JP2004172433A - Electronic parts and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To control a distance between electronic parts by adopting very simple and easy means, and shape a solder ball intervened between the electronic parts into the shape of a hand drum with respect to the electronic parts, and to provide its manufacturing method. <P>SOLUTION: In the electronic parts, a substrate 11 and a substrate 12 are restricted in their distance owing to the height of a bump 13B comprising a material having a predetermined melting point T2 and are opposed, and are further electrically connected through a bump 13A comprising a material having a lower melting point T1 compared with the predetermined melting point T2 and being configured into the hand drum. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an electronic component having a connection structure suitable for electrically connecting a semiconductor chip, a package, a printed board, and the like, and a method of manufacturing the electronic component.
[0002]
[Prior art]
For example, in a hybrid semiconductor device in which a large number of sensor elements are integrated, such as an image sensor, the number of electrical connections of each sensor element is increasing remarkably.
[0003]
Conventionally, the electrical connection has relied on wire bonding or the like. However, due to a problem such as an increase in the number of connections, the electrical connection has been made using a conductive bump.
[0004]
FIG. 5 is a cutaway side view of an essential part showing an electronic component for explaining a connection structure using a conductor bump. In FIG. 5, 1 is a first substrate, 2 is a metal portion, and 3 is a second substrate. Reference numeral 4 denotes a metal part, and reference numeral 5 denotes a solder ball (conductor bump) connecting the metal part 2 and the metal part 4.
[0005]
When a connection structure using conductor bumps as shown in FIG. 5 is adopted, the shape of the solder ball 5 is determined by the surface tension, so that not only an arbitrary shape but also a shape that can avoid stress concentration is obtained. Cannot be obtained.
[0006]
FIG. 6 is a cutaway side view of an essential part showing an electronic component for explaining the concentration and dispersion of stress in a solder ball. The same symbols as those used in FIG. It has meaning.
[0007]
When a stress due to thermal strain is applied as indicated by arrows A and B in FIG. 6A, the stress is applied to a position indicated by arrow C, that is, a portion at the root of the solder ball 5. Focus on
[0008]
It is known that in order to avoid concentration of stress at the base of the solder ball as described above, it is better to make the shape of the solder ball into a drum shape (for example, see Non-Patent Document 1).
[0009]
When a stress due to thermal strain is applied to the drum-shaped solder ball 6 shown in FIG. 6 (B), the stress is not concentrated at the root of the solder ball 6 and the arc surface in the drum-shaped Is known to be dispersed over the entire surface.
[0010]
By the way, in order to shape the solder ball into a drum shape as described above, it is necessary to precisely control the distance between the objects to be connected while keeping the size of the solder ball (volume of the solder) constant. , Its through put is significantly worse.
[0011]
As for the technology related to bumps, various known technologies are known in addition to the above-described conventional technology, and therefore, some examples will be described.
[0012]
There is known an invention in which two types of bumps having different melting points are formed, and precise alignment is performed on an xy plane by using the surface tension of the bump having a lower melting point (for example, see Patent Document 1). .
[0013]
In the invention of Patent Literature 1, the control of the gap between the objects to be connected, which is the control in the z direction for determining the bump shape to be a drum shape, is not performed.
[0014]
In addition, an invention is provided in which a gap between connection objects is determined in advance by a spacer, and the temperature is set to a temperature equal to or higher than the melting point of the bump material, so that the bumps hang down on the underlying metal side of the lower object to perform connection. The shape of the base metal and the area can be optimized to form a drum shape (for example, see Patent Document 2).
[0015]
In the invention of Patent Document 2, since the spacers are fixed in advance, the self-alignment effect in the xy plane cannot be expected, and the bumps are fixed after the gap between the connection objects is fixed in advance. Because of the fusion connection, the degree of freedom regarding the bump shape is reduced.
[0016]
Furthermore, the heat radiation fin- (solder 1) -semiconductor chip- (solder 2) -substrate are laminated in this order, and in this case, the melting point of the solder 1 is higher than the melting point of the solder 2; The connection between the semiconductor chip and the substrate is carried out by means of, and then the temperature is increased, and the radiation fins and the semiconductor chip are connected by means of the solder 1. At this time, the solder spreads between the chips to narrow the gap, thereby lifting the semiconductor chip and making the solder 2 into a drum shape. (See, for example, Patent Document 3). In the invention of Patent Document 3, an extra radiating fin is provided.
[0017]
Furthermore, there is known an invention in which a chip-type component is used as a spacer to determine a gap between objects to be connected to perform flip chip bonding (for example, see Patent Document 4).
[0018]
In the invention of Patent Document 4, since the spacer is fixed in advance, a self-alignment effect on the xy plane cannot be expected, and the bumps are fixed after the gap between the connection objects is fixed in advance. Because of the fusion connection, the degree of freedom regarding the bump shape is reduced.
