JPH0399448A - Inner lead bonding method - Google Patents

Abstract

PURPOSE:To improve a connected part in reliability by a method wherein solder bumps are formed on the inner leads of a film carrier through plating, and the electrodes of a semiconductor chip are electrically connected to the inner leads. CONSTITUTION:A metal foil 2 is laminated on the upside of a film 1, photoresist 3 is applied onto a part of the metal foil 2 which serves as an inner lead, and the photoresist 3 formed on parts 4 where solder bumps are to be arranged are removed. Solder bumps 5 are formed on the parts 4 through an ultrasonic solder plating method or the like. Protective resist 6 is applied onto the under side of the metal foil 2, and an inner lead pattern is formed after photoresist 7 is applied onto the upside of the metal foil 2. The protective resist 6 and the photoresist 7 are removed, and thus a film carrier 9 provided with an inner lead 8 on which the solder bumps 5 are formed can be obtained. Electrodes 11 of a semiconductor chip 10 previously heated at a temperature higher than the melting point of the solder bumps 5 are brought into contact with the solder bumps 5. The solder bumps 5 are fused to electrically connect the inner lead 8 with the electrode 11.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for inner lead bonding of a semiconductor chip to a film carrier.

[Prior Art] The film carrier method, which can be made smaller and thinner, has been attracting attention as a method for mounting semiconductor chips. A common method is to form wafer bumps such as AU or solder on the electrodes, and then bond the wafer bumps and the inner leads of the film carrier by thermocompression bonding or soldering.

On the other hand, JP-A-57-152147 and JP-A-59-8
In No. 8861, metal bumps previously formed on a bump-forming substrate are transferred to inner leads of a film carrier using a separate dedicated device to form transfer bumps, and the transfer bumps are connected to electrodes of a semiconductor chip without bumps. A method of bonding by thermocompression bonding is disclosed.

On the other hand, in JP-A No. 58-48445, a protruding pan 1 tab is formed by etching on a predetermined portion of the inner lead of a film carrier, and the pan 1 tab and the electrode of a semiconductor chip without the pan 1 are heated. A method of bonding by pressure bonding is disclosed.

[Problem to be solved by the invention] A method of inner lead bonding of a semiconductor chip to a film carrier is easier to implement, lowers manufacturing cost, increases the strength of the bonded part, and increases the number of electrodes. However, it is desired to be able to bond even large-sized semiconductor chips without reducing the reliability of the bonded portion.

However, the method using wafer bumps described above requires an atmosphere and complicated equipment similar to those used in semiconductor manufacturing to form wafer bumps, so it is difficult to manufacture film carriers or assembly factories that have the equipment to simply mount semiconductor chips. It cannot be carried out in a factory, and even in a factory with the same atmosphere and complex equipment as semiconductor manufacturing, relatively complicated processes such as photo-etching, vapor deposition, and water washing processes are required in a clean room. Yes, manufacturing costs will be high. In particular, there is a problem in that the bump cost increases because gold for Au bumps is expensive.

The above-mentioned method using transfer bumps and bump tabs solves problems such as the above-mentioned wafer bump manufacturing process by forming transfer bumps or bump tabs on the film carrier side rather than on the wafer side. Because bonding by pressure bonding is used, as the number of electrodes on a semiconductor chip increases and the size of the semiconductor chip increases, it becomes difficult to apply the pressure necessary for thermocompression bonding evenly to all electrodes, which may cause problems with the reliability of some bonded parts. There is a problem in that the value decreases. Also,
Thermocompression bonding must be carried out at a high temperature of, for example, 500° C. to 600° C., and it is necessary to use a relatively expensive film with high heat resistance made of, for example, polyimide. In particular, the method using transfer bumps has the problem that a dedicated device and process are required to transfer the bumps, and that the adhesive strength between the bumps and the inner lead due to transfer is relatively weak. .

An object of the present invention is to provide an inner lead bonding method that can improve the reliability of the connection between the electrodes of a semiconductor chip and the inner leads of a film carrier, and can be easily implemented.

[Means for Solving the Problems] According to the present invention, the object is to form solder bumps on the inner leads of a film carrier by plating, bring electrodes of a semiconductor chip into contact with the solder bumps, and heat the solder bumps to a melting point. This is achieved by an inner lead bonding method characterized in that the electrode and the inner lead are electrically connected by melting the solder bump by heating to the above temperature.

[Function] According to the inner lead bonding method of the present invention, in the step of forming bumps, half-[U] bumps are formed on the inner leads of the film carrier by plating, so advanced technology and techniques for forming bumps on the wafer are required. Solder bumps can be formed easily and relatively inexpensively from half-[n] without any equipment. Furthermore, the adhesive strength between the inner lead and the bump can be increased compared to a transfer bump. In the process of actually connecting the electrodes of the semiconductor chip and the inner leads of the film carrier using the solder bumps, the electrodes of the semiconductor chip are brought into contact with the solder pan 1, and the bumps are heated to a temperature above the melting point. To melt the solder bumps and electrically connect the electrodes and the inner leads, the electrodes of the semiconductor chip heated above the melting point of the solder bumps should be brought into contact with the solder bumps, or the electrodes of the semiconductor chip should be brought into contact with the solder bumps. By melting the solder bumps at a lower temperature than in thermocompression bonding, there is no need to apply any particular pressure as long as the solder bumps are heated above the melting point of the semi-11 bumps after contact with the solder bumps. and the inner lead can be electrically connected with high reliability. Moreover, variations in the contact relationship between multiple electrodes and the inner lead during connection are sufficiently compensated for by the difference in melting deformation of each solder bump, so it is difficult to deal with the increase in the number of electrodes on semiconductor chips and the increase in the number of electrodes on semiconductor chips, which is difficult to deal with with thermocompression bonding. It can easily accommodate larger sizes.

