JP2000164629A - Thickwise conductive sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To ensure electrical and mechanical connection between a semiconductor chip and a substrate in the thickness direction by a method wherein a conductor is provided penetrating through a thermosetting insulating sheet to be electrically connected to the other surface of the sheet, and the thermosetting insulating sheet is thermally cured at a higher temperature to bond a connector. SOLUTION: A thickwise conductive sheet 3, a semiconductor device 4, and a substrate 6 are stacked up aligning the conductor terminals 2 of the thickwise conductive sheet 3, the electrodes 5 of the semiconductor device 4 as the terminal of a connector, and connection terminals 7 located on the substrate 6 with each other. Then, a thermosetting insulating sheet 1 is heated at a certain temperature at which it hardly gets cured so as to be softened and melted to be fixed, and the conductor terminals 2 of the thickwise conductive sheet 3 are made to penetrate through the thermosetting insulating sheet 1, so that the conductor terminals 2 and the connection terminals 7 are brought into contact with each other and electrically connected together. Furthermore, the thermosetting insulating sheet 1 is thermally cured by heating at a high temperature and bonded to a connector at the same time. By this setup, the semiconductor chip 4 and the substrate 6 can be surely connected together keeping high in thickwise electrical and mechanical connection reliability.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a conductive sheet in a thickness direction which can simultaneously and electrically connect a plurality of electrode terminals of a semiconductor element or an electric / electronic component at the same time.

[0002]

2. Description of the Related Art With the recent demand for higher functionality and lighter, thinner and smaller electronic equipment, high-density integration and high-density mounting of electronic components have been progressing. Semiconductor packages used in these electronic devices have been reduced in size and number of pins, and mounting substrates for mounting electronic components including the semiconductor packages have also been reduced in size. Further, in order to enhance the storability in electronic devices, a rigid-flex board, in which a rigid board and a flexible board are laminated and integrated and can be bent, has been used as a mounting board.

[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, a method of electrically connecting electrodes of a semiconductor chip to terminals of a substrate made of various materials such as plastics and ceramics, which is called a semiconductor package substrate having a function of a lead frame of a conventional semiconductor package. As a wire bonding method or TAB
(Tape Automated Bonding) method and FC (Flip Chip) method are known. Recently, BGA and CSP structures using FC connection method which is advantageous for miniaturization of semiconductor packages have been actively proposed. I have. In this FC connection method, generally, a connection bump is formed in advance on a semiconductor chip electrode, and the bump and the terminal on the substrate are aligned and connected by thermocompression bonding. The formation process is complicated and bump manufacturing costs are high, and it is necessary to fill the gap between the chip and the substrate with a resin called underfill to seal the connection part in order to obtain the moisture resistance reliability of the bump connection part. In addition, there is a problem that a process of filling and curing the underfill resin is required, so that the manufacturing process is complicated and the manufacturing cost is increased. Accordingly, a method of using an anisotropic conductive sheet as a connection material instead of a bump for electrical connection between a semiconductor chip and a substrate has been focused on and studied.

[0004] An anisotropic conductive sheet is a sheet in which conductive fine particles are dispersed in a resin, and the resin flows during thermocompression bonding to obtain electrical connection in the thickness direction by the conductive fine particles sandwiched between connection terminals. It is. The anisotropic conductive adhesive used for the sheet is classified into a thermoplastic and a thermosetting one.Recently, the thermoplastic resin has a more reliable thermosetting property than the thermoplastic one. Things are widely used.
As a method of using the anisotropic conductive sheet, the anisotropic conductive sheet is temporarily bonded between connected objects, pressurized at a temperature of 150 to 200 ° C., and contacted with conductive particles dispersed in the anisotropic conductive sheet between the connected objects. In general, a method is used in which the resin is thermally cured and bonded at the same time as the conduction is performed.

Conventionally, anisotropic conductive sheets have been used for electrical connection between circuits such as connection between LCD (liquid crystal display) and TCP (tape carrier package) and connection between TCP and PCB (printed circuit board). I have.

