JP2567866B2 - Semiconductor device - Google Patents

Description

TECHNICAL FIELD The present invention relates to a semiconductor device in which a semiconductor chip such as an IC or LIS is fixed by a lead frame.

[Conventional technology]

2. Description of the Related Art Conventionally, a metal lead frame has been used for assembling a semiconductor device in which a semiconductor chip is integrated with a resin mold and a plurality of pins are projected. This lead frame is formed by punching a thin metal plate with a press, etching, etc., and its shape is as shown in FIG.
Tab leads 3 supporting rectangular tabs 2 to which the semiconductor chip 1 is attached at four corners thereof, a plurality of fingers 4 having inner ends facing the periphery of the tabs 2, and frame portions supporting outer ends of these fingers 4 and tab leads 3. 5 and sprocket holes 6 provided at regular intervals along both side edges of the frame portion 5.

In order to assemble a semiconductor device using such a lead frame 10, first, the semiconductor chip 1 is mounted on the tab 2, and then each electrode of the semiconductor chip 1 and the inner end of the finger 4 corresponding thereto is attached with a wire or a wire. Direct connection without using, then the inner region of the rectangular frame 5 is molded with synthetic resin to cover the semiconductor chip 1, then the frame 5 is cut off,
A flat lead or in-line type semiconductor device is obtained.

By the way, in the above semiconductor device, it is extremely difficult to connect the finger 4 of the lead frame 10 to the electrode of the semiconductor chip 1. As the number of pins of the semiconductor device, that is, the number of fingers 4 of the lead frame 10 has increased recently, and further, due to the miniaturization, the interval between the adjacent fingers 4 becomes small and the width of the fingers 4 itself becomes narrow. The efficiency and reliability of the connection work are not negligible with respect to the product cost. Therefore, as shown in FIG. 5, the aluminum electrode 8 formed on the silicon 7 is thinner than the protective film 9 formed on the silicon surface, and the aluminum electrode 8 formed on the inner side of the semiconductor chip 1 has a conventional structure. Further, a bump 4a is provided at the tip of the finger 4 which is connected to the electrode 8 so as to ensure the contact. However, in recent years, when a semiconductor device having a large number of pins is required, the width of the finger is inevitably narrower and it is becoming difficult to form the bump.

As a method for eliminating these drawbacks, facilitating manufacturing, and forming a fine portion, a lead frame using an electroforming technique has recently been developed.

6 (a) to 6 (g) are process drawings for explaining a method of manufacturing a lead frame using an electroforming technique.

First, as shown in FIG. 6 (a), a resin material such as polyimide or polyester is provided on the surface of the metal film of the base material 11 on which a conductive metal film of aluminum, copper, stainless steel or the like is formed. One resist layer 12 is applied. At the time of applying the resist layer 12, the application surface of the base material 11 is previously subjected to a peeling process.

Next, as shown in FIG. 6B, a mask 13 for forming bumps is set (that is, masked) on the surface of the resist layer 12, and in this state, exposure is performed from above the mask 13. In the mask 13, only the portions where bumps are desired to be formed are made non-transparent, and the other portions are made transparent. Further, the resist layer 12 is made of a material that is cured by being irradiated with an ultraviolet ray or an electron beam. Therefore, the exposure hardens the resist layer portion immediately below the transparent portion 13a of the mask 13 and leaves the resist layer portion immediately below the light shielding portion 13b uncured.

Next, as shown in FIG. 6 (c), the uncured portion of the resist layer 12 is removed, the surface of the base material 11 exposed from this portion is etched to form a recess, and a gold plating is formed at this etching portion. Give. Then, the resist layer 12 left on the surface of the base material 11 is removed. The gold plating formed on the etching portion becomes the bump 14.

Next, as shown in FIG. 6D, a second resist layer 15 is applied to the surface of the base material 11 on which the bumps 14 are formed.

Next, as shown in FIG. 6 (e), a mask 16 for forming the lead portion is mounted. In this mask 16, only the lead forming portion is made non-translucent and the other portions are made transparent.
In this state, when exposed to ultraviolet rays as in the case of FIG. 6B, the resist layer 15 immediately below the transparent portion of the mask 16 is cured, and the resist layer portion immediately below the non-light-transmitting portion is uncured. This uncured portion is removed from the surface of the base material 11,
Only the cured resist layer 15 is left.

Next, as shown in FIG. 6 (f), lead portions made of copper material are formed on the surfaces of the base material 11 and the bumps 14 other than the resist layer 15.
Electroform 17 By this electroforming, the bumps 14 are connected to the lead portions 17
Connected to.

