JP3021508B2 - Method of forming conductive protrusions - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for forming a conductive projection used as a connecting material when connecting electric circuit components in the field of microelectronics, and in particular, to a method for forming a conductive projection on an electrode of an IC chip. The present invention relates to a method for forming a conductive protrusion that can form a protrusion with high accuracy.

[Prior Art] As a connection method between components corresponding to a mounting technology of a semiconductor product, a wire bonding method, a film carrier method (TAB (Tape Automated Bonding) method), a flip chip method and the like are known. Each of these connection methods will be briefly described by taking the connection between the electrode of the IC chip and the lead on the substrate side as an example.

FIG. 10 is a schematic diagram showing the mounting method of the wire bonding method, in which each electrode 42 of the IC chip 41 and the printed wiring board
The connection portions of the 43 corresponding leads 44 are connected one by one by wires 45 made of Au or Al. In such a method, the electrode 42 and the lead 44 are joined in order one by one so that the production efficiency is low, and there is interference at the time of joining between adjacent wires, so the minimum connection pitch has a limit. It may not be applicable to high-density mounting technology.

A connection method for realizing high-density mounting with a short connection pitch is a film carrier method. FIG. 11 is a schematic view showing a mounting method of a film carrier method. This method is an automatic bonding method by a tape carrier method, and each electrode 42 of an IC chip 41 on which a conductive projection 47 is formed in advance.
After positioning the film leads 46 and the respective film leads 46, they are connected together by thermocompression bonding. Thereafter, the respective film leads 46 and the respective leads 44 of the printed wiring board 43 are positioned and then connected together. FIG. 12 is a schematic diagram showing the mounting method of the flip chip method, and after positioning and mounting the IC chip 41 provided with the conductive projection 47 in advance on each electrode 42 on the printed wiring board 43, The electrodes 42 of the IC chip 41 are connected to the corresponding leads 44 of the printed wiring board 43 by heating and melting the conductive protrusions 47.

In the above two methods (film carrier method and flip chip method), conductive protrusions are required as connecting members, and it is necessary to form conductive protrusions on the electrodes 42 of the IC chip 41 prior to connection work. is there. As a method of forming the conductive protrusion, a method of forming the conductive protrusion directly on the electrode 42 using a plating method is known.

FIG. 13 is a cross-sectional view showing one example of the steps of such a conventional method for forming a conductive projection, and the steps will be briefly described with reference to FIG.

First, the electrode 42 of the IC chip 41 and the passivation film 50
On top of this, a Cr layer 51, a Cu layer 52, and an Au layer 53 are formed by vapor deposition in this order by sputtering (FIG. 13 (a)).
(FIG. 13 (b)) Next, after filling the opening of the resist 54 with gold 55 by a plating method (FIG. 13 (c)),
The resist 54 is removed (FIG. 13D). Finally, the exposed multilayer metal film (Cr layer 51, Cu layer 52, Au layer 53) is removed by etching, and heat treatment is performed in a nitrogen atmosphere to form a conductive projection 47 made of the multilayer metal film and gold 55 on the electrode 42. (FIG. 13 (e)).

[Problems to be solved by the invention]

In the conventional method for forming conductive protrusions as described above, since conductive protrusions are formed on the electrodes of the IC chip via a multilayer metal film (barrier metal), complicated processes and equipment are required.
High cost. In addition, since the completed IC chip is subjected to chemical treatment to form conductive protrusions, there is a problem that the yield of the IC chip is reduced with the formation of the conductive protrusions.

The present invention has been made in view of such circumstances, and uses a conductor holding material in which a plurality of conductors are scattered in a holding body made of an electrical connection member, and uses the conductor as a conductive protrusion to form an IC chip. By transferring to the electrodes, conductive protrusions can be easily formed on the electrodes of the IC chip, and highly reliable connection can be achieved even in high-density connection with the lead on the substrate side. An object of the present invention is to provide a method for forming a projection.

