JP2013065875A - Package for electronic component and electronic device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a package for an electronic component capable of sufficiently withstanding a severe temperature environment for on-vehicle use and a piezoelectric vibrator.SOLUTION: A package for electronic components is composed of: a package body 6 which has a recessed part on an upper surface side, is mounted with an electronic component 20 in the recessed part, has a rectangular shape and is made of a laminated ceramic; and a lid member 30 hermetically sealing an opening space on the upper surface side of the package body 6 including the electronic component 20. A pair of electrode pads 15 is provided in the recessed part on an upper surface of the package body 6, and a pair of mounting terminals (terminal electrodes) 10 and 11 composed of terminal bases 10a and 11a and bumps 10b and 11b is formed on a mounting surface at both sides of a bottom surface of the package body 6 in a short side direction. Further, the pair of electrode pads 15 and the pair of mounting terminals 10 and 11 formed inside the package body 6 are individually and electrically connected to one another by a plurality of connection electrodes 14.

Description

  The present invention relates to an electronic component package and a piezoelectric vibrator, and more particularly, to an electronic component package whose mounting terminal structure is improved so as to increase the connection strength with a circuit board, and a piezoelectric vibrator using the same.

Piezoelectric vibrators, especially surface-mounted quartz vibrators, are small in size, easily obtain high-precision and high-stable frequencies, and have little secular change. Is widely used. In recent years, devices have become smaller and lighter, and the demand for further miniaturization of surface-mounted crystal units has been increasing.
As is well known, a surface-mount crystal unit is formed by forming a metal film (excitation electrode) on both main surfaces of a crystal plate using a vacuum deposition method or a sputtering method, and accommodating the metal film in a package body. A lid is hermetically sealed by seam welding or the like at the periphery of the main body.

  When a crystal resonator is used for a vehicle-mounted device, the connection strength with the circuit board is particularly important. The reason for this is that in-vehicle devices are exposed to severe temperature environments from low temperature to high temperature, and the linear expansion coefficient of the piezoelectric vibrator package and the circuit board on which the piezoelectric vibrator is mounted are different. This is because the solder connecting the package and the circuit board is distorted due to the temperature change, and the solder may be fatigued. Further, in recent years, the shape of the surface-mounted crystal resonator has been reduced in size, and the area of the package mounting terminal has been further reduced. Patent Document 1 discloses an example of a surface-mounted crystal resonator in which the connection strength between a mounting terminal (terminal electrode) and a circuit board is reinforced. FIG. 9A is a side sectional view of the surface-mount type crystal resonator, and FIG. 9B is a bottom view. The surface-mounted crystal resonator 70 is bonded to a planar rectangular package body 71 having a recess with an upper opening, a crystal resonator element 75 housed in the package body 71, and an upper opening of the package body 71. And a lid 72. The surface mount type crystal unit 70 is connected to the wiring pattern 91 of the circuit board 90 via the solder 85.

As shown in the bottom view of FIG. 9B, the pair of terminal electrodes 82 and 83 formed along the opposite sides of the bottom surface of the package main body 71 includes regions 82a and 83a formed to face each other, Regions 82b and 83b where only the terminal electrodes are not formed. These regions are arranged point-symmetrically with respect to the center point of the package body 71. Further, castellations C1 to C4 are formed at the four corners of the package body 71, and the castellations C1 and C3 are connected to terminal electrodes 82 and 83, respectively. By configuring the package body 71 as described above, even if the temperature environment changes and a stress is generated in the terminal electrodes 82 and 83 due to a difference in thermal expansion between the package body 71 and the circuit board 90, one terminal electrode is not formed. Since the stress is released from each other toward the corner regions 82b and 83b, the stress is generated so as to be rotated in a plane at the center point of the package body 71, and the stress is relieved. As a result, it is disclosed that the occurrence of solder cracks and the like can be remarkably suppressed.
Patent Document 2 discloses a package in which four terminal electrodes are formed at the four corners of the back surface of the package, and a small protrusion is formed at the center of each terminal electrode. When a piezoelectric vibrator using this package is mounted on a circuit board, a gap is obtained between the terminal electrode and the circuit board, and a sufficient amount and thickness of solder enters this gap, so that sufficient bonding strength is obtained. Is disclosed.

