JP3116395B2 - Metal lead with bump and method of manufacturing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a metal lead with a bump for bonding to an electrode of a semiconductor chip and a method for manufacturing the same.

[0002]

2. Description of the Related Art An example of the prior art is disclosed in
88948 “Method for forming bonding bumps”. The method of forming a bump disclosed in this publication will be briefly described with reference to FIG.
As shown in A, the tip of the copper wire 101 is made spherical using a capillary chip 100, and this spherical portion is ball-bonded on a copper lead 103. Next, as shown in FIG. 21B, the copper wire 101 is pulled and cut at the upper portion of the ball 104. At this time, the protrusion 105 remains on the ball 104 due to plastic deformation. This protrusion 105 damages the semiconductor chip during tape carrier bonding,
Since the bondability is extremely lowered and is not preferable, FIG.
As shown in (1), a processing tool 106 having a concave surface is used to form and process the surface so as to have a spherical or gentle convex surface, thereby obtaining a bump 107 having a shape suitable for bonding.

[0003]

Although copper is used as the material of the leads 103 and the bumps 107, their purity and hardness are not mentioned and it is unknown, but usually copper of high hardness is used. As shown in FIG. 22, even if the surface shape of the bump is configured to be a spherical surface or a gentle convex surface as shown in the above-mentioned invention, the bump is formed on the aluminum electrode 109 formed on the surface of the semiconductor chip 108 as shown in FIG. Therefore, when the copper lead with copper bump 103 having such a configuration is joined, a crack 110 is often found inside the semiconductor chip 108, and there is a defect that the semiconductor chip 108 becomes defective.

In the method of manufacturing the copper lead 103 with the copper bump having the above-described structure, 1. It is necessary to apply 300 ° C. heat in order to sufficiently maintain the bonding between the copper ball 104 and the copper lead 103. In order to prevent oxidation of the copper ball 104 and the copper lead 103 due to heat, it is necessary to set the periphery of the joint to an atmosphere of nitrogen gas or an atmosphere of nitrogen gas and hydrogen gas. When the work is performed at a high temperature, the lead 103 is softened by the heat, and the lead 103 is easily deformed. 4. The bonding strength between the copper ball 104 and the copper lead 103 tends to be uneven. 5. The shape of the bump 107 formed by the copper ball 104 is likely to be uneven. 0.1 to 0.2 for bonding the bump 107 at one place
It takes seconds and productivity is extremely poor. For example, it takes about 10 to 20 seconds to manufacture a lead having about 100 pins, and is not suitable for mass production. Despite the necessity of considerable equipment, it takes a long time to manufacture, and has disadvantages such as an enormous manufacturing cost. Accordingly, the present invention seeks to solve the above problems.

[0005]

SUMMARY OF THE INVENTION Therefore, the present invention provides a lead made of high-hardness copper in which a bump made of pure copper is clad-joined to the tip of the lead, and a center part of the lead.
Leave a pure copper layer thinner than the bump thickness on the
The same pure copper layer as the pump was left. In manufacturing such metal leads with bumps, a mask for leads is applied to the surface of the high-hardness copper thin film of the clad plate in which a high-hardness copper thin film is formed with a pure copper thin film, and the corresponding mask is used. Then, a mask for bumps is applied to the thin film surface of the pure copper, and then high-hardness copper and pure copper in portions not covered with both masks are removed by etching and partially removed, and then both masks are removed. Thus, a metal lead with a bump as described above is obtained.

[0006]

Accordingly, the bumped metal lead of the present invention has a Vickers hardness of 40 to 80 of pure copper of the bump,
On the other hand, since the aluminum of the electrode of the semiconductor chip is 20 to 50, the two are very easy to be joined, and therefore do not adversely affect the semiconductor chip at the time of joining. In addition, since there is no heating during the manufacturing process, the metal leads are not oxidized or deformed, and furthermore, the shape of the bumps can be freely changed by masking. Therefore, it is possible to cope with miniaturized bonding. Furthermore, since the production equipment can be mass-produced without much expense, the production cost can be reduced.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below in detail with reference to the drawings. 1 to 5 are process diagrams showing a first method of manufacturing a metal lead with a bump according to an embodiment of the present invention. FIG. 1 is a perspective view of a clad plate used in the method of manufacturing a metal lead with a bump according to the present invention. 2 shows a second step, FIG. 2A is a top view of the clad plate, FIG. 2B is a bottom view thereof, and FIG. 2C is a cross-sectional view taken along line X ₁ -X ₂ of FIG. 3 is a partial sectional view showing a third step, FIG. 4 is a partial sectional view showing a fourth step, and FIG. 5 is a partial sectional view showing a fifth step.

