JP4045471B2 - Electronic component mounting method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an electronic component mounting method effective when a substrate on which a chip is mounted is mounted on another electronic component.
[0002]
[Prior art]
With the miniaturization and thinning of semiconductor chips and electronic components, the circuits and electrodes used for these have become higher in density and higher in definition. For the connection of such fine electrodes, a method using an adhesive has recently been frequently used. In this case, the conductive particles are blended in the adhesive, and electrical connection is obtained in the thickness direction of the adhesive by pressurization (for example, Japanese Patent Application Laid-Open No. 55-104007). There is one that obtains an electrical connection by direct contact of fine irregularities on the electrode surface by pressure (for example, JP-A-60-262430).
The connection method using an adhesive can be connected at a relatively low temperature, and the connection part is flexible, so it has excellent reliability. In addition, when a film or tape adhesive is used, it has a certain length. Since it is supplied in the form of a scale, it is attracting attention because the mounting line can be automated.
In recent years, a multi-chip module (MCM) that has developed the above-described method and mounts a plurality of chips on a relatively small substrate with high density has attracted attention. In this case, it is common to first form an adhesive layer on the entire surface of the substrate, then peel off the separator, if any, and then align and adhesively bond the substrate electrode and the chip electrode. As chips used for MCM, there are many types (hereinafter referred to as chips) such as a semiconductor chip, an active element, a passive element, a resistor, and a capacitor.
[0003]
[Problems to be solved by the invention]
There are many types of chips used for MCM, and there are many types of chip sizes (area, height) accordingly. For this reason, when connecting to the substrate using an adhesive, unprecedented problems have arisen due to the thermocompression bonding method with the substrate. For example, a circuit sink of a multilayer circuit board occurs at the time of chip connection, and there is a phenomenon that reliability is lowered due to residual stress. This is because the interlayer adhesive of the multilayer substrate generally has low heat resistance. For example, the glass transition point of the interlayer adhesive is 130 ° C. or lower, while the temperature at the time of chip connection needs to be 150 ° C. or higher. For this measure, an expensive heat-resistant substrate must be applied at the time of chip connection, but the heat-resistant substrate generally has a contradiction that cannot be applied to a multilayer substrate because of its low interlayer adhesion. On the other hand, since the MCM has a large number of extraction electrodes, the substrate needs to be multi-layered.
In addition, when connecting the MCM to, for example, a mother board as another electronic component, connection is performed by a solder reflow furnace, which is a conventional technique. In this case, the temperature of the solder reflow furnace is as high as 200 to 300 ° C. In many cases, the adhesive heat resistance of the MCM connection portion cannot withstand this temperature, and the connection reliability is insufficient.
As another electronic component, there is a chip case. In this case, since it is mounted on both sides of the substrate, the chip position is rarely placed in the target state on the front and back sides. Therefore, means for applying pressure suitable for bonding of fine electrodes that require uniform pressure without pressure unevenness. There is no state.
The present invention has been made in view of the above disadvantages, and is an effective electronic component mounting method when a substrate on which a chip is mounted is mounted on another electronic component such as a multilayer circuit board, a motherboard, or a chip having a different height. provide.
[0004]
[Means for Solving the Problems]
The present invention is a microcapsule type curing activity temperature between the first back surface and the electronic components of the board on which a chip to obtain the electrical connection of an adhesive is interposed in the chip and the substrate is 50 to 150 ° C. A buffer layer is provided on the chip surface of the substrate on which the chip is mounted, with a second adhesive containing an agent interposed therebetween, at a temperature lower than the glass transition point of the first adhesive on the substrate on which the chip is mounted. An electronic component mounting method characterized in that an electrical connection between electrodes is obtained by direct contact between an electrode on the back surface of a substrate and an electrode of another electronic component by heating and pressing, and the substrate and the other electronic component are bonded. About. In addition, conductive particles in which a conductive layer is formed on the polymer core material between the back surface of the substrate on which the chip having the electrical connection is obtained by interposing a first adhesive between the chip and the substrate and other electronic components, and the active particles temperature is interposed a second adhesive you containing a microcapsule-type curing agent is 50 to 150 ° C., the buffer layer on the chip surface of the substrate mounted with chips provided, the board mounted with the tip first Conductive particles are interposed between the electrode on the back surface of the substrate and the electrode of the other electronic component by heating and pressing at a temperature lower than the glass transition point of one adhesive to obtain electrical connection between the electrodes and maintenance of the thickness, The present invention relates to an electronic component mounting method characterized by bonding a substrate and another electronic component.
[0005]
DETAILED DESCRIPTION OF THE INVENTION
The present invention will be described below with reference to the drawings.
