JP2010016759A - Air-tightly sealed electronic component - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an air-tightly sealed electronic component which deals with a lead-free state of the air-tightly sealed electronic component and more improves reliability so that a metal film is prevented from being peeled, without reducing insertion property and fitting characteristics when pressing a base into a cap and without reducing connectivity with an external terminal. <P>SOLUTION: The invention relates to an air-tightly sealed electronic component constituted of: a base 1, in which a metallic shell 10 is filled with insulated glass 13 and metallic lead terminals 11, 12 are fixed through the insulated glass; an electronic element 2 mounted on the base; and a metallic cap 3 which is pressed into the base to air-tightly seal the electronic element. In the metallic shell and the metallic lead terminals, a first layer 101 constituted of an alloy of tin and copper is formed via a background layer 100 of copper or nickel, a second layer 102 constituted of copper is formed on the upper surface of the first layer, and a third layer 103 constituted of nickel or silver is formed. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an electronic component such as a crystal resonator, and more particularly to a hermetically sealed electronic component that is hermetically sealed by press-fitting a base into a cap and has heat resistance.

  A hermetic sealing configuration in which a metal shell is filled with insulating glass and a metal lead terminal is fixed to the insulating glass and a cylindrical metal cap is press-fitted into the base is, for example, a cylinder. It is commonly used in tuning-fork type crystal units housed in mold containers. In the hermetic sealing, a soft metal is formed at one or both of the base and the cap, and a cylindrical cap is press-fitted into a substantially cylindrical base having a relatively large diameter. Sealing is performed by plastic deformation.

  In the conventional configuration, for example, the base of the base metal shell is made of Kovar, and a solder plating layer containing tin and lead as main components is formed on the surface of the shell and the lead terminal. Moreover, the cap was comprised from copper nickel type alloys, such as a western white. With the above metal film configuration, the solder layer on the base side is soft and excellent in ductility, so that the two metals are plastically deformed by press-fitting in a state of being in close contact with each other, thereby facilitating press-fitting.

  By the way, in recent years, it is necessary to cope with a reflow soldering environment, and in order to mount it on a mounting board in a high temperature environment such as 240 to 270 ° C., an inner lead on which this press-fitted portion and an electronic element such as a crystal vibrating piece are mounted. The metal film structure of the part is also required to have heat resistance.

  In order to meet such requirements, solder having a high melting point, for example, lead 9: tin 1 and lead content has been used. However, since lead is a harmful substance to the human body, there is a tendency to suppress or prohibit its use worldwide, and the above solder composition is contrary to the trend of lead-free, and an alternative is required. ing.

  A configuration considering such lead-free is disclosed in Japanese Patent Laid-Open No. 2001-9587 (Patent Document 1). In Patent Document 1, a lead-free solder plating layer such as a tin-copper alloy is applied to the surface of the base and the cap including the lead terminals, and the lead-free solder plating layer is used as a sealing material. Since the melting temperature of copper is high, the base and cap after plating can be processed at a high temperature, and can be applied to a so-called heat-resistant specification product. If the temperature is relatively low, it can be used in a reflow soldering environment.

  However, in the lead-free high-temperature solder plating layer, there is a possibility that the brazing property with the external terminal may be reduced as compared with the solder plating layer containing lead. In addition, a solder plating layer made of a tin-copper alloy may be in a semi-molten state and inferior in heat resistance, as compared with a high-temperature solder plating layer containing lead. For this reason, it may be alloyed with a high-temperature solder for bonding containing lead to lower the melting point or generate gas.

  Japanese Patent Laid-Open No. 2005-175654 (Patent Document 2) discloses a configuration that takes into account the problems associated with such a lead-free solder made of a tin-copper alloy. That is, in Patent Document 2, an anti-alloying layer (nickel, chromium, titanium) for preventing diffusion of tin, etc. on the upper surface of the seal layer mainly composed of tin, and the best for improving the soldering quality. What formed the upper layer (silver, gold) is disclosed. However, in such a configuration, when the reflow soldering environment is used, the seal layer and the alloying prevention layer are not familiar and the sealing layer having a lower melting temperature than the alloying prevention layer is melted first. For this reason, there has been a problem that the metal film on the upper surface of the alloying prevention film is integrally peeled off at these boundary portions.

Japanese Patent Laid-Open No. 2001-9587 JP-A-2005-175654

  The present invention has been made to solve the above-described problems, and is compatible with lead-free hermetic sealing electronic components, and has insertability and fitting characteristics when a base is press-fitted into a cap, and external terminals. It is an object of the present invention to provide an airtight sealed electronic component that is more reliable and does not cause peeling of a metal film without reducing connectivity.

  In order to achieve the above object, in the present invention, as shown in claim 1, a base made of a metal shell filled with insulating glass, and a metal lead terminal penetrated and fixed to the insulating glass, An airtightly sealed electronic component comprising an electronic element mounted on the base and a metal cap that hermetically seals the electronic element by being press-fitted into the base, wherein the metal shell and the metal A lead terminal made of tin is formed with a first layer made of a tin-copper alloy through a copper or nickel underlayer, a second layer made of copper is formed on the upper surface, and a third layer made of nickel or silver is formed. A layer is formed.

  With the above configuration, the metal shell and the metal lead terminal are formed into a metal film having the same layer configuration, so that the metal film for sealing for press-fitting the base into the cap and the joint for soldering with the lead terminal are used. The metal film can be integrally formed easily and inexpensively by a technique such as plating.