In recent years, research on FC mounting using the anisotropic conductive sheet technology has been rapidly developed. For example, F
As an anisotropic conductive sheet for C connection, there is a flip-tack made by Hitachi Chemical. In flip-tack, an anisotropic conductive sheet in which conductive particles having an average particle size of 3 μm are dispersed is pressed under pressure in
It is characterized in that the chip and the substrate are connected by heating to 70 to 190 [deg.] C. and maintained for 10 to 20 s, and simultaneously bonded by thermosetting.

However, the anisotropic conductive sheet obtained as described above has the following problems. First, in the case of a structure in which conductive fine particles are dispersed in a thermoplastic or thermosetting resin, the terminals are narrow because electrical connection is obtained by the conductive fine particles that are stochastically present between the electrodes and the terminals. As the pitch becomes smaller, it is necessary to disperse the conductive fine particles more and more finely, thereby increasing the density of the fine particles and narrowing the distance between the fine particles, thereby deteriorating the electrical insulation property and the connection area between the fine particles and the terminals. There is a problem that the connection resistance increases due to the decrease. In addition, since the anisotropic conductive sheet having the above structure does not allow the connection points to be arbitrarily selected in the sheet surface, for example, when used for interlayer connection of a multilayer board, a circuit other than terminals to be connected is covered with an insulating resin in advance. Further, it is necessary to adopt a structure in which only the portion to be electrically connected receives pressure. In practice, it is difficult to arrange the anisotropic conductive sheet having the above structure on the entire surface of the multilayer board to achieve electrical conduction.

On the other hand, the electrical connection is ensured even when the pitch of the terminals is reduced by using the electrical and mechanical connection in the thickness direction such as the connection between the semiconductor chip and the substrate or the interlayer connection of the multilayer board. As well as having electrical insulation between adjacent terminals and can be manufactured at low processing cost.
Independent terminals made of conductors are arranged on one surface of an insulating sheet having adhesiveness, and the above-mentioned conductors are insulated by softening of the insulating sheet at the time of heating and compression bonding with a connected body. Sink until it reaches the opposite side of the
A conductive sheet in the thickness direction has been proposed, in which conduction with the opposite surface of the insulating sheet is obtained and, at the same time, adhesion with the connected object is performed. (Japanese Unexamined Patent Publication No. 9-176994) Even in the thickness direction conductive sheet, when a heat-resistant thermoplastic resin is used for high reliability, molding at a high temperature is required, and the connected substrate and the like are defective. May occur or conduction may be insufficient when molded at a low temperature. In addition, when a certain kind of thermosetting resin is used, when a conductor penetrates the insulating sheet, thermosetting also proceeds, so that a large internal stress is accumulated and connection reliability after bonding may be lacking.

[0009]

SUMMARY OF THE INVENTION Accordingly, the present invention relates to a conventional anisotropic conductive sheet or an insulating sheet having an adhesive property, in which one or both surfaces have independent terminals made of conductors arranged. In view of the above problems that the direction conductive sheet has, it was made as a result of earnest research,
It is an object of the present invention to provide a thickness direction conductive sheet which reliably performs electrical and mechanical connection in a thickness direction of connection between a semiconductor chip and a substrate and has high reliability after connection.

[0010]

