JP5025616B2 - Electronic components - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electronic component wherein an IC chip as an element is strongly connected to a container while reducing its malfunction and connection failure by reducing stress on an IC when a resin filled, hardened and formed in and around the lower part of the IC chip is heated/cooled in the following processes. <P>SOLUTION: The electronic component stores an element and the thermosetting resin arranged around the element, in the cavity of the container on its bottom face. The cavity has an opposite face opposite to the bottom face at a position lower than its opening portion and higher than the height position of the lower face of the element. The thermosetting resin is filled in a remaining cavity space between a position higher than the height position of the opposite face and the bottom face. <P>COPYRIGHT: (C)2009,JPO&amp;INPIT

Description

  The present invention relates to an electronic component in which a flip chip IC element is accommodated in a container having a cavity, and more particularly to a piezoelectric device such as an oscillator combined with a piezoelectric vibrator.

  An electronic component having a structure in which a flip chip IC element is mounted in a cavity formed on the bottom surface of a container by a face bonding method via a bump, and a gap is filled between the flip chip IC element and the bottom surface of the container is known. .

  For example, in a temperature compensated crystal oscillator on which a flip chip IC element (hereinafter simply referred to as “IC chip”) for performing temperature compensation of a crystal resonator is mounted, as shown in FIG. The IC chip 54 on which the Au bump 53 is formed is accommodated in the cavity 52 of the laminated container 51 so that the Au bump 53 contacts an electrode pad (not shown) on the bottom surface of the cavity 52. The IC chip 54 is bonded to the bottom surface of the cavity 52 of the container 51 via the Au bump 53 and the electrode pad by means such as adhesion using Ag paste or fusion using ultrasonic waves. The mounting by the face bonding method is due to the recent demand for smaller and thinner electronic components.

  However, bonding strength such as adhesion by Ag paste or ultrasonic fusion alone is so low that the bumps are peeled off with a weight of about 6 g per bump. Therefore, after bonding, the bottom surface of the IC chip 54 and the cavity 52 The gap was filled with a thermosetting resin 55 called an underfill resin having a high shrinkage rate, and the IC chip 54 was fixed to the bottom surface of the cavity 52 as the resin was cured.

  The crystal resonator is mounted on the surface of the container 51 opposite to the surface on which the cavity 52 is formed and hermetically sealed, but is not shown in the conventional example.

  However, while there is a growing demand for thinner containers, components that exist on the back side of the portion where the IC chip 54 is mounted, particularly a quartz crystal resonator that completes assembly such as mounting and hermetic sealing before mounting the IC chip 54 are mounted. In consideration of the effect of mounting the IC chip 54, it is necessary to reduce the amount of Ag paste applied and the power of ultrasonic waves for bonding. Therefore, the thermosetting resin 55 for underfilling the remaining space other than the IC chip 54 in the cavity 52 after the connection is made by providing the Au bump 53 of the IC chip 54 on the container 51 and applying ultrasonic waves or the like. Filled and cured.

  However, when the temperature-compensated crystal oscillator is soldered to the circuit board thereafter, the thermosetting resin 55 expands and contracts in order to heat and cool the entire component. At this time, the region 50 formed around the end face of the IC chip 54 and the inner wall surface 51a of the cavity 52 is subjected to the composite stress T from the bottom surface of the cavity 52 toward the upper side in the figure where the upper space is open, It works in the direction of weakening the stress G that holds the tip 54 against the container 51. As a result, the IC chip 54 may be distorted and the contact may become unstable. As a result, the operation may become unstable, causing an abnormality such as an abnormality or no operation.

 The present invention has been devised in view of the above-described problems, and an object of the present invention is to provide an electronic component that can reduce the distortion of the IC chip and increase the strength at which the IC chip is bonded to the container. is there.

In order to solve the above-described problems, the present invention provides an electronic component in which an IC element flip-chip mounted on the bottom surface of the cavity and a thermosetting resin disposed around the IC element are accommodated in the cavity of the container. The cavity has a facing surface facing the bottom surface at a position lower than the opening and higher than the height position of the lower surface of the IC element. The remaining space is filled with the thermosetting resin between the bottom surface from a position higher than the height position of the facing surface.

 The present invention is characterized in that the facing surface is formed so as to circulate along the inner wall surface of the cavity.

  In the invention, it is preferable that a height position of the facing surface is located between an upper surface height position and a lower surface height position of the element.

  Further, the present invention is characterized in that the element is flip-chip mounted on the bottom surface.