These effects of the present invention will become clearer from the following examples of the present invention, and other effects of the present invention will become clearer.

[Example] An example of the present invention will be described in order based on FIGS. 1 to 7. Note that the steps shown in FIGS. 1 to 5 are steps for manufacturing a film carrier having bumps,
The process shown in FIGS. 6 and 7 is a process of inner lead bonding of a semiconductor chip to a film carrier using the bump.

In the process shown in FIG. 1, gold is added to the upper side of the film 1! I?
! Laminate 2. The film 1 is preferably made of polyimide, polyester, etc. The film 1 made of polyimide has excellent heat resistance, and the film 1 made of polyester is advantageous in terms of cost. The metal foil 2 is preferably copper foil, but may be made of other metals.

In the process shown in FIG. 2, a photoresist 3 is coated on the lower side of the metal foil 2 at a portion that will become the inner lead of the metal foil 2, and then a photoresist 3 is applied to a portion 4 where a solder bump is to be placed using a photolithography technique. Remove 3.

In the process shown in FIG. 3, half bumps 5 are formed at locations 4 where solder bumps are to be placed by ultrasonic solder plating, electroless solder plating, electrolytic solder plating, etc., and the photoresist 3 is once removed. The height of the solder bump 5 is preferably 40 μm to 100 μm.

In the process shown in FIG. 4, a protective resist 6 for protecting the solder bumps 5 is applied to the lower side of the metal foil 2 on the part that will become the inner lead of the metal foil 2, and a photoresist is applied on the upper side of the metal foil 2. After coating No. 7, an inner lead pattern is formed using photolithography technology. Incidentally, when forming the pattern, the shape of the inner lead may be modified, for example, by changing the width or making it uneven to prevent the solder bumps 5 from flowing out and spreading too much during melting and deformation.

In the step shown in FIG. 5, the protective resist 6 and photoresist 7 are removed to obtain a film carrier 9 having inner leads 8 on which solder bumps 5 are formed. In addition, for the film carrier 9 obtained in this way, the inner lead 8 is provided with a means for preventing the half [U] from flowing out, such as a protruding wall to prevent the solder bumps 5 from flowing out and spreading too much during melting and deformation. It may be set in

In the process shown in FIG. 6, the semiconductor chip 10, which has been heated in advance to a temperature higher than the melting point of the solder bumps 5, is attached to the inner lead 8 of the film carrier 9.
After arranging the solder bumps 5 to face the solder bumps 5, the solder bumps 5 and the electrodes 11 are brought into contact with each other.

In the process shown in FIG. 7, since the semiconductor chip 10 including the electrodes 11 is heated above the melting point of the solder bumps 5, the solder bumps 5 melt and electrically connect the inner leads 8 and the electrodes 11. At this time, each 'rIrkN! The distance between the electrode 11 and the inner lead 8 varies somewhat, that is, the distance between the electrode 1
Even if there is some variation in the contact relationship between the solder bumps 1 and the inner leads 8, this variation is sufficiently compensated for by the difference in melting deformation of each solder bump 5. Therefore, when there are a large number of electrodes 11, it is difficult to deal with this by thermocompression bonding. This embodiment has the advantage that it can be easily applied even when the size of the semiconductor chip 10 is large.

In the above embodiments, the inner leads 8 were formed after the solder bumps 5 were formed in the steps shown in FIGS. 2 to 5, but according to another embodiment of the present invention, the photo A film carrier 9 similar to that shown in FIG. 5 can also be obtained by forming the inner leads 8 by lithography and then forming the solder bumps 5 by plating.

In the above embodiment, after the semiconductor chip 10 is heated in advance in the steps shown in FIGS. 6 and 7, the half [0 bumps 5 and the electrodes 11 are brought into contact to melt the half 11 bumps 5. However, according to another embodiment of the present invention, the electrode 11 is first
After contacting the solder bumps 5, the semiconductor chip 10 and the film carrier 9 may be heated above the melting point of the bumps 5 to melt the solder bumps 5.

[Effects of the Invention] According to the inner lead bonding method of the present invention, in the step of forming the bread 1, the bumps are formed on the film carrier side rather than on the wafer side, so that a sophisticated technique for forming the wafer bumps is not required. Bumps can be easily formed without the need for the same. Since the bumps are made of solder, the bump cost can be lowered compared to bumps made of Au.

Since the bumps are formed by plating, the adhesive strength between the inner lead and the bumps can be increased compared to transfer bumps, and a dedicated device and process for transferring the bumps can be made unnecessary. Furthermore, in the process of actually connecting the electrodes of the semiconductor chip and the inner leads of the film carrier using the solder bumps, the connection is made by melting the semi-openings, so the connection is made at a lower temperature than with thermocompression bonding. Therefore, a lower cost material with poor heat resistance can be used as the film material. Since the connection is made by melting in half a day, it is possible to electrically connect individual electrodes and inner leads with high reliability, and the increase in the number of electrodes of semiconductor chips and the increase in the size of semiconductor chips, which are difficult to handle with thermocompression bonding. can also be easily accommodated.

[Brief explanation of drawings]

1 to 7 are schematic cross-sectional views sequentially showing each step in an embodiment of the present invention. 1...Film, 2...Metal foil, 3.
7...Photoresist, 5...Solder bump, 6...Protection resist, 8...
Inner lead, 9...Film carrier, 10
... Semiconductor chip, 11 ... Electrode.

Claims (1)

[Claims] Solder bumps are formed on the inner leads of the film carrier by plating, the electrodes of the semiconductor chip are brought into contact with the solder bumps, and the solder bumps are melted by heating the solder bumps to a temperature higher than the melting point. An inner lead bonding method characterized by electrically connecting the leads.