FIG. 1 shows a state in which an adhesive 3 is interposed between a formation surface of an electrode 5 on a substrate 1 and the electrodes 4 of a plurality of chips 2, 2a, 2b, and the electrodes of the chips facing each other are aligned. It is a cross-sectional schematic diagram shown. The electrode 5 on the substrate 1 or the electrode 4 on the chip 2 may be formed by using a wiring circuit as a connection terminal as it is, or further forming a protruding electrode. It is preferable that the electrodes 4 and / or 5 have a protruding shape because electrical connection is easy because pressure is concentrated between the electrodes facing each other. The adhesive 3 may be a film, a liquid, or a paste.
As a method of aligning the electrode 4 of the chip to be connected and the electrode 5 of the substrate, the electrode 5B of the substrate 1 to be connected and the electrode 4A of the chip 2 are aligned using a microscope, an image storage device or the like. At this time, the use or use of the alignment mark is also effective.
The substrate 1 and the chip 2 after the alignment can be held by temporarily connecting them using the adhesive property of the adhesive 3 and the cohesive force. In addition, auxiliary means such as a clip and an adhesive tape can be applied alone or in combination. Since the temporary connection may be non-uniform as long as the heating and pressurization is performed to some extent, a conventionally used thermocompression bonding apparatus can be used.
[0006]
The chip electrode on which the alignment of the electrodes has been completed and the electrode on the substrate are heated and pressed to obtain electrical connection of the chip on the substrate. At this time, the chip 2, 2a, if the height from the substrate 1 is different as 2b, or form a buffer layer of rubber or the like between the chip surface and the pressure-type, electrostatic by autoclave or the like water pressure A substrate with a chip can be produced by pressurizing by pressing, pressing between rubber rolls having cushioning properties, or by pressing the head independently for each chip. It is also possible to perform a continuity test between the electrodes to be connected in the electrode positioning step and the electrical connection step. Since the adhesive can be inspected for continuity in an uncured state or in a state where the curing reaction is insufficient, the repair work of the adhesive is easy. Similarly, it is possible to add a step of removing excess adhesive around the chip. According to this method, since a good connection product that has completed the continuity test advances the curing reaction of the adhesive in the next step, the defective product is regenerated and the process loss time is short.
[0007]
FIG. 2 is a schematic cross-sectional view showing an embodiment of the present invention for explaining that an adhesive 10 is interposed between an electronic component 9 and a substrate 8 with a chip manufactured as shown in FIG. It is. The bonding temperature at this time is preferably lower than the glass transition of the adhesive 3 as the chip mounting material because the adhesive to the chip substrate does not decrease.
As an adhesion method, the above-described buffer layer, rubber roll, and hydrostatic pressure can be applied. Further, at the time of bonding the two substrates, it is sufficient that the chip is aligned and fixed to the substrates, and the cured state of the adhesive on each substrate is not limited.
That is, the chip connection to the substrate can be performed even if the curing reaction of the adhesive 3 and the adhesive layer 10 is simultaneously performed in the bonding process of both substrates in a state where the adhesive is not cured or the curing reaction is insufficient. The adhesive for chip connection may be one in which the curing reaction has been completed. In the former case, it is effective for shortening the manufacturing process time and repair work, and in the latter case, since the variation of the chip connection state to the substrate during storage is small, stable characteristics can be obtained.
[0008]
FIG. 3 is a schematic cross-sectional view showing an embodiment of the present invention for explaining a structure in which an electronic component 9 is bonded with an adhesive 10 interposed between the chip-attached substrate 8 and the electronic component 9.
The electrode 4 of the chip 2 and the electrode 5 of the substrate 1 are electrically and mechanically connected by the adhesive 3. In the case of FIG. 2 as well, a similar structure can be obtained after connection, but the description will be substituted by FIG. The electrical connection between the electrodes 4-5 and 5-6 at this time may be the direct contact between the electrodes 4-5 and 5-6, the conductive particles 11 interposed between the electrodes, or a mixture of these. Good. Moreover, the electrical connection of the electrode 5-6 may be unnecessary. The adhesive 10 between the substrate 8 and the electronic component 9 may be formed on the entire surface of the substrate 8 or more as shown in FIG. In the former case, since the adhesion area is large, sufficient adhesion can be obtained, and the electrodes 5 and 6 can be protected from corrosion and the like.
Conventionally, the connection between the chip-equipped substrate 8 and the electronic component 9 is generally performed by solder bonding by a process such as solder reflow. Connection reliability is improved because high temperature is not applied.
