JPH0436574B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to an electronic component bonding method for adhesively bonding an electronic component to a substrate surface.

[Technical background of the invention and its problems]

Conventionally, wire bonding has been used to connect electronic components such as semiconductor pellets to the wiring board surface, but since wire bonding is inefficient, hot-melt insulating adhesives have recently been used. It has been considered to adhesively bond electronic components to the surface of a wiring board using an anisotropic conductive adhesive in which conductive particles are mixed into the adhesive at a mixing rate such that the particles do not come into contact with each other.

This method of bonding electronic components includes an electronic component bonding portion on a wiring board surface, including the upper surface of a component connecting terminal portion formed in the electronic component bonding portion in correspondence with a terminal portion of the electronic component. In this method, an adhesive is applied by screen printing, and the electronic components are stacked and heat-pressed on top of the adhesive with their terminals facing the component connection terminals. When the components are stacked and heated and pressurized, the insulating adhesive melts and the insulating adhesive between the electronic component and the terminals on the board surface is pushed out to the surroundings, and the terminals on the electronic component and the board surface are bonded between the terminals. Since they are electrically connected to each other by contacting the conductive particles, if the adhesive is cured in this state, it is possible to adhesively bond the electronic component and the wiring board with their terminals electrically connected. can.

However, in the method for bonding electronic components using the above-mentioned anisotropic conductive adhesive, conductive particles mixed into the anisotropic conductive adhesive during heating and pressurization are mixed with the adhesive from above the terminal part on the board surface to between the terminal part. Because it flows, it has serious drawbacks such as poor conductivity between electronic components and terminals on the board surface, and short circuits between adjacent terminals. Until now, this joining method has not been adopted in actual mass production.

[Purpose of the invention]

This invention was made in view of the above-mentioned circumstances, and its purpose is to provide a method for adhesively bonding electronic components to the surface of a circuit board, while also ensuring that the electronic components and terminals on the surface of the circuit board are connected securely. It is an object of the present invention to provide a method for attaching electronic components that can conductively connect and completely prevent short circuits between adjacent terminal portions, thereby significantly improving reliability and yield.

[Summary of the invention]

That is, the present invention prints a bonding agent containing conductive particles in a heat-melting paste on a substrate surface to form a component connection terminal portion corresponding to a terminal portion of an electronic component, and then dries this bonding agent. After that, a hot-melt insulating adhesive is applied to the component joint portion on the board surface, including the upper surface of the component connection terminal portion, and the electronic component is placed on top of the adhesive and heat-pressed to bond the board. Electronic components are adhesively bonded to the surface.

In other words, in this invention, the component connection terminals formed on the board surface are formed by printing a bonding agent containing conductive particles in a heat-melting paste, so that conductive particles are present only in the terminals. At the same time, a heat-melting insulating adhesive is applied to the component joining portion of the board surface, including the upper surface of the component connection terminal part, and the electronic component and the board are bonded with this insulating adhesive. According to the present invention, since there are no conductive particles between adjacent terminal parts, there is no short circuit between adjacent terminal parts, and the amount of particles in the bonding agent can be increased. Therefore, it is possible to increase the number of particles in the terminal portion and reliably conductively connect the electronic component and the terminal portion on the board surface.

[Embodiments of the invention]

Hereinafter, a first embodiment of the present invention will be described with reference to the drawings regarding joining of LSI pellets.

Figure 1 shows the method for joining LSI pellets in the order of steps, Figure 2 shows the state when the LSI pellet is joined to the wiring board surface, and Figure 3 shows the state when the LSI pellet is joined to the wiring board surface. It shows.

First, a description will be given of the wiring board to which the LSI pellets are bonded. In FIGS. 2 and 3, 1 is the wiring board. This wiring board 1 has a large number of wiring lines 2, 2 formed in a pattern as shown in FIG. It is led out from the LSI pellet joint of the board 1, and the end of each wiring 2, 2 on the LSI pellet joint side is connected to the main surface (wiring board joint surface) of the LSI pellet 10 along its outer periphery. A large number of terminal parts 11, 11 arranged in an array and corresponding LSI pellet connecting terminal parts 2a, 2, respectively.
It is said to be a. These wirings 2, 2 and LSI pellet connection terminal parts 2a, 2a are formed by forming a heat-melting conductive paste layer 4, such as a carbon paste (also referred to as carbon ink) layer 4, on a conductive metal layer 3 made of copper, aluminum, etc. The carbon paste layer 4 has a two-layer structure in which a plurality of conductive particles (solder particles, nickel particles, etc.) 5, 5 having a diameter larger than the layer thickness are embedded at approximately constant intervals.
Note that the carbon paste layers 4, 4 on the upper layer of the wirings 2, 2 serve as an oxidation prevention film for the conductive metal layer 3 below. Further, 6 is the wiring board 1.
LSI pellet connection terminal part 2 at LSI pellet joint part
The LSI pellet 10 is a heat-melting insulating adhesive that is applied to the upper surfaces of the LSI pellet 10 including the upper surfaces of the LSI pellets 11 and 2a. are bonded with the insulating adhesive 6 while facing each other, and
Each terminal portion 11, 11 of the LSI pellet 10 is connected to each LSI on one surface of the wiring board via the conductive particles 5, 5.
It is electrically connected to the pellet connecting terminal portions 2a, 2a.

