JP2000286281A - Transfer bump sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To transfer a copper core solder bump of high reliability to a semiconductor chip at high yield by using an epoxy resin, in a specific range of weight average molecular weight as well as a base resin which contains amino silane as an essential component as a base of a transfer bump sheet. SOLUTION: As a base resin of a transfer bump sheet, a resin composition is used which comprises, as essential components thermoplastic silicon modified polyamide resin 100 pts.wt. which has in its main chain, a structure represented with an expression (R1 and R2 are monovalent aliphatic or aromatic hydrocarbon radical, with carbon number of 6 or less, while n is an integer in the range of 6 to less than 16, epoxy resin 1-100 pts.wt. with weight average molecular weight range of 2,000 to less than 200,000 which is obtained by reacting oligoethyleneglycol diglycidylether with bisphenol A, and amino silane 0.15-10 pts.wt. Thus, a sufficient adhesive strength is provided at manufacturing bump, while no base resin remains on the bump surface at transfer of bump.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transfer bump sheet for mounting bumps for flip chip connection of semiconductor chips by batch transfer.

[0002]

2. Description of the Related Art In recent years, with the demand for higher functionality and lighter, thinner and smaller electronic devices, high-density integration and high-density mounting of electronic components have been advanced, and semiconductors used in these electronic devices have been developed. Packages are becoming smaller and more multi-pin than ever before.

[0003] With the miniaturization of semiconductor packages,
Since the miniaturization of a package using a conventional lead frame has reached its limit, it has recently been proposed to mount a chip on a circuit board and use a BGA (Ball G
Rid Array) and CSP (Chip Scale)
A new package method of area mounting type such as “Package” has been proposed. In these semiconductor packages, the electrical connection between the electrodes of the semiconductor chip and the terminals of the substrate made of various insulating materials such as plastics and ceramics called a semiconductor mounting substrate having the function of a lead frame of a conventional semiconductor package and conductive wiring. As a method, a wire bonding method or TAB (Tape)
Automated Bonding (FC) systems and FC (Flip Chip) systems are known. Recently, BGA and CSP structures using an FC connection system that is advantageous for miniaturization of semiconductor packages have been actively proposed. In general, the FC connection method is a method in which a bump is previously formed on an electrode of a semiconductor chip, and the bump and a terminal on a substrate are aligned and connected by thermocompression bonding.

As methods for forming bumps on a semiconductor chip in advance, there are a method using electrolytic plating and a method using stud bumps. In the method of forming bumps by electrolytic plating,
Since the bumps are formed to a desired size using only the solder, manufacturing time and manufacturing cost are required. In addition, it is difficult to make the current distribution in the plating tank completely uniform in the electrolytic plating, so that the formed bumps vary in size. Variations in the size of the bumps become more pronounced as the plating time increases, and it is difficult to solve the problem by forming the bumps only with solder. In addition, in order to obtain the moisture resistance reliability of the bump connection part, it is necessary to adopt a bump having a metal core such as a copper core solder bump instead of using only a solder for the bump. In order to realize this, it is necessary to form a copper core solder bump by reflow after the steps of solder plating, copper plating, and solder plating, and the manufacturing cost is increased due to further complication of the manufacturing process. On the other hand, stud bumps are formed by bonding and cutting gold wires to electrodes of a semiconductor chip. In this method, one electrode is applied to the electrode of the semiconductor chip.
Since each bump is formed, not only the manufacturing time is increased, but also the manufacturing cost is increased due to the high price of the gold wire.

In view of the above, there is known a transfer bump method in which bumps are formed on a semiconductor chip by transferring the bumps collectively instead of forming the bumps on the semiconductor chip through several steps. This is a method of aligning a transfer bump sheet with solder bumps formed on a sheet-like base material and a semiconductor chip, and applying heat and pressure to transfer the bumps on the transfer bump sheet side to the semiconductor chip side at once. It is.

A conventionally known transfer bump sheet is one in which solder bumps are formed on a base metal serving as a base of the transfer bump sheet. In the manufacturing process, a plating mask is applied to the base metal, a solder is formed by electrolytic plating, and then the plating mask is removed. In order to form bumps to the desired thickness using only solder,
Manufacturing time and manufacturing cost are required. Further, in the electrolytic plating, it is difficult to make the current distribution in the plating tank completely uniform, so that the formed bumps have thickness variations. Since the thickness variation becomes more prominent as the plating time is longer, it is difficult to solve the problem by a method in which bumps are formed only by solder.

[0007]

SUMMARY OF THE INVENTION Accordingly, the present invention has been made as a result of intensive studies in view of the problems of the configuration and the manufacturing method of the conventional transfer bump sheet, and has been developed to provide a semiconductor chip with a highly reliable copper core. It is an object of the present invention to provide a transfer bump sheet that can not only transfer solder bumps in high yield but also form solder bumps of various structures.

