JPH0538882U - Circuit connection method - Google Patents

Abstract

(57) [Summary] The present invention sandwiches and bonds an insulating adhesive or an adhesive in which conductive fine particles are dispersed in an insulating adhesive between connecting circuits formed by facing each other. In the circuit connecting method, one of the circuit boards is transparent, and light is emitted from the back surface of the transparent circuit board among the connecting circuits that sandwich the adhesive and the light is emitted through a lens. ,
The light is irradiated from the lick at an angle larger than the critical angle of the transparent substrate, and by curing the adhesive by the irradiation of the light, it is possible to conduct the conductive bonding of the connection circuit for the relative surface to bond and fix. Characteristic circuit connection method.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a method for mounting a liquid crystal panel and other circuit parts that can be carried in a pocket TV, a wall-mounted TV, a projection TV, a laptop computer, a game console, etc.

[0002]

[Prior Art]

 Conventionally, in order to incorporate a liquid crystal panel such as a pocket TV, it is necessary to construct a small-sized, high-density mounted liquid crystal panel. As an example of such measures, there has been proposed a method of directly mounting an IC chip on a glass substrate forming a liquid crystal panel.

A conventional liquid crystal panel will be described below with reference to the drawings. 5 and 6 show an example of a conventional liquid crystal panel. FIG. 5 shows an insulating adhesive or an adhesive in which conductive fine particles are dispersed in an insulating adhesive between the IC chip and the electrode pattern of the liquid crystal panel glass, which is a connection circuit formed by facing each other. The process of squeezing and holding the above-mentioned connecting circuits relative to each other is shown in Fig. 6. In Fig. 6, the adhesive is heated and cured by irradiating light from the back surface of the liquid crystal panel glass, and the electrode pattern of the IC chip and liquid crystal panel glass The state of pressure bonding is shown.

In FIGS. 5 and 5, 21 is an IC chip, 22 is a liquid crystal panel, 23 is an electrode pattern formed on the substrate of the liquid crystal panel, and 24 is an adhesive layer in which conductive fine particles are dispersed in an insulating adhesive. , 25 indicates Au bumps, 26 indicates a crimping tool, 27 indicates light, and 28 indicates a lens. Electrode pads are formed on the IC chip. Au bumps are formed on the electrode pads. A connection circuit is formed on the substrate of the liquid crystal panel, facing the connection electrodes of the IC chip.

[0005]

[Problems to be solved by the device]

 In FIG. 5, an insulating adhesive or an adhesive in which conductive fine particles are dispersed in the insulating adhesive is used for heating a connection circuit formed by facing each other, that is, between the IC chip and the electrode pattern of the liquid crystal panel glass. At this time, the circuit for connection, which is sandwiched without pressure and formed relative to each other, that is, the electrode pattern of the IC chip and the liquid crystal panel glass is simply aligned. After that, in FIG. 6, the adhesive layer is heated by irradiating light from the back surface of the liquid crystal panel while being pressed from above the IC chip by a tool at a relatively low temperature, and the adhesive layer is heat-cured to cure the IC chip and the liquid crystal panel. The glass electrode pattern is electrically connected. At this time, the epoxy-based adhesive that is generally used as an adhesive is completely cured.

However, as is clear from FIGS. 5 and 6, the connection structure using the conventional adhesive for connecting a circuit generally scatters when the light is white light. Therefore, the light is focused on the adhesive layer using a condenser lens. Then, there arises a problem that the temperature distribution due to the light of the adhesive is high at the center of the focal point and gradually becomes low around the focal point as shown in FIG. In FIG. 7, the horizontal axis represents the position in the cross-sectional direction of the IC, and the vertical axis represents the temperature of that portion. If there is a large temperature variation depending on the IC portion, the curing rate of the adhesive will be different.