[0019]
[Patent Document 1]
JP-A-6-112463 [Patent Document 2]
JP-A-6-177438 [Patent Document 3]
JP-A-7-94626 [Patent Document 4]
Japanese Patent Application Laid-Open No. 9-130031 [Non-Patent Document 1] "Bear Chip Mounting" edited by Technical Information Association, Technical Information Association, Ltd., published on January 31, 1990, pages 144 to 146.
[Problems to be solved by the invention]
In the present invention, the distance between the electronic components is precisely controlled and the solder balls interposed between the electronic components are shaped like a drum by employing extremely simple and easy means.
[0021]
[Means for Solving the Problems]
In the electronic component and the method of manufacturing the same according to the present invention, the first electronic component (for example, the substrate 11; see FIG. 4, the same applies hereinafter) and the second electronic component (for example, the substrate 12) are made of a material having a predetermined melting point T2. The first bumps (bumps 13B having a melting point T2) made of a material having a melting point T1 lower than the predetermined melting point T2 and having an interval defined by the height of the first bumps (bumps 13B having the melting point T2) Basically, electrical connection is made with the bump 13A) having the melting point T1.
[0022]
By taking the above measures, the distance between the electronic components is precisely controlled, and the solder balls interposed between the electronic components are shaped like a drum, so that they are generated by thermal cycling or mechanical shock. Stress concentration is eliminated and reliability is improved.
[0023]
BEST MODE FOR CARRYING OUT THE INVENTION
In the present invention, electronic components such as a semiconductor chip, a package, and a printed board, which are objects to be connected, are connected by using bumps each formed of a material having a different melting point. However, the bump made of a material having a high melting point does not have a main purpose of connection, but plays a role of defining a space between electronic components and maintaining the space.
[0024]
Here, the melting point of a bump made of a material having a low melting point is denoted by T1, the melting point of a bump made of a material having a high melting point is denoted by T2, and the melting point of a bump having a melting point T2 in an electronic component is determined. It is assumed that one of the surfaces has a configuration in which bumps are not easily bonded, for example, a configuration in which a base such as metal is not provided.
[0025]
In order to connect the electronic components, first, all the bumps are melted at a temperature higher than the melting point T2 to wet the base, and in this state, the gap between the electronic components is slightly separated, and then the temperature is raised above the temperature T1. Further, when the temperature is lowered to a temperature lower than the temperature T2, the bump having the melting point T2 solidifies in a hemispherical shape due to the surface tension, and is separated from the electronic component having a surface which is hardly bonded.
[0026]
Next, when the holding of at least one of the two electronic components is released, the two electronic components are attracted due to the surface tension at the bump having the melting point T1, but are not attracted without limitation. Suppressed by the already solidified melting point T2 bump, the interval between the two electronic components is kept constant, that is, the height of the melting point T2 bump is maintained, and the melting point T1 bump is shaped like a drum. .
[0027]
Thereafter, by lowering the temperature of the two connected electronic components to the melting point T1 or lower, the bump having the melting point T1 is solidified while maintaining the hourglass shape. Therefore, the stress due to the thermal strain is dispersed throughout the bump, and You no longer concentrate on the root.
[0028]
The final height of the above-mentioned bump having the melting point T2 is determined by the size and the amount of the base metal formed on one of the electronic components to be connected, and thus is controlled. Thus, the interval between the connected electronic components can be determined in advance.
[0029]
As described above, since the gap between the electronic components is maintained constant by the bump having the melting point T2, the size of the base metal and the amount of the metal are set to desired values also for the bump having the melting point T1. This allows the bump to have a desired shape.
[0030]
EXAMPLES The present invention is particularly suitable for being applied to a hybrid infrared detector (IRFPA) using a compound semiconductor such as mercury cadmium telluride.
[0031]
In this hybrid infrared detector, a photodiode array made of a compound semiconductor such as mercury cadmium tellurium and a readout IC made of silicon, which has a different coefficient of thermal expansion from the compound semiconductor, are attached by bumps. Since bumps are required for each photodiode, a large number of bumps are densely spread on a readout IC using silicon.
[0032]
FIGS. 1 to 4 are cutaway side views of a main part of the IRFPA at key process steps for explaining a process of assembling the IRFPA. The following description will be made with reference to these drawings.
[0033]
Refer to FIG. 1 (1)
A photodiode array made of mercury cadmium tellurium or the like is formed, and a substrate 11 having a base metal film 11A formed on the surface thereof, a readout IC made of silicon as a material are formed, and Underlayer metal films 12A and 12B are formed at the same time, an In bump 13A having a melting point T1 (low temperature) is connected to the underlying metal film 12A, and an InZn bump 13B having a melting point T2 (high temperature) is connected to the underlying metal film 12B. The substrate 12 is aligned so as to face it.
[0034]
Here, the InZn bump 13B having a melting point T2 is for defining the distance between the substrate 11 and the substrate 12, and the In bump 13A having a melting point T1 is for electrically connecting the substrate 11 and the substrate 12. Needless to say, there is. The melting point T1 of In is 156 [° C.], and the melting point T2 of the InZn alloy of In 90 [%] · Zn 10 [%] is about 200 [° C.].