First, the first step of the method for manufacturing a bumped metal lead according to the present invention will be described with reference to FIG. Reference numeral 1 indicates a clad plate as a whole. The clad plate 1 includes a high-hardness copper thin film layer 2 having a thickness of about 30 μm into which impurities such as Fe, Cr, and P are mixed, and a pure copper thin film layer 3 having a thickness of about 30 μm and having extremely low impurities. Although the thermocompression bonding is performed, the pure copper thin film layer 3 may be formed on the high hardness copper thin film layer 2 by using a thin film technique such as plating. The Vickers hardness of high hardness copper is 100 or more, while the Vickers hardness of pure copper is about 40 to 80.

In the second step shown in FIG. 2, a lead mask 4, a tie bar mask 5 and a frame mask as shown in FIG. 1A are formed on the surface of the high hardness copper thin film layer 2 of the clad plate 1 of FIG. 6 are connected by a photoresist technique or the like.
The front end portions 4a, 4a of the read masks 4 arranged in the center
b are arranged at equal intervals, and the opposing intervals between 4a and 4b are preferably arranged at equal intervals. On the surface of the pure copper thin film layer 3 of the clad plate 1, a mask 7 for a bump, a mask 8 for a lead base, as shown in FIG.
The tie bar mask 9 and the frame mask 10 are formed by a photoresist technique or the like. The masks 8, 9 and 10
Are connected to each other. As shown in FIG. 4C, the position of the bump mask 7 is set at the tips 4a and 4a of the lead mask 4.
It is essential that the lead base mask 8 is formed at the base of the lead mask 4, the tie bar mask 9 is formed on the tie bar mask 5, and the frame mask 10 is formed on the front and back of the frame mask 6. is there. Actually, a plurality of unit lead frame masks as shown in FIG. 2 are formed and arranged at equal intervals on the long clad plate 1, but in this embodiment, the explanation will be simplified. For this purpose, only the mask configuration of the one-unit lead frame is shown, and the subsequent processing steps will be described accordingly.

[0010] The clad plate 1 thus masked is
In the next step, for example, it is immersed in an etchant for chemical etching. FIG. 3 is a cross-sectional view shown in FIG. 2C and shows a state in which the etching has progressed. The surface portion A where both surfaces of the clad plate 1 are not masked is about 2 times larger than the surface portion B where it is not masked. Etching proceeds twice as fast.

[0011] After a certain controlled time has passed, as shown in FIG. 4, the surface portion A is completely etched and separated from both the hard copper thin film layer 2 and the pure copper thin film layer 3. . The pure copper thin film layer 3 on the surface portion B is etched to some extent, but has a slight thickness. Of course, this pure copper thin film layer 3
However, the reason why the slight thickness is left is to reinforce the high-hardness copper thin film layer 2 with the remaining pure copper thin film layer 3.

Next, all the masks 4, 5, 6, 7,
8, 9 and 10 are removed (FIG. 5). Then, only the entire surface is further etched to adjust the surface properties, whereby a copper lead 12 having a desired pure copper bump 11 attached to the tip can be obtained. At the base of the lead 12, the thickness of the bump 11, that is, the pure copper thin film layer 3 having substantially the same thickness as the original thickness of the pure copper thin film layer 3 is left.
Together with the remaining pure copper thin film layer, it serves to further reinforce the lead 12. These metal leads 12 with bumps
Are connected by a tie bar composed of a pure copper thin film layer 3 and a high-hardness copper thin film layer 2 which are covered with the tie bar mask 5 and not etched.