[0007] Recently, there is an urgent need to take measures to reduce the mounting cost of an IC on such a panel, and especially the cost of the IC itself is urgently reduced. As a measure to reduce the cost of the IC itself, the method of increasing the aspect ratio of the IC and making it slender to minimize the space loss of the IC and maximize the number of ICs taken from one wafer. Has been actively tried. As described above, when the aspect ratio of the IC is increased, the COG mounting method in which the IC is directly attached to the panel has an effect of reducing the outer dimension of the panel. However, when the external dimensions of the IC are elongated in this way, the temperature variation of the adhesive under the IC becomes even greater, and the curing progress of the adhesive at the corners of the IC and at the center of the IC differs. As described above, if the curing progress of the adhesive is different, the reliability of IC bonding is significantly reduced. In particular, even though the residual stress in the adhesive material at the IC corner is large, the curing progress of the adhesive at the IC corner tends to be low, so the connection reliability at the IC corner is extremely reduced. It was something that would end up.

Therefore, the present invention solves the above-mentioned drawbacks of the related art and improves the reliability of the connection of the connection circuits formed by facing each other.

[0009]

[Means for Solving the Problems]

 The circuit connecting method according to the present invention is a circuit in which an insulating adhesive or an adhesive in which conductive fine particles are dispersed in an insulating adhesive is sandwiched and bonded between connecting circuits formed by facing each other. In the connection method, one of the circuit boards is transparent, and light is radiated from the back surface of the transparent circuit board among the connecting circuits that hold the adhesive while holding the adhesive, and the light is radiated through the lens. The light is emitted from the lick at an angle larger than the critical angle of the transparent substrate, and the adhesive is cured by the irradiation of the light, so that the connection circuit for the relative surface is electrically connected and fixed. Is characterized by.

[0010]

【Example】

 1 to 3 show a circuit connecting process according to the present invention. FIG. 1 shows a connection circuit formed by facing each other, that is, an insulating adhesive or an adhesive in which conductive fine particles are dispersed in the insulating adhesive is sandwiched between the IC chip and the electrode pattern of the liquid crystal panel glass. Fig. 2 and 3 show the process of aligning the above-mentioned connection circuits that are relatively facing each other, and Figs. The light passing through is radiated obliquely.

In FIGS. 1, 2, and 3, 1 is an IC chip, 2 is a liquid crystal panel, 3 is an electrode pattern formed on a substrate of the liquid crystal panel, 4 is an adhesive, 5 is light, and 6 is Au. Bumps, 7 are lenses, and 8 is a crimping tool.

Further, FIG. 4 is a diagram showing a temperature distribution under the IC when the adhesive is cured in the present invention with respect to a cross section of the IC.

In FIGS. 1, 2 and 3, when the IC is placed on the liquid crystal panel and strong light is irradiated from the back surface of the liquid crystal panel, the heat of the light causes adhesion between the IC and the liquid crystal panel. The agent cures and can basically bond and cure the IC and the liquid crystal panel.

As shown in FIG. 2 and FIG. 3, when light is radiated obliquely through the lens to the back surface of the glass, the range of light radiated to the adhesive layer on the back surface of the IC is not circular, but is horizontal. It becomes slender. Then, even if the outer shape of the IC is long and slender, the light irradiation range can be the entire lower surface of the IC. Then, the temperature rise of the adhesive layer due to the light irradiation on the lower surface of the IC can be made relatively uniform. FIG. 2 shows that light is emitted from one oblique direction, and FIG. 3 shows that light is emitted from two oblique directions. In Fig. 2, the irradiation intensity of light on the bottom of the IC is slightly high on the light irradiation side and weak on the opposite side, causing a slight imbalance in the light intensity, but in Fig. 3, the light is oblique from both the longitudinal direction of the IC. Since the light is radiated onto the IC, the imbalance of the light intensity on the lower surface of the IC is extremely small. For example, when using visible light as the irradiation light, a lens is generally used to collect the light in order to raise the light to the curing temperature of the adhesive. Considering the aperture of the lens, it is difficult to direct two lights from the glass back surface to the IC bottom surface in parallel. Therefore, it is more effective to make the lens oblique and irradiate the light obliquely.

