JPH04296031A - Metallic lead with bump and manufacture thereof - Google Patents

Abstract

PURPOSE:To provide the title metallic lead with bumps fit for mass production causing no damage to a semiconductor chip. CONSTITUTION:The bumps 11 comprising pure copper are cladjunctioned to the ends of leads 12 comprising high hardness copper. In order to manufacture said leads, the masks 4 for the leads 12 and the other masks 7 for bumps are fitted to both surfaces of a clad plate 1 composed of a thin film comprising low hardness pure copper formed on a high hardness copper thin film while the copper parts having no masks at all are etched away. At this time, the bumps comprising pure copper are so easily junctioned to the electrode of a semiconductor chip having no unfavorable effect on the semiconductor chip during the junction step. Furthermore, said leads can be manufactured by etching step fit for the mass production using no specific manufacturing devices resultantly at low cost.

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 bumps that is bonded to an electrode of a semiconductor chip and a method for manufacturing the same.

0002

[Prior art] As an example of the prior art, JP-A-63-1
88948 "Method for forming bonding bumps". The bump forming method disclosed in this publication will be briefly explained using FIG. 21.
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 onto the copper lead 103. Next, as shown in FIG. 21B, the copper wire 101 is pulled and cut above the ball 104. At this time, a protrusion 105 remains on the upper part of the ball 104 due to plastic deformation. This protrusion 105 may damage the semiconductor chip during tape carrier bonding.
Fig. 21C
As shown in FIG. 2, a processing tool 106 having a concave surface is used to process and form the surface into a spherical or gently convex surface to obtain a bump 107 having a shape suitable for bonding.

0003

[Problems to be Solved by the Invention] Copper is used as the material for the leads 103 and bumps 107, but their purity and hardness are not mentioned and are unknown; As shown in FIG.
When the copper lead 103 with copper bumps having such a configuration is bonded from above the aluminum electrode 109 formed on the surface of 08,
Cracks 110 often appear inside the semiconductor chip 108, resulting in a defective semiconductor chip 108.

[0004] Furthermore, in the method of manufacturing the copper lead 103 with copper bumps having the above-mentioned configuration, 1. 2. In order to maintain sufficient bonding between the copper ball 104 and the copper lead 103, it is necessary to apply heat of 300°C. In order to prevent the copper ball 104 and the copper lead 103 from being oxidized by heat, it is necessary to create an atmosphere of nitrogen gas or nitrogen gas and hydrogen gas around the joint.3. When working at high temperatures, the lead 103 softens due to the heat, and the lead 103
4. becomes easier to deform. 5. The bonding strength between the copper ball 104 and the copper lead 103 tends to be uneven.5. 6. The shape of the bump 107 caused by the copper ball 104 tends to be uneven.6. 0.1 to 0.2 to bond one bump 107
It takes seconds and productivity is extremely low. For example, it takes about 10 to 20 seconds to make a lead with about 100 pins, so it is not suitable for mass production7. Although it requires a considerable amount of equipment, it takes time to manufacture, so it has drawbacks such as an enormous manufacturing cost. Therefore, the present invention aims to solve the above-mentioned problems.

[0005]

[Means for Solving the Problems] Therefore, in the present invention, a bump made of pure copper is clad-bonded to the tip of a lead made of high hardness copper. In manufacturing such bumped metal leads, a lead mask is applied to the surface of the high hardness copper thin film of a clad plate made of a pure copper thin film formed on a high hardness copper thin film, and a lead mask is applied to the surface of the high hardness copper thin film. Then, a bump mask is applied to the thin film surface of the pure copper, and then the high hardness copper and pure copper in the areas not covered by the two masks are removed by etching and a portion thereof is removed, and then both the masks are removed. , a metal lead with bumps as described above is obtained.

[0006]

[Function] Therefore, in the bumped metal lead of the present invention, the pure copper of the bump has a Vickers hardness of 40 to 80,
On the other hand, since the aluminum of the electrode of the semiconductor chip has a molecular weight of 20 to 50, the two are very easy to bond, and therefore the semiconductor chip is not adversely affected during bonding. In addition, since there is no heating during the manufacturing process, the metal lead will not be oxidized or deformed, and the shape of the bump can be changed freely by masking, so the smaller the bump, the better the bond. Therefore, it is possible to correspond to miniaturized bonding. Furthermore, since mass production is possible without spending much on manufacturing equipment, manufacturing costs can be reduced.

