 / A2B2) = θ1, tan ⁻¹ (E2D2 / C2D2) = θ2, ( A2B2) 2+ (B2C2) 2 = (R1) 2, (C2D2) 2+ (D2E2) 2 = (R2) 2, the first reverse angle θ1 defines the tension acting on the thin metal wire W near the pad center A1. , The second reverse angle θ
2 specifies the tension acting on the thin metal wire W between the points C2 and E2. The first reverse length R1 defines the height (hereinafter referred to as loop height) h1 from the upper surface of the pad 1a of the semiconductor element 1 to the horizontal portion 5b of the loop wire 5, and the second reverse length R2 defines the loop wire 5 , That is, the horizontal length L1 from the pad center A2 to the bending point J.

If the first reverse angle θ1, the second reverse angle θ2, and the second reverse length R2 are within predetermined ranges, the tip of the capillary 10 is moved to the point F2 while the feeding of the thin metal wire W is stopped. By moving the point G2 and the point H2, the tension in the thin metal wire W is balanced, and an appropriate loop wire 5 as shown in FIG. 1 is formed between the semiconductor element 1 and the lead 3. In this case, the thin metal wire W between the points E2 and F2 corresponds to the inclined descending portion 5c of the loop wire 5, and the second reverse length R2 substantially corresponds to the horizontal length L1. Further, the first reverse angle θ1 becomes substantially zero because the thin metal wire W between the point A2 and the point C2 becomes the rising portion 5a of the loop wire 5, and the first reverse angle θ1 becomes 90 ° C2E2D2, that is, 90 °.
−θ2 is expanded to ΔH2JK.

Next, the first and second reverse angles θ1, θ2, and the second
The optimum range of the reverse length R2 will be described with reference to FIGS. FIG. 2 shows the horizontal length from the pad center A2 to the stitch bond point H2 (hereinafter referred to as loop length).
4 is a graph showing an optimum range of the second reverse length R2 with respect to the loop length L2 by a hatched portion. FIG. 3 is a graph showing an optimum range of the second reverse angle θ2 with respect to the loop length L2 by a hatched portion.
FIG. 5 is a view showing a shape of the loop wire 5 when the second reverse length R2 and the second reverse angle θ2 are in inappropriate ranges.

The optimum range obtained in the experiment of the second reverse length R2 is that the loop length L2 is 0.5 ≦ L2 ≦ 12.
In the case of (unit mm), as shown in FIG. 2, it is determined by (2/15) × L2 ≦ R2 ≦ (8/15) × L2 (1). For example, if R2> (8/15) × L2,
As shown in FIG. 4A, the second reverse length R2
Is excessively large, and a state is left around the rising portion 5a of the loop wire 5 at the time of reverse processing. Also, R2 <
In (2/15) × L2, as shown in FIG. 4B, the second reverse length R2 becomes too small, and the inclined descending portion 5c of the loop wire 5 becomes longer, and the inclined descending portion 5c
Is hung downward.

Further, the step distance between the upper surfaces of the semiconductor element 1 and the lead 3 is defined as h2, and K = (h1 + h2) / (L2
−L1), the optimal range obtained in the experiment for the second reverse angle θ2 (unit degree) is tan ⁻¹ K ≦ θ2 ≦ (7/2) × tan ⁻¹ K... · (2) θ2 ≦ 60 (3) Here, when the loop height h1 = 0.2 mm and the step distance h2 = 0.4 mm, the minimum value of L1 is L
1 {R2 = (2/15) × L2, the maximum value of L1 is L1}
Since R2 = (8/15) × L2, the equation (2) can be expressed as follows: tan ⁻¹ {9 / (13 × L2)} ≦ θ2 ≦ (7/2) × tan
⁻¹ {9 / (7 × L2)} · (4), which is shown in FIG. For example, θ2> (7/2) × tan
^{In the case of −1} {9 / (7 × L2)}, as shown in FIG. 4C, a dent occurs in the horizontal portion 5b of the loop wire 5 and θ2 <tan ⁻¹ ｛9 / (13 × In L2), as shown in FIG. 4D, the horizontal portion 5b of the loop wire 5 is inclined toward the lead 3, so that the horizontal state cannot be maintained and the loop wire 5 has a triangular loop shape.