Further, as shown in FIG. 6 (g), the lead portion 17 with bumps, that is, the inner lead is peeled from the base material 11. In the description of FIG. 6, the manufacturing process of the pair of leads has been described, but as shown in FIG. 4, a large number of semiconductor chips 1 are simultaneously formed corresponding to the number of electrodes.

The lead frame manufactured in this way can accommodate a large number of electrodes.

However, according to the method of manufacturing the lead frame as shown in FIG. 6, it is required that the bump 14 is connected to the lead portion 17 so as to come to the center of the electrode 8 in FIG. 7 (a). Instead, the bumps 14 may be displaced as shown in FIG. 7 (b). If the bumps 14 are misaligned, it may result in poor connection to the electrodes 8 and contact with adjacent electrodes.

As a solution to such a problem, there is, for example, Japanese Patent Application No. 60-49433. That is, as shown in FIG.
The second upper mold C, which is movably provided with respect to the upper mold A, is slightly moved down while the frame 5 of the lead frame 10 and the base 4b of the finger 4 are preloaded by the lower mold B. As a result, as shown in FIGS. 9 (a) and 9 (b), the thin portion 4c is formed in the middle portion of the finger 4 to be somewhat wide, and
A bulging bump 4a is simultaneously formed at the tip of the finger that is not pressed by the upper mold and the lower mold. The height of the bump 4a (step between the upper surface of the thin portion 4c and the upper surface of the bump 4a) is generally 12 to
It should be about 30μ.

[Problems to be solved by the invention]

However, in the semiconductor device using the lead frame as shown in FIG. 9 (b), since the thin portion bulges from the lead portion, as shown in FIG.
Becomes smaller, making it easier to contact.

The present invention has been made in view of the above-mentioned conventional circumstances, and does not cause a portion bulging from the lead portion,
An object of the present invention is to provide a semiconductor device in which bumps can be formed at accurate positions.

[Means for solving problems]

In order to solve the above-mentioned problems, the present invention provides a semiconductor device in which a conductor portion for an electrode of a semiconductor chip is formed by using a lead frame in which a bump is formed at a tip of a lead portion, and the bump has a contact surface with the electrode. The bumps are shaped like arcuate sides, and the bumps are formed over the entire width of the tip of the lead portion, and the axial direction thereof is orthogonal to the length direction of the lead portion.

[Action]

By forming a bump-shaped bump over the entire width of the tip of the lead part, it is connected to the electrode of the semiconductor chip by line contact over the entire width of the tip of the lead part, so that the contact point may be displaced outside the electrode surface as in the past. Never,
A stable connection is obtained.

Also, since the contact surface side of the bump with the electrode has an arcuate shape, even if the pressing pressure or angle of the lead frame against the electrode varies, it adapts well and corresponds to any part of the arc surface. Are in line contact, and the contact is reliable. If the axial direction of the bump-shaped bump is inclined with respect to the length direction of the lead part, it will be a single contact at the contact part with the electrode of the bump, and the good familiarizing effect as described above cannot be obtained. If the axial direction of the semi-cylindrical bump is orthogonal to the length direction of the lead portion as in the invention, the above-mentioned familiar effect can be sufficiently exerted. Bumps can be formed without bulging the leads,
There is no need to narrow the gap between the lead parts.

〔Example〕

 An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a perspective view showing a lead frame of an embodiment of a semiconductor device according to the present invention. The lead frame 20 is
It is composed of a lead portion 20a and a bump-shaped bump 20b formed on the tip of the lead portion 20a so as to be orthogonal to the length direction of the lead portion 20a and formed over the entire width thereof. The bump 20b is formed as shown in FIG. 2 through a process using resist and electroforming.

2 (a) to (j) are process drawings explaining the process just before the second resist treatment in the process of manufacturing the lead frame according to the present invention.

First, as shown in FIG. 2 (a), a resin material such as polyimide or polyester is provided with a conductive metal film such as aluminum, copper, or stainless on the surface of the metal film of the base material 21. One resist layer 22 is applied. At the time of applying the resist layer 22, the application surface of the base material 21 is previously subjected to a peeling process.

Next, as shown in FIG. 2B, a bump forming mask 23 is set (that is, masking) on the surface of the resist layer 22, and in this state, exposure is performed from above the mask 23. As shown in FIG. 3, the mask 23 is composed of an annular light-shielding portion 23a in which only portions where bumps are desired to be formed are made non-transparent, and transparent portions 23b in which other portions are made transparent. Further, the resist layer 22 is made of a material that is cured by being irradiated with ultraviolet rays. Therefore, the exposure cures the resist layer portion immediately below the transparent portion 23a of the mask 23, and leaves the resist layer portion immediately below the light shielding portion 23b uncured.