  According to the configuration of the present invention, since the cavity has a shape in which a facing surface facing the cavity bottom surface is provided at a position below the opening, when heat is applied to the electronic component, the direction from the cavity bottom to the opening The stress generated in the channel cancels out with the stress generated from the upper wall surface of the groove toward the bottom surface of the cavity. Therefore, it is possible to weaken the resultant stress finally generated from the bottom surface of the cavity toward the opening, and to suppress the bending of the IC chip.

 In this case, if the area of the opening is made smaller than before, the resultant stress during resin expansion and contraction becomes smaller, and the stress for fixing the IC chip than the conventional electronic component is not weakened. I'm sorry.

  According to the present invention, distortion due to stress conventionally applied to the IC chip can be reduced, and further, the substantial bonding strength of the IC chip to the container can be increased. Can be achieved.

  An embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a cross-sectional view of a temperature-compensated crystal oscillator in the electronic component of the present invention, FIG. 2 is a plan view seen from the IC chip side, and FIG. 3 illustrates the cavity side on which the IC chip of the electronic component is mounted. FIG. 4 is a partial cross-sectional view taken along line XX for the purpose.

  The temperature compensated crystal oscillator 10 of the present invention has a ceramic container 1 having an H-shaped cross section having two cavities 2a and 2b at the top and bottom, and a crystal oscillator 11 in which a crystal resonator 7 is mounted in the upper cavity of the container 1. However, in the lower cavity, an oscillation component storage portion 12 in which the oscillation IC chip 4 of the crystal resonator 7 is stored is formed.

  The structure of the oscillating component storage portion 12 has a wiring pattern, and the frame-shaped ceramic insulating layers 1a and 1b and the plate-shaped ceramic insulating layers 1a are sequentially laminated to form the frame-shaped ceramic insulating layer 1a. A space surrounded by the inner periphery of 1b and the flat ceramic insulating layer 1c is a cavity 2b for accommodating the IC chip 4.

  In the present invention, as shown in FIGS. 2 to 4, the opening area of the frame-shaped ceramic layer 1 a is smaller than the opening area of 1 b in the oscillation component housing portion 12. Thereby, the groove part 1d is formed in the corner | angular part of the bottom face 20 of the cavity 2, and the inner wall face of the container 1 (inner wall face of the ceramic layers 1a-1c). The groove 1d may be formed around the outer periphery of the cavity 2b.

  Further, the Au bump 3 is formed in advance on the electrode portion 4a of the IC chip 4, and the IC chip 4 is bonded to the electrode pad 6 on the ceramic insulating layer 1c by Ag paste or fusion by ultrasonic wave. By being joined, the electrode pad 6 formed on the bottom surface of the container 1 is electrically connected. The IC chip 4 is also mechanically fixed by this bonding, but it has a strength surface that is filled with a thermosetting resin 5 for underfilling the remaining space of the cavity 2b other than the IC chip 4 and is heated and cured. Reinforced and fixed with.

  As the thermosetting resin 5, for example, an epoxy resin having a viscosity of 3000 cps, a linear expansion coefficient of 30 ppm, and a shrinkage rate of 1.7% is used. The thermosetting resin 5 is filled without a gap until the surface completely covers the upper surface of the IC chip 4 and is lower than the opening edge of the cavity 2b. And after filling, it heats up to the curing temperature of resin at a stretch. As a result, a stress G that the surface hardens first and shrinks is generated, and the IC chip 4 is pressed against the bottom surface 20 of the cavity portion 11 of the container 1, that is, the ceramic insulating layer 1c side.

  Furthermore, as shown in FIG. 4, the filling amount of the thermosetting resin 5 is such that the distance between the end face of the IC chip 4 and the outermost peripheral wall surface 110 d of the groove portion 1 d of the container 2 is B, and the bottom surface 20 of the cavity 2 of the groove portion 1 d. When the width to the upper surface 111d is C, it is preferable that B <C. This is because considering the relationship between the stress G holding the IC chip 4 and the distance B, the stress G decreases as B increases as shown in FIG. 5, and becomes constant when B exceeds the value of C. is there. The reason for this is that, considering the area S portion of a C × B rectangle, when the shape is C> B, the area becomes vertically long, the contraction force in the vertical direction increases, and conversely, the area S portion when C <B is The stress G holding the IC chip 4 is weakened only by becoming horizontally long and increasing the contraction force in the lateral direction.

  More preferably, 2 × B <C. If this condition is satisfied, the angle of the resultant stress shown in FIG. 4 approaches the vertical direction, that is, the direction of the resultant stress is also substantially vertical, so that a sufficient effect can be obtained by forming the concave portion on the inner peripheral wall surface of the container. Become.