Note that each terminal portion 11 of the LSI pellet 10,
11 has a structure in which a bump 13 made of gold, solder, carbon, etc. is formed on a terminal electrode pad 12 made of aluminum or the like, and the conductive particles 5, 5 are attached to the bump 13 on the surface of the terminal part. are in contact. Further, in FIG. 3, 20 is a molding resin such as epoxy resin for molding the LSI pellet 10 bonded to one surface of the wiring board.
This molding resin 20 is applied after the LSI pellets 10 are bonded.

Next, a method for joining the LSI pellets 10 will be explained with reference to FIG.

In this bonding method, first, wires 2, 2 having a two-layer structure consisting of a conductive metal layer 3 and a carbon paste layer 4 mixed with conductive particles 5, and an LSI pellet connecting terminal portion 2a are attached to the surface of the film substrate 1a. ,2
A is formed to fabricate the wiring board 1. After that, a heat-melting insulating adhesive 6 is applied to the joint part of the LSI pellet on the wiring board 1, and the LSI pellet 1 is placed on top of it.
0 to the wiring board 1 by overlapping them and heat-pressing them.
The LSI pellet 10 is adhesively bonded, and the wiring board 1 is manufactured as follows.

First, as shown in Figure 1a, copper or aluminum foil is laminated over the entire surface of the board.
Wiring 2, 2 and LSI pellet connection terminal part 2a,
A mesh screen 7 is disposed at a predetermined interval (an interval approximately equal to the diameter of the conductive particles 5, 5) on the film substrate 1a on which the conductive metal layer 3 forming the lower layer part of the conductive metal layer 2a is formed. Above, LSI pellet connection terminal parts 2a, 2 formed on one side of the wiring board.
a and the opening 8 corresponding to the pattern of the wirings 2, 2
A bonding agent in which conductive particles 5, 5 are mixed at a high mixing rate into a carbon paste that has been mixed with a solvent to lower the viscosity by stacking a hard screen (metal screen, etc.) 8 provided with a, 8a. A is printed on the surface of the film substrate 1a (on the conductive metal layer 3), and a bonding agent A is applied to each terminal part 11, 11 of the LSI pellet 10, the corresponding LSI pellet connecting terminal part, and the wiring pattern connected thereto. Film substrate 1
Apply to the surface. In FIG. 1A, 9 is a squeegee, and the bonding agent A is spread on the hard screen 8 by this squeegee 9, passes through the openings 8a of the hard screen 8 and the mesh screen 7, and is applied to the film substrate. Printed on side 1a. Further, the mesh screen 7 is for distributing the conductive particles 5, 5 in the bonding agent A printed on the surface of the film substrate 1a at equal intervals. Openings 7a, 7a slightly larger than the diameter of the particles 5, 5 are formed at evenly spaced minute intervals.

In this way, each terminal part 1 of the LSI pellet 10
After printing the bonding agent A for the LSI pellet connection terminals corresponding to 1 and 11 and the wiring patterns connected thereto on one side of the film substrate, dry the bonding agent A printed on the side of the film substrate 1a. Bonding agent A is fixed on the surface of the film substrate 1a. When this bonding agent A is dried, the solvent in the carbon paste evaporates and the thickness of the carbon paste layer 4 decreases by that amount as shown in FIG. It will be in a state where it protrudes above the carbon paste layer 4. In addition, conductive particles 5, 5
The particle size is selected to be approximately 1.5 to 3 times the thickness of the carbon paste layer 4 after drying.

