JP3928913B2 - Crystal oscillator - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a crystal oscillator in which an IC chip is bonded by ultrasonic thermocompression using a bump as an industrial technical field, and more particularly to a crystal oscillator that prevents cracks generated in terminal electrodes of an IC chip.
[0002]
[Prior art]
(Background of the Invention) An IC chip in which various electronic circuits are integrated is used in many electronic devices and is a driving force for miniaturization. In recent years, so-called face-down bonding, in which one main surface on which terminal electrodes are formed, is directly bonded to a substrate has been adopted in a crystal oscillator in order to further promote downsizing compared to wire bonding. One such method is a bonding method using ultrasonic thermocompression bonding using bumps.
[0003]
(Example of Prior Art) FIG. 4 is a cross-sectional view of a crystal oscillator for explaining a conventional example.
The crystal oscillator is made of a laminated ceramic, and an IC chip 2 and a crystal piece 3 are accommodated in a container body 1 having a recess and a step, and a cover 4 is bonded and sealed. A conductive path 5 as a circuit pattern is formed on the bottom surface 1a of the concave portion of the container body 1 as shown in FIG. The conductive terminal portion 6 is formed so as to be exposed at the tip of the conductive path 5, and the other portions are covered with an insulating film such as alumina oxide. The conductive terminal portions 6 are arranged in two rows on the left and right sides as a rectangular shape that is long in one direction. A crystal terminal (not shown) is formed on the stepped portion.
[0004]
The IC chip 2 integrates circuit elements such as an oscillation circuit amplifier (not shown) and has a terminal electrode 7 on one main surface. The terminal electrode 7 is formed on a pair of opposite sides corresponding to the conductive terminal portion 6. The distance L between the centers of the terminal electrodes 7 on both sides is 1.78 mm, and the planar outer dimension of the IC chip 2 is 1.9 × 1.9 mm. Then, bumps 8 made of, for example, gold grains for ultrasonic thermocompression bonding are connected on the terminal electrode 7 and fixed to the bottom surface of the container body 1. The bumps 8 are generally spherical and have a height of 35-50 μm.
[0005]
In the ultrasonic thermocompression bonding, the bump 8 of the IC chip 2 is brought into contact with the conductive terminal portion 6, the ultrasonic vibration is applied to the length direction of the conductive terminal portion 6, and the bump 8 is crushed into an ellipse shape while being heated. To do. The height T of the bump 8 after being crushed is approximately 20 to 25 μm. The crystal piece 3 is fixed to the stepped portion by the conductive adhesive 9 at both ends.
[0006]
In such a case, since the bump 8 is vibrated and thermocompression bonded in the length direction of the conductive terminal portion 6, the bump 8 does not jump out of the conductive terminal portion. In addition, since the bumps 8 are arranged in a range of 3: 2 on both sides of a pair of opposing sides, the pressing force at the time of thermocompression is evenly distributed. Therefore, ultrasonic thermocompression bonding is improved.
[0007]
[Problems to be solved by the invention]
(Problems of the prior art) However, the crystal oscillator having the above configuration has the following problems due to ultrasonic thermocompression bonding. That is, the IC chip 2 made of silicon and the container body 1 made of alumina ceramic have different thermal expansion coefficients, and the container body 1 is larger than the IC chip 2. Therefore, before and after heating, the terminal electrode 7 of the IC chip 2 is cracked due to stress, and the function of the IC chip 2 is impaired. As a result, there is a problem that the productivity of the crystal oscillator is deteriorated.
[0008]
(Object of the Invention) An object of the present invention is to provide a crystal oscillator having good thermal shock characteristics by preventing cracking of a terminal electrode due to a difference in expansion coefficient.
[0009]
[Means for Solving the Problems]
The present invention has terminal electrodes only on a pair of opposite sides of one main surface of an IC chip, bumps are provided on the terminal electrodes, and the bottom surfaces of the recesses of the container body are long in one direction facing each other. A conductive terminal portion is provided, the bump is brought into contact with the conductive terminal portion, the bump is vibrated in the length direction of the conductive terminal, thermocompression bonded, and the IC chip is mounted on the bottom surface of the container body. A crystal oscillator in which a crystal piece is housed in the container body, wherein the distance between the centers of the terminal electrodes between the sides of the IC chip is L, and the ultrasonic thermocompression bonding of the bumps When the subsequent height is T, T / L is 0.022 to 0.042 as a basic solution.