[0035]
Refer to FIG. 2 (2)
The temperature is raised to a temperature T satisfying T>T2> T1, for example, T = 210 ° C., and the substrate 11 and the substrate 12 are bonded.
In this case, the base metal film 11A is prepared on the surface on the substrate 11 side for the In bump 13A, so that it is electrically connected to the In bump 13B. Since there is no film and the material is not easily compatible with metal, for example, a SiO ₂ film, no electrical connection is made.
[0037]
Refer to FIG. 3 (3)
When the distance between the substrate 11 and the substrate 12 is increased while maintaining the temperature T at 210 ° C., the In bump 13A is in a bonding state between the base metal films 11A and 12A and forms a drum shape. The InZn bump 13B separates from the surface on the substrate 11 side and is restored to a hemispherical shape.
[0038]
(4)
Next, when the temperature T is 180 ° C., that is, T2>T> T1, the InZn bump 13B is solidified, and the In bump 13A is still in a molten state.
[0039]
Refer to FIG. 4 (5)
When the temperature T is maintained in the state of T2>T> T1, the holding of the substrate 11 and the substrate 12 is loosened and the interval is reduced, so that the top portion of the solidified InZn bump 13B again comes into contact with the substrate 11, and the substrate 11 and the substrate Since the distance between the In bump 13 and the In bump 13A is restricted, the In bump 13A in the molten state can maintain the shape of a drum.
[0040]
(6)
Assuming that the temperature T is T2>T1> T, all the bumps are in a solidified state, and the substrates 11 and 12 maintain a predetermined interval and are electrically connected by the drum-shaped In bump 13A. Does not concentrate at the root of the In bump 13A, and peeling does not occur.
[0041]
【The invention's effect】
In the electronic component and the method of manufacturing the same according to the present invention, the first electronic component and the second electronic component face each other with a distance defined by the height of the first bump made of a material having a predetermined melting point T2. At the same time, it is made of a material having a melting point T1 lower than the predetermined melting point T2, and is electrically connected by a second bump forming a drum shape.
[0042]
By adopting the above configuration, the distance between the electronic components is precisely controlled, and the solder balls interposed between the electronic components are shaped like a drum, so that they are generated by thermal cycling or mechanical shock. Stress concentration is eliminated and reliability is improved.
[Brief description of the drawings]
FIG. 1 is a cutaway side view of a main part of an IRFPA at an important point in a process for explaining a process of assembling the IRFPA.
FIG. 2 is a cross-sectional side view of a main part of the IRFPA at a key step for explaining a step of assembling the IRFPA.
FIG. 3 is a cutaway side view of a main part of the IRFPA at a key step for explaining a step of assembling the IRFPA.
FIG. 4 is a side cutaway view of a main part of the IRFPA at an important point in the process for explaining the step of assembling the IRFPA;
FIG. 5 is a fragmentary side view showing an electronic component for explaining a connection structure using conductor bumps.
FIG. 6 is a cutaway side view of an essential part showing an electronic component for describing concentration and dispersion of stress in a solder ball.
[Explanation of symbols]
11 Substrate 11A Underlying metal film 12 Substrates 12A and 12B Underlying metal film 13A In bump 13B InZn bump

Claims (4)

The first electronic component and the second electronic component oppose each other at a distance defined by the height of a first bump made of a material having a predetermined melting point T2, and a material having a melting point T1 lower than the predetermined melting point T2. An electronic component characterized by being electrically connected by a second bump forming a drum shape. A first electronic component having a region on which a base metal film to be electrically connected to the surface is formed and a first bump for defining a space between the electronic components to contact, and a base metal film not electrically connected to the surface; A first bump made of a material having a melting point of T2 (T2> T1) is formed on the base metal film on which the base metal film to be formed is formed and not electrically connected, and on the base metal film to be electrically connected. A step of aligning and facing a second electronic component having a second bump formed of a material having a melting point of T1 (T1 <T2).
Raising the temperature T (T>T2> T1) to perform bonding between the first electronic component and the second electronic component;
The distance between the first electronic component and the second electronic component is increased to form a second bump having a melting point of T1 in the shape of a drum, and then the temperature T (T2>T> T1) is decreased to obtain a first bump having a melting point of T2. A process of restoring to approximately the original shape and solidifying,
The distance between the first electronic component and the second electronic component is reduced, the distance is defined by the first bump having the melting point T2, and then the temperature T (T2>T1> T) is further lowered to reduce the temperature between the first and second electronic components. A step of solidifying the second bump in a drum-shaped shape to complete the bonding. 3. The method according to claim 2, wherein the shapes of the first and second bumps are controlled by adjusting the diameter, height, and melting point of the bumps. 3. The method for manufacturing an electronic component according to claim 2, wherein the height of the first bump is adjusted by an area of the base metal film and a metal amount.

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