JPH04264731A - Formation of electrical connection contact and mounting board using it - Google Patents

Abstract

PURPOSE:To easily form an electrically connecting point and finely and closely bond the electrode pads of electronic component directly with electrodes on a board allowing reliability by selectively transferring metal paste on protruding contact points formed on the electrode pads of an IC chip. CONSTITUTION:Low-melting point alloy or metal paste 2 whose major ingredient is metal is filled in recessed parts provided on the surface of a supporting board 1. The supporting base material 1 is heated and the filled metal paste 2b is melted. Then, protruding contact points 6 are formed on electrode pads 5 which are on the IC chip 4 and that require connection. When the protruding contact points 6 are faced to the melted metal paste 2c and press-bonded with the paste, the metal paste 2d is transferred only on the protruding contacts 6 and electrically connecting contact points are formed.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention provides electrical connection contacts that are precisely placed only on the terminal electrodes on the substrate in order to connect chip-shaped electronic components such as IC chips to a group of terminal electrodes on the substrate. The present invention relates to a method of forming electrical connection contacts.

0002

[Prior Art] In the past, solder was often used to connect the connection terminals of electronic components and the circuit pattern terminals on the board, but in recent years, with the miniaturization of IC flat packages, etc. The pitch spacing has become progressively narrower, making it increasingly difficult to address with traditional soldering techniques. Furthermore, in recent years, there has been a movement toward efficient use of mounting area by directly attaching bare IC chips to electrodes on glass substrates in products such as calculators, electronic watches, and liquid crystal displays. Electrical connection means are highly desired. A known method for electrically connecting a bare IC chip to an electrode on a substrate is to use protruding contacts (bumps) formed on the electrode pads of the IC chip by plating technology. Known methods for forming protruding contacts include:
First, chromium (Cr) was placed on the electrode pad on the IC substrate.
After forming a metal plated portion of copper (Cu), gold (Au), etc., excess resist and metal vapor deposition film are removed to form protruding contacts.

0003

However, in such a method, the method of forming the protruding contacts is quite complicated, requiring a large number of processing steps and sophisticated etching and plating techniques. It is also possible to transfer a low melting point metal by dipping a protruding contact into the molten alloy surface, but it has been impossible to quantitatively control the amount of transfer.

The present invention has been made in view of the above-mentioned problems, and its purpose is to provide a method for directly and reliably bonding electrode pads of electronic components and electrode groups on a substrate finely and densely. The object of the present invention is to easily and reliably form electrical connection contacts on a group of electrodes on a substrate or on electrode pads of an electronic component, such as an IC chip. Another object of the present invention is to obtain a high-density mounting board using the electrical connection contacts.

[0005]

[Means for Solving the Problems] In order to solve the above-mentioned problems, the present invention uses a low melting point alloy in forming electrical connection contacts on fine terminal electrodes of a substrate on which fine pitch and fine terminal electrodes are formed. Alternatively, a metal paste containing metal as a main component is filled into the recesses provided on the surface of the support base material. The supporting base material is heated to melt the metal paste filled in the recess, and the protruding contact surface of the substrate on which the protruding contact is formed on the micro terminal electrode group is applied to the molten low melting point alloy or metal surface in the recess. The purpose is to realize the formation of an electrical connection contact by pressing them together and transferring the low melting point alloy or metal only onto the protruding contact.

[0006]

[Operation] According to the above-described method of the present invention, protruding contacts can be easily and reliably formed on fine terminal electrodes on a substrate, and only the protruding contacts can be selectively made of low melting point alloy or metal. can be uniformly transferred in a quantitative manner, and simple and highly reliable electrical connection contacts can be formed.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A method for forming an electrical connection contact according to an embodiment of the present invention and a mounting board using the same will be described in detail below with reference to the drawings.

FIGS. 1A to 1D are process cross-sectional views showing a first embodiment of the method for forming an electrical connection contact of the present invention. Further, FIG. 1(e) shows a cross-sectional view of the process of mounting an IC chip on a substrate using the method for forming electrical connection contacts of the present invention.

In FIG. 1, 1 is a support base material having a recessed part, 2 is a metal paste whose main component is a low melting point alloy or metal, 3 is a squeegee, 4 is an IC chip, 5 is an electrode pad of the IC chip, and 6 is a metal paste containing a metal as a main component. Bumps (protruding contacts), 7 and 10 are heating heads, 8 is a transparent terminal electrode (ITO electrode), and 9 is a glass substrate.