Examples of the substrate 1 of the present invention include plastic films such as polyimide and polyester, composites such as glass fiber / epoxy, semiconductors such as silicon, and inorganic materials such as glass and ceramics. Also, the electronic component 9 can be applied to a case where electrical connection is not required, such as a multilayer circuit board (FIG. 2), a mother board (FIG. 3) or the like having electrical wiring, a housing or a support. .
[0009]
As the adhesives 3 and 10 used in the present invention, thermoplastic materials and materials exhibiting curability by heat and light can be widely applied. Since these are excellent in heat resistance and moisture resistance after connection, application of a curable material is preferable. Among them, an epoxy adhesive containing a latent curing agent is particularly preferable because it can be cured for a short time, has good connection workability, and is excellent in adhesion due to its molecular structure. The latent curing agent has a relatively clear active site of reaction initiation by heat and / or pressure, and is suitable for the present invention involving heat and pressure processes.
Examples of latent curing agents include imidazole series, hydrazide series, boron trifluoride-amine complex, amine imide, polyamine salt, onium salt, dicyandiamide, and modified products thereof. These may be used alone or in combination of two or more. Can be used as a body.
These are catalyst type curing agents of so-called ionic polymers such as anion or cation polymerization type, and are preferable because they can easily obtain fast curability and require less chemical equivalent consideration. Of these, imidazole-based compounds are non-metallic, are less susceptible to electrolytic corrosion, and are particularly preferable from the viewpoints of reactivity and connection reliability. In addition, polyamines, polymercaptans, polyphenols, acid anhydrides, and the like can be used as the curing agent, and the catalyst-type curing agent can be used in combination. Moreover, it is preferable that the microcapsule type curing agent having a curing agent as a nucleus and the surface thereof coated with a polymer substance or an inorganic substance has characteristics of long-term storage and fast curing.
As for the active temperature of the hardening | curing agent of this invention, 40-200 degreeC is preferable. If the temperature is less than 40 ° C, the temperature difference from room temperature is small and a low temperature is required for storage. If the temperature exceeds 200 ° C, the other members of the connection are affected by heat. More preferred. The active temperature of the present invention indicates an exothermic peak temperature when the temperature is raised from room temperature to 10 ° C./min using a DSC (differential scanning calorimeter) as a sample of a mixture of an epoxy resin and a curing agent. The activation temperature is superior to the reactivity at the low temperature side, but tends to decrease the storage stability, and is determined in consideration of these.
In the present invention, the preserving of the substrate with the adhesive is improved by temporary connection by a heat treatment below the activation temperature of the curing agent, and a multi-chip connection with excellent reliability is obtained by the heat treatment above the activation temperature.
[0010]
It is preferable to add conductive particles or insulating particles to these adhesives 3 and 10 because they act as a thickness-retaining material at the time of heating and pressing at the time of manufacturing a chip with an adhesive. In this case, the ratio of conductive particles or insulating particles is about 0.1 to 30% by volume, and 0.5 to 15% by volume for anisotropic conductivity. As the adhesive layer , a multi-layer component in which an insulating layer and a conductive layer are separately formed is also applicable. In this case, since the resolution is improved, electrode connection with a high pitch is possible. Examples of the conductive particles include metal particles such as Au, Ag, Pt, Ni, Cu, W, Sb, Sn, and solder, carbon, graphite, and the like. These conductive particles are used as a core material or non-conductive. A core material made of a polymer such as glass, ceramics, or plastic may be coated with a conductive layer made of the above-described material. Furthermore, the insulating coating particles formed by coating a conductive material with an insulating layer, or the combined use of conductive particles and insulating particles such as glass, ceramics, and plastics can be applied because the resolution is improved. Among these conductive particles, those in which a conductive layer is formed on a polymer core material such as plastic, and hot-melt metal such as solder are deformable by heating or pressurization, and contact with a circuit for connection This is preferable because the area is increased and the reliability is improved. In particular, when a polymer is used as a nucleus, it does not show a melting point like solder, so that the softening state can be widely controlled by the connection temperature, and it is easy to cope with variations in electrode thickness and flatness, which is particularly preferable. Also, for example, in the case of hard metal particles such as Ni and W, or particles having a large number of protrusions on the surface, the conductive particles pierce the electrode and the wiring pattern, so that even when an oxide film or a contaminated layer exists, a low connection resistance is obtained. It is preferable because it is obtained and reliability is improved. In the above description, the case where a film adhesive is used has been described, but the present invention can be similarly applied to a liquid or paste. Further, the case where the chip heights are different has been described, but the case where the chip heights are equivalent is also applicable. Further, the number of chips mounted on the substrate may be single.