In order to achieve the above-mentioned object, in the thickness direction conductive sheet of the present invention, one or both surfaces of the thermosetting insulating sheet having an adhesive property are formed by an independent conductor made of a conductor. Terminals are arranged, and the thermosetting insulating sheet is softened and melted at the time of thermocompression bonding with the connected body, so that the conductor penetrates the thermosetting insulating sheet and is opposite to the thermosetting insulating sheet. Continuity with the surface is obtained,
Further, it is characterized in that it is thermoset by heating at a high temperature and is simultaneously bonded to a connected body.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the drawings. 1 to 5 are examples of schematic diagrams of a process for connecting a semiconductor element and a substrate using a conductive sheet in the thickness direction of the present invention. FIG. 1 shows an example in which a thickness direction conductive sheet 3 is shown. Terminals 2 made of a conductor are arranged on one surface of a thermosetting insulating sheet 1 having adhesiveness. There is also a structure of a thickness direction conductive sheet 31 in which terminals 2 made of a conductor are arranged on both surfaces of a thermosetting insulating sheet 1 having adhesiveness (FIG. 2). 3 to 5 show examples of a method of connecting a connected body.
Shown in First, the conductor terminal 2 of the thickness direction conductive sheet 3, the electrode 5 of the semiconductor element which is the terminal of the body to be connected, and the connection terminal 7 on the substrate are aligned and overlapped (FIG. 3). In the first step of crimping, the thermosetting insulating sheet 1 is heated at a temperature that does not harden by heat, softened and melted and crimped (FIG. 4), and the conductor terminals 2 of the thickness direction conductive sheet 3 are converted into thermosetting insulating sheets. 1 through which the conductors are brought into contact to establish electrical continuity. Further, as a second step of thermocompression bonding, the thermosetting insulating sheet 1 is heat-cured by heating at a high temperature, and is simultaneously bonded to a connected body (FIG. 5).

The thermosetting insulating sheet used in the present invention has a property of being solid at room temperature and softening and melting at a temperature that does not cause thermosetting. In the first step of thermocompression bonding, the softening and melting temperature at which the thermosetting insulating sheet is not thermoset is 50
C. or higher is required, and although it depends on the type of thermosetting insulating sheet to be used, it is preferably in the range of 50 to 200.degree. In the case of a thermosetting insulating sheet having a softening and melting temperature lower than 50 ° C., tack occurs on the sheet surface, and workability is significantly reduced. In the case of a thermosetting insulating sheet having a softening and melting temperature exceeding 200 ° C., when the conductor terminals penetrate the thermosetting insulating sheet and make contact between the conductors for electrical conduction, heat is applied before the conductor terminals penetrate. Curing may proceed, causing poor connection. Further, it is important that the thermosetting temperature of the thermosetting insulating sheet in the second step of thermocompression bonding is higher by at least 10 ° C. than the softening and melting temperature. If the temperature difference is smaller than this, it is difficult to control the temperature, which leads to the same connection failure as described above.

The objects to be connected by the thickness direction conductive sheet of the present invention include a semiconductor element and a lead frame, a semiconductor element and a substrate, a semiconductor package and a mounting substrate circuit, and chip components used for surface mounting. It can be widely used for electrical connection in the thickness direction, such as mounting substrates, mounting substrates and mounting substrates, mounting substrates and flexible substrates, etc. It is particularly useful when used for the electrical connection of

The resin used for the thermosetting insulating sheet of the present invention is not particularly limited as long as it is a solid at room temperature and softens and melts at a temperature that does not cause thermosetting. Specifically, a resin such as an epoxy resin, an acrylic resin, a maleimide resin, a fluorine resin, a bromo resin, and a silicone resin can be used singly or in combination. Among them, epoxy resins are most preferable.

The resin used for the thermosetting insulating sheet may be mixed with a thermoplastic resin having excellent sheet forming ability. For example, polyester resins, polyurethane resins, polyimide resins, polybutadiene, polypropylene, styrene-butadiene-styrene copolymer, polyacetal resin, polyvinyl butyral resin, butyl rubber, chloroprene rubber, polyamide resin, acrylonitrile-butadiene copolymer, acrylonitrile- Butadiene-methacrylic acid copolymer, acrylonitrile-butadiene-styrene copolymer, polyvinyl acetate resin, nylon, styrene-isoprene copolymer, styrene-butylene-styrene block copolymer, styrene-ethylene-butylene-styrene block copolymer A polymer, a polymethyl methacrylate resin, or the like can be used. Among them, considering the properties such as adhesiveness and connection reliability when the thickness direction conductive sheet is formed, acrylonitrile-butadiene-
Methacrylic acid copolymer, polyester, polyamide resin, nylon, polyvinyl butyral resin, styrene
An ethylene-butylene-styrene block copolymer or the like can be more preferably used.