Further, the first reverse angle θ1 needs to be set small according to the loop length L2 in order to balance the tension of each part of the thin metal wire W when the capillary 10 is moving in an arc shape. . The optimum range obtained by the experiment of the first reverse angle θ1 (unit degree) is as follows: 5 ≦ θ1 ≦ 50 (5)

As described above, when the loop length L2 is 0.5 ≦
In the range of L2 ≦ 12 (unit: mm), equation (1)
(2), (3) and (5), while feeding out the thin metal wire W, the capillary 1 is moved from the pad center A2.
The vertical movement of the leading end of the capillary 10 and the horizontal movement of the lead 3 to the opposite side are repeated twice, and then the leading end of the capillary 10 is vertically moved up by a predetermined distance, and then the relative movement between the capillary 10 and the thin metal wire W is performed. Capillary 10
Is moved horizontally to the lead 3 side by a predetermined distance, and is then moved down in an arc shape onto the lead 3, so that the pad 1a and the lead 3 of the semiconductor element 1 are connected to the proper rising portion 5a and the proper horizontal position. The connection can be made with an appropriate loop wire 5 having an appropriate inclined descending portion 5c.

Embodiment 2 FIG. A semiconductor device according to the second embodiment will be described with reference to FIG. When the loop wire 5 is formed between the pad 1a of the semiconductor element 1 and the lead 3 by the wire bonding method described in the first embodiment, the shape of the loop wire 5 satisfies the following conditions.

First, the horizontal length L1 of the loop wire 5 from the pad center A2 to the bending point J is equal to the second reverse length R2.
From the equation (1), the condition that the horizontal length L1 satisfies is that when the loop length L2 is in the range of 0.5 ≦ L2 ≦ 12 (unit mm), (2/15) × L2 ≦ L1 ≦ (8/15) × L2 (6)

The angle α on the side of the semiconductor element 1 formed by the horizontal portion 5b and the inclined descending portion 5c of the loop wire 5 is ΔF2E
Since 2C2, that is, approximately equal to (180 degrees−θ2), the condition that the angle α (unit degree) satisfies from the equation (2) is 180− (7/2) × tan ⁻¹ K ≦ α ≦ 180−tan ⁻¹ K (7) and from equation (3), 120 ≦ α ≦ 180 (8)

The loop height h1 of the loop wire 5
Is 1 from the formula (5), the diameter of the thin metal wire W, and heat curing.
00 ≦ h1 ≦ 300 (unit μm).

Therefore, the loop wire 5 of the semiconductor device formed by the wire bonding method described in the first embodiment satisfies the equations (6), (7) and (8).

Embodiment 3 FIG. The wire bonding method of the third embodiment is the same as that of the first and second embodiments.
The reference numerals and symbols used in the description of the wire bonding methods of the first and second embodiments are used as they are in the third embodiment.

The wire bonding method according to the third embodiment clarifies an inherent problem that arises when the pad 1a of the semiconductor element 1 and the lead 3 are connected by a trapezoidal loop-shaped loop wire 5. The content is clarified. Therefore, the inherent problem will be described first with reference to FIGS.

FIG. 7 is a diagram showing a movement route of the tip of a capillary for forming a trapezoidal loop wire in wire bonding, and FIG. 8 is a plan view around a semiconductor element during wire bonding.

In the figure, reference numeral 11 denotes a capillary which is attached to the tip so as to form an angle of approximately 90 degrees, and this capillary 10 is moved in the left-right direction shown by an arrow A in FIG.
This is a US horn as a bonding head that moves in the front-back direction indicated by an arrow B and the up-down direction indicated by an arrow C in FIG. The US horn 11 is disposed, for example, on the 0 degree side of the semiconductor element 1 behind the semiconductor element 1 so as to face the front-rear direction B, and is disposed in an inclined state with the tip side upward as shown in FIG. I have. Therefore, the capillary 10 is in a state of being inclined such that the lower end (front end) side faces the front Ba side.