In the first embodiment of the present invention, first, FIG.
) and (b), a squeegee is slid into the recesses provided on the surface of the support base material 1 to fill the metal paste 2 containing a low melting point alloy or metal as the main component. The supporting base material 1 is a glass substrate etched in a hydrofluoric acid aqueous solution to provide a recess of 100 μm □ 20 μm deep, and the metal paste 2 whose main component is a low melting point alloy or metal is made of particles of 500 mesh or less. A eutectic solder paste consisting of Next, the supporting base material 1 is heated to 230° C. and the filled metal paste 2b is melted to obtain a molten low melting point alloy or metal 2c as shown in FIG. 1(c). The protruding contacts 6 are manufactured separately using a conventional wire bonding machine. The manufacturing method is to apply thermal energy to the tip of a metal wire passed through a capillary to form a ball, and then attach the formed ball to 5 portions of a 100 μm square electrode pad on an IC substrate 1 by thermocompression bonding, ultrasonic waves, or a combination thereof. After it is fixed, it is formed by cutting the metal wire at the base of the ball. In this way, protruding contacts 6 were formed on the electrode pads 5 on the IC chip 4 that required connection. Thereafter, a protruding contact 6 is formed on the electrode pad 5.
When the protruding contacts 6 on the C-chip 4 are pressed against the molten low melting point alloy or metal 2d, the low melting point alloy or metal 2 is transferred only onto the protruding contacts 6, as shown in FIG. A physical connection contact is formed. Also, Figure 1(e)
As shown in FIG. 2, protruding contacts made of gold (Au) etc. formed on the electrode pads 5 of the IC chip 4 obtained in the first example, electrical connection contacts made of a low melting point alloy or metal 2, and a glass substrate. After pressing the 100 μm square ITO electrode 8 on the protruding contact 6 with the ITO electrode 8 facing each other, the heating head 10 melts and fixes the low melting point alloy or metal 2 on the protruding contact 6.
It is possible to connect the chip and the glass substrate.

Next, a second embodiment of the present invention will be described. FIG. 2 is a process sectional view showing a second embodiment of the present invention. Reference numeral 11 denotes a two-step protruding contact, and the molten low-melting point alloy or metal in the recess provided in the support base 1 was transferred onto the two-step protruding contact. This two-step protruding contact 11 was formed into a loop-like two-step protrusion structure by drawing a loop-like locus on the capillary using a wire bonding device.

FIG. 3 shows a cross-sectional view of a mounting using the electrical connection contact of the present invention using a two-stage protruding contact.

[0013] In the above embodiment, an example was shown in which the IC chip 4 on which electrical connection contacts were formed was mounted on the glass substrate 9, but the substrate on which the IC chip is mounted is not limited to a glass substrate. Needless to say, for example, a glass epoxy substrate, a ceramic substrate, a flexible printed circuit board, etc. may be used. As the metal paste 2 whose main component is a low melting point alloy or metal, we used a eutectic solder paste consisting of particles of 500 mesh or less, but the material is mainly lead (Pb), tin (Sn), and indium (In). alloy or its simple substance, or Au
-A low melting point alloy or metal such as 20% Sn may be used.

[0014]

As explained above, according to the method for forming an electrical connection contact of the present invention, an electrical connection contact is formed on the electrode pad portion of an IC chip using a conventional nail head bonding technique. It can be easily formed by selectively and precisely transferring a low-melting point alloy or metal onto the contact, and is useful not only for connecting to electrodes on glass substrates of IC chips but also for electrical connections to various substrates. , it is effective for ultra-fine connections that are difficult to make in the past, so it has extremely high practical value. Moreover, the board mounted using the electrical connection contact of the present invention has no leads around the IC chip, and the mounting board area can be effectively and minimized.

[Brief explanation of the drawing]

[Fig. 1] Process cross-sectional diagram showing the first embodiment of the present invention

[Figure 2
] Process cross-sectional diagram showing the second embodiment of the present invention

[Fig. 3] Implementation cross-sectional view showing a second embodiment of the present invention

[Explanation of symbols]

1 Support base material 2 Metal paste mainly composed of a low melting point alloy or metal 3 Squeegee 4 IC chip 5 Electrode pad of IC chip 6 Bump (protruding contact) 7 Heating head 8 Transparent terminal electrode (ITO electrode) 9 Glass substrate 10 Heating head

Claims (6)

[Claims] Claim 1: In forming electrical connection contacts on fine terminal electrodes of a substrate on which fine pitch and fine terminal electrodes are formed, a metal paste containing a low melting point alloy or metal as a main component is applied to the surface of the supporting base material. a step of heating the support base material to melt the metal paste filled in the recess; a step of filling the protruding contact surface of the substrate with the protruding contacts formed on the fine terminal electrode group into the recess; A method for forming an electrical connection contact, comprising the step of transferring the low melting point alloy or metal only onto the protruding contact by pressing it onto a molten low melting point alloy or metal surface. 2. While heating the substrate on which the protruding contacts are formed on the micro terminal electrode group, the protruding contacts on the substrate are pressed against the molten low melting point alloy or metal surface in the recess to reduce the low melting point. 2. The method of forming an electrical connection contact according to claim 1, further comprising the step of transferring an alloy or metal only onto the protruding contact. 3. A mounting board characterized in that a protruding electrode having a low melting point metal at its tip and an electrode on the substrate are connected using the low melting point metal at the tip of the protruding electrode. 4. The mounting board according to claim 3, wherein the protruding electrode has a two-stage protrusion structure. 5. The mounting board according to claim 3, wherein the protruding electrode has a loop-like structure. [Claim 6] The protruding electrode mainly consists of gold,
4. The mounting board according to claim 3, having a loop-like structure.