JP 2005-108923 A JP 2006-186667 A

However, in the package main body 71 described in Patent Document 1, the terminal electrodes 82 and 83 are electrically connected to the piezoelectric vibration element accommodated in the package via one castellation C1 and C3 formed at the corners of the package main body, respectively. Therefore, there is a problem that the crystal resonator may not function if a crack occurs in the connection portion between the terminal electrodes 82 and 83 and the castellations C1 and C3.
The technique of Patent Document 2 has a problem in that although the amount of solder between the terminal electrode surface of the package and the land electrode surface of the circuit board increases, the amount of solder at a location where distortion concentrates is not necessarily large.
The present invention has been made to solve the above problem, and provides a package for an electronic component with enhanced connection strength between a package mounting terminal and a land electrode of a circuit board, and a piezoelectric vibrator using the same. It is in.

  SUMMARY An advantage of some aspects of the invention is to solve at least a part of the problems described above, and the invention can be implemented as the following forms or application examples.

  Application Example 1 An electronic component package comprising a rectangular package body and a lid member for hermetically sealing the package body, the electrode pad formed inside the package body, and the package body An electronic component package comprising a mounting terminal formed in the vicinity of at least four corners of the bottom surface of the substrate and having a stepped portion on the mounting surface, and a plurality of connection electrodes for electrically connecting the pad and the mounting terminal. It is characterized by.

  When the electronic component package is configured in this manner, the stepped portion provided on the mounting surface can increase the thickness of the solder in the region where the distortion is large, so that the connection strength between the mounting terminal and the land electrode of the circuit board can be enhanced. There is an effect.

  Application Example 2 An electronic component package according to Application Example 1 in which castellations are formed at the four corners of the package body and the connection electrodes are formed on the castellations, respectively.

  When the electronic component package is configured as described above, there is an effect that the connection strength between the package and the circuit board can be increased as well as conduction between the piezoelectric vibration element inside the package and the mounting terminal by castellation.

  Application Example 3 In the application example 1 or 2, the step portion has a shape such that the solder formed around the four corners on the mounting terminal is thick when the mounting terminal is joined to the circuit board by solder. 2 is a package for electronic components.

  When the electronic component package is configured in this manner, the stepped portion provided on the mounting surface thickens the solder at the farthest position from the center of the package where the distortion is large and the peripheral portion of the mounting terminal excluding the central portion of the package. Therefore, there is an effect that it greatly contributes to strengthening the connection strength between the mounting terminal and the land electrode of the circuit board.

  Application Example 4 The electronic component package according to any one of Application Examples 1 to 3 in which a pair of dummy electrodes is formed on the package.

  When an electronic component package is configured in this manner, the connection between the package terminal and the circuit board is added in addition to the connection using the mounting terminal, and the distortion applied to the mounting terminal is dispersed. There is an effect that the strength is further increased.

  Application Example 5 An electronic component package according to Application Example 4 in which a plurality of the pair of dummy electrodes are formed is characterized.

  When the electronic component package is configured in this way, the connection between the package and the circuit board by the plurality of dummy electrodes is strengthened and the distortion applied to the mounting terminal is dispersed, so that the connection between the mounting terminal and the circuit board is further strengthened. There is an effect.

  [Application Example 6] A piezoelectric vibrator including the electronic component package according to any one of Application Examples 1 to 5, wherein a piezoelectric vibrating piece is mounted on the electrode pad of the package body.

  When the piezoelectric vibrator is configured in this way, when the piezoelectric vibrator is mounted on an in-vehicle electronic device, the connection strength between the piezoelectric vibrator package and the circuit board of the electronic device is large, so a large temperature change, vibration, and shock There is an effect that an electronic device that can endure can be configured.

BRIEF DESCRIPTION OF THE DRAWINGS It is the schematic which shows the structure of the package of 1st Example based on this invention, (a) is sectional drawing, (b) is a bottom view, (c) is a bottom view. The principal part enlarged side view at the time of mounting the package of a circuit board. (A)-(d) is a bottom view of a package, (e) is a figure which shows the relationship between the shape of a mounting terminal, and relative solder distortion. (A) is a top view of the pattern for conductive resistance measurement, (b) is a top view of the pattern for measurement distribute | arranged on the board | substrate. The figure which shows the relationship between the heat cycle frequency and conduction resistance. The bottom view of the package of 2nd Example. The bottom view of the package of 3rd Example. The bottom view of the package of 4th Example. (A) is sectional drawing and (b) is a bottom view of the conventional package.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. 1A and 1B are schematic views showing the structure of the electronic component package according to the first embodiment of the present invention and the structure of a piezoelectric vibrator using the same. FIG. The figure and the figure (b) are bottom views. As shown in FIG. 1A, the electronic component package 1 includes a rectangular multilayer ceramic package body 6 having a concave portion on the upper surface side and mounting the electronic component 20 in the concave portion, and the electronic component 20. And a lid member 30 that hermetically seals the opening space on the upper surface side of the package main body 6. In the concave portion on the upper surface of the package body 6, a pair of lead electrodes of a housed electronic component 20, for example, a piezoelectric vibration element, and a pair of electrode pads 15 to be connected are provided. In the mounting surface, a pair of mounting terminals (terminal electrodes) 10 and 11 including mounting terminal bases 10a and 11a and step portions (bumps) 10b and 11b are formed. The pair of electrode pads 15 and the pair of mounting terminals 10 and 11 formed inside the package body 6 are electrically connected to each other by a plurality of connection electrodes 14.

The example shown in FIG. 1A is a case where a tuning fork crystal resonator element is used as the electronic component 20, and a pair of lead electrodes (not shown) of the tuning fork crystal resonator element 20 is a pair of electrode pads 15 of the package body 6. Are bonded and fixed using a conductive adhesive. When a metal lid is used as the lid member 30, the lid member 30 is welded to a seal ring formed on the upper peripheral edge of the package body 6 using means such as resistance welding (seam welding), and the package body 6. Is hermetically sealed. Further, as shown in FIG. 1B, castellations C1, C2, C3, and C4 are formed at four corners of the package body 6, and the castellations C1, C2, C3, and C4 are connected to the mounting terminals 10 and 11, respectively. In addition, it functions as the connection electrode 14. On the other hand, the castellations C1 to C4 have an effect of increasing the connection strength between the circuit board and the package 1 due to solder rising (fillet) when the package 1 is mounted on the circuit board.
Further, as shown in the bottom view of FIG. 1C, the castellation C ′ may be provided at one central portion on both sides in the short direction of the bottom surface of the package body 6.

As shown in FIG. 1B, the mounting terminals 10 and 11 provided on the bottom surface of the package body 6 are provided at one location at each of the center portions on both sides in the short direction. The mounting terminals 10 and 11 are first applied to the package body 6 by using a method such as screen printing, and stepped portions (bumps) are respectively formed on the surfaces of the mounting terminal bases 10a and 11a. ) 10b and 11b are applied by using a method such as screen printing and baked at the same time as the package body 6. Since the thickness of the stepped portion after baking is about 10 μm to 15 μm by one application of screen printing, stepped portions (bumps) 10 b and 11 b having appropriate thicknesses are formed. The feature of the present invention is the positional relationship between the mounting terminal bases 10a and 11a of the mounting terminals 10 and 11 and the step portions (bumps) 10b and 11b. The mounting terminal 11 will be described as an example. The length and width of the mounting terminal base 11a are L1 and w1, respectively, and the length and width of the step portion 11b are L2 and w2, respectively, and the mounting terminal base 11a and the step portion 11b are set so as to satisfy L1> L2 and w1> w2. Set the length and width respectively. In addition, as shown in the bottom view of FIG. 1B, the right end of the mounting terminal base 11a in the drawing and the right end of the stepped portion 11b are substantially aligned, and in the vertical direction (short side direction) of the mounting terminal base 11a. The step portion 11b is positioned substantially at the center. That is, the stepped portion 11b excludes at least the position farthest from the center of the electronic component package 1 and the central portion of the package body 6 when the mounting terminal 11 is joined to the land electrode on the circuit board side by soldering. The shape is such that the solder with the peripheral edge of the mounting terminal 11 is thick.
The same applies to the mounting terminal base 10 a and the stepped portion 10 b of the mounting terminal 10, and is formed symmetrically with the mounting terminal 11 with respect to the center of the package body 6.

  FIG. 2 is an enlarged side view of a main part of the mounting terminal 11 when the package 1 is mounted on the land electrode 26 of the circuit board 25, that is, the mounting terminal base 11a and the stepped portion 11b. As can be seen from FIG. 2, the package is mounted such that the thickness of the solder 28 is larger than h2 (the thickness of the solder under the stepped portion 11b) h1 (the thickness of the solder under the mounting terminal base 11a). The terminal 11 is configured. As will be described later, the stepped portion 11b is provided on the mounting terminal 11 so that the amount of solder in the region where the stress caused by the difference in linear expansion coefficient between the circuit board 25 and the package 1 is the largest is increased. Form.

  When the package is mounted on a circuit board, distortion occurs in the solder joint due to a difference in linear expansion coefficient between the package and the circuit board due to a change in ambient temperature. In order to investigate the relationship between the shape of the package mounting terminals and the generated distortion, four types as shown in the bottom views of FIGS. 3A to 3D were selected as the types of package mounting terminals 10 and 11. 3A is a package in which the mounting terminals 10 and 11 have a standard area, FIG. 3B is a package having a mounting terminal area larger than that in FIG. 3A, and FIG. The package is provided with two stepped portions (bumps) 10b and 11b, and FIG. 4D is a package provided with one castellation C ′ at the center on both sides in the lateral direction. When the packages shown in FIGS. 3A to 3D are mounted on a circuit board via solder, the magnitude of distortion generated in the solder of the bonding material and its region were obtained by simulation. In the case of the package shown in FIGS. 3A, 3B, and 3D, the bonding when the solder thickness h1 of the bonding portion is 70 μm and the step portions 10b and 11b are provided as shown in FIG. 3C. The thickness h1 of the solder of the part was 100 μm. Also, the simulation conditions are that the solder freezing point (+ 218 ° C.) is assumed to be the starting point of stress (stress free), and the temperature change (−40 ° C. + 125 ° C.) has the largest temperature change from + 218 ° C. Under the load condition of −40 ° C., the magnitude of strain applied to the solder and the area with large strain were obtained by simulation. That is, no distortion occurs in the package and the circuit board at the solder freezing point (+ 218 ° C.), but distortion occurs when the temperature returns to room temperature, and the distortion is maximum at −40 ° C. Note that temperature fluctuations occur uniformly in the model, and the residual stress of the material constituting the package was not considered.

The figure overwritten on the mounting terminal on the right side of FIG. 3 (a) shows a region having a large distortion generated when the package is mounted on a circuit board and a temperature cycle test of −40 ° C. to + 125 ° C. is applied. As a result of the simulation, it was found that large distortion occurs in the regions indicated by A, B, C, D, and E, particularly the regions indicated by D and E. Needless to say, distortion on the left side of the mounting terminal in FIG. In addition, in the packages of FIGS. 3B to 3D, the region where the large distortion occurs was almost the same as the right side of FIG.
Moreover, the maximum distortion which arises in the castellations C1-C4 of a mounting terminal when the temperature cycle of -40 degreeC- + 125 degreeC was added was calculated | required about the shape of each mounting terminal of Fig.3 (a)-(d). FIG. 3 (e) shows the maximum generated in the caster of the mounting terminal in FIGS. (B) to (d) when the maximum distortion generated in the castellation of the mounting terminal shape shown in FIG. In the figure which showed distortion by the relative value, the horizontal axis | shaft is the figure number (a)-(d) which shows the shape of a mounting terminal, and a vertical axis | shaft is a figure which shows a relative solder distortion. From FIG. 3 (e), it was found that when the stepped portions 10b, 11b are provided on the mounting terminals 10, 11 as in the package of FIG. 3 (c), the maximum distortion generated in the castellation is minimized.

  This is also due to the fact that by providing the stepped portions 10b and 11b in a part of the mounting terminal, the solder interposed between the circuit board and the bottom surface of the mounting terminal becomes thick, and the distortion is alleviated. Further, the relationship between the thickness of the solder and the connection strength is disclosed in Japanese Patent Laid-Open No. 5-308179, and the connection strength has a maximum value with respect to the solder thickness and has an appropriate thickness. Based on the results of the above simulations, a package having mounting terminals that increase the solder thickness in the region where the distortion is large, that is, the position farthest from the center of the package and the peripheral edge of the mounting terminal excluding the portion near the center of the package. Various manufactured. And the crack rate (ratio of the crack length with respect to the solder full length in a certain cross section) was investigated. As a result, it was found that the package shown in FIG. 1 has a lower cross-sectional solder crack ratio than the package shown in FIG.

When the package according to the present invention shown in FIG. 1 is mounted on a mounting board, that is, when the mounting terminal of the package is joined to the land electrode of the mounting board via solder, the conduction resistance between the land electrode and the mounting terminal is − An experiment was conducted on how the temperature cycle (heat cycle) of 40 ° C. to + 125 ° C. changed. FIG. 4A shows a measurement pattern 40 on a substrate on which a package is mounted. 41a and 41b are land electrodes, 42a and 42b are wiring conductors, and 43a and 43b are terminal electrodes for measuring conduction resistance. FIG. 4B is a plan view of the substrate 45 actually used for the conduction resistance measurement in which a plurality of measurement patterns 40 are arranged in a lattice pattern.
The package used in the conduction resistance experiment includes a package having a stepped mounting terminal shown in FIG. 1 and a package having a general mounting terminal shown in FIGS. 3A to 3D for comparison. Was used. Since it is for measuring the conduction resistance of the solder that joins the mounting terminal and the land electrode, the electrode pads inside the package body, for example, the two electrode pads 15 in FIG. It was. The measurement point measured the conduction | electrical_connection resistance after the heat cycle test of 500 times, 1000 times, 1500 times, 2000 times, 2500 times, and 3000 times before a heat cycle.

FIG. 5 is a line graph showing the conduction resistance after each heat cycle test. The broken lines A, B, and C are diagrams showing the relationship between the number of heat cycles and the conduction resistance of the package having the mounting terminals shown in FIGS. 3A, 3D, and 1C, respectively. .
From FIG. 5, it was found that the package having the mounting terminal with a stepped portion of the present invention shows a good result even in a heat cycle test of conduction resistance.

  FIG. 6 is a bottom view showing the configuration of the package 2 of the second embodiment, and includes four mounting terminals 10, 11, 12, and 13. Each of the mounting terminals 10 to 13 includes a mounting terminal base 10a to 13a and a stepped portion 10b to 13b. The mounting terminal bases 10a to 13a are arranged at the four corners of the bottom surface of the package. C4 is formed. The step portions 10b to 13b are arranged at corners near the center of the package on the surfaces of the mounting terminal bases 10a to 13a. Due to the positional relationship between each of the mounting terminal bases 10a to 13a and each of the step portions 10b to 13b, the thickness of the solder in the region where the distortion is the largest can be increased.

  FIG. 7 is a bottom view showing the configuration of the package 3 of the third embodiment, which includes two mounting terminals 10 and 11 and two dummy electrodes 16 and 17. The mounting terminals 10 and 11 include mounting terminal bases 10a and 11a and stepped portions 10b and 11b, respectively. The stepped portions 10b and 11b are similar to the mounting terminal bases 10a and 11a as in the example of FIG. Be placed. The dummy electrodes 16 and 17 are formed on both sides in the longitudinal direction of the package 3 and closer to the end in the short side direction, and are composed of dummy electrode bases 16a and 17a and step portions 16b and 17b. The step portions 16b and 17b are formed near the center of the package 3 on the surfaces of the dummy electrode bases 16a and 17a. By providing the dummy electrodes 16 and 17 to which the step portions 16b and 17b are added, the connection strength between the package 3 and the circuit board is enhanced.

  FIG. 8 is a bottom view showing the configuration of the package 4 of the fourth embodiment, and four dummy electrodes 16, 17, 18, 19 are added to both sides in the longitudinal direction of the package 2 of the second embodiment shown in FIG. It is a package. Each dummy electrode 16, 17, 18, 19 comprises a dummy electrode base 16a, 17a, 18a, 19a and stepped portions 16b, 17b, 18b, 19b. The stepped portions 16b-19b are the surfaces of the dummy electrode bases 16a-19a. It is formed near the center of the package 4 above. By providing the plurality of dummy electrodes 16 to 19 on the package, the connection strength between the package and the circuit board is further increased.

In the first embodiment shown in FIG. 1, an example in which a tuning fork type crystal vibrating element is mounted on the electrode pad 15 formed in the concave portion of the package 1 is shown, but the second to fourth shown in FIGS. A piezoelectric vibration element may be mounted in the recesses of the packages 2, 3, and 4 of the embodiment to constitute a surface-mount type piezoelectric vibrator.
A package having a convex portion on the terminal electrode is disclosed in Patent Document 2, but the configuration of the mounting terminal of the package according to the present invention is greatly strained, excluding a region far from the center of the package and a portion near the center of the package. The difference is that the structure of the mounting terminal is such that the thickness of the solder in the peripheral region of the mounting terminal is increased.

  1, 2, 3, 4 ... package, 6 ... package body, 10, 11 ... mounting terminal, 10a, 11a, 12a, 13a ... mounting terminal base, 10b, 11b, 12b, 13b, 16b, 17b, 18b, 19b ... Step part (bump), 16, 17, 18, 19 ... dummy electrode, 16a, 17a, 18a, 19a ... dummy electrode base, 14 ... connection electrode, 15 ... electrode pad, 20 ... electronic component, 25 ... circuit board, 26 ... land electrode, 28 ... solder, 30 ... lid member, C ', C1, C2, C3, C4 ... castellation, A, B, C, D, E ... large distortion region, 40 ... measurement pattern, 41a, 41b ... land electrodes, 42a, 42b ... wiring conductors, 43a, 43b ... terminal electrodes for measurement, 45 ... substrate.

Claims (6)

An electronic component package comprising a rectangular package body and a lid member for hermetically sealing the package body,
An electrode pad formed inside the package body;
A mounting terminal formed in the vicinity of at least four corners of the bottom surface of the package body and having a stepped portion on the mounting surface;
An electronic component package comprising: a plurality of connection electrodes that electrically connect the pad and the mounting terminal.   2. The electronic component package according to claim 1, wherein a castellation is formed at each of the four corners of the package body, and the connection electrode is formed on each of the castellations.   The step portion is shaped such that when the mounting terminal is joined to a circuit board with solder, the solder formed around the four corners on the mounting terminal is thickened. The package for electronic components as described in 2.   The electronic component package according to any one of claims 1 to 3, wherein a pair of dummy electrodes is formed on the package.   The electronic component package according to claim 4, wherein a plurality of the pair of dummy electrodes are formed.   A piezoelectric vibrator comprising the electronic component package according to claim 1, wherein a piezoelectric vibrating piece is mounted on the electrode pad of the package body.

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