Represents a pad 1a and a lead 3 of the semiconductor device 1.
Of the angles formed by the direction on the plane of the loop wire 5 connecting between them and the direction m in which the US horn 11 moves horizontally toward the semiconductor element 1, the angle on the US horn 11 side toward the lead 3 (hereinafter referred to as loop) Angle). In this case, the loop angle ψ takes various values between 0 and 180 degrees depending on the position of the lead 3 arranged around the semiconductor element 1. For example, if the pad 1a of the semiconductor element 1 is on the front side of the lead 3, the loop angle ψ becomes an acute angle smaller than 90 degrees (hereinafter, the loop angle の in this state is indicated by ψ1), and the pad 1a of the semiconductor element 1 On the rear side of 3, the loop angle ψ becomes an obtuse angle larger than 90 degrees (hereinafter, the loop angle の in this state is indicated by ψ2).

Q1 is for connecting the pad 1a of the semiconductor element 1 and the lead 3 with the trapezoidal loop wire 5 when the lead 3 is arranged in the state of ψ1 where the loop angle と becomes an acute angle. The setting movement route in which the tip of the capillary 10 moves while feeding out the thin metal wire W is shown.
As shown in FIG. 7, the set movement route Q1 includes a vertical rise from the pad center A10 to the point B10,
Horizontal movement from the point to the point C10 on the opposite side of the lead 3, and C
The vertical movement from the point D10 to the point D10, the horizontal movement from the point D10 to the point E10 opposite to the lead 3, and the vertical rise from the point E10 to the point F10.

Q2 indicates a set movement route in which the tip of the capillary 10 similarly moves when the lead 3 is arranged in the state of ψ2 where the loop angle ψ becomes an obtuse angle.
As shown in FIG. 7, the set movement route Q2 is similar to the set movement route Q1 from the pad center A20 to B2.
It is formed from vertical ascent and horizontal movement through points 0, C20, D20, E20, and F20. S is the set movement amount of the capillary 10 when the tip of the capillary 10 follows the set movement route Q1 or the set movement route Q2.

When the tip of the capillary 10 reaches the point F10 through the set movement route Q1, the thin metal wire W is fed out of the capillary 10 so as to reach the point C10 from the pad center A10 and the point F10 through the point E10. The pad 1 of the semiconductor element 1 is formed by the unwound metal wire W.
An appropriate loop wire 5 is formed between a and the lead 3. In addition, the tip of the capillary 10 is set to the set movement route Q.
2, the metal thin wire W is fed out of the capillary 10 from the pad center A20 to the point C20, passes through the point E20 and reaches the point F20, and the semiconductor element 1 is moved by the fed metal thin wire W. Pad 1a
An appropriate loop wire 5 is formed between the wire 3 and the lead 3.

On the other hand, when the tip of the capillary 10 moves horizontally along the set movement route Q1, as shown in FIG.
The angle β between a and the direction in which the tip of the capillary 10 moves is an obtuse angle. For this reason, the frictional force acting on the capillary 10 and the thin metal wire W at the tip of the capillary 10 has a larger value than when the angle β is a right angle. When the capillary 10 moves horizontally in the set movement route Q2, the angle β between the feeding axis 10a of the thin metal wire W of the capillary 10 and the direction in which the tip of the capillary 10 moves becomes an acute angle. For this reason, capillary 1
At the zero point, the frictional resistance acting on the capillary 10 and the thin metal wire W has a smaller value than when the angle β is a right angle.

FIG. 9 is a diagram showing a comparison between the set movement route at the tip of the capillary and the actual movement route. On the set movement route Q1 side where the frictional resistance during horizontal movement is large, B1
The tip of the capillary 10 from point 0 to point C10 cannot reach point C10 and moves only to point C11. For this reason, the tip of the capillary 10 vertically rises from point C11 to point D11 at the same height as point D10,
It moves horizontally from point 11 to point E11. In this case, D1
The distance between point 1 and point E11 is shorter than the distance between point D10 and point E10. Then, the tip of the capillary 10 moves from the point E11 to the point F11 at the same height as the point F10. Therefore, on the set movement route Q1 side, the capillary 10
The tip of moves along the actual travel route, which is partially indicated by a broken line,
The moving amount of the capillary 10 is smaller than the set moving amount S.