Thereafter, the conductive metal layer 3 laminated over the entire surface of the film substrate 1a is removed by etching using an etching solution using the bonding agent A printed thereon as a mask, as shown in FIG. 1c. , a two-layer structure of wiring 2, 2 consisting of a conductive metal layer 3 and a carbon paste layer 4 mixed with conductive particles 5, 5, and an LSI pellet connection terminal part 2a,
2a to complete the wiring board 1. Note that the portions of the conductive particles 5, 5 in the bonding agent A that protrude above the carbon paste layer 4 are also thinly covered with carbon paste adhering to the surface thereof.
Therefore, when etching the conductive metal layer 3, the conductive particles 5, 5 are not etched together.

After this, first, the first side of the wiring board is
A heat-melting insulating adhesive 6 is screen printed on the outer circumference of the LSI pellet joint, including the upper surfaces of the LSI pellet connection terminals 2a and 2a, as shown in Figure 1d.
As shown in Figure 2, the LSI pellet 10 is printed and adhered thereon, with each terminal part 11, 11 facing each LSI pellet connecting terminal part 2a, 2a on one side of the wiring board (see Fig. 2). The LSI pellet 10 and the wiring board 1 are stacked on top of each other using a heating and pressing jig (not shown).
and heat-press. When the LSI pellet 10 is stacked on top of the hot-melt insulating adhesive 6 and heated and pressed, the hot-melt insulating adhesive 6 melts and the LSI
Since the insulating adhesive 6 between the terminal parts 11, 11 of the pellet 10 and the LSI pellet connecting terminal parts 2a, 2a on the surface of the wiring board 1 is extruded to the periphery, the carbon paste layers 4, 4 are pushed out by the pressurizing force. As shown in Figure 1e, the conductive particles 5, 5 held in the LSI
Contacting the terminal parts 11, 11 of the pellet 10,
The terminal portions 11, 11 of the LSI pellet 10 and the LSI pellet connecting terminal portions 2a, 2a on the surface of the wiring board 1 are electrically connected via the conductive particles 5, 5. Also,
At this time, the LSI pellet connection terminal parts 2a, 2a
Since the carbon paste layers 4 and 4 are also melted, the conductive particles 5 and
The conductive particles 5, 2a are also in direct contact with the conductive metal layers 3, 3 below, and therefore the conductive particles 5,
5 and the LSI pellet connection terminal portions 2a, 2a can be further improved. Note that the molten carbon paste is also pushed out around the terminal part by the pressure, but the amount is extremely small, so the conductive particles 5, 5 held in the carbon paste layers 4, 4 are pushed out around the terminal part. It will not be extruded together with the carbon paste that is extruded around it.

After this, it is only necessary to cure the insulating adhesive 6 while maintaining the pressurized state. By curing the insulating adhesive 6, the LSI pellet 10 and the wiring board 1 are bonded to the terminal portions 11 and 2a of both of them. are adhesively bonded while electrically connected.

That is, as described above, this LSI pellet bonding method involves bonding the LSI pellet connecting terminal portions 2a, 2a formed on one surface of the wiring board using heat-melting carbon paste mixed with conductive particles 5, 5. By printing agent A, conductive particles 5, 5 are formed only on the LSI pellet connecting terminal portions 2a, 2a.
At the same time, the LSI on one side of this wiring board
The LSI pellet connection terminal part 2 is attached to the pellet joint part.
A heat-melting insulating adhesive 6 is applied to the upper surfaces of the LSI pellet 10 and the wiring board 1, including the upper surfaces of the LSI pellet 10 and the wiring board 1. For example, adjacent one side of the wiring board
Since there are no conductive particles between the LSI pellet connecting terminal parts 2a, 2a, the wiring board 1 and the LSI pellet 10 are connected to the adjacent terminal parts 2a, 2a and 11, 11.
There is no short circuit at all, and the bonding agent A
Since it is possible to increase the amount of conductive particles 5, 5 inside, the LSI pellet connecting terminal parts 2a, 2a
By increasing the number of conductive particles 5, 5, the wiring board 1
The terminal portions 2a, 2a of the LSI pellet 10 can be reliably electrically connected.