The curing agent for the resin used in the thermosetting insulating sheet of the present invention is not particularly limited as long as it is a curing agent which starts curing at a temperature of 60 ° C. or higher. Specifically, as a curing agent for the epoxy resin, a latent curing agent such as dicyandiamide, imidazole compound, organic acid hydrazide, diaminomaleonitrile, melamine derivative, amine imide compound, aromatic diazonium salt, diallyliodonium salt,
Triallylsulfonium salts, triallylselenium salts,
A ketimine compound or the like can be used alone or as a mixture of two or more. Further, a colorant, an inorganic filler, various coupling agents, and the like may be added to the resin used for the thermosetting insulating sheet.

As a method for producing the thermosetting insulating sheet of the present invention, a varnish obtained by dissolving a thermosetting resin or a mixture of a thermosetting resin and a thermoplastic resin in a solvent is provided on a metal foil by using a bar coater, a die coater and a comma coater. And a method such as spin coating can be used. afterwards,
It is necessary to sufficiently dry the thermosetting insulating sheet at a temperature at which the thermosetting insulating sheet does not thermoset. Usually, a rolled copper foil, an electrolytic copper foil, a stainless steel foil, a nickel foil, a titanium foil, and a solder foil can be used as the metal foil. This metal stay can be used to form a conductor terminal, and by using a copper foil such as a rolled copper foil or an electrolytic copper foil, connection with low electric resistance can be achieved.

As a method of forming the conductor terminals on the surface of the thermosetting insulating sheet of the thickness direction conductive sheet of the present invention, the above-mentioned metal pad is used, or the thermosetting insulating sheet and the metal foil are laminated in advance. In advance, a method of forming the metal foil by etching, the resin used for the thermosetting insulating sheet is cast and applied on the metal foil, and then the metal foil of the composition obtained by dry film formation is etched and formed. Or a method in which a mask is formed on the surface of the thermosetting insulating sheet by plating, or the like. The conductor terminals may be arranged in a lattice at an arbitrary pitch, or may be arranged so as to correspond to the terminals of the body to be connected, and may be selected according to the purpose. The height of the conductor terminal is preferably 0.7 to 1.5 times the thickness of the thermosetting insulating sheet to be used. If the height is lower than 0.7 times that of the thermosetting insulating sheet, the conductor terminals do not reach the back surface of the thermosetting insulating sheet at the time of thermocompression bonding, so that conduction between the front and back cannot be obtained. On the other hand, if it is higher than 1.5 times, the conductor terminals become pillars when heated and press-bonded, and a gap is formed between the connected body and the thermosetting insulating sheet, so that they cannot be bonded to each other. A second conductor layer may be formed on the surface of the conductor terminal for the purpose of further improving electrical connection. For example, electrolytic plating or electroless plating is used as the method, and a metal such as gold, tin, lead, or indium can be used for the conductor.

[0019]