That is, when the tip of the capillary 10 actually follows the movement route, the thin metal wire W
It is fed out from 10 so as to pass through points C11, E11 and F11. For this reason, the first reverse length R1 is shorter than the required amount, the loop height h1 of the loop wire 5 is reduced, and the second reverse length R2 is also shorter than the required amount. 1 pad 1a
And the lead 3 is pulled and the loop height h
1 gets lower and lower.

On the set movement route Q2 side where the frictional resistance during horizontal movement is small, the tip of the capillary 10 from the point B20 to the point C20 exceeds the point C20 and moves to the point C21.
Reach the point. Therefore, the tip of the capillary 10 is C
After ascending vertically from point 21 to point D21 having the same height as D20, it moves horizontally from point D21 to point E21. In this case, the distance between the points D21 and E21 is longer than the distance between the points D20 and E20. Then, the tip of the capillary 10 moves from the point E21 to the point F21 having the same height as the point F20. Therefore, on the set movement route Q2 side, the tip of the capillary 10 moves on the actual movement route partially shown by the broken line, and the movement amount of the capillary 10 becomes larger than the set movement amount S.

That is, when the tip of the capillary 10 actually follows the movement route, the thin metal wire W is moved to the pad center A2.
It is fed out from 0 through the points C21, E21 and F21. For this reason, the first reverse length R1 is longer than the required amount, the loop height h1 of the loop wire 5 is increased, and the second reverse length R2 is also longer than the required amount. H1 is getting higher and higher.

As described above, the loop height h1 of the formed loop wire 5 varies depending on the positions of the leads 3 arranged around the semiconductor element 1, and the quality of the completed semiconductor device varies. The problem that it comes out occurs. And this tendency is the loop length L2
The longer the is, the larger it is.

[0053]

[Table 1] Table 1 shows a change in loop height h1 (μm) when the loop wire 5 is formed between the set movement route Q1 (ψ = 0 °) and the set movement route Q2 (ψ = 180 °). ing. On the set moving route Q1 side, the loop height h1 decreases as the loop length L2 increases, and on the setting moving route Q2 side, the loop height h1 increases as the loop length L2 increases. Therefore, the difference in the loop height h1 between the set moving route Q1 side and the set moving route Q2 side gradually increases as the loop length L2 increases.

Next, a wire bonding method according to an embodiment of the present invention will be described with reference to FIGS.

FIG. 5 is a diagram showing a comparison between a set movement route of the tip of the capillary and an example of a correction movement route. When the lead 3 is arranged in a state where the loop angle と becomes an acute angle ψ1 (see FIG. 8), even when the tip of the capillary 10 is moved along the set movement route Q1, the capillary 10 is not moved when the capillary 10 is horizontally moved. Therefore, the capillary 10 cannot move by the set movement amount S because the frictional resistance between the wire 10 and the metal wire W becomes large. Also, when the lead 3 is arranged in the state of ψ2 where the loop angle 鈍 is an obtuse angle (FIG. 8).
Reference), set the tip of the capillary 10 Movement route Q2
When the capillary 10 is moved along the horizontal axis, the frictional resistance between the capillary 10 and the thin metal wire W decreases when the capillary 10 moves horizontally, so that the capillary 10 moves more than the set movement amount S.

Therefore, in the wire bonding method of the third embodiment, the moving amount of the capillary 10 is changed depending on the magnitude of the loop angle ψ. That is, in the state of ψ1 in which the loop angle と becomes an acute angle, the amount of movement of the capillary 10 moving while feeding out the metal wire W is increased, and the amount of the metal wire W deficient in the loop wire 5 is compensated for by this. In the state of ψ2 where ψ is an obtuse angle, the moving amount of the capillary 10 moving while feeding out the thin metal wire W is reduced, and the loop wire 5
In this case, the excess amount of the fine metal wire W is absorbed by this.

Specifically, when the tip of the capillary 10 moves along the set movement route Q1, the tip of the capillary 10 is moved along the actual movement route from the pad center A10 to the points B10, C11, D11 and E11. After the movement, it is moved to a point F12 higher by Δ1 than the point F11. As a result, the amount of the fine metal wire W drawn out from the capillary 10 is also drawn out long by the shortage Δ1, and the loop wire 5 is pulled between the pad 1a and the lead 3 of the semiconductor element 1, and the loop height h1 is drawn.
Is never lower.