FIG. 4 shows the temperature distribution of the lower surface of the IC when light is obliquely irradiated from both the longitudinal direction of the IC and the temperature distribution of the lower surface of the IC when light is irradiated from one direction. As is clear from FIG. 4, the temperature distribution on the lower surface of the IC is almost uniform. When the light is radiated from one direction, a slight distortion can be seen as shown in Fig. 4, but by irradiating another light obliquely from the opposite direction, the light of the first lamp can be seen. Light with a little symmetric line-symmetry is added to the intensity distribution, and the light intensity distribution is almost uniform as a whole.

As described above, when the temperature distribution on the lower surface of the IC becomes uniform, the curing progress of the adhesive also becomes uniform over the entire lower surface of the IC. That is, there is very little variation in the curing degree of the adhesive after curing by light irradiation. In this way, when the variation in the degree of curing of the adhesive on the lower surface of the IC becomes small, there is no portion where the adhesive strength is weak. Therefore, the connection reliability can be greatly improved. In particular, the IC corner is originally a place where the residual stress due to the joining is large, and thus it is said that the place where the residual stress is large is sufficiently irradiated with light and the curing progress of the adhesive is not inferior to other places. The reliability will be further improved.

In particular, when the outer shape of the IC has a large aspect ratio and a long and thin shape, the above-described measure for uniforming the light intensity becomes more effective.

[0018]

[Effect of the device]

 As described above, the present invention provides a method of connecting a circuit in which an IC chip and an electrode of a liquid crystal panel are sandwiched and bonded with an adhesive sheet, so that the curing progress of the adhesive on the entire lower surface of the IC is made uniform and the bonding reliability is improved. Has the effect of improving.

[Brief description of drawings]

FIG. 1 is a process diagram in which an adhesive sheet is sandwiched between a liquid crystal panel and an IC chip in an embodiment of the present invention.

FIG. 2 is a process diagram of fixing the IC to the liquid crystal panel by irradiating the back surface of the liquid crystal panel with light to cure the adhesive in the embodiment of the present invention.

FIG. 3 is a diagram showing another example of steps of fixing the IC to the liquid crystal panel by irradiating the back surface of the liquid crystal panel with light to cure the adhesive in the embodiment of the present invention.

FIG. 4 is a temperature distribution diagram at the time of crimping the lower surface of the IC in the present invention. That is, a light intensity distribution map.

FIG. 5 is a process diagram in which an adhesive sheet is sandwiched between a liquid crystal panel and an IC chip in a conventional example.

FIG. 6 is a process diagram of fixing an IC to a liquid crystal panel in a conventional example.

FIG. 7 is a temperature distribution diagram when the lower surface of the IC is pressure bonded in the conventional example.

[Explanation of symbols]

1,21 IC chip 2,22 Liquid crystal panel 3,23 Electrode pattern 4,24 Adhesive 5,27 Light 6,25 Au bump 7,28 Lens 8,26 Crimping tool 9 Light intensity when irradiating light obliquely to the right Distribution 10 Light intensity distribution when light is applied obliquely from the left 11 Light intensity distribution when light is applied obliquely from both sides

Claims (1)

[Scope of utility model registration request] 1. A method for connecting a circuit in which an insulating adhesive or an adhesive in which conductive fine particles are dispersed in the insulating adhesive is sandwiched and bonded between the connecting circuits formed by facing each other. , One of the circuit boards is transparent, and light is radiated from the back surface of the transparent circuit board among the connecting circuits that face each other while sandwiching an adhesive, the light is radiated through a lens, and the light is transparent. A circuit characterized by irradiating from a lick at an angle larger than a critical angle of a substrate, and curing the adhesive by irradiating the light to electrically connect and bond the relative connecting connection circuit. Connection method.