[0007]

Embodiments Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. 1 to 5 are process diagrams showing a first method of manufacturing a metal lead with bumps, which is an embodiment of the present invention, and FIG. 1 is a perspective view of a clad plate used in the method of manufacturing a metal lead with bumps of the present invention. FIG. 2 shows the second step; FIG. 2A is a top view of the clad plate, FIG. 2B is a bottom view, and FIG. 3 is a partial sectional view showing the third step, FIG. 4 is a partial sectional view showing the fourth step, and FIG. 5 is a partial sectional view showing the fifth step.

First, the first step of the method for manufacturing a metal lead with bumps according to the present invention will be explained with reference to FIG. Reference numeral 1 indicates a clad plate as a whole. This clad plate 1 has a high hardness copper thin film layer 2 with a thickness of about 30 μm mixed with impurities such as Fe, Cr, P, etc., and a pure copper thin film layer 3 with a thickness of about 30 μm with extremely low impurities mixed therein. Although it is bonded by thermocompression, the pure copper thin film layer 3 may be formed using a thin film technique such as plating pure copper on the high hardness copper thin film layer 2. Although the Vickers hardness of high-hardness copper is 100 or more, 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. 6 are connected using a photoresist technique or the like. Tips 4a, 4 of each lead mask 4 arranged in the center
It is preferable that 4a and 4b are arranged at equal intervals, and the opposing distances between 4a and 4b are also arranged at equal intervals. Further, on the surface of the pure copper thin film layer 3 of the clad plate 1, a bump mask 7, a lead base mask 8, as shown in FIG.
A tie bar mask 9 and a frame mask 10 are formed using a photoresist technique or the like. The masks 8, 9 and 10
are connected to form. As shown in FIG.
In b, it is important to form the lead base mask 8 on the base of the lead mask 4, the tie bar mask 9 on the tie bar mask 5, and the frame mask 10 on the frame mask 6 with front and back alignment aligned. be. In reality, 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. In order to do this, only the mask structure of one unit lead frame is shown and the subsequent processing steps will be explained using it.

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

After a certain controlled period of time has elapsed, as shown in FIG. 4, both the high-hardness copper thin film layer 2 and the pure copper thin film layer 3 are completely etched and separated from the surface portion A. . The pure copper thin film layer 3 on the surface portion B was etched to some extent, but a slight thickness remained. Of course, this pure copper thin film layer 3 may also be removed by etching, but the reason why a slight thickness is left in this way is to reinforce the high hardness copper thin film layer 2 with this remaining pure copper thin film layer 3.

Next, all the masks 4, 5, 6, 7,
Remove 8, 9 and 10 (Figure 5). By further etching only the entire surface and adjusting the surface quality, a copper lead 12 having a desired pure copper bump 11 at the tip can be obtained. At the base of this lead 12, a pure copper thin film layer 3 of approximately the same thickness as the bump 11, that is, 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 strengthen the lead 12. These bumped metal leads 12
are connected by a tie bar consisting of a pure copper thin film layer 3 and a high hardness copper thin film layer 2, which are covered with a tie bar mask 5 and not etched.

Next, an embodiment of a second method for manufacturing a metal lead with bumps according to the present invention will be described. 6 to 13 are process diagrams showing a second manufacturing method of the bumped metal lead 12 according to the embodiment of the present invention, and FIG. Figure 7 is a plan view of the carrier tape, Figure B is a partially enlarged sectional view taken along the line 8 are diagrams showing the third step, FIG. 8A is a plan view, FIG. is a cross-sectional view showing the fifth step, FIG.
1 is a sectional view showing the sixth step, FIG. 12 is a sectional view showing the seventh step, and FIG. 13 is a plan view of the completed metal lead with bumps of the present invention.

An embodiment of the second method for manufacturing a metal lead with bumps according to the present invention will be described with reference to these figures. Note that the same parts as in FIGS. 1 to 5 are given the same reference numerals. In FIG. 6, reference numeral 13 denotes a carrier tape made of polyimide film with a thickness of approximately 30 to 70 μm. A plurality of unit lead carriers 16 are formed in the longitudinal direction so as to surround the four sides and are formed by punching ladder-shaped holes 15 with a die in parallel to each side. In the following description, only one unit lead carrier 16 will be illustrated and explained.