When the tip of the capillary 10 moves along the set movement route Q2, the tip of the capillary 10 is moved along the actual movement route from the pad center A20 to B20.
After moving the point, E21 point and E21 point,
Move to the F22 point lower by Δ2 than the point. As a result, the fine metal wire W fed out of the capillary 10
Is also reduced by the excess Δ2, so that the loop wire 5
Does not become excessive and the loop height h1 does not increase. The movement amount of the capillary 10 may be increased or decreased not only when the capillary 10 is vertically moved but also when the capillary 10 is horizontally moved.

Next, when the loop length L2 and the loop angle ψ change, the capillary 1 required to form the optimum loop wire 5 having the same loop height h1 is formed.
The details of the movement amount of 0 will be described. Here, the reason why the loop length L2 is used as a variable is that the horizontal movement amount of the capillary 10 significantly changes depending on the increase or decrease of the loop length L2. At the time of horizontal movement, the angle β between the feeding axis 10a of the fine metal wire W of the capillary 10 and the moving direction of the tip of the capillary 10 changes due to the loop angle ψ, and the frictional resistance between the fine metal wire W and the capillary 10 changes. is there.

When the tip of the capillary 10 follows the set movement route Q 1 or Q 2, the set amount of the thin metal wire W from the capillary 10, that is, a trapezoidal loop between the pad 1 a of the semiconductor element 1 and the lead 3. The feeding amount of the metal wire W from the capillary 10 set for connection by the metal wire W (loop wire 5) is P1
When the loop length is L2 (unit mm), the loop angle is ψ (unit radian), and the proportional constant is N,
Feed amount P after correction of the fine metal wire W from the capillary 10
2 is experimentally shown as P2 = {N × (L2−3) × (ψ−π / 2) +1} × P1 (9)

Therefore, when n = P2−P1, if n is a positive value, for example, the position where the capillary 10 finally rises while feeding out the thin metal wire W (point E10 in the case of the set movement route Q1) ) Is increased by n, then the loop height h between the semiconductor element 1 and the lead 3 is increased.
An optimum loop wire 5 having equal 1 is formed.
If n is a negative value, for example, if the position where the capillary 10 finally rises while feeding the thin metal wire W (point E20 in the case of the set movement route Q2) is lowered by n, then the semiconductor element 1 Loop height h between lead 3
An optimum loop wire 5 having equal 1 is formed.

Here, when the step distance h2 between the surface of the semiconductor element 1 and the lead 3 is 0.2 mm and the loop length L2 is 3 to 6 mm, the proportionality constant N is experimentally -2.
It is determined in the range of 3 × 10 ⁻⁵ to −4.0 × 10 ⁻⁵ .

FIG. 6 shows a correction coefficient M when the proportionality constant S is in the above range, that is, N × (L2−3) × (ψ−π /
2) shows a change in the value of +1.

[0064]

[Table 2] Table 2 shows that the loop wire 5 is formed on the set movement route Q1 (ψ = 0 degree) side and the set movement route Q2 (ψ = 180 degree) side when the movement amount of the capillary 10 is corrected by the equation (9). 9 is a table showing changes in the loop height h1 (μm) and the like in the case of performing the above. As can be seen from Table 2, regardless of the size of the loop length L2, the loop height h1 of the loop wire 5 on the set moving route Q1 side and the set moving route Q2 side is substantially equal, and the loop heights of both are set. It can be seen that the difference in h1 is almost equal to zero.