[0008]

According to the present invention, there is provided a transfer bump sheet comprising a base resin serving as a base of the transfer bump sheet and a thermoplastic silicone modified resin having a structure represented by the general formula (1) in its main chain. 100 parts by weight of polyimide resin,
Weight average molecular weight obtained by reacting oligoethylene glycol diglycidyl ether with bisphenol A 2,
Epoxy resin 1 to 10 having a size of 2,000 or more and less than 200,000
It is characterized by using a resin composition containing 0 parts by weight and 0.15 to 5.10 parts by weight of aminosilane as essential components.

[0009]

Embedded image In the formula, R ₁ and R ₂ are monovalent aliphatic or aromatic hydrocarbon groups having 6 or less carbon atoms, and n represents an integer of 6 or more and less than 16.

As the base resin, a resin having adhesive properties can be widely used, but thermoplastic silicone-modified polyimide, a mixture of thermoplastic silicone-modified polyimide and epoxy resin, or one-part thermosetting epoxy resin is particularly preferable. Used for Thermoplastic silicone-modified polyimide can control the adhesive force by the amount of silicone introduced, and enables high-accuracy transfer.

Further, by mixing the epoxy resin with the thermoplastic silicone-modified polyimide, it is possible to prevent the resin from remaining on the bumps after the transfer, which is suitable for the base resin of the transfer bump sheet. Particularly, 100 parts by weight of a thermoplastic silicone-modified polyimide resin having a structure represented by the general formula (1) in its main chain, oligoethylene glycol diglycidyl ether and bisphenol
Weight average molecular weight 2,000 or more obtained by reacting A 2
By using a resin composition containing 1 to 100 parts by weight of an epoxy resin less than 00,000 and 0.15 to 5.10 parts by weight of an aminosilane as essential components, it has sufficient adhesive strength at the time of bump production. When a bump is transferred to a semiconductor chip, no base resin remains on the bump surface.
A transfer bump sheet can be obtained.

The thermoplastic silicone-modified polyimide resin used for the base resin used in the present invention needs to have a polysiloxane structure represented by the general formula (1) in its main chain. The chain length n of this polysiloxane is 6
To 15 are preferable, and a range of n to 6 to 12 is particularly preferable in terms of glass transition temperature, adhesiveness, and heat resistance. When n is 5 or less, the film has no flexibility, and when n is 16
In the case described above, the heat resistance of the polyimide is reduced, and the displacement of the bump occurs due to the heat at the time of transfer. This polysiloxane structure can be introduced by using a silicone diamine such as α, ω-bis (3-aminopropyl) polydimethylsiloxane as a raw material when producing a polyimide.

As the diamine used as a raw material of the thermoplastic silicone-modified polyimide, aromatic diamines such as 2,2'-bis (4- (4-aminophenoxy) phenyl) propane and 1,3-bis (3- Aminophenoxy) benzene, 2,2′-bis (4- (4-aminophenoxy) phenyl) hexafluoropropane, 2,2 ′
One or more of bis- (4-aminophenoxy) hexafluoropropane, bis-4- (4-aminophenoxy) phenylsulfone, bis-4- (3-aminophenoxy) phenylsulfone, and the silicone diamine Combined.

As the acid anhydride, 3,3 ', 4,
4'-biphenyltetracarboxylic dianhydride, 3,
One or more tetracarboxylic acids obtained from the group consisting of 3 ', 4,4'-benzophenonetetracarboxylic dianhydride, 4,4'-oxydiphthalic dianhydride and ethylene glycol bistrimellitic dianhydride Use carboxylic dianhydride.

The epoxy resin used as the base resin used in the present invention has a weight average molecular weight of 2,000 to 200,000 obtained by reacting oligoethylene glycol diglycidyl ether with bisphenol A.
It is preferred to use less than the epoxy resin. If the weight average molecular weight is less than 2,000, gas is generated by heating at the time of bump transfer, which is not preferable. On the other hand, if the weight average molecular weight is 200,000 or more, it is not preferable because it has no flexibility and the adhesive strength is poor. For reference, such an epoxy resin has a structure represented by the general formula (2).

[0016]

Embedded image In the formula, m is an integer of 3 or more, and n represents an integer of 2 or more and less than 8.

As a phenol compound used as a raw material of the epoxy resin, a bifunctional phenol compound such as bisphenol A, bisphenol F or biphenol can be used. Most preferably, it is used. In order to obtain a chain-extended epoxy resin having excellent flexibility, it is best to use oligoethylene glycol diglycidyl ether as the other raw material. The number of repetitions n in the general formula (2) is preferably 2 or more. It is better to be less than 8. n
Is 1, the flexibility of the chain-extended epoxy resin is relatively low, and the properties are comparable to those of a high molecular weight bisphenol A type epoxy resin. On the other hand, if n is 8 or more, the flexibility of the chain-extended epoxy resin becomes too high, so that the flow becomes too large at the time of bump transfer, resulting in displacement.