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

Next, in the 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 cladding plate 1 using a photoresist technique. In this case, the tips 4a and 4b of the lead mask 4 are connected to the unit lead carrier 16 bonded on the surface of the high-hardness copper thin film layer 2.
(indicated by a dotted line) so as to fully face the hole 14,
Further, the center portion of the lead mask 4 is formed so as to straddle the hole 15. The lead mask 4 has a width of about 100 to 200 μm, a pitch of about 200 μm, and a thickness of 7 μm.
00 nanometers. Figure 8B is X1 -X in Figure A.
2, a mask 17 is also formed on the front surface of the unit lead carrier 16 using a photoresist technique.

After forming the masks 4 and 17 in this way, in the next fourth step, as shown in FIG.
The portions of the pure copper thin film layer 3 that are not covered by the etching process are etched. An etched depression 18 is then formed over the hole 14.

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

Then, as a sixth step, as shown in FIG. 11, etching is performed, and the recess 18 is further etched until the high hardness copper thin film layer 2 is reached, and the lead 12 is etched.
The other leads 12 are etched until only a small amount of the pure copper thin film layer 3 remains. Then, bumps 11 are formed as shown.

Thereafter, in a seventh step, as shown in FIG. 12, the bump mask 7 is removed to obtain the bumped metal lead 12 of the present invention attached to the unit lead carrier 16. FIG. 13 shows the unit lead carrier 1 of the bumped metal lead 12 held by this unit lead carrier 16.
6 is a plan view seen from the side of FIG. In reality, such unit lead carriers 16 are formed and arranged at equal intervals in the longitudinal direction of the carrier tape 13. Note that even in this second manufacturing method, the base portions of the leads 12 formed in the first manufacturing method can be reinforced depending on the formation method and shape of the lead mask 4.

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

An embodiment of the third method for manufacturing a metal lead with bumps according to the present invention will be described below with reference to these figures. Although FIG. 14 is the same as FIG. 7 and is shown again for the purpose of explaining the process, since the configuration is the same, the explanation thereof will be omitted. FIG. 15 shows the second step. As the first masking, a bump mask 7 is applied to a predetermined location on the surface of the pure copper thin film layer 3 using a photoresist technique, and a mask is applied to the entire surface of the unit lead carrier 16. form 17.

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

After masking in this manner, as a first step, as shown in FIG. 17, the unmasked portion of the pure copper thin film layer 3 is etched to form a recess 18.

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 recess 18 is further etched, the high-hardness copper thin film layer 2 is shaved off, and the pure copper thin film layer 3 is etched so as to leave a small amount of the pure copper thin film layer 3 at the tip covered with the bump mask 7. Bumps 11 are formed on portions 4a and 4b.

Finally, as the sixth step, FIG.
As shown in FIG. 3, by removing the bump mask 7 and the mask 17, which are the first masking, the bumped metal lead 12 of the present invention can be obtained while being held by the unit lead carrier 16. The plan view of the finished metal lead 12 with bumps is the same as that in FIG. 13, so it will be omitted.

The bumped metal leads 12 of the present invention manufactured by the three manufacturing methods described above are all made in such a way that pure copper bumps 11 are bonded to aluminum pads formed on a semiconductor chip. Bonding can be performed while applying pressure, heat, or ultrasonic vibration. Bonded semiconductor chip and lead tip 4a
, 4b and its vicinity are, for example, molded with resin, as shown in FIG.
In Figure 13, cut off the tie bar and frame.
In this step, the holes 15 are cut off along the long sides, and the tips of the leads 12 opposite to the tips 4a and 4b are made free ends, and then these free ends of the leads are bent to complete the IC package. be able to. Also, Figure 1
The leads 12 held in a tape-shaped carrier as shown in 3 are tape automated bonding (TA
It is also possible to attach the semiconductor chip directly to the printed wiring board surface using method B).

[0028] The above-mentioned etching usually uses a chemical etching method, but a solid-gas two-phase mixed flow containing fine powder of abrasive grains with a particle size of about 1 μm is injected in the form of a beam to form a beam on the workpiece. A so-called powder beam that etches objects.
When the etching method is used, good surface texture and structure of the processed surface can be obtained. In particular, on December 5, 1990, the applicant
The powder beam etching method described in Japanese Patent Application No. 2-400410 “Method for surface processing of objects” filed on
This is suitable for manufacturing the bumped metal lead 12 of the present invention.