In addition, when forming the LSI pellet connecting terminal parts 2a, 2a having a two-layer structure consisting of the conductive metal layer 3 and the carbon paste layer 4 mixed with conductive particles 5, 5, the conductive metal paste is first applied to the substrate surface. LSI
If you print the adhesive over the LSI pellet connecting terminal after forming the pellet connecting terminal and the wiring connected to it, positioning work is required to determine the printing position of the adhesive. In the example, a conductive metal layer 3 is formed over the entire surface of the film substrate 1a, and a bonding agent A, which is a carbon paste mixed with metal conductive particles 5, is applied to each of the LSI pellets 10. After printing and drying the LSI pellet connecting terminal portions corresponding to the terminal portions 11, 11 and the wiring patterns connected thereto, unnecessary portions of the conductive metal layer 3 are etched away using the bonding agent A as a mask. In particular, the wiring 2, 2 and the LSI pellet connection terminal portions 2a, 2, each having a two-layer structure consisting of a conductive metal layer 3 and a carbon paste layer 4 mixed with conductive particles 5, 5, may be used.
a, there is no need to position the bonding agent A with respect to the conductive metal layer 3 during printing. Although it has a two-layer structure consisting of a carbon paste layer 4 mixed with conductive particles 5 and 5, the wiring board 1 can be easily manufactured. In this example, since the wirings 2, 2 of the wiring board 1 are also formed by etching away unnecessary parts of the conductive metal layer 3 using the bonding agent A as a mask, the surfaces of the wiring parts are also conductive. The particles 5, 5 will be distributed in a protruding state, but the conductive particles 5, 5 in this wiring part
5 has its protruding parts covered with carbon paste, so there is no risk of short circuits even if it comes into contact with other electronic parts, and if the wiring parts are insulated with insulating resin, short circuits with other electronic parts can be avoided. can be prevented even more reliably.

In this embodiment, the wiring portion of the wiring board 1 also has a two-layer structure consisting of a conductive metal layer 3 and a carbon paste layer 4 mixed with conductive particles 5,5. Carbon paste layer 4 without mixing metal layer 3 and conductive particles 5, 5
It is also possible to have a two-layer structure consisting of
Bonding agent A, which is a mixture of conductive particles 5 and 5 in carbon paste, is printed on the parts that will become the LSI pellet connection terminals 2a and 2a, and carbon paste is printed on the parts that will become the wiring (however, in this case, the bonding agent It is necessary to align the printing positions of A and carbon paste so that their edges overlap) or
Alternatively, the width of the opening corresponding to the wiring pattern of the mesh screen 7 shown in FIG. Just do it.

Furthermore, in the above embodiment, the LSI pellet connecting terminal portions 2a, 2a have a two-layer structure consisting of a conductive metal layer 3 and a carbon paste layer 4 mixed with conductive particles 5,5. The connecting terminal parts 2a, 2a may have a single-layer structure consisting only of the carbon paste layer 4 mixed with conductive particles 5, 5. In that case, a heat-melting conductive paste is used, and the conductivity is higher than that of the carbon paste. A solder paste with a high resistance may also be used. In addition, when the LSI pellet connecting terminal parts 2a, 2a have a two-layer structure, heat-melting insulating paste (LSI pellet 10 and wiring board 1) is used instead of conductive carbon paste as the heat-melting paste. The same material as the insulating adhesive 6 to be bonded may be used. Even in that case, the insulating paste also melts during heat-pressing and the conductive particles 5, 5 are bonded to the underlying conductive metal layers 3, 3. Since they are in contact, it is possible to ensure electrical continuity between the conductive particles 5, 5 and the underlying conductive metal layers 3, 3.

Further, in the above embodiment, the bonding of LSI pellets 10 has been described, but the present invention can be widely applied to bonding electronic components such as liquid crystal displays to substrates in addition to LSI pellets.

FIG. 4 shows an embodiment in which the film substrate to which electronic parts are bonded has the function of, for example, a connector for connecting a liquid crystal display.One surface 16a of the film substrate 16 has a conductive Carbon paste layer 4, 4 mixed with particles 5, 5
are printed in parallel stripes. In this case, a conductive metal layer having higher conductivity than the carbon paste may be provided between the carbon paste layer 4 and the film substrate surface 16a, as in the embodiments shown in FIGS. 1 to 3. Then, the carbon paste layer 4 is directly applied to the film substrate surface 16a.
It may also be formed by printing. Also, the film substrate surface 16
Insulating adhesives 6, 6 are printed on both end edges of a in a direction perpendicular to the striped carbon paste layers 4, 4, and these portions serve as joints for electronic components. The method of forming the insulating adhesives 6, 6 is as described above, but the film substrate 16 used as a connector is dried in this state, and has adhesive strength at room temperature. It is convenient in actual use to prevent this from happening.