Next, an embodiment of a second method for manufacturing a metal lead with a bump according to the present invention will be described. 6 to 13 are process diagrams showing a second method of manufacturing the metal lead 12 with bumps according to the embodiment of the present invention. FIG. 6 is a process diagram of a polyimide film used in the method of manufacturing the metal lead with bumps of the present invention. FIG. 7A is a plan view of the carrier tape, FIG. 7B is a partially enlarged cross-sectional view taken along line X ₁ -X _{2 of} FIG. 7A, and FIG. FIG. 8 is a view showing a third step, FIG. 8A is a plan view, and FIG.
X ₁ over X ₂ line sectional view of FIG. 9 is a sectional view showing a fourth step, FIG. 10 is a sectional view showing a fifth step, FIG. 11 is a sixth
FIG. 12 is a sectional view showing a seventh step, and FIG. 13 is a plan view of a completed metal lead with bumps of the present invention.

An embodiment of the second method for manufacturing a metal lead with a bump according to the present invention will be described with reference to these drawings. The same parts as those in FIGS. 1 to 5 are denoted by the same reference numerals.
In FIG. 6, reference numeral 13 denotes a carrier tape made of a polyimide film having a thickness of about 30 to 70 μm. The carrier tape 13 has a quadrangular shape in the center, a rectangular hole 14 in this embodiment, and a rectangular hole 14. A plurality of unit lead carriers 16 are formed in the longitudinal direction by punching and opening a trapezoidal hole 15 with a mold in parallel with each side so as to surround the four sides. In the following description, only one unit read carrier 16 will be illustrated and described.

In the second step shown in FIG. 7, the unit lead carrier 16 is bonded to the surface of the high-hardness copper thin film layer 2 of the clad plate 1 shown in FIG.

Next, in a third step, a desired number of lead masks 4 as shown in FIG. 8A are formed on the surface of the pure copper thin film layer 3 of the clad plate 1 by a photoresist technique. In this case, the tip portions 4a and 4b of the lead mask 4 are connected to the unit lead carrier 16 adhered on the surface of the high-hardness copper thin film layer 2.
Extending enough to face the hole 14 (indicated by the dotted line),
The central portion of the lead mask 4 is formed so as to straddle the hole 15. The width of the read mask 4 is about 100 to 200 μm, the pitch is about 200 μm, and the thickness of the mask is 7 μm.
It is about 00 nanometers. FIG. 8B shows X ₁ -X ₂ of FIG.
Although shown in the sectional view on the line, a mask 17 is also formed on the front surface of the unit lead carrier 16 by a photoresist technique.

After the masks 4 and 17 are formed in this manner, in the next fourth step, the pure copper thin film layer 3 not covered with the mask 4 is etched as shown in FIG. Then, an etched depression 18 is formed on the hole 14.

Next, as shown in FIG. 10, in a fifth step, the lead mask 4 is removed, and the pure copper thin film before forming a complete lead 12 corresponding to the tips 4a and 4b of the lead mask 4 is formed. A bump mask 7 is formed on the layer 3 also by a photoresist technique.

As a sixth step, as shown in FIG. 11, etching is performed to further etch the recess 18 until it reaches the high-hardness copper thin film layer 2, and the lead 12 is etched.
And the other lead 12 is etched until the pure copper thin film layer 3 slightly remains. Then, the bump 11 is formed as shown.

Thereafter, as a seventh step, as shown in FIG. 12, the bump mask 7 is removed, and the bumped metal leads 12 of the present invention attached to the unit lead carrier 16 are obtained. FIG. 13 shows the unit lead carrier 1 of the metal leads 12 with bumps held by the unit lead carrier 16.
FIG. 6 is a plan view as seen from the plane No. 6; Actually, such unit lead carriers 16 are formed and arranged at equal intervals in the longitudinal direction of the carrier tape 13. In the second manufacturing method, the base of the lead 12 formed by the first manufacturing method can be reinforced by the forming method and the shape of the lead mask 4.

Next, an embodiment of a third method of manufacturing a metal lead with a bump according to the present invention will be described. 14 to 2
0 is a process drawing showing a third manufacturing method of the bumped metal lead 12 according to the embodiment of the present invention. FIG. 14 is the same as FIG. 7 and is a cross-sectional view showing the first step, and FIG. 2 is a partial cross-sectional view showing a second step, FIG. 16 is a view showing a third step, FIG.
7 is a sectional view showing a fourth step, FIG. 18 is a sectional view showing a fifth step, FIG. 19 is a sectional view showing a sixth step, and FIG. 20 is a sectional view showing a seventh step.