[0029]

As is clear from the above description, in the metal lead with bumps of the present invention, the Vickers hardness of the pure copper of the bumps is 40 to 80, while that of the aluminum of the semiconductor chip electrode is 20 to 50. Therefore, the two are very easy to bond, and therefore, there is no adverse effect on the semiconductor chip during bonding. In addition, since it was manufactured from the same clad material,
The lead does not warp. Furthermore, the base of the lead, etc. can be constructed with desired strength. Furthermore, since the manufacturing method of the present invention does not require heating during the manufacturing process, the metal lead will not be oxidized or deformed.
Furthermore, since the same cladding material is used, there is no need to worry too much about the etching process, such as the etching solution and etching speed. Furthermore, since the shape of the bump can be freely changed by masking, the smaller the bump, the better the bonding can be obtained, making it possible to respond to miniaturized bonding. Furthermore, since it can be mass-produced without spending much on manufacturing equipment, it has many effects such as being able to lower manufacturing costs.

[Brief explanation of drawings]

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

[Fig. 2] Showing the second process, Fig. 2A is a top view of the clad plate, Fig. 2B is a bottom view, and Fig. C is the X1 - X2 of Fig. A.
It is a sectional view on a line.

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 cross-sectional view showing a fifth step.

FIG. 6 is a diagram showing a carrier tape made of polyimide film used in the second manufacturing method of a metal lead with bumps according to the present invention, in which FIG. 6A is a plan view of the tape, and FIG. -X2 line is a partially enlarged sectional view.

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

8A and 8B are diagrams showing a third step; FIG. 8A is a plan view, and FIG. 8B is a sectional view taken along the line X1-X2 of FIG.

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 cross-sectional view showing a seventh step.

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

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

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

FIG. 16 is a cross-sectional view showing the 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 cross-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 conventional method of manufacturing a metal lead with copper bumps.

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

[Explanation of symbols]

1 Clad 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 Hollow

Claims (7)

[Claims] 1. A metal lead with bumps, characterized in that a bump made of pure copper is clad-bonded to the tip of a lead made of high hardness copper. 2. The bumped metal lead according to claim 1, wherein the lead is reinforced by leaving a pure copper layer thinner than the pure copper bump in the center of the lead. 3. The bumped metal lead according to claim 1, wherein the lead is reinforced by leaving a pure copper layer same as that of the bump at the base of the lead. 4. A lead mask and a bump mask corresponding to the mask are applied to a clad plate in which a thin film of pure copper with low hardness is formed on a thin film of copper with high hardness, and then the portions not covered by both of the masks are applied. A method for manufacturing a metal lead with bumps, which comprises removing and partially removing high-hardness copper and pure copper by etching, and then removing both of the masks. 5. A lead mask is applied to the surface of the high-hardness copper thin film layer of the clad plate, a bump mask is applied to the pure copper thin film layer corresponding to the mask, and then both the masks are applied. 5. The method of manufacturing a metal lead with bumps according to claim 4, comprising removing and partially removing the high hardness copper and pure copper in the uncovered portions by etching, and then removing both the masks. 6. A carrier tape on which a plurality of unit lead carriers are formed 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, and the pure copper A lead mask is applied to the surface of the thin film layer and the pure copper thin film layer is etched, and then the lead mask is removed and a bump mask is applied to the tip of the pure copper thin film layer left by the lead mask. ,
5. The method for manufacturing a metal lead with bumps according to claim 4, wherein the pure copper thin film layer and the high-hardness copper thin film layer not covered with the bump mask are etched again, and then all the masks are removed. . 7. A carrier tape on which a plurality of unit lead carriers are formed 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, and the pure copper A bump mask is applied to the surface of the thin film layer, and a lead mask is applied to cover the bump mask and extend to the surface of the pure copper thin film layer, and the pure copper thin film layer is etched, and then the lead mask is applied. 5. The bumped bump according to claim 4, further comprising removing and further etching, etching the pure copper thin film layer and the high hardness copper thin film layer left by the lead mask, and then removing all the masks. Method of manufacturing metal leads.