[Means for solving the problem]

According to a first aspect of the present invention, there is provided a method for forming a conductive projection for connection on an electrode of an IC chip,
A plurality of conductors are scattered in a sheet-shaped holder made of an electrically insulating material, with both ends protruding from both sides of the holder, insulated from each other, and the holders of these conductors are scattered. Using a conductor holding material having a protruding portion from one surface larger than a portion in the holder, aligning the protruding end of the conductor from the one surface with the electrode of the IC chip, and positioning. The conductive members thus formed are transferred to the electrodes of the IC chip to form conductive protrusions.

A method of forming a conductive projection according to a second invention according to the present invention is characterized in that, after performing the first invention, the holder of the conductor holding material is removed.

The method for forming a conductive projection according to the third invention of the present application is the first method.
In the present invention, a plurality of electrodes of the IC chip are provided, and when transferring the conductor of the conductor holding material to the electrodes of the IC chip, a method of collectively transferring the electrodes to all the electrodes, It is characterized by adopting any one of a method of transferring images to a plurality of them at once, and a method of transferring images sequentially to one electrode.

[Action]

According to a first aspect of the present invention, a plurality of conductors are scattered in a sheet-like holder made of an electrically insulating material in a state in which a plurality of conductors are insulated from each other. After aligning the protruding end on one side, which is larger than the part in the holder, with the electrode of the target IC chip, each conductor is transferred to the electrode to which it is aligned, and the conductor is transferred. Form protrusions. Then, a conductive protrusion is easily formed on each electrode. In the second invention, thereafter, the holder is removed as necessary. Then, only the conductive protrusion can be formed. Here, when forming the conductive protrusions by transferring the conductor, the conductive protrusions may be formed collectively for all the electrodes, or the conductive protrusions may be formed individually for one electrode sequentially. Alternatively, the electrodes may be divided into a plurality of groups, and each group may be collectively formed with conductive protrusions. When the conductive protrusions are formed collectively for all the electrodes, the working efficiency is excellent, and when the conductive protrusions are formed individually for one electrode, the joining accuracy is excellent.

〔Example〕

FIG. 1 is a plan view of a conductor holding member 1 used in the method for forming a conductive projection of the present invention, and FIG. 2 is a sectional view taken along the line II-II of FIG. The conductor holding material 1 includes a plurality of conductors 2 made of, for example, gold, and a holder 3 (thickness) made of a polyimide resin such that the conductors 2 are electrically insulated from each other.
(About 10 μm). Both ends of each conductor 2 are projected from both sides of the holder 3, and the end 2 a projecting to one side of the holder 3 is a portion whose diameter (about 25 μm) is embedded in the holder 3. Diameter (about 15μm)
So-called projecting shape (projection height 4
程度 8 μm). On the other hand, the other end 2b of each conductor 2 only slightly protrudes toward the other surface of the holder 3, and its diameter is substantially equal to the diameter of a portion embedded in the holder 3. Note that the formation pitch of the conductors 2 matches the pitch of the electrodes of the IC chip described later.

Next, an example of a method for manufacturing the conductor holding material having such a configuration will be described with reference to FIG.

First, after applying an adhesion aid to the prepared copper plate 11 by a spinner, a negative polyimide resin 12 serving as a holding body is applied.
Is applied by a spinner (FIG. 3A). Polyimide resin applied here in consideration of the decrease in film thickness due to curing
The film thickness of 12 is larger than the desired film thickness of the holder in the conductor holding material to be manufactured. Next, after the polyimide resin 12 is irradiated with light (exposed) through a photomask (not shown) having a predetermined pattern, development is performed. In this example, the polyimide resin 12 remains in the exposed portion, and the unexposed portion removes the polyimide resin 12 by a development process to form a hole 13. Thereafter, the temperature is raised to cure the polyimide resin 12 (FIG. 3 (b)). Next, the copper plate 11 thus treated is immersed in an etching solution to perform etching. A portion of the copper plate 11 near the hole 13 is removed by etching, and a concave portion 14 communicating with the hole 13 is formed in the copper plate 11 (FIG. 3C). Use copper plate 11 as common electrode
15 electroplating, gold plating until the gold 15 slightly protrudes from the upper surface of the polyimide resin 12, holes 13, recesses 14
Is filled with gold 15 (FIG. 3 (d)). Finally, the copper plate 11 is removed by metal etching to manufacture the conductor holding material 1 (the up-down relationship is reversed) as shown in FIGS.