Next, as shown in FIG. 2C, the uncured portion of the resist layer 22 is removed, and the surface of the base material 21 exposed from this portion is etched to form the sub-groove groove 24. Second
As shown in FIG. 6E, the second resist layer 25 is formed on the surface of the base material 21. This resist layer 25 consists of two layers,
A solution-type resist layer applied to such an extent that the concave groove 24 is buried.
25a, and a resist sheet 25b set on the resist layer 25a and adhered under pressure or heat.

Next, as shown in FIG. 2 (f), using a mask 26 in which the portion corresponding to the finger 4 shown in FIG. Expose. Thereby, the resist layer immediately below the transparent portion of the mask 26
25 is hardened, and the resist layer 25 immediately below the light shielding part is uncured.

Next, as shown in FIG. 2 (g), the uncured portion is removed from the surface of the base material 21, leaving only the resist layer 25 in the cured portion.

Next, as shown in FIG. 2 (h), a bump tip 27 is formed on at least the bottom of the recess groove 24 by electroforming of gold, and copper is further formed on the upper portion of the bump tip 27 and the removed portion of the resist layer 25. Electroforming is performed to form the lead portion 28. Through this step, the bump and the lead portion are formed.

Further, as shown in FIG. 2 (j), the lead portion 28 with bumps, that is, the inner lead is peeled from the base material 21. In the description of FIG. 2, the manufacturing process of the pair of leads has been described. However, as shown in FIG. 4, a large number of semiconductor chips are simultaneously formed corresponding to the number of electrodes of the semiconductor chip 1.

Assembly of the inner leads manufactured according to FIGS. 2 (a) to (j) is the same as that performed in the description of FIG. The obtained inner lead is as shown in FIG. 1, and since it becomes a line contact as opposed to the conventional point contact, the connection to the electrode 8 is surely made, and
It does not cause connection failure due to bump crushing.

Although FIG. 2 shows an example in which the resist layer 25 has two layers, this means that when a resist sheet is used, the concave groove 24 obtained by the step of FIG. 2 (d) is present. It is due to. That is, the resist sheet has an advantage that the thickness of the resist layer can be easily secured and the thickness of the lead portion can be correspondingly increased. However, in the case of only the resist sheet, as shown in FIG. 11, since the recessed groove 24 is closed, air is accumulated in the premises, and this air expands by pressurizing and heating the resist sheet 25b and faces the recessed groove 24. Then, the resist sheet 25b is lifted to impair the adhesion. As a result, it becomes difficult to manufacture a precise lead frame.

In order to eliminate such an inconvenience, the inside of the concave groove 24 may be filled with a resist member so that air is not present. For this reason, in the present invention, the concave groove 24 is filled with the solution resist layer 25a, and the resist sheet 25b is adhered to the surface of the solution resist layer 25a.

〔The invention's effect〕

As described above, according to the present invention, the bumps are formed in the semi-spherical shape instead of the conventional hemispherical shape, so that the bumps can be easily formed and the connection with the electrode of the semiconductor chip can be ensured.

[Brief description of drawings]

FIG. 1 is a perspective view showing a structure of an inner lead of a semiconductor device according to an embodiment of the present invention, and FIGS. 2 (a) to (j) are process drawings for explaining a manufacturing process of the lead frame shown in FIG. FIG. 3 is a perspective view showing a mask used in the step of FIG. 2 (f), FIG. 4 is a plan view showing a general lead frame shape, and FIG. 5 shows a relationship between bumps and electrodes of semiconductor chips. 6 is a sectional view showing the manufacturing process of a conventional lead frame, FIGS. 7 (a) and 7 (b) are plan views and perspective views showing non-defective and defective lead frames according to FIG.
FIG. 8 is a sectional view for explaining a pressing operation in another conventional lead frame manufacturing process, and FIGS. 9 (a) and 9 (b) are sectional views and perspective views showing a finger shape in another conventional lead frame, FIG. 10 is an explanatory view showing the lead interval of the lead frame according to FIG. 9, and FIG. 11 is the second resist layer.
FIG. 6 is an explanatory diagram showing a defect when 25 is only a resist sheet. 1 ... Semiconductor chip, 4 ... Finger, 8 ... Electrode, 20
...... Lead frame, 20a ...... Lead part, 20b ...... Bump.

Claims (1)

(57) [Claims] 1. A semiconductor device in which a conductor portion for an electrode of a semiconductor chip is formed by using a lead frame having a bump formed at a tip of a lead portion, wherein the bump has an arc surface on a contact surface side with the electrode. A semiconductor device, wherein the bump is formed into a shape, and the bump is formed over the entire width of the tip of the lead portion and the axial direction thereof is orthogonal to the length direction of the lead portion.