[0065]

Since the present invention is configured as described above, it has the following effects. According to the wire bonding method of claim 1 of the present invention, the inverse tangent of the horizontal movement amount to the first vertical rise amount of the capillary is θ1 (unit degree), and the inverse tangent of the horizontal movement amount to the second vertical rise amount of the capillary is The inverse tangent of the horizontal movement is θ2
(Unit degree), the distance from the point after the first horizontal movement of the capillary tip to the point after the second horizontal movement of the capillary tip is R2, and the distance from the bonding point to the pad to the trapezoidal loop-shaped thin metal wire is L1 is the horizontal distance from the starting point of the descent to the lead side, L2 is the horizontal distance from the bonding point to the pad to the bonding point to the lead, h1 is the height of the rising portion of the trapezoidal loop-shaped thin metal wire, and h1 is the height of the pad. When the step distance between the lead and the surface is h2, K =
If (h1 + h2) / (L2-L1), then 0.5 ≦ L2 ≦
Under conditions of 12 (unit: mm), 5 ≦ θ1 ≦ 50, tan
⁻¹ K ≦ θ2 ≦ (7/2) × tan ⁻¹ K, θ2 ≦ 6
0, (2/15) × L2 ≦ R2 ≦ (8/15) × L2,
Since the capillary is moved so as to satisfy the following condition, the pad and the lead of the semiconductor element can be reliably and properly connected by the trapezoidal loop-shaped thin metal wire.

According to a second aspect of the present invention, the horizontal distance from the bonding point to the pad to the start point of the inclination of the trapezoidal loop-shaped thin metal wire toward the lead side is L1, the bonding point to the pad is L1. L2 is the horizontal distance from the lead to the bonding point to the lead, h1 is the height of the rising portion of the trapezoidal loop-shaped thin metal wire, h2 is the step distance between the surface of the pad and the lead, and horizon of the trapezoidal loop-shaped thin metal wire. K = (h1 + h2) / (L2-L1) where α (unit degree) is the angle on the semiconductor element side of the angle formed by the angle and the inclined descending portion.
Then, (2/15) × L2 ≦ L1 ≦ (8/15) ×
L2, 0.5 ≦ L2 ≦ 12 (unit mm), 180− (7 /
2) × tan ⁻¹ K ≦ α ≦ 180−tan ⁻¹ K, 1
Since the trapezoidal loop-shaped fine metal wire is formed between the pad and the lead of the semiconductor element so as to satisfy the condition of 20 ≦ α ≦ 180, the trapezoidal loop-shaped fine metal wire is more appropriately formed, and the quality of the semiconductor device is improved. Is further improved.

According to the wire bonding method of the third aspect of the present invention, when the angle between the axial direction in which the thin metal wire of the capillary is fed out and the moving direction of the capillary during the horizontal movement is an obtuse angle, The moving amount of the capillary moving while feeding out the thin line is increased from a set value, and when the angle is an acute angle, the moving amount of the capillary moving while moving out the thin metal wire is made smaller than the set value. In the case of the invention, the height of the trapezoidal loop-shaped thin metal wire formed between the pad and the lead of the semiconductor element can be made uniform, and the pad and the lead of the semiconductor element can be properly connected by the trapezoidal loop-shaped thin metal wire. it can.

According to the wire bonding method of the fourth aspect of the present invention, the horizontal moving direction of the bonding head for moving the capillary toward the semiconductor element side is determined by:
The loop angle between a line connecting the pad of this semiconductor element and the lead on the plane is ψ (unit radian), and the horizontal distance of the trapezoidal loop-shaped thin metal wire from the bonding point to the pad to the bonding point to the lead is L2. (Unit m
m), when the feeding amount of the thin metal wire from the capillary set for connecting the pad and the lead with the trapezoidal loop thin metal wire is P1 and the proportional constant is M,
P2 = {M × (L2-3) × (ψ−π / 2) +1} × P
The amount of movement of the capillary at the time of feeding out the thin metal wire is determined so that the thin metal wire is fed out by the corrected feeding length P2 of the thin metal wire calculated in 1.
The height of the trapezoidal loop-shaped thin metal wires formed between the pads and the leads of the semiconductor element can be further uniformized, and the pads and the leads of the semiconductor element can be properly connected by the trapezoidal loop-shaped thin metal wires.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of a wire bonding method according to a first embodiment of the present invention.