In this embodiment, in the manufactured conductor holding member 1, the conductor 2 and the holder 3 are made of gold 15 and polyimide resin 1 respectively.
2, one end 2a of the conductor 2 protruding to one surface side of the holder 3 is made larger than a portion in the holder 3 including the other end 2b, and has a projecting shape. No.

FIG. 4 is a cross-sectional view showing another step of manufacturing the conductor holding material of the present invention. After the polyimide resin 12 is applied on the copper plate 11 (FIG. 4 (a)), the polyimide resin 12 is exposed and developed in a predetermined pattern, and the holes 13 are formed.
Is formed, and the temperature is increased to cure the polyimide resin 12 (FIG. 4 (b)). The concave portion 14 is formed by etching the copper plate 11 thus treated with an etching solution in the same manner as in the above-described embodiment, but in this embodiment, the etching time is longer than that in the above-described embodiment. Shorten.
Then, a shallow concave portion 14 is formed in the copper plate 11 as compared with the above-described embodiment (FIG. 4C). Thereafter, electroplating of gold 15 is performed using the copper plate 11 as a common electrode, and gold 15 is
In this embodiment, the polyimide resin 12 is filled.
Gold plating is continued until the gold 15 protrudes to a predetermined height from above (FIG. 4 (d)). Finally, the copper plate 11 is removed by metal etching, and the conductor holding material 1 as shown in FIGS.
To manufacture.

Next, a method for forming a conductive projection of the present invention using such a conductor holding material will be specifically described.

FIG. 5 is a plan view of the electrode forming surface of the IC chip, and FIG. 6 is a sectional view taken along line VI-VI of FIG. In the figure, reference numeral 21 denotes an IC chip in which an electrode 22 made of A1 is formed on an electrode forming surface, and a passivation film 30 is formed on a surface of the IC chip 21 on which the electrode 22 is not formed. IC like this
After positioning each conductor 2 (end 2a) of the conductor holding material 1 as shown in FIGS. 1 and 2 with each electrode 22 of the chip 21, the bonding jig 28 is moved in the direction of the white arrow. Then, the conductors 2 serving as conductive protrusions are collectively transferred and bonded to all the electrodes 22 by a thermocompression bonding method (FIG. 7A). The conductive projections 2 (Au) and the electrodes 22 (Al), which have been pressed and transferred, are metal-bonded to form a strong bond. Next, the holder 3 is mechanically peeled off, and only the conductive protrusions 2 are formed on the electrodes 22 (the seventh step).
Figure (b). Here, since the diameter of the end 2b of the conductor 2 on the side not in contact with the electrode 22 is substantially the same as the diameter of the part in the holder 3, the holder 3 can be easily removed. Note that, unlike mechanical peeling (peeling), the holder 3 may be removed by a chemical dissolution treatment.

FIG. 8 is a cross-sectional view showing another example of the transfer and formation of the conductive projection.
The conductive protrusions 2 are formed by moving the bonding jig 28 by a thermocompression bonding method. FIG. 9 shows the transfer of conductive protrusions,
It is sectional drawing which shows another example of formation, In this example, 1
The conductive protrusions 2 are individually formed by moving the bonding jig 28 with respect to the individual electrodes 22. In this method, the conductive protrusions can be formed by a thermocompression bonding method using ultrasonic waves in addition to the thermocompression bonding method.

The above-described three methods (a method in which conductive protrusions are formed on all electrodes at once (FIG. 7: hereinafter referred to as a collective formation method), a method in which conductive protrusions are formed on a plurality of electrodes at once ( The advantages and disadvantages of the method of individually forming conductive projections for each electrode (FIG. 8: hereinafter referred to as a partial formation method) (FIG. 9: hereinafter referred to as an individual formation method) will be described.

In the collective formation method, since the conductive protrusions can be formed on all the electrodes at the same time, the operation time is short. However, if the protrusion heights of the respective conductors in the used conductor holding material vary, a joint failure is likely to occur. On the other hand, in the individual formation method, since the conductive protrusions are reliably formed on the electrodes one by one, the reliability of bonding is extremely high, but there is a disadvantage that a long working time is required. In addition, the partial formation method has characteristics that are intermediate between the two.