With reference to these drawings, an embodiment of a third method of manufacturing a metal lead with a bump according to the present invention will be described below.
FIG. 14 is the same as FIG. 7 and is shown again for the description of the process. FIG. 15 shows the second step. As a first masking, a mask 7 for bumps and a mask on the entire surface of the unit lead carrier 16 are also formed at predetermined positions on the surface of the pure copper thin film layer 3 by the photoresist technique. 17 is formed.

Next, as a third step, as shown in FIG. 16, as a second masking, a lead mask 4 is formed also by a photoresist technique so as to cover the bump mask 7.

After masking in this manner, as a first step, the unmasked portion of the pure copper thin film layer 3 is etched to form a depression 18, as shown in FIG.

Next, as a fourth step, as shown in FIG. 18, the second masking is removed, and as a fifth step,
As shown in FIG. 19, the dent 18 is further etched to cut the high-hardness copper thin film layer 2 and the pure copper thin film layer 3 is etched so as to slightly remain. The bumps 11 are formed on the portions 4a and 4b.

Finally, as a sixth step, FIG.
As shown in (1), by removing the bump mask 7 and the mask 17 which are the first masking, the metal leads 12 with bumps of the present invention can be obtained in a state held by the unit read carrier 16. The plan view of the completed metal lead with bump 12 is the same as FIG.

The bumped metal leads 12 of the present invention manufactured by the above-described three manufacturing methods are formed such that the pure copper bumps 11 are bonded to the aluminum pads formed on the semiconductor chip. Bonding can be performed while applying pressure, heating, or ultrasonic vibration.
Bonded semiconductor chip and tip 4 of lead
In the vicinity of a and 4b, for example, resin molding is performed. In FIG. 2, the tie bar and the frame are cut off.
In step 3, the tip of the lead 12 is cut off along the long side of the hole 15, and the tip of the lead 12 opposite to the tip 4a, 4b is made a free end. Thereafter, the lead at the free end is bent to complete the IC package. Can be done. The leads 12 held on a tape-shaped carrier as shown in FIG.
The semiconductor chip can be directly attached to the surface of the printed wiring board by the AB) method.

The etching is usually performed by a chemical etching method, and a gas-solid two-phase mixed flow containing fine abrasive particles having a particle diameter of about 1 μm is jetted in a beam form to be processed. When a so-called powder beam etching method for etching an object is used, good surface properties of the processed surface,
A surface structure is obtained. In particular, the powder beam etching method described in Japanese Patent Application No. 2-400410 “Method for processing the surface of an object” filed on Dec. 5, 1990 by the present applicant is capable of manufacturing the metal lead 12 with bumps according to the present invention. It is suitable for.

[0029]

As is apparent from the above description, the bumped metal lead of the present invention has a Vickers hardness of 40 to 80 of pure copper of the bump, while the aluminum of the electrode of the semiconductor chip has a Vickers hardness of 20 to 50. As a result, the two are very easy to join, and therefore do not adversely affect the semiconductor chip at the time of joining. Also, because it was manufactured from the same clad material,
Lead does not warp. Furthermore, the base of the lead and the like can be configured with a desired strength. Also, in the manufacturing method of the present invention, since the heating is not performed in the manufacturing process, the metal leads are not oxidized or deformed, and the same clad material is used. The nerve is not excessively used for the isoetching process. Furthermore, since the shape of the bumps can be freely changed by masking, a smaller bonding can provide better bonding, and thus can be applied to miniaturized bonding. Furthermore, since the production equipment can be mass-produced without incurring much cost, there are many effects such as a reduction in the production cost.

[Brief description of the drawings]

FIG. 1 is a perspective view of a clad plate used in a first method of manufacturing a metal lead with a bump according to the present invention.

2A and 2B show a second step, wherein FIG. A is a top view of the clad plate, FIG. B is a bottom view thereof, and FIG. C is a cross-sectional view taken along line X ₁ -X ₂ of FIG.

FIG. 3 is a partial cross-sectional view showing a third step.

FIG. 4 is a partial cross-sectional view showing a fourth step.

FIG. 5 is a partial sectional view showing a fifth step.