Thus, the film substrate 1 on which the carbon paste layer and the insulating adhesive 6, 6 are formed is formed.
6 is used as follows. In Figure 4,
In the figure, 15 is a liquid crystal display, and this liquid crystal display 1
Electrode terminals 15a arranged on one side edge of 5,
The striped carbon paste layers 15a are arranged at the same pitch as the striped carbon paste layers 4, 4 formed on the film substrate 16. And this liquid crystal display body 15
The terminal array part is connected to each electrode terminal 15a, 15
A is placed on the insulating adhesive 6 printed on one edge of the film substrate 16 in correspondence with one end of each carbon paste layer 4, 4 of the film substrate 16, and the liquid crystal display 15 and the film substrate 16 are heated. They are joined by applying pressure. Further, the other end of the carbon paste layers 4, 4 is connected to the other edge of the film substrate 16 (the part where the insulating adhesive 6 is printed) to the side edge of the wiring board 1 shown in FIG. Thus, the film substrate 16 and the wiring board 1 are connected to the display body connecting terminal portions 2b, 2b arranged on the side edges of the wiring board 1, and the bonding of the film board 16 and the wiring board 1 is also performed by the method described above. In this case, the surface 16a on which the carbon paste layers 4, 4 and the insulating adhesive 6 at the edge of the film substrate 16 are formed is placed on the wiring board 1.
Display body connection terminal portion 2b formed on the top surface of
2b, but this can be done by turning either the film board 16 or the wiring board 1 upside down, or by folding the wiring board joining edge of the film board 16 to the back side of the film board 16. It can be solved. Also,
Wiring board 1 to which the other edge of film board 16 is bonded
is the wiring 2, 2 and the display connection terminal part 2
b, 2b may be formed of a carbon paste layer 4 mixed with conductive particles 5, 5, or the wirings 2, 2 and display body connection terminal portions 2b, 2b may be formed of metal as in a conventional wiring board. It may also be a formed one. Note that in this embodiment, the film substrate 1
Although 6 is an independent connector, the film board 16 used as this connector may be an integral part of the wiring board 1, which is an extension of a part of the film board 1a of the wiring board 1 shown in FIG. .
Also in this embodiment, the film substrate 16
The heat-melting paste layer formed on the surface may be formed of a solder paste having higher conductivity than carbon paste.

〔Effect of the invention〕

This invention involves printing a bonding agent containing conductive particles in a heat-melting paste on the board surface to form component connection terminals corresponding to the terminals of electronic components, and then drying the bonding agent. , a heat-melting insulating adhesive is applied to the component joint portion on the board surface including the upper surface of the component connection terminal portion, and the electronic component is placed on top of the adhesive and heat-pressed to bond the electronic component to the board surface. Since this method is designed to adhesively bond electronic components, although it is a method for adhesively bonding electronic components to the board surface, it not only ensures conductive connection between the electronic components and the terminals on the board surface, but also ensures that there is no connection between adjacent terminals. It is also possible to completely prevent short circuits, greatly improving reliability and yield.

[Brief explanation of drawings]

Figures 1 to 3 show an embodiment of the present invention. Figure 1 is an enlarged cross-sectional view along the terminal section showing the LSI pellet bonding method in the order of steps, and Figure 2 is an enlarged cross-sectional view along the terminal section showing the method of joining LSI pellets. A perspective view of the attached wiring board and LSI pellet, and FIG. 3 is a sectional view along the terminal portion of the LSI pellet bonded to the wiring board surface. FIG. 4 is a perspective view showing another embodiment of the present invention, showing a film substrate functioning as a connector with an insulating adhesive applied thereto. 1...Wiring board, 1a...Film board, 2...
...Wiring, 2a...LSI pellet connection terminal section, 3...
...Conductive metal layer, 4...Carbon paste layer, 5
... Conductive particles, 6 ... Insulating adhesive, 7 ... Mesh screen, 8 ... Hard screen, A
... bonding agent, 10 ... LSI pellet, 11 ... terminal section, 16 ... film substrate, 16a ... one side of the film substrate.

[Claims]

1 One end is connected to a predetermined potential point or a bias supply circuit, and a predetermined reverse bias voltage is applied.
A signal path is connected to the other end of the first PN junction element, and an output point of a current mirror circuit is connected to the other end of the first PN junction element, and the input point of the current mirror circuit is connected to the first A semiconductor integrated circuit characterized in that a second PN junction element is connected to which a second PN junction element generates a leakage current equal to the leakage current generated in the PN junction element. 2. The second PN junction element has the same structure as the first PN junction element, and has the same structure as the first PN junction element.
2. The semiconductor integrated circuit according to claim 1, wherein the same reverse bias voltage as that applied to the PN junction element is applied.