[0010]
[Action]
In the present invention, since the ratio T / L between the distance L between both sides and the height T of the bump is set to 0.022 to 0.042 , the stress due to the thermal expansion difference is absorbed by the bump. An embodiment of the present invention will be described below.
[0011]
FIGS. 1 and 2 are diagrams for explaining an embodiment of the present invention. FIG. 1 is a partial cutaway view of a crystal oscillator before ultrasonic thermocompression bonding, and FIG. 2 is a part after ultrasonic thermocompression bonding. FIG. In addition, the same number is attached | subjected to the same part as a prior art example figure, and the description is abbreviate | omitted or abbreviate | omitted.
In the crystal oscillator, the IC chip 2 is bonded to the bottom surface of the container body 1 where the conductive terminal portion 6 is formed by ultrasonic thermocompression bonding, and the crystal piece 3 is fixed to the stepped portion by the conductive adhesive 9 as described above. Join and seal (see previous Fig. 4).
[0012]
As described above, the IC chip 2 has six terminal electrodes 7 on one side of a set of opposing faces and five terminal electrodes 7 on the other side, and the distance L between centers of the terminal electrodes 7 is 1.78 mm. In this embodiment, the bumps 8 are doubled on the terminal electrode 7 of the IC chip 2 (FIG. 1). As a result, the bump 8 after ultrasonic thermocompression bonding has an elliptical shape and a height T of 40 to 50 μm (FIG. 2).
[0013]
FIG. 3 is a table showing the thermal shock characteristics of such a case. The terminal electrode 7 with respect to the thermal shock when the bump 8 is a conventional one and the two bumps (double bumps) of this embodiment is used. It is a table | surface which shows the number of crack generations, and an incidence rate.
[0014]
The thermal shock characteristic here is that a crystal oscillator having the IC chip 2 fixed to the bottom of the container by ultrasonic thermocompression bonding is left at -40 ° C. and + 80 ° C. for 30 minutes, and this is one cycle. Then, after applying 1, 5, 7, 10, 50, 70, 100, 700, 1000 cycles of thermal shock, the IC chip 2 was removed from the bottom of the container, and even one of the terminal electrodes 7 was cracked. The number of IC chips 2 is counted. However, the number of IC chip 2 used in the experiment are the ten pieces respectively in each cycle, which is 90 in total 180 pieces in both the examples and the conventional example.
[0015]
As is clear from this experimental result, in this embodiment, there are no IC chips 2 that generate cracks at 10, 50, and 70 cycles, and there are 1 IC chip 2 at 100 and 700 cycles and 2 IC chips 2 at 1000 cycles. Produce. On the other hand, in the conventional example, one IC chip 2 is cracked at 50 and 70 cycles, and two IC chips 2 are cracked at 100 cycles and three IC chips 2 at 700 and 1000 cycles.
[0016]
In short, in this embodiment, the number of cycles until a crack is generated is 90 cycles more than that in the conventional example, and the number of IC chips 2 that cause a crack in the same number of cycles is 1.5 times or less.
That is, since the bump 8 is a double bump and the height T after crushing by ultrasonic thermocompression is increased, the stress due to the difference in expansion coefficient between the IC chip 2 (silicon) and the container body 1 (alumina ceramic) is absorbed. The crack which arises in the terminal electrode 7 is prevented. Therefore, the present embodiment significantly improves the thermal shock characteristics as compared with the conventional example and improves the productivity of the crystal oscillator.
[0017]
Here, paying attention to the relationship between the center distance L of the terminal electrodes 7 (bumps 8) and the thickness T of the bumps 8, the longer the center distance L, the greater the stress due to the difference in expansion coefficient. Accordingly, the height T of the bump 8 depends on the center-to-center distance L. Since the ratio T / L between the center-to-center distance L and the thickness T of the bump 8 in this embodiment is 0.022 to 0.028, the effect of this embodiment is obtained when T / L is 0.022 or more. Can be obtained.