FIGS. 6A and 6B are views showing a polyimide film carrier tape used in the second method of manufacturing the bumped metal lead of the present invention, wherein FIG. A is a plan view of the tape, and FIG. is a partially enlarged cross-sectional view of _one over X ₂ line.

FIG. 7 is a partial cross-sectional view showing a second step.

[8] a view showing a third step, the Figure A is a plan view, FIG. B is a sectional view of X ₁ over X ₂ line of Figure A.

FIG. 9 is a cross-sectional view showing a fourth step.

FIG. 10 is a sectional view showing a fifth step.

FIG. 11 is a sectional view showing a sixth step.

FIG. 12 is a sectional view showing a seventh step.

FIG. 13 is a plan view of the completed metal lead with bump of the present invention.

FIG. 14 is a cross-sectional view showing a first step, which is the same as FIG. 7 in which a carrier tape used in a third method for manufacturing a metal lead with bumps of the present invention is adhered to a clad plate.

FIG. 15 is a partial cross-sectional view showing a second step.

FIG. 16 is a cross-sectional view showing a third step.

FIG. 17 is a cross-sectional view showing a fourth step.

FIG. 18 is a sectional view showing a fifth step.

FIG. 19 is a sectional view showing a sixth step.

FIG. 20 is a cross-sectional view showing a seventh step.

FIG. 21 is a cross-sectional view showing a method for manufacturing a conventional metal lead with a copper bump.

FIG. 22 is a side view when a conventional metal lead with a copper bump is bonded to a semiconductor chip.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Cladding plate 2 High hardness copper thin film layer 3 Pure copper thin film layer 4 Lead mask 4a Tip 4b Tip 5 Tie bar mask 6 Frame mask 7 Bump mask 8 Lead base mask 9 Tie bar mask 10 Frame mask 11 Bump 12 Lead 13 Carrier Tape 14 Hole 15 Hole 16 Unit Lead Carrier 17 Mask 18 Depression

Claims (6)

(57) [Claims] 1. A metal lead with bumps in which a bump made of pure copper is clad-bonded to the tip of a lead made of high-hardness copper, and a pure copper layer thinner than the thickness of the pure copper bump remains at the center of the lead. A metal lead with bumps, wherein the lead is reinforced. 2. The metal lead with bump according to claim 1, wherein the lead is reinforced by leaving a pure copper layer identical to the pure copper of the bump at the base of the lead. 3. A lead mask and a bump mask corresponding to the mask are applied to a clad plate having a high hardness copper thin film and a low hardness pure copper thin film formed thereon. 2. A method for manufacturing a metal lead with bumps, comprising removing and partially removing high-hardness copper and pure copper by etching, and then removing the two masks. 4. A mask for a lead is provided on the surface of the high-hardness copper thin film layer of the clad plate, and a mask for a bump is provided on the surface of the pure copper thin film layer in correspondence with the mask. 4. The method of manufacturing a metal lead with a bump according to claim 3 , comprising removing and partially removing high-hardness copper and pure copper in an uncovered portion, and then removing the two masks. 5. A carrier tape having a plurality of unit lead carriers formed thereon is adhered to the surface of the high-hardness copper thin film layer of the clad plate, and a mask is applied to the entire surface. A mask for lead is applied to the surface of the thin film layer to etch the pure copper thin film layer. Thereafter, the mask for lead is removed, and a mask for bump is applied to the tip of the pure copper thin film layer remaining by the lead mask. ,
4. The method for manufacturing a metal lead with bump according to claim 3 , wherein the pure copper thin film layer not covered with the bump mask and the hard copper thin film layer are etched again, and thereafter all the masks are removed. . 6. A carrier tape having a plurality of unit lead carriers formed thereon is adhered to the surface of the high-hardness copper thin film layer of the clad plate, and a mask is applied to the entire surface. A mask for bumps is applied to the surface of the thin film layer, the mask for bumps is further covered, a mask for leads is applied so as to extend also to the surface of the pure copper thin film layer, and the pure copper thin film layer is etched. 4. The bump-equipped bump according to claim 3 , wherein the etching is performed by removing and further etching the pure copper thin film layer and the high-hardness copper thin film layer remaining by the lead mask, and thereafter removing all the masks. 5. Manufacturing method for metal leads.