[0011]
According to the electronic component mounting method of the present invention, since the adhesive is interposed between the substrate on which the chip is mounted and the electronic component for bonding and integration, the characteristics of the substrate and the electronic component can be separated and connected. For example, the chip mounting substrate can be reduced in cost by using a heat-resistant substrate that does not cause sinking of the circuit, and using, for example, a general-purpose multilayer substrate that does not have much heat resistance as another electronic component. This can cope with the diversity of combinations of substrate types. In other words, an expensive substrate that can handle a high-precision pitch is placed on one side, and a combination of characteristics such as an inexpensive general substrate or a price-compatible combination, or a combination of materials such as a glass substrate and an organic substrate is possible on the other side. Become. According to the electronic component mounting method of the present invention, by making a conductive connection between the substrate on which the chip is mounted and the electronic component, the conventional solder connection becomes unnecessary, so that a high temperature process such as a reflow process is eliminated, Connection reliability is improved. In addition, it is surface bonding with an adhesive, and in addition, flexible bonding with an adhesive allows tough connection. According to the electronic component mounting method of the present invention, since the adhesive is bonded, the adhesive can be used in various forms such as a sheet, a liquid, and a prepreg, and the adhesive can be selected according to the required characteristics. Therefore, the degree of freedom of selection is improved. Furthermore, by setting the adhesive to an appropriate thickness, the adhesive acts as a cushion material at the time of connection, and uniform pressure without pressure unevenness can be obtained. Further, the heat curing reaction of the chip mounting portion can be accelerated later by heating at the time of bonding the substrate, which is also effective for repairing the chip mounting portion. In other words, a characteristic check such as continuity inspection is performed with insufficient curing reaction of the chip mounting part to the substrate, and the chip is reconnected when the characteristic is poor, but at this time the adhesive curing reaction is insufficient So peeling is easy.
[0012]
【Example】
Hereinafter, although an Example demonstrates in detail, this invention is not limited to this.
Examples 1-2
(1) Preparation of substrate with adhesive 30% solution of ethyl acetate with a ratio of liquid epoxy resin (epoxy equivalent 185) containing phenoxy resin (high molecular weight epoxy resin) and microcapsule type latent curing agent to 25/75 Got. To this solution, 2% by volume of conductive particles having a Ni / Au thickness of 0.2 / 0.02 μm formed on polystyrene particles having a particle diameter of 3 ± 0.2 μm were added and mixed and dispersed.
This dispersion was applied to a separator (silicone-treated polyethylene terephthalate film) with a roll coater and dried at 100 ° C. for 20 minutes to obtain a film adhesive having a thickness of 40 μm.
An IC chip having a circuit of 18 μm in height on a double-sided circuit board (FR-5 grade Tg180 ° C.) of a heat-resistant glass epoxy substrate having a thickness of 5 mm × 11 mm and a thickness of 0.4 mm, and the circuit end portion of which is described later The film adhesive was applied to the connection region of two types of substrates having connection electrodes corresponding to the bump pitch, and the separator was peeled off. The activation temperature by DSC of this adhesive layer was 120 ° C., and the glass transition point (Tg) after curing at 200 ° C. for 10 minutes was 135 ° C.
[0013]
(2) Positioning and connection of electrodes Three IC chips (height 0.3, 0.55, 1.0 mm) were placed on the above-mentioned substrate with adhesive, and the position of the electrodes was adjusted by a CCD camera. . The adhesive was in a state where there was a slight stickiness even at room temperature, and it could be easily held on the substrate by pressing against the adhesive surface at room temperature, and a temporary substrate for chip was obtained. The temporary substrate for the chip was placed on the surface plate of AC-SC450B (COB connection device manufactured by Hitachi Chemical Co., Ltd.) so that the substrate surface would come. TC-80A (Shin-Etsu Chemical Co., Ltd. heat dissipation silicon rubber, thickness 0.8 mm, JIS rubber hardness 75, thermal conductivity 3 × 10 ⁻³ cal / cm / sec / ° C.) as a buffer layer on the chip surface. The chip connection part was covered and covered with the same size as the substrate. The connection was established by heating and pressing at 20 kgf / mm ² for 10 seconds. The temperature was adjusted to 170 ° C. after 20 seconds.
(3) Adhesion with multilayer substrate The substrate with chips and a four-layer multilayer substrate (FR-4... Tg 120 ° C.) made of a general-purpose material were added without the addition of the adhesive (Example 1) and conductive particles of (1) ( Example 2) was formed between two types of substrates, and both substrates were bonded together and treated with AC-SC450B at 130 ° C., 20 kgf / mm ² for 10 minutes, and then cooled to room temperature and taken out.