EXAMPLES Examples using the means of the present invention will be described below, but the present invention is not limited to these examples. Example 1 100 parts of an epoxy resin (epoxy equivalent: 620, softening point: 90 ° C.) and 40 parts of a bisphenol F type epoxy resin (epoxy equivalent: 175) were dissolved in 180 parts of methyl ethyl ketone (hereinafter abbreviated as MEK) with stirring,
4-phenyl-4-methylimidazole (4 parts) as a curing agent and silica (average particle size: 1 μm) as an inorganic filler
By adding 40 parts, a varnish for a thermosetting insulating sheet was prepared. This varnish is rolled into 18 μm thick rolled copper foil (manufactured by Nippon Mining)
After casting with a comma coater with the gap interval adjusted to 40 μm, it was dried at 80 ° C. for 20 minutes, and the thickness of the insulating layer was 15 μm.
A thermosetting insulating sheet with a copper foil of μm was obtained. The softening and melting onset temperature of the obtained thermosetting insulating sheet was 60 ° C., and the reaction onset temperature was 100 ° C. A semiconductor element having external connection electrodes around the circuit surface as an adherend,
A substrate having connection terminals at positions corresponding to the electrodes of the semiconductor element was prepared. Laminating a dry film resist on the copper foil surface of the thermosetting insulating sheet with copper foil, and forming conductor terminals at positions corresponding to the electrodes of the semiconductor element by mask exposure, dry film development, etching and dry film peeling steps. The obtained thickness direction conductive sheet was obtained. Conductor terminals of the thickness direction conductive sheet, electrodes of the semiconductor element, and corresponding terminals on the substrate,
After the respective electrode terminal positions are aligned and overlapped, the thermosetting insulating sheet is heated from the semiconductor element surface by a heat block.
While heating to 0 ° C., pressure was applied at a pressure of 10 kgf / cm ² to penetrate the conductor terminals through the thermosetting insulating sheet. The conductor terminal that reaches the opposite side of the thermosetting insulating sheet is
It was joined to the electrode of the semiconductor element and the connection terminal on the substrate to obtain electrical continuity. Further, the thermosetting insulating sheet was heated to 180 ° C., and the thermosetting insulating sheet was thermoset to bond the surface of the semiconductor element and the surface of the substrate.

Example 2 Epoxy resin (epoxy equivalent: 620, softening point: 90 ° C.) was replaced by epoxy resin (epoxy equivalent: 920, softening point: 110 ° C.), and 2-phenyl-4 was replaced by 2-phenyl-4-methylimidazole. -Methyl-5
A thermosetting insulating sheet having a softening / melting start temperature of 80 ° C and a reaction start temperature of 120 ° C was obtained in the same manner as in Example 1 except that -hydroxymethylimidazole was used. Using this thermosetting insulating sheet, a sample was prepared in the same manner as in Example 1 except that the thermosetting insulating sheet was heated from a semiconductor element surface to 100 ° C. by a heat block.

Example 3 Epoxy resin (epoxy equivalent: 620, softening point: 90 ° C.) was changed to epoxy resin (epoxy equivalent: 920, softening point: 110 ° C.), and 2-phenyl-4 was changed to 2-phenyl-4-methylimidazole. A thermosetting insulating sheet having a softening / melting start temperature of 80 ° C and a reaction start temperature of 150 ° C was obtained in the same manner as in Example 1 except for using 1,5-dihydroxymethylimidazole. Using this thermosetting insulating sheet, a sample was prepared in the same manner as in Example 1 except that the thermosetting insulating sheet was heated from a semiconductor element surface to 100 ° C. by a heat block.

Comparative Example 1 100 parts of an epoxy resin (epoxy equivalent 1800, softening point 130 ° C.) and 30 parts of a bisphenol F type epoxy resin (epoxy equivalent 175) were mixed with ME.
K170 was dissolved with stirring, and 4 parts of 2-phenyl-4-methylimidazole as a curing agent and 40 parts of silica (average particle size: 1 μm) were added thereto to prepare a varnish for a thermosetting insulating sheet. Using this varnish, a thermosetting insulating sheet having a softening / melting start temperature of 120 ° C. and a reaction start temperature of 100 ° C. was obtained in the same manner as in Example 1. Using this thermosetting insulating sheet, a sample was produced in the same manner as in Example 1 except that the thermosetting insulating sheet was heated from a semiconductor element surface to 130 ° C. by a heat block.

Comparative Example 2 70 parts of an epoxy resin (epoxy equivalent: 620, softening point: 90 ° C.) and 70 parts of a bisphenol F type epoxy resin (epoxy equivalent: 175) were added to MEK18.
0 parts were dissolved with stirring, and 4 parts of 2-phenyl-4-methyl-5-hydroxymethylimidazole as a curing agent and 40 parts of silica (average particle size: 1 μm) were added thereto to prepare a thermosetting insulating sheet varnish. Produced. Using this varnish, a thermosetting insulating sheet having a softening / melting start temperature of 40 ° C. and a reaction start temperature of 120 ° C. was obtained in the same manner as in Example 1. Using this thermosetting insulating sheet, a sample was prepared in the same manner as in Example 1 except that the thermosetting insulating sheet was heated from a semiconductor element surface to 60 ° C. by a heat block.