FIG. 2 is a graph showing an optimum range of a second reverse length with respect to a loop height in the wire bonding method of FIG. 1;

FIG. 3 is a graph showing an optimum range of a second reverse angle with respect to a loop length in the wire bonding method of FIG. 1;

FIG. 4 is a view showing a shape of a loop wire when a second reverse length and a second reverse angle are in an inappropriate range in the wire bonding method of FIG. 1; (A)
Shows a case where the second reverse length is too long, and (b) shows a case where the second reverse length is too short. (C) shows a case where the second reverse angle is too large, and (d) shows a case where the second reverse angle is too small.

FIG. 5 is an explanatory diagram of a wire bonding method according to a third embodiment of the present invention.

FIG. 6 is a diagram showing values of a correction coefficient with respect to a loop angle when a proportional constant is in a certain range in the wire bonding method of FIG. 5;

7 is a diagram that is a prerequisite for explaining the wire bonding method of FIG. 5, and is a diagram illustrating a movement route of a tip of a capillary for forming a trapezoidal loop-shaped loop wire.

8 is a prerequisite diagram for explaining the wire bonding method of FIG. 5, and is a plan view around a semiconductor element during wire bonding.

9 is a diagram that is a prerequisite for explaining the wire bonding method of FIG. 5, and is a diagram illustrating a comparison between a set movement route of a capillary tip and an actual movement route.

FIG. 10 is an explanatory diagram of a conventional wire bonding method.

FIG. 11 shows a conventional wire bonding method.
It is a figure which shows the shape of the formed loop wire when a loop length is long.

FIG. 12 is a diagram illustrating the shape of a trapezoidal loop-shaped loop wire.

[Explanation of symbols]

Reference Signs List 1 semiconductor element, 1a pad, 3 lead, 5
Loop wire (trapezoidal loop-shaped thin metal wire), 5a
Rising part, 5b horizontal part, 5c inclined descending part, 10
Capillary, 11 US horn (bonding head), h1 loop height (height of rising part), h2
Step distance, L1 horizontal distance, L2 loop length (horizontal distance), R1 first reverse length (distance), R2
Second reverse length (distance), θ1 first reverse angle (inverse tangent), θ2 second reverse angle (inverse tangent),
W Fine metal wire, ル ー プ Loop angle.

Continuation of the front page (56) References JP-A-3-142941 (JP, A) JP-A-4-273135 (JP, A) JP-A-2-189942 (JP, A) JP-A-4-318943 (JP) JP-A-6-177195 (JP, A) JP-A-5-211193 (JP, A) JP-A-5-67643 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB (Name) H01L 21/60 301

Claims (4)