(4) Evaluation The electrode of each chip and the electrode of the multilayer substrate could be connected satisfactorily. Although the cross section of the substrate with the chip was observed, the circuit did not sink. Further, since the adhesive is present only in the vicinity of the chip, there was almost no unnecessary adhesive on the substrate surface. In this example, three IC chips having different heights could be connected to the multilayer substrate.
In the case of Example 1, since the substrate is insulative, it is possible to use the same adhesive as the chip connection, and the process is simple. In addition, the conductive particles became a gap adjusting material between the substrates, and it was possible to bond the substrates with the same thickness. In the case of Example 2, the two substrates were bonded in a form that conformed to the IC chip height to some extent.
[0014]
Comparative Example 1
Similar to Example 1, but the chip was directly connected to a 6-layer multilayer substrate made of FR-4. In this case, the electrodes of each chip and the electrodes of the multilayer substrate cannot be connected. When the cross section of the substrate was observed, there were many cases where the part where the circuit was depressed and the inability to connect the electrodes were mixed. This is thought to be because pressure unevenness occurred at the time of connection because the chip was different in height and was a multilayer circuit board, and each layer of metal circuit, glass fiber, and resin was mixed depending on the location and had irregularities.
[0015]
Examples 3-4
Although it is the same as that of Examples 1-2, it replaced with the multilayer substrate and set it as the glass epoxy board | substrate which consists of FR-4. The electrode of each chip and the electrode of the multilayer substrate could be connected well.
When the cross section of the connecting portion was observed, in the case of the insulating adhesive of Example 3, the electrode was in direct contact, and in the case of the additive of the conductive particle of Example 4, the conductive particles were interposed between the electrodes. It had been.
In Examples 3 to 4, since the substrates are connected to each other with an adhesive, both the substrates are firmly bonded.
[0016]
Comparative Example 2
Similar to Example 4, but the electrodes were connected in a solder reflow oven (up to 240 ° C.). The electrode of each chip and the electrode of the multilayer substrate could not be connected due to the heat of the reflow furnace. In addition, since only the electrode portion is a metal joint, the fixing between the substrates is extremely weak, and a separate reinforcement is required.
[0017]
【The invention's effect】
As described above in detail, according to the present invention, there is provided an electronic component mounting method that is effective when a substrate on which a chip is mounted is mounted on an electronic component such as a multilayer circuit board, a motherboard, or a chip having a different height. it can.
[Brief description of the drawings]
BRIEF DESCRIPTION OF DRAWINGS FIG. 1 is a schematic cross-sectional view illustrating a state where an adhesive is interposed between an electrode on a substrate and a chip electrode and is positioned, explaining an embodiment of the present invention.
FIG. 2 is a schematic cross-sectional view for explaining an embodiment of the present invention and explaining bonding of both substrates by interposing an adhesive between the chip-attached substrate and the electronic component.
FIG. 3 is a schematic cross-sectional view illustrating a structure in which an electronic component is bonded with an adhesive interposed between the chip-attached substrate and the electronic component, according to an embodiment of the present invention.
[Explanation of symbols]
1 Substrate 2 Chip 3 Adhesive A
4 Electrode A
5 Electrode B
6 Electrode C
7 Inner layer circuit 8 Substrate with chip 9 Electronic component 10 Adhesive layer B
11 Conductive particles

Claims (2)

The microcapsule-type curing agent activity temperature of 50 to 150 ° C. during the first back surface and other electronic components of the board on which a chip to obtain an electrical connection by interposing an adhesive to the chip and the substrate A buffer layer is provided on the chip surface of the substrate on which the chip is mounted, with the second adhesive contained , and heating at a temperature lower than the glass transition point of the first adhesive on the substrate on which the chip is mounted. An electronic component mounting method characterized in that an electrical connection between electrodes is obtained by direct contact between an electrode on a back surface of a substrate and an electrode of another electronic component by pressure, and the substrate and the other electronic component are bonded. Conductive particles having a conductive layer formed on the polymer core material between the back surface of the substrate on which the first adhesive is interposed between the chip and the substrate to obtain electrical connection, and other electronic components, and the activation temperature are is 50 to 150 ° C. is interposed a second adhesive you containing a microcapsule type curing agent, a buffer layer on the chip surface of the substrate mounted with chips provided, a first substrate mounted with the tip Conductive particles are interposed between the electrode on the backside of the substrate and the electrode of another electronic component by heating and pressing at a temperature lower than the glass transition point of the adhesive to obtain electrical connection between the electrodes and maintenance of the thickness, An electronic component mounting method characterized by bonding another electronic component.

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