  Moreover, as shown in FIG. 6, when the distance between the end face of the IC chip and the inner peripheral wall surface of the ceramic layer 1a of the container 1 is A, B / 2 <BA <B-0.05 (mm). Preferably there is.

  In consideration of the stress G holding the IC chip, B <C as described above is sufficient, but if B / 2 ≧ B−A, the entire resin portion is the object of the present invention. This is because it is necessary to satisfy B / 2 <B−A because it is difficult to achieve a sufficient effect when trying to achieve a reduction in the composite stress. Also, for B-A <B-0.05 (mm), that is, A> 0.05 (mm), if A is smaller than 0.05 mm, the current assembly technology allows the IC chip 4 to be placed in the cavity 2. This is because when the IC chip 4 is accommodated, the IC chip 4 comes into contact with the wall surface of the cavity 2 so that the IC chip 4 cannot be stably accommodated, and the IC chip 4 may be missing.

  Further, as shown in FIG. 7, when the distance between the top surface of the IC chip 4 and the surface of the thermosetting resin 5 is D, and the distance between the IC chip 4 and the bottom surface of the cavity 2 is F, the stress G is as shown in FIG. As D increases, it becomes the maximum when D is equal to F. This is because when D is larger than F, the shrinkage force of the resin on the upper part of the IC chip 4 becomes larger than the shrinkage force of the resin on the lower part of the IC chip 4.

  In addition to the IC chip 4, a circuit element 4b such as a capacitor is accommodated in the cavity 2b. For example, when the electronic component 10 is a crystal resonator and the IC chip 4 is used for temperature compensation of the crystal resonator, it is superimposed on the power supply voltage supplied to the oscillation inverter integrated (IC) on the IC chip 4. It is necessary to cut high frequency noise. It is also necessary to prevent a direct current component from being superimposed on the output signal of the oscillation inverter. In order to achieve these objects without complicating the external circuit, a capacitor is also mounted in the cavity 2. In this case, if the capacitor is thinner than the IC chip 4, the resin 5 covers the IC chip 4 and also the capacitor. On the contrary, even when the capacitor is thicker, as long as it does not exceed the opening edge of the cavity 2, the thermosetting resin 5 is preferably filled to the extent that the capacitor is covered.

  In the crystal oscillator 11, a ring-shaped ceramic layer 1 e is laminated on a flat ceramic substrate 1 d of the container 1, and a cavity portion 11 is formed. An electrode pad (not shown) is formed at one end in the longitudinal direction of the cavity portion 11, a crystal resonator mounting bump 13 is formed on the electrode pad, and the crystal resonator 7 is interposed via the conductive adhesive member 8. Bonded on the crystal resonator mounting bump 13. Reference numeral 9 denotes a lid that can be hermetically sealed by seam welding.

  Next, the manufacturing method of the electronic component of this invention is demonstrated. First, a ceramic package as a container 1 is prepared and cured on the cavity 2b for mounting the IC chip 4 of the container 1 and the crystal resonator mounting bumps 13 of the cavity 2a formed on the opposite surface. Then, a conductive resin paste that becomes the conductive adhesive member 8 is supplied, and the crystal resonator 7 is placed on the conductive resin paste so that the lead electrode of the crystal resonator 7 is connected to the crystal resonator mounting bump 13. To do. Then, the conductive resin paste is cured, and the crystal unit 7 is fixed to the ceramic package.

  Next, frequency adjustment of the crystal unit 7 is performed. Specifically, a crystal oscillator while connecting a power supply voltage, a ground, and a measurement probe with an electrode pad formed around the opening on the side where the IC chip 4 of the ceramic package is mounted, oscillating, and measuring the oscillation frequency The oscillation frequency is adjusted by substantially increasing or decreasing the mass of the excitation electrode by the Ag deposition method on the excitation electrode 7 or the ion beam irradiation method.

  Next, the oscillation frequency is stabilized by thermal aging at 150 ° C. to 250 ° C., and then hermetically sealed with the metal lid 9. At this time, the metal lid body 9 is placed on the sealing conductor of the ceramic package, and the metal lid body 9 is welded by seam welding or the like in a gas or vacuum atmosphere such as N2 or He. Welding is performed by bringing a roller head into contact with the periphery.

  Next, the IC chip 4 and the electronic components 4a and 4b are mounted in the cavities 2a and 2b. Specifically, first, the IC chip 4 is mounted by positioning and mounting the IC chip 4 so that each Au bump 3 formed on the IC chip 4 and each IC electrode pad coincide with each other. They are bonded to each other by bonding with Ag paste or fusion with ultrasonic waves.