(57) [Claims] 1. A trapezoidal loop having a rising portion from a pad of a semiconductor element, a horizontal portion extending from the rising portion toward a lead, and an inclined lowering portion extending from the horizontal portion toward the lead. A wire bonding method for connecting a pad of the semiconductor element and the lead with a thin metal wire, wherein after bonding one end of the thin metal wire drawn out from the tip of a capillary to the pad, the thin metal wire is separated from the capillary. The vertical movement of the capillary and the horizontal movement to the opposite side of the lead are performed for 2 seconds while being extended.
After the repetition, the capillary is further vertically raised to a predetermined height, and then, in a state where the relative movement between the capillary and the fine metal wire is eliminated, the capillary is horizontally moved by a predetermined amount toward the lead side. After the movement, the capillary is moved to the lead side in an arc shape, and the other end side of the thin metal wire is bonded to the lead by a wire bonding method. The inverse tangent of the movement amount is θ1 (unit degree), the inverse tangent of the horizontal movement amount with respect to the second vertical rise amount of the capillary is θ2 (unit degree), and the point of the capillary tip after the first horizontal movement The distance to the point after the second horizontal movement of the tip of the capillary is R2, and the trapezoidal loop is formed from the bonding point to the pad. L1 is the horizontal distance of the thin metal wire from the bonding point to the pad to the lead point, and L2 is the horizontal distance from the bonding point to the pad to the bonding point to the lead. When the height is h1 and the step distance between the surface of the pad and the lead is h2, K = (h1 + h2)
/ (L2-L1), 0.5 ≦ L2 ≦ 12 (unit m
Under the condition of m), 5 ≦ θ1 ≦ 50, tan ⁻¹ K ≦ θ2 ≦ (7/2) × tan ⁻¹ K, θ2 ≦ 60, (2/15) × L2 ≦ R2 ≦ (8/15) × L2, The wire bonding method, wherein the capillary is moved so as to satisfy the following condition. 2. A trapezoidal loop having a rising portion from a pad of a semiconductor element, a horizontal portion extending from the rising portion toward a lead, and an inclined descending portion extending from the horizontal portion toward the lead. In the semiconductor device in which the pad of the semiconductor element and the lead are connected by a thin metal wire, a horizontal line from a bonding point to the pad to a start point of the trapezoidal loop-shaped thin metal wire inclined downward to the lead side. The distance is L1, the horizontal distance from the bonding point to the pad to the bonding point to the lead is L2, the height of the rising portion of the trapezoidal loop-shaped thin metal wire is h1, and the distance between the surface of the pad and the lead is When a step distance is h2 and an angle on the semiconductor element side is α (unit degree) among angles formed by the horizontal portion and the inclined descending portion of the trapezoidal loop-shaped thin metal wire, If K = (h1 + h2) / (L2-L1), (2/15) × L2 ≦ L1 ≦ (8/15) × L2, 0.5 ≦ L2 ≦ 12 (unit mm), 180− (7 / 2) The trapezoidal loop-shaped thin metal wire is formed so as to satisfy the following condition: × tan ^-1 K ≦ α ≦ 180−tan ⁻¹ K, and 120 ≦ α ≦ 180. 3. Bonding one end of a thin metal wire drawn from the tip of the capillary to a pad of a semiconductor element, and then feeding the thin metal wire from the capillary.
After repeating the vertical raising of the capillary and the horizontal movement to the side opposite to the lead twice, the vertical raising of the capillary is further performed to a predetermined height, and then the capillary and the fine metal wire are connected to each other. After the capillary is horizontally moved by a predetermined amount to the lead side in a state where the relative movement is eliminated, the capillary is moved in an arc shape to the lead side, and the other end side of the fine metal wire is bonded to the lead. The pad of the semiconductor element and the lead, a rising part from the pad, a horizontal part from the rising part to the lead side, and an inclined descending part from the horizontal part on the lead. A wire bonding method for connecting with a trapezoidal loop-shaped thin metal wire, comprising: an axial direction in which the thin metal wire of the capillary is drawn out; When the angle between the horizontal moving direction and the moving direction is an obtuse angle, the moving amount of the capillary moving while feeding the thin metal wire is increased from a set value, and when the angle is an acute angle, the thin metal wire is fed. A wire bonding method, wherein the moving amount of the capillary moving while moving is reduced below a set value. 4. Bonding one end of a thin metal wire drawn from the tip of a capillary to a pad of a semiconductor element, and then feeding the thin metal wire from the capillary.
After repeating the vertical raising of the capillary and the horizontal movement to the side opposite to the lead twice, the vertical raising of the capillary is further performed to a predetermined height, and then the capillary and the fine metal wire are connected to each other. After the capillary is horizontally moved by a predetermined amount to the lead side in a state where the relative movement is eliminated, the capillary is moved in an arc shape to the lead side, and the other end side of the fine metal wire is bonded to the lead. The pad of the semiconductor element and the lead, a rising part from the pad, a horizontal part from the rising part to the lead side, and an inclined descending part from the horizontal part on the lead. A wire bonding method for connecting with a trapezoidal loop-shaped thin metal wire, wherein water is supplied to the semiconductor element side of a bonding head for moving the capillary. The trapezoidal loop from the bonding point to the pad to the bonding point to the lead is defined as ル ー プ (unit radian), where ル ー プ is a loop angle between the moving direction and a line connecting the pad and the lead of the semiconductor element on a plane. L2 (unit: m)
m), when the feeding amount of the fine metal wire from the capillary is set to P1 and the proportionality constant is set to N for setting the connection between the pad and the lead by the trapezoidal loop-shaped fine metal wire, P2 = {N × (L2−3) × (ψ−π / 2) +1} × P1, by the corrected feeding amount P2 of the fine metal wire,
A wire bonding method, wherein an amount of movement of the capillary at the time of feeding out the thin metal wire is determined so as to feed out the thin metal wire.