The base resin used in the present invention is based on 100 parts by weight of a thermoplastic silicone-modified polyimide resin having a structure represented by the general formula (1) in its main chain.
The weight average molecular weight obtained by reacting oligoethylene glycol diglycidyl ether and bisphenol A is 2,000 or more and less than 200,000, preferably 1 to 100 parts by weight, more preferably 20 to 50 parts by weight. . If the amount is less than 1 part by weight, the adhesive strength is low, and if it exceeds 100 parts by weight, the heat resistance of the resin composition decreases, which is not preferable. The mixing ratio of the aminosilane is 0.15 to 5.10 parts by weight with respect to 100 parts by weight of the thermoplastic silicone-modified polyimide resin, which means that the active hydrogen of the epoxy group and the chemical equivalent of the amine are mixed. .

The transfer bump sheet of the present invention comprises a step of forming the above-mentioned base resin on a metal foil in the form of a film, a step of forming an etching mask on the metal foil, and a step of etching the metal foil to form the metal of the conductor terminal. It is manufactured by a step of forming a core, a step of removing an etching mask, and a step of forming a solder coat on the surface of a metal core of a conductor terminal by electroless plating.

As the metal foil, a metal such as copper or aluminum capable of forming a bump having a required shape by etching can be used, but copper having low electric resistance and excellent heat conductivity is most preferable. . The solder used for the solder coat may be any as long as it can be electrolessly plated, and includes, for example, Sn-Pb eutectic solder.

[0021]

FIG. 1 is a sectional view showing the structure of a transfer bump sheet 1 according to an embodiment of the present invention. Transfer bump sheet 1
Is composed of a base resin 2 and a conductor terminal 3. The conductor terminal 3 includes a metal core 4 and a solder coat 5.

FIG. 2 is a sectional view showing a transfer method for collectively transferring the bumps 12 to the semiconductor chip 10 using the transfer bump sheet 1 according to the first embodiment. The transfer bump sheet 1 is placed at a predetermined position on a substrate receiving table 22 of a bonding apparatus, and the semiconductor chip 10 is sucked by a heating / pressing tool 20 having suction holes 21. A positioning mark formed in advance on the transfer bump sheet 1 and the semiconductor chip 10 is read by an image recognition device, and the conductor terminals 3 of the transfer bump sheet 1 and the electrodes 11 of the semiconductor chip 10 are opposed to each other and accurately aligned (FIG. a)). Heating and pressing tool 2
0, the semiconductor chip 10 is transferred to the transfer bump sheet 1
At a predetermined temperature and pressure (Fig. 2
(B)). When the solder coat 5 reaches the melting temperature, the solder coat 5 changes to a shape in which the surface tension is balanced (FIG. 2C). After heating and pressing for a predetermined time, the heating and pressing tool 20 is raised, and the semiconductor chip 10 and the transfer bump sheet 1 are removed from the heating and pressing tool 20. The semiconductor chip 10 having the bumps 12 is obtained by removing the base resin 2 after the solder coat 5 has solidified (FIG. 2D). Through the above steps, the bumps 12 can be collectively transferred to the semiconductor chip 10 using the transfer bump sheet 1.

When the bumps 12 are collectively transferred to the semiconductor chip 10 using the transfer bump sheet 1, a self-transfer
An alignment effect can be used. That is,
In the alignment of the conductor terminals 3 of the transfer bump sheet 1 and the electrodes 11 of the semiconductor chip 10, even if the transfer is performed in a state where the respective positions are slightly shifted, due to the surface tension of the solder, the center of the electrodes 11 of the semiconductor chip 10 is maintained. This means that the bumps 12 can be formed accurately. Therefore, even if a bonding apparatus having low alignment accuracy is used, some positional deviation is corrected by the self-alignment effect, and the bumps 12 can be formed accurately at the center of the electrodes 11 of the semiconductor chip 10.

In the transfer bump sheet 1 of the present invention, since the metal cores 4 of the conductor terminals 3 are formed by etching a metal foil having a uniform thickness, the thickness of the metal core 4 of each conductor terminal 3 is very uniform. . Further, since the solder coat 5 is formed by electroless plating, the thickness is very uniform. Therefore, the thickness of the conductor terminal 3 is very uniform, and no bump transfer error due to thickness variation of the conductor terminal 3 occurs.