[0018]
In the above experiment, the number of IC chips 2 having a crack in one of the terminal electrodes 7 was counted. However, in any IC chip 2, only one terminal electrode 7 was cracked. This is presumed to be the result of stress concentration at one weakest place due to thermal shock.
[0019]
[Other matters]
In the above embodiment, the bump 8 is doubled, and the ratio T / L between the distance L between the centers of the terminal electrodes 7 and the height T of the bump 8 is 0.022 or more. Expected to improve impact properties. In this case, the height T of the bump 8 after ultrasonic thermocompression bonding is 60 to 75 μ, and T / L is 0.033 to 0.042.
[0020]
And it is not realistic from the point of cost increase to overlap the bump 8 beyond this. Therefore, in the present invention, the upper limit value of T / L is set to 0.042, and from this, T / L is defined as 0.022 to 0.042 as shown in claim 1.
[0021]
In addition, although the bumps 8 are double and triple, as described above, if the distance between the centers of the terminal electrodes 7 is reduced, the height of the bumps 8 is reduced. In this case, one bump 8 is not overlapped. Good. In addition, since it is conceivable that bumps 8 having a large height appear, it is not always necessary to overlap the bumps 8 in the present invention.
[0022]
Moreover, although the crystal oscillator which accommodated the IC chip 2 and the crystal piece 3 in the container main body 1 which has the recessed part and the step part on the one main surface side was demonstrated as an example, for example, the crystal piece in the container main body 1 which has a recessed part in both main surfaces 3 and the IC chip 2 can be applied to other electronic components.
[0023]
【The invention's effect】
The present invention has terminal electrodes only on a pair of opposite sides of one main surface of an IC chip, bumps are provided on the terminal electrodes, and the bottom surfaces of the recesses of the container body are long in one direction facing each other. A conductive terminal portion is provided, the bump is brought into contact with the conductive terminal portion, the bump is vibrated in the length direction of the conductive terminal, thermocompression bonded, and the IC chip is mounted on the bottom surface of the container body. A crystal oscillator in which a crystal piece is housed in the container body, wherein the distance between the centers of the terminal electrodes between the sides of the IC chip is L, and the ultrasonic thermocompression bonding of the bumps Since the T / L is 0.022 to 0.042 when the subsequent height is T, it is possible to provide a crystal oscillator with excellent thermal shock characteristics that prevent cracking of the terminal electrode due to a difference in expansion coefficient. .
[Brief description of the drawings]
FIG. 1 is a partial cutaway view of a crystal oscillator before ultrasonic thermocompression bonding, illustrating an embodiment of the present invention.
FIG. 2 is a partial cutaway view of a crystal oscillator after ultrasonic thermocompression bonding, illustrating an embodiment of the present invention.
FIG. 3 is a table showing thermal shock characteristics of a crystal oscillator after ultrasonic thermocompression bonding, illustrating an embodiment of the present invention.
FIG. 4 is a cross-sectional view of a crystal oscillator for explaining a conventional example.
FIG. 5 is a diagram of a circuit pattern provided on the bottom surface of a concave portion of a container body for explaining a conventional example.
FIG. 6 is a plan view of one main surface of an IC chip for explaining a conventional example.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Container body, 2 IC chip, 3 Crystal piece, 4 Cover, 5 Conductive path, 6 Conductive terminal part, 7 Terminal electrode, 8 Bump, 9 Conductive adhesive agent.

Claims (1)

A terminal electrode is provided only on both sides of a pair of opposing main surfaces of the IC chip, bumps are provided on the terminal electrodes, and conductive terminal portions that are long in one direction facing each other on the bottom surface of the concave portion of the container body. The bump is brought into contact with the conductive terminal portion, the bump is vibrated in the length direction of the conductive terminal and thermocompression bonded, and the IC chip is mounted on the bottom surface of the container body, and the container body A crystal oscillator in which a crystal piece is housed, wherein the distance between the centers of the terminal electrodes between the sides of the IC chip is L, and the height of the bump after ultrasonic thermocompression bonding A crystal oscillator, wherein T / L is 0.022 to 0.042 , where T is T.

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