Each forming method has the above characteristics, so it is most suitable for these three methods in consideration of the conditions such as the shape of the conductor holding material used and the shape of the electrode of the IC chip to be transferred. What is necessary is just to select and adopt a suitable method. For example, one of the following three methods may be selected according to the degree of variation in the height of protrusion of the conductor in the conductor holding material.

When the variation is small: Batch formation method When the variation is medium: Partial formation method When the variation is large: Individual formation method In the above-described embodiment, the holder 3 is removed after the conductor 2 is transferred. Alternatively, the holder 3 may be left. There is an advantage and disadvantage as to whether the holder 3 is removed or left. An advantage of removing the holding member 3 made of an insulating resin is that the characteristics of the holding member 3 having high moisture absorption can be prevented from adversely affecting the IC package to be manufactured. The advantage is the holder 3
Is a point that a short circuit between adjacent conductors can be prevented because of an insulating material. Whether the holder 3 is removed or left may be arbitrarily selected according to the pattern of forming the electrodes of the IC chip.

〔The invention's effect〕

As described in detail above, by using the method for forming conductive protrusions of the present invention, conductive protrusions for connection can be easily formed on electrodes of an IC chip at low cost and with high reliability. High precision connection between the electrodes of the IC chip and the leads on the substrate side can be realized even in a simple mounting. Further, since the chemical treatment is not performed on the electrodes of the completed IC chip unlike the conventional method, there is no possibility that the yield of the IC chip is reduced due to the forming process. When the holder is removed after transferring the conductor to the electrode, only the conductive protrusion can be formed on the electrode of the IC chip.

[Brief description of the drawings]

FIG. 1 is a plan view of a conductor holding material used in the method for forming a conductive projection of the present invention, FIG. 2 is a cross-sectional view taken along the line II-II of FIG. 1, and FIG. FIG. 4 is a cross-sectional view showing an example of the process, FIG. 4 is a cross-sectional view showing another example of the manufacturing process of the conductor holding material, FIG. 5 is a plan view of the electrode forming surface of the IC chip, and FIG. FIG. 7 is a cross-sectional view taken along line VI-VI of FIG. 7, and FIG.
8 and 9 are cross-sectional views showing another embodiment of the method for forming conductive projections according to the present invention, FIGS. 10 to 12 are schematic views showing a mounting method, and FIG. 13 is a conventional method for forming conductive projections. It is sectional drawing which shows a method. 1 ... conductor holding material, 2 ... conductor (conductive protrusion), 2a, 2
b ... end, 3 ... holder, 21 ... IC chip, 22 ... electrode, 28 ... bonding jig

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-64-59944 (JP, A) JP-A-64-22048 (JP, A) JP-A-1-243554 (JP, A) Table of Japanese Patent Application No. 59-1984 500394 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) H01L 21/60

Claims (3)

(57) [Claims] 1. A method of forming conductive projections for connection on an electrode of an IC chip, wherein a plurality of conductors are provided in a sheet-like holder made of an electrically insulating material, with both ends of the conductors being placed on both sides of the holder. Using a conductor holding material, in which the conductors are scattered in an insulated state from each other, and projecting portions of these conductors from one surface of the holder are made larger than portions in the holder. The protruding end of the one surface is aligned with the electrode of the IC chip, and each aligned conductor is mounted on the IC.
A method for forming a conductive projection, wherein the conductive projection is formed by transferring to a chip electrode. 2. The method according to claim 1, wherein the conductor of the conductor holding material is transferred to an electrode of the IC chip, and then the holder of the conductor holding material is removed. 3. The method according to claim 1, wherein the plurality of electrodes of the IC chip are plural, and when the conductor of the conductor holding material is transferred to the electrodes of the IC chip, the electrodes are collectively transferred to all the electrodes. 2. The method according to claim 1, wherein one of a method of collectively transferring a plurality of electrodes and a method of sequentially transferring a plurality of electrodes individually is adopted.