  The electronic components 4a and 4b are joined by applying a conductive resin paste containing Ag powder to the element electrode pads, placing the electronic components 4a and 4b, and curing the conductive resin paste to cure.

  Next, the IC chip 4 and the electronic components 4 a and 4 b are filled and covered with the filling resin 5. Specifically, the entire IC chip 4 and electronic components 4a and 4b disposed in the cavity 2b are completely made of, for example, an epoxy-based thermosetting resin as described above by a method generally referred to as underfill. Cover, heat and cure. Thereby, the electronic component 10 is comprised.

  As described above, the ceramic insulating layers 1a and 1b forming the cavity 2b of the container 1 have an opening area 1a that is smaller than 1b. Therefore, as shown in FIG. When viewed, a groove 1 d is formed along the bottom surface 20 of the cavity 11.

  Accordingly, when the conventional container 1 is used, the cured underfill resin is eventually cooled again after being heated in the subsequent process, and as shown in FIG. In addition, the synthesized stress is perpendicular to the opening surface of the container and a large stress is applied depending on the shape of the container. As a result, when this stress becomes large, the Au bumps distort the IC chip once connected with a weak force of about 6 g for each bump and weaken the adhesive strength of the IC, causing abnormal operation as a circuit. In some cases, it may lead to poor conduction.

  However, when the container of the present invention is used, as shown in FIG. 4, the groove 1d is formed along the bottom surface 20 of the cavity 12 of the container 1, and stress from the upper surface 111d of the groove 1d is applied. The combined stress can be reduced as a whole. As a result, the stress that distorts the IC chip can also be reduced, and abnormal operation and poor connection can be prevented.

  Further, in this case, the crystal resonator 7 is mounted on the crystal resonator mounting bump 13 on the opposite side of the cavity by the conductive adhesive member 8 and hermetically sealed by the metal lid 9 with the container as a partition. With this configuration, the cavity is mounted on the motherboard with the motherboard facing, so that when the resin 5 is underfilled, the capacitor is simultaneously covered to prevent a short circuit between the capacitor electrode and the board wiring. An effect is also obtained.

  As described above, according to the present invention, distortion due to stress conventionally applied to an IC chip can be reduced, and further, the substantial bonding strength of the IC chip to the container can be increased. Can be achieved stably.

It is a center sectional view showing the whole temperature compensation type crystal oscillator which is an electronic part of the present invention. It is the top view seen from the IC chip side of the temperature compensation type crystal oscillator which is an electronic part of the present invention. FIG. 3 is a cross-sectional view of the main part of FIG. 2 for explaining an oscillation part housing part of a temperature compensated crystal oscillator which is an electronic part of the present invention. It is principal part sectional drawing to which the groove part of the oscillation component accommodating part of the temperature compensation type | mold crystal oscillator which is an electronic component of this invention was expanded. It is a graph which shows the relationship between the distance G of an IC chip and the outermost peripheral wall surface of a groove part, and the stress G which acts on an IC chip by thermosetting resin. It is a graph which shows the relationship between the difference (BA) of distance B of an IC chip and the outermost peripheral wall surface of a groove part, distance A of an IC chip and the inner peripheral wall surface of a container, and a synthetic stress by thermosetting resin. It is a graph which shows the relationship between the stress F which presses an IC chip, and the distances F and D which a thermosetting resin occupies. It is principal part sectional drawing explaining the oscillation component accommodating part of the temperature compensation type | mold crystal oscillator which is the conventional electronic component. It is a figure explaining the groove part of the conventional oscillation component accommodating part.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1,51 ... Container 2,52 ... Cavity 3,53 ... Bump 4,54 ... IC chip 5,55 ... Resin 10 ... Electronic component

Claims (3)

An electronic component containing an IC element flip-chip mounted on the bottom surface of the cavity and a thermosetting resin disposed around the IC element in the cavity of the container,
The cavity has a facing surface facing the bottom surface at a position below the opening and higher than the height position of the lower surface of the IC element, and is a remaining space in the cavity. The thermosetting resin is filled between the bottom surface from a position higher than the height position of the facing surface. The electronic component according to claim 1,
The said opposing surface is formed so that it may wrap around along the inner wall face of the said cavity, The electronic component characterized by the above-mentioned. The electronic component according to claim 1,
The electronic component according to claim 1, wherein a height position of the opposing surface is located between an upper surface height position and a lower surface height position of the IC element.

Images