The transfer bump sheet 1 of the present invention comprises, as a base resin, 100 parts by weight of a thermoplastic silicone-modified polyimide resin having a structure represented by the general formula (1) in its main chain:
Weight average molecular weight obtained by reacting oligoethylene glycol diglycidyl ether with bisphenol A 2,
Epoxy resin 1 to 10 having a size of 2,000 or more and less than 200,000
0 parts by weight, the resin composition containing 0.115 to 5.10 parts by weight of aminosilane as an essential component,
In the metal foil etching process, there is sufficient adhesive force, it is possible to produce fine bumps with high precision, and after the solder coat is melted and the semiconductor chip is bumped, the bonding strength is smaller than the bonding strength between the solder and the chip electrode. Since the adhesive strength of the base resin to the bump is lower, the bump is successfully transferred to the semiconductor chip when the base resin film is removed, and the base resin does not remain on the bump surface.

[0026]

The present invention will be described in more detail with reference to Examples, but it should not be construed that the invention is limited thereto.

Embodiment 1 FIG. (Preparation of a base resin) In the general formula (1), a thermoplastic silicone-modified polyimide having a glass transition temperature of 145 ° C containing polydimethylsiloxane in which n is 10 in a main chain;
Weight average molecular weight of 5000 obtained by reacting ethylene glycol diglycidyl ether with bisphenol A
No. 0 epoxy resin and aminosilane compound were prepared, and 100 parts by weight of polyimide, 10 parts by weight of epoxy resin, and 0.51 part by weight of aminosilane compound were mixed to obtain a base resin.

The above-mentioned base resin was applied to a rolled copper foil having a thickness of 70 μm to obtain a two-layer sheet comprising a copper foil and a base resin layer having a thickness of 30 μm. The copper foil surface of the two-layer sheet is subjected to a dry film lamination, exposure, development, copper foil etching, and dry film peeling steps to obtain a pitch of 250.
μm, 100 μm diameter copper cylinder (metal core 4)
Six were formed. Further, a 10 μm-thick solder (solder coat 5) was formed by electroless plating Sn—Pb eutectic solder. Through the above steps, the transfer bump sheet 1 according to the first embodiment of the present invention was manufactured.

Using the transfer bump sheet 1 obtained,
An attempt was made to transfer the bump 12 to the semiconductor chip 10. The transfer condition is as follows: the temperature of the heating and pressing tool 20: 150
° C, the temperature of the substrate holder 22: 250 ° C, the load: 6 kgf
/ 4096 bump, heating and pressing time: 10 seconds. Ten samples were prepared for each example, and a transfer experiment was performed under the above conditions. As a result, it was confirmed that 4096 bumps were completely transferred to the semiconductor chip side in all the samples. The bumps mounted on the semiconductor chip had a pitch of 250 μm and a diameter of 120 μm. The height of the bump was 75 μm.

[0030]

As described above in detail, by using the transfer bump sheet of the present invention, not only can the bumps be easily mounted on the semiconductor chip, but also the transferred bumps have a metal core. Therefore, the moisture resistance reliability can be greatly improved, and when copper is used for the metal core, the electric resistance can be significantly reduced and the thermal conductivity is excellent.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating a method for manufacturing a transfer bump sheet according to a first embodiment of the present invention.

FIG. 2 is a cross-sectional view showing a transfer method for collectively transferring bumps to a semiconductor chip using a transfer bump sheet according to the first embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Transfer bump sheet 2 Base resin 3 Conductor terminal 4 Metal core 5 Solder coat 10 Semiconductor chip 11 Electrode 12 Bump 13 Passivation film 20 Heating and pressing tool 21 Suction hole 22 Substrate support

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification code FI Theme coat ゛ (Reference) H01L 21/92 604F F-term (Reference) 4J002 CD012 CD052 CD202 CM041 DB016 EX076 GQ00 GQ05 5E346 CC08 CC10 CC32 CC40 DD23 DD44 EE08 EE13 FF34 FF37 GG17 GG18

Claims (2)

[Claims] 1. A transfer bump sheet in which a conductor terminal is formed on a base resin and the conductor terminal is constituted by at least a metal core and a solder coat covering a part or the entire surface of the metal core. 100 parts by weight of a thermoplastic silicone-modified polyimide resin having a structure represented by the general formula (1) in the main chain, and a weight average molecular weight of 2,000 or more 200 obtained by reacting oligoethylene glycol diglycidyl ether with bisphenol A ,
A transfer bump sheet comprising a resin composition containing, as essential components, 1 to 100 parts by weight of an epoxy resin of less than 000 and 0.15 to 5.10 parts by weight of an aminosilane. Embedded image In the formula, R ₁ and R ₂ are monovalent aliphatic or aromatic hydrocarbon groups having 6 or less carbon atoms, and n represents an integer of 6 or more and less than 16. 2. The transfer bump sheet according to claim 1, wherein the metal core is copper.