Table 1 shows the thermal properties, processing conditions and results of reliability tests of the conductive sheet in the thickness direction. The connection resistance of the obtained sample was measured by a four-terminal method, and the connection resistance was 10 mΩ.
Marked in the following cases. Further, after performing the IR reflow treatment twice, a cooling / heating cycle test (−55 to 125 ° C .: 30 for each)
, 1000 cyc, room temperature exposure time of 5 minutes), and when the connection resistance after the test hardly changed, it was marked with ○.

[0025]

[Table 1]

In Comparative Example 1, since the reaction start temperature was higher than the softening and melting start temperature, thermosetting proceeded during molding, and the conductor could not penetrate the thermosetting insulating sheet, and electrical connection could not be obtained. . Further, even when the conductor penetrated the thermosetting insulating sheet, internal stress was accumulated due to large resin deformation, and connection reliability could not be obtained.

In Comparative Example 2, since the softening and melting temperature of the thermosetting insulating sheet was 40 ° C. and close to room temperature of 25 ° C., the tack of the surface of the thermosetting insulating sheet was too strong and the thermosetting insulating sheet was heat-cured. When laminating the dry film resist on the copper foil surface of the mold insulating sheet, the thermosetting insulating sheet sticked to the roll of the laminating machine, and the dry film resist could not be laminated.

[0028]

According to the thickness direction conductive sheet of the present invention,
Compared to conventional anisotropic conductive sheet, electrical connection and mechanical connection in the thickness direction such as connection between semiconductor chip and substrate, interlayer connection of multilayer board, etc. can be reliably performed, and reliability after connection is higher. Get higher.

[Brief description of the drawings]

FIG. 1 is a schematic view of a thickness direction conductive sheet in which conductive terminals are arranged on one surface of an adhesive thermosetting insulating sheet.

FIG. 2 is a schematic view of a thickness direction conductive sheet in which conductor terminals are arranged on both surfaces of a thermosetting insulating sheet having adhesiveness.

FIG. 3 is a schematic diagram in which conductor terminals of a thickness direction conductive sheet having conductor terminals arranged on one surface are aligned with electrodes of a semiconductor element and connection terminals on a substrate.

FIG. 4 is a schematic diagram of a first step of heat compression bonding in which a thermosetting insulating sheet is heated, softened, melted, and compressed.

FIG. 5 is a schematic view of a second step of thermocompression bonding in which conductors are brought into contact with each other to thermally cure a thermosetting insulating sheet by heating at a high temperature, and at the same time adhere to a contacted body.

[Explanation of symbols]

 1: Thermosetting insulating sheet 2: Conductive terminal 3: Thickness conductive sheet 31: Thickness conductive sheet 4: Semiconductor element 5: Electrode of semiconductor element 6: Substrate 7: Connection terminal on substrate 8: Heat block

Claims (3)

[Claims] An independent terminal made of a conductor is arranged on one or both surfaces of a thermosetting insulating sheet having an adhesive property. By softening and melting, the conductor penetrates the thermosetting insulating sheet, and conduction with the opposite surface of the thermosetting insulating sheet is obtained. A conductive sheet in the thickness direction, wherein the sheet is bonded. 2. The thickness direction conductive sheet according to claim 1, wherein the thermosetting insulating sheet is solid at room temperature and is softened and melted at a temperature that does not cause thermosetting. 3. The thermosetting insulating sheet is a solid at room temperature, softens and melts at an arbitrary temperature of 50 ° C. or more that does not thermoset, and thermosets at a temperature higher than the softening melting temperature by 10 ° C. or more. The thickness direction conductive sheet according to claim 1, characterized in that: