JP2011199228A - Base of package for electronic component, and package for electronic component - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a base of a package for electronic component preventing solder cracks to increase the reliability in mounting bonding between the package for electronic component and a circuit board, and the package for electronic component.SOLUTION: In the base of the package for electronic component holding an electronic component element, a bottom surface of the base is rectangular when viewed in plane, at least a pair of almost L-shaped terminal electrodes to be bonded with an external circuit board with a conductive bonding material are formed, and each of the almost L-shaped terminal electrodes is disposed along the base bottom surface in close proximity to or in contact with its long and short sides.

Description

  The present invention relates to a base for an electronic component package used in an electronic device or the like, and an electronic component package.

  Examples of electronic components that require hermetic sealing include piezoelectric vibration devices such as crystal resonators, crystal filters, and crystal oscillators. In each of these products, a metal thin film electrode is formed on the surface of the crystal diaphragm, and the crystal diaphragm (specifically, the metal thin film electrode) is hermetically sealed to protect the metal thin film electrode from the outside air. .

  Due to the demand for surface mounting of components, these piezoelectric vibration devices are increasingly being stored in a package made of an insulating material such as ceramic. For example, Patent Document 1 discloses a package made of a ceramic material, which includes a base (mounting substrate) having a quartz vibration plate mounting portion and a lid (cover) having an inverted concave cross section, and these are hermetically sealed. A configuration that is mounted on a circuit board and bonded via a conductive bonding material such as solder is disclosed.

  In this conventional piezoelectric vibration device, a terminal electrode is formed on the bottom surface of the base, and in order to confirm the connection state due to the rising of the solder (conductive bonding material), the terminal electrode is formed by a castellation formed on the side surface of the base. It extends from the bottom of the base to the side.

  By the way, a so-called glass epoxy substrate in which a mesh-like glass fiber is impregnated with an epoxy resin material is widely used for a circuit board on which the conventional piezoelectric vibration device is mounted because of ease of processing and cost advantages. . In addition, a solder paste is applied to the upper part of the electrode pattern of the circuit board by a method such as screen printing. Then, the terminal electrode of the package of the piezoelectric vibration device is mounted on the electrode pattern of the circuit board, and the solder paste is melted in a melting furnace (such as a heating furnace) to cause piezoelectric vibration on the circuit board. Solder the device.

JP 2002-76813 A JP 2009-141455 A

  However, due to a difference in thermal expansion coefficient between the package and the circuit board, stress may be generated in the solder that joins the package and the circuit board, and cracks may occur. In particular, when a ceramic material such as alumina is used as a package and a glass epoxy board is used as a circuit board, and when it is used for applications that are used in harsh environments such as in-vehicle use, high and low temperatures Since the package and the circuit board are used in an environment, fatigue breakdown is likely to occur from the solder due to the difference between the thermal expansion coefficient of the package and the thermal expansion coefficient of the circuit board. As described above, the problem of solder cracks, which did not become a serious problem in a normal temperature environment, appears remarkably in high and low temperature environments, and further, when an impact is applied to the package and the circuit board, peeling occurs from the solder crack portion. There was a problem.

  On the other hand, in the above-mentioned Patent Document 2, the terminal electrode on the bottom surface of the base is divided into a plurality of parts, and the base material is exposed between the divided terminal electrodes, so that bubbles or the like in the joint solder are separated between the divided terminals. It is intended to suppress the occurrence of solder cracks.

  However, when stress is applied to the solder that joins the package and the circuit board due to the difference in thermal expansion coefficient between the package and the circuit board as described above, the stress is generated at the outer peripheral edge of the base bottom surface, which is the maximum stress generation point. In many cases, a solder crack is generated from an adjacent region, and the solder crack generated by being affected by the same stress continuously expands toward the center point of the base bottom surface. And finally, the solder crack progresses in the whole terminal electrode, and the joint point by the solder of the package and the circuit board is peeled off, so that the terminal electrode is completely peeled from the circuit board in the electrical connection state with the electronic component element. State (hereinafter referred to as an open state).

  Until this state is reached, in the configuration of the terminal electrode of Patent Document 2 described above, the area of one functional terminal electrode itself electrically connected to the electronic component element is divided. May be encouraged. Further, in the configuration of the terminal electrode of Patent Document 2, there is a region where one terminal electrode is not electrically connected to the electronic component element, and the region where the electronic component device is electrically connected has a maximum stress generation point. Since it is formed in a region close to the outer peripheral edge of a certain base bottom surface, the life until the open state is shortened. That is, the configuration of the terminal electrode of Patent Document 2 still cannot solve the problem of solder cracks.

  The present invention has been made to solve the above-described problems, and provides an electronic component package base and an electronic component package that prevent solder cracks and improve the reliability of mounting and bonding between the electronic component package and the circuit board. It is intended to provide.

In the present invention, in the base of the electronic component package holding the electronic component element,
The bottom surface of the base is rectangular in plan view, and at least a pair of substantially L-shaped terminal electrodes that are joined to an external circuit board using a conductive bonding material are formed. It is arranged along the long side and the short side of the base bottom surface in a state of being close to or in contact with the long side and the short side.

  With the above-described configuration, the terminal electrode is formed in a substantially L shape, and is disposed along the long side and the short side of the base bottom so as to be close to or in contact with the base, and the base and circuit board constituting the electronic component package Even if a thermal expansion coefficient difference occurs between the base and the base, a substantially L-shaped terminal electrode is provided along the outer peripheral edge of the base where the stress is large. It becomes difficult to occur, and the stress is uniformly distributed in both side directions. The progress of cracks can be delayed compared to the case where stress is generated in one direction. That is, the adverse effect of stress strain on the conductive bonding material for bonding the base and the circuit board can be reduced without increasing the area of the terminal electrode more than necessary. As a result, it is possible to contribute to miniaturization of the base of the electronic component package, and it is possible to suppress the occurrence of cracks.

  In addition to the above configuration, bumps having a smaller plane area than the terminal electrodes may be integrally formed on the terminal electrodes.

  The inventor found that in most cases of cracks in the conductive bonding material, the starting point of the crack in the conductive bonding material occurred at the bottom edge of the terminal electrode, and if there were no obstacles between the starting point and the bottom position of the terminal electrode. I know that they run almost in parallel. From this knowledge, in addition to the above-described effects, in this configuration, bumps having a smaller planar area than each of the terminal electrodes are integrally formed on the pair of terminal electrodes, thereby forming a crack in the conductive bonding material. It is possible to shift the position where the crack near the end in the long side direction of the terminal electrode where the crack first occurs is shifted from the position where the crack progresses near the center in the long side direction of the terminal electrode. Initially, the crack that tries to travel almost parallel to the bottom surface of the terminal electrode is changed in the direction of the circuit board that is not parallel to the bottom surface of the terminal electrode due to the influence of the end of the bump close to the end of the terminal electrode. In the middle, a bending point of the crack can be provided. The presence of this bending point of the crack can delay the progress of the crack. As a result of the above, it is possible to prevent the terminal electrode from being opened and not functioning as an electronic component while improving the electromechanical connectivity of the terminal electrode.

  Further, the electronic component package may include a lid that hermetically seals the electronic component element with respect to the base of the electronic component package described above. With this configuration, an electronic component package hermetically sealed using a base that can obtain the above-described operational effects can be obtained. Therefore, an electronic component package that is inexpensive and can be downsized to improve the reliability of circuit board mounting and bonding. Can be provided.

  According to the present invention, it is possible to further reduce and prevent the adverse effects of cracks (for example, solder cracks) in a conductive bonding material, and to reduce the cost and improve the reliability of circuit board mounting bonding. And an electronic component package can be provided.

1 is a bottom view of a surface-mounted crystal resonator showing an embodiment of the present invention. Sectional drawing along the AA line of the state which mounted the surface mount-type crystal oscillator of FIG. 1 in the circuit board. Sectional drawing along the BB line of the state which mounted the surface mount-type crystal oscillator of FIG. 1 in the circuit board. The bottom view of the surface mount-type crystal resonator which shows the modification 1 of embodiment of this invention. FIG. 10 is a bottom view of a surface-mounted crystal resonator showing a second modification of the embodiment of the present invention.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In each of the following embodiments, the case where the present invention is applied to a surface-mount type crystal resonator as a package for an electronic component is shown.

  As shown in FIGS. 1, 2, and 3, the surface-mount type crystal resonator according to the embodiment of the present invention includes a crystal vibrating plate 3 that is an electronic component element and a crystal vibration having a concave portion that is open at the top. A base 1 for holding (accommodating) the plate 3 and a lid 2 for hermetically sealing the crystal diaphragm 3 held on the base 1 by being joined to the opening of the base 1.

  The base 1 is a rectangular parallelepiped as a whole, and has a configuration in which a ceramic such as alumina and a conductive material such as tungsten or molybdenum are appropriately laminated. As shown in FIGS. 2 and 3, the base 1 includes a storage portion 10 having a concave shape in cross section, and a bank portion 11 provided around the storage portion 10 so as to surround the storage portion 10. Specifically, the base 1 is a rectangular (planar view rectangular) flat plate-shaped ceramic base base 1a, and a ceramic having a large central portion and an outer size (planar view outer size) substantially equal to the base base 1a. The base body 1a, the frame body 1b, and the sealing member 11a are integrally fired. The top surface of the bank portion 11 (frame body 1b) is flat, and a sealing member 11a (a sealing material, a metal layer, or the like) is formed on the bank portion 11. In the first embodiment, for example, glass is formed as the sealing member 11a. However, when the lid 2 described later is a metal lid, the sealing member 11a is formed on the upper surface of a metallized layer made of tungsten, molybdenum, or the like. It is good also as a structure by which each layer of the nickel plating layer and the gold plating layer was formed, and also the structure by which the metal ring was formed in the upper part of these each layer.

  Further, there are four corners K1, K2, K3, and K4 on the outer periphery (outer peripheral edge in plan view) of the base 1, and the casters C1, C2, and C3 are vertically arranged on the side surface of the base 1 from the base bottom surface to the top surface (upper surface). , C4 are formed, and castellations C5, C6 are formed vertically on the side surface near the center of the long side of the base 1 from the base bottom surface to the top surface (top surface).

  The bottom surface of the base 1 has a rectangular shape in plan view, and a pair of L-shaped terminal electrodes 12 and 13 in plan view that are biased to diagonal positions (K1 and K3) of the base bottom surface are formed. Specifically, the terminal electrode 12 has an outer bent corner portion 12a in an L shape in plan view close to the corner K1, and is flat with respect to the long side and the short side of the base bottom surface in contact with the corner K1 of the base bottom surface. The long branch part 12b and the short branch part 12c which are L-shaped in view are arranged in parallel in a state where they are close to each other. That is, the terminal electrode 12 is formed in a state along the corner K1 and each side in contact with the corner K1. In addition, the terminal electrode 13 has an L-shaped outer bent corner portion 13a close to the corner K3 and is L-shaped in plan view with respect to the long side and the short side of the base bottom surface in contact with the corner K3 of the base bottom surface. The long branch portion 13b and the short branch portion 13c having a shape are arranged in parallel with each other in close proximity. That is, the terminal electrode 13 is formed in a state along the corner K3 and each side in contact with the corner K3. The pair of terminal electrodes 12 and 13 are configured to be symmetrical with each other, and are configured to be point-symmetric with respect to the center point O of the base bottom surface.

  Further, the dimensions of the long branches 12b and 13b of the terminal electrodes 12 and 13 are configured to exceed half of the long side dimension of the base bottom surface, and the dimensions of the short branches 12c and 13c of the terminal electrodes 12 and 13 are based on the dimensions. It is configured with a dimension that exceeds half of the short side dimension of the bottom surface. In particular, when the long side dimension L2 equal to the dimension of the long branch portions 12b and 13b of the terminal electrodes 12 and 13 is configured to exceed half of the long side dimension L1 of the base bottom surface, the terminal electrodes 12 and 13 are formed on the base bottom surface. The ratio of L2 to L1 is 70% or more in order to ensure a region that is opposed to the base bottom surface in the short side direction near the center of the long side of the base bottom surface. It is more desirable to comprise. Specifically, in this embodiment, the length of the long branches 12c and 13c of the terminal electrodes 12 and 13 is 2 mm with respect to the long side dimension 2.5 mm of the base bottom, and the ratio is formed at 80%. .

  The terminal electrodes 12 and 13 are electrode pads 122 and 132 formed on the bottom surface inside the base 1 via side terminal electrodes 121 and 131 formed on the castellations C5 and C6 (the electrode pads 132 are not shown). It extends to and is electrically connected.

  These terminal electrodes 12 and 13, side terminal electrodes 121 and 131, and electrode pads 122 and 132 are formed by metallizing a metallized material such as tungsten or molybdenum integrally with the base 1, and nickel plating is formed on the upper part. It is formed, and gold plating is formed on the upper part.

  Bumps 12B and 13B that are concentric and have substantially the same shape (similar shape in plan view) are formed on the terminal electrodes 12 and 13 in a concentric manner and slightly smaller in plane area than the terminal electrodes 12 and 13, respectively. The bumps 12B and 13B are integrally formed by laminating the same material metallization (tungsten, molybdenum, etc.) in the same shape on the metallization upper portions of the terminal electrodes 12 and 13. Therefore, the bumps 12B and 13B can be formed very easily and inexpensively. The terminal electrodes 12 and 13 and the bumps 12B and 13B are formed by firing these metallized materials integrally with the base 1, forming nickel plating on the metallized upper part, and forming gold plating on the upper part. .

  Further, in the present invention, the dimension L3 of the bumps 12B and 13B of the terminal electrodes in the same direction with respect to the long side of the base bottom surface is compared with the dimension L2 of the terminal electrodes 12 and 13 in the same direction with respect to the long side of the base bottom surface. Is preferably 90% or more. Further, in the present invention, it is desirable that the peripheral width dimension W from the end portions of the terminal electrodes 12 and 13 to the end portions of the bumps 12B and 13B is located within a range of 0.01 to 0.5 mm. . Specifically, in this embodiment, the dimension L2 of the long branches 12c and 13c of the terminal electrodes 12 and 13 is 2 mm, and the dimension L3 of the long branches 12Bc and 13Bc of the bumps 12B and 13B is 1.8 mm. The ratio is 90%. Further, the width dimension W is about 0.1 mm.

  In this way, by forming bumps that are concentric with the terminal electrode and have substantially the same shape (similar shape in plan view), the progress of the crack can be similarly delayed even for cracks that occur in any plane direction of the terminal electrode. . In addition, by adopting a bump configuration with the dimensional ratio and width as described above, a bump having a slightly smaller flat area than the terminal electrode and having substantially the same shape (similar shape in plan view) can be obtained. Thus, at the initial stage where a crack is generated, the crack progress angle can be changed to provide a bending point of the crack, and the progress of the crack can be remarkably suppressed. As a result, it becomes a desirable form that can further suppress the terminal electrode from being opened and not functioning as an electronic component while further improving the electromechanical connectivity of the terminal electrode.

  Between the electrode pads 122 and 132, a crystal diaphragm 3 (an electronic component element in the present invention) is mounted. A pair of excitation electrodes and extraction electrodes (not shown) are formed on the front and back surfaces of the crystal diaphragm 3. The pair of excitation electrodes and extraction electrodes are in contact with, for example, the quartz diaphragm 3 (from the top of the quartz diaphragm 3) in the order of chromium, gold, chromium, gold, chromium, chromium, silver, chromium, or chromium, It is formed by laminating in the order of silver. Each of these electrodes (a pair of excitation electrode and extraction electrode) can be formed by a thin film forming means such as a vacuum evaporation method or a sputtering method. The extraction electrode of the crystal diaphragm 3 is conductively bonded to the electrode pads 122 and 132 by a conductive bonding material (not shown), and the crystal diaphragm 3 is held on the base 1. For example, a conductive bonding material such as a conductive resin adhesive, a metal bump, a metal plating bump, or a brazing material is used for conductive bonding between the excitation electrode of the crystal diaphragm 3 and the electrode pads 122 and 132 of the base 1. Can do.

  As the lid 2 that hermetically seals the base 1, a ceramic material such as plate-like alumina formed with a sealing member 11 a such as a glass sealing material is used. The plan view outline of the lid 2 is substantially the same as or slightly smaller than the outline of the base 1. The lid 2 is not limited to a ceramic material but may be a glass material or a metal material.

  The crystal vibrating plate 3 is housed in the storage portion 10 of the base 1 and covered with the lid 2 and hermetically sealed by a technique such as fusion bonding using a heating furnace, whereby a surface-mounted crystal resonator (electronic The component package is completed. The method for hermetic sealing between the base 1 and the lid 2 is not limited to fusion bonding, and other methods such as welding and brazing are used depending on various materials (base, lid, sealing member, etc.). be able to. Further, as shown in FIG. 2, the completed crystal resonator is bonded to the upper part of the electrode patterns 41 and 42 of the circuit board 4 made of glass epoxy material via a conductive bonding material D such as solder. .

  Further, in the first modification of the embodiment of the present invention shown in FIG. 4, the corners of the terminal electrodes 12 and 13 are formed in a curved shape with respect to the above-described embodiment, and are configured in a substantially L shape with small dimensions of each branch portion. That the terminal electrodes 12 and 13 are at opposite corner positions (K4 and K2), and side terminal electrodes 121 and 131 extending from the terminal electrodes 12 and 13 are formed. The castellations C5 and C6 are different in that the positions of the castellations C5 and C6 are the sides near the center of the short side of the base 1. Other parts adopt the same configuration, and the detailed description is omitted by assigning the same number. In the first modification, the corner portions of the terminal electrodes are formed in a curved shape, so that the stress can be dispersed more uniformly. In particular, not only the outer bent corner portions 12a and 13a of the L-shaped terminal electrode in a plan view but also the inner bent corner portions facing the outer bent corner portions 12a and 13a are formed in a curved shape, so that the region where cracks start It becomes a preferable form by the stress dispersion | distribution to.

  Further, in the second modification of the embodiment of the present invention shown in FIG. 5, four terminal electrodes 12, 13, and 14 are provided for all the corners (K1, K2, K3, K4) and the sides in contact with the above-described embodiment. , 15 is different. That is, a pair of L-shaped terminal electrodes 12 and 13 in plan view that are biased to the diagonal positions (K1 and K3) of the base bottom surface are formed, respectively, and a pair of plan view L that is biased to the diagonal positions (K2 and K4) of the base bottom surface. Character-shaped terminal electrodes 14 and 15 are formed, respectively. The terminal electrode 12 has an L-shaped outer bent corner portion 12a in contact with the corner K1 and an L-shape in plan view with respect to the long and short sides of the base bottom surface in contact with the corner K1 of the base bottom surface. The long branch portion 12b and the short branch portion 12c are arranged in parallel with each other in contact with each other. The terminal electrode 12 is formed in a state along the corner K1 and each side in contact with the corner K1. The terminal electrode 13 contacts the corner K3 with an outer bent corner 13a having an L shape in plan view, and has an L shape in plan view with respect to the long side and the short side of the base bottom surface in contact with the corner K3 of the base bottom surface. The long branch portion 13b and the short branch portion 13c are arranged in parallel with each other in contact with each other. The terminal electrode 13 is formed in a state along the corner K3 and each side in contact with the corner K3. The terminal electrode 14 contacts the corner K2 with an outer bent corner portion 14a having an L shape in plan view, and has an L shape in plan view with respect to the long side and the short side of the base bottom surface in contact with the corner K2 of the base bottom surface. The long branch portion 14b and the short branch portion 14c are arranged in parallel with each other in contact with each other. The terminal electrode 14 is formed in a state along the corner K2 and each side in contact with the corner K2. The terminal electrode 15 contacts the corner K4 with an outer bent corner portion 15a having an L shape in plan view, and has an L shape in plan view with respect to the long side and the short side of the base bottom surface in contact with the corner K4 of the base bottom surface. The long branch portion 15b and the short branch portion 15c are arranged in parallel with each other in contact with each other. The terminal electrode 15 is formed in a state along the corner K4 and each side in contact with the corner K4. These terminal electrodes 12, 13, 14, 15 are configured to be symmetrical with each other, and are configured to be point-symmetric with respect to the center point O on the base bottom surface. In the second modification, the castellations C5 and C6 are not formed on the sides of the base 1, and the terminal electrodes 12 and 13 are connected to the base 1 via the side terminal electrodes 121 and 131 formed on the castellations C1 and C2. It extends and is electrically connected to electrode pads 122 and 132 (not shown) formed on the inner bottom surface. Other parts adopt the same configuration, and the detailed description is omitted by assigning the same number. This modification 2 shows that the present invention can be applied to a case where there are four terminal electrodes. Even if a difference in thermal expansion coefficient occurs between the base 1 and the circuit board 4, the base is less affected by the stress. It can be uniformly dispersed so as to rotate from the center point O of the bottom surface. Also, the strength of the base 1 can be improved.

  Even if a thermal expansion coefficient difference occurs between the base 1 constituting the surface-mount type crystal resonator and the circuit board 4 due to the configuration of the above-described embodiment, it is substantially L along the outer peripheral end portion of the base 1 where the stress is large. Since the terminal electrodes 12, 13, or the terminal electrodes 12, 13, 14, 15 are provided, the stress difference between the short side and the long side of the base is less likely to occur, and stress is applied to both sides. Evenly distributed. The progress of cracks can be delayed compared to the case where stress is generated in one direction. That is, the adverse effect of stress strain on the conductive bonding material D for bonding the base 1 and the circuit board 4 can be reduced without increasing the area of the terminal electrode more than necessary. As a result, it is possible to contribute to the miniaturization of the base 1 of the surface-mount type crystal resonator, and it is possible to suppress the occurrence of cracks.

  In the terminal electrode configuration of the above embodiment, each terminal electrode is configured to be point-symmetric with respect to the center point O of the bottom surface of the base 1, and the difference in thermal expansion coefficient between the base 1 and the circuit board 4. Even if this occurs, it is more preferable that it can be uniformly dispersed so as to rotate from the center point O of the bottom surface of the base 1 that is less affected by the stress.

  Further, bumps 12B and 13B having a smaller area than the terminal electrodes or bumps 12B, 13B, 14B, and 15B are laminated and integrated on the terminal electrodes 12 and 13 or on the terminal electrodes 12, 13, 14, and 15, respectively. As a result, the terminal electrode 12, 13 where the crack of the conductive bonding material D first occurs, or the position where the crack advances near the end in the long side direction of the terminal electrode 12, 13, 14, 15 is formed. And the position where the crack advances near the center in the long side direction can be shifted. Initially, the cracks that are going to travel substantially parallel to the bottom surface position of the terminal electrodes 12, 13, or the terminal electrodes 12, 13, 14, 15 are the ends of the bumps 12B, 13B close to the end of the terminal electrode, or the bumps. Under the influence of the ends of 12B, 13B, 14B, and 15B, the angle is changed in the direction of the circuit board 4 that is not parallel to the terminal electrodes, and a crack bending point can be provided in the middle. The presence of this bending point of the crack can delay the progress of the crack. As a result of the above, it is possible to prevent the terminal electrode from being opened and not functioning as an electronic component while improving the electromechanical connectivity of the terminal electrode.

  In the above-described embodiment, a surface-mount type crystal resonator is taken as an example, but the present invention can also be applied to other surface-mount type electronic component packages used in electronic devices such as crystal filters and crystal oscillators. Further, although a ceramic material is disclosed as an insulating package (base), a glass material or crystal may be used. Although metallization is disclosed as the metal film of the terminal electrode, a plating material may be used.

  The present invention can be implemented in various other forms without departing from the spirit or main features thereof, and should not be interpreted in a limited manner. The scope of the present invention is indicated by the claims, and is not limited by the text of the specification. Further, all modifications and changes belonging to the equivalent scope of the claims are within the scope of the present invention.

  The present invention can be applied to an electronic component package such as a crystal resonator and a base of an electronic component package.

1 Base 2 Lid 3 Crystal Diaphragm (Electronic Component Element)
4 Circuit board

Claims (3)

In the base of the electronic component package that holds the electronic component element,
The base bottom has a rectangular shape in plan view, and is formed with at least a pair of substantially L-shaped terminal electrodes that are bonded to an external circuit board using a conductive bonding material,
A base for an electronic component package, wherein each of the substantially L-shaped terminal electrodes is disposed along or in contact with the long side and the short side of the bottom surface of the base. The base of the electronic component package according to claim 1, wherein bumps having a smaller area than the terminal electrodes are laminated and integrated on the terminal electrodes, respectively. An electronic component package comprising: a base for an electronic component package according to claim 1; and a lid for hermetically sealing the electronic component element.

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