  By forming the first layer made of a tin-copper alloy as the metal film for sealing, the softness of tin-copper functions effectively to ensure airtightness during press-fitting, and it is more heat-resistant without reducing the air-tightness after press-fitting. It is possible to improve the performance and cope with lead-free. That is, a heat-resistant lead-free seal material having excellent insertability and fitting characteristics when the base is press-fitted into the cap can be obtained. Since the underlayer of copper or nickel is formed on the lower surface of the first layer made of such a tin-copper alloy, it is possible to form the first layer made of a tin-copper alloy that is easy to control the thickness in a stable state. Not only that, but also the familiarity with the base matrix and lead terminal matrix is improved and the adhesion strength is improved. Solderability to an electronic element or a mounting board can also be improved. By forming the first layer with a thickness of 5 μm or more, the stress at the time of press-fitting the cap into the base is relieved without lowering the hermeticity after press-fitting, and a smoother hermetic sealing can be performed. By forming the thickness of the first layer to 20 μm or less, it is possible to eliminate the wraparound from the shell to the lead terminal due to the non-uniform thickness of the first layer. Short circuit between the shell and the lead terminal can be suppressed. In addition, the stress that the press-fitted cap receives from the base and the stress that the press-fitted base receives from the cap are minimized to prevent cracks in the insulating glass of the cap and base. Airtight defects can be eliminated.

  As the bonding metal film, since the third layer made of nickel or silver is formed on the upper surface of the first layer made of tin-copper alloy, the bonding solder and the tin-copper alloy that is the first layer are formed. Heat resistance can be improved while preventing alloying, and generation of molten gas from the first layer can be suppressed when reflow soldering is performed. Since such a molten gas is not generated inside the electronic component, the molten gas does not adhere to the electronic component element and cause deterioration of electrical characteristics. In particular, when the electronic component element is a crystal resonator element, it does not adhere to the electrode surface and cause fluctuations in frequency characteristics or a decrease in series resonance resistance value (CI value). By forming the third layer with a thickness of 0.05 μm or more, the effect of preventing alloying with the bonding solder is increased, and the heat resistance is improved. By forming the third layer with a thickness of 5 μm or less, the influence of stress when the cap is pressed into the base can be reduced, and a smoother hermetic sealing can be performed.

  Further, since the second layer made of copper softer than the third layer is formed between the first layer made of tin-copper alloy and the third layer made of nickel or silver which is the alloying prevention layer, the solder for joining And the first layer can be prevented from being alloyed, and the influence of stress when the cap is press-fitted into the base can be mitigated to achieve a smoother hermetic sealing. In addition, the adhesion strength between the first layer to the third layer can be further improved. That is, even if it corresponds to a reflow soldering environment, it does not peel off at the boundary between these metal layers. Further, diffusion occurs between the first layer made of a tin-copper alloy and the second layer made of copper, so that a second tin-copper alloy layer having a higher weight percentage of copper than the first layer can be formed. Further, it is possible to contribute to further improvement in adhesion strength between the first layer and the second layer. By forming the second layer with a thickness of 0.5 μm or more, an effective region for forming the second tin-copper alloy layer is secured, and the first and third layers function effectively as isolation films. To do. By forming the thickness of the second layer to 2 μm or less, it is possible to minimize the expansion stress received by the press-fitted cap from the base and the tightening stress received by the press-fitted base from the cap to minimize the cap and base insulation. Since the glass is prevented from cracking, it is possible to eliminate the airtight defect of the electronic component.

  As a result, it is compatible with the reflow soldering environment and lead-free, and it is more reliable than the metal film without peeling, without reducing the insertability and fitting characteristics when pressing the base into the cap. A hermetically sealed electronic component can be provided.

  In addition to the above-described configuration, the first layer may be a tin-copper alloy layer containing 10 to 20 wt% of copper. In addition to the above-described effects, the first layer may be used for sealing. Since the liquid phase temperature of the first layer, which is a metal film, is 300 ° C. or higher, the liquid phase temperature is higher than that of the heat resistant solder, and alloying with the heat resistant solder is less likely to occur. Moreover, by using a tin copper alloy layer with copper of 20 wt% or less, it is possible to suppress the base from becoming hard and to be less affected by the tightening stress that the press-fit base receives from the cap. As a result, it is possible to prevent cracks in the insulating glass of the base, thereby eliminating the airtight defect of the electronic component.

  Moreover, as shown in claim 3, in addition to the above-described configuration, a fourth layer of gold or silver may be formed on the upper surface of the third layer. The solder wettability at the time of solder joining is improved, and the soldering quality can be improved. By forming the fourth layer with a thickness of 0.01 μm or more, an effect of improving solder wettability can be expected. By forming the thickness of the fourth layer to 0.5 μm or less, it is possible to minimize the stress that the press-fitted cap receives from the base and the stress that the press-fitted base receives from the cap. Moreover, cost can be suppressed.

  According to the hermetically sealed electronic component according to the present invention, the lead-free hermetic sealed electronic component is compatible with the insertability and fitting characteristics when the base is press-fitted into the cap, and the connectivity with the external terminal. Without lowering, it is possible to provide a hermetically sealed electronic component with higher reliability that does not cause peeling of the metal film.

  Hereinafter, a preferred embodiment of the present invention will be described with reference to the drawings, taking a tuning fork type crystal resonator as an example of a hermetically sealed electronic component to be press-fitted and sealed. FIG. 1 is a diagram showing an exploded internal structure of a tuning fork type crystal resonator, FIG. 2 is a partially enlarged view of a base portion showing an embodiment of the present invention, and FIG. 3 is a further enlarged view of a round portion of FIG. It is. FIG. 2 shows only one lead terminal portion.

  The base 1 includes a metal shell 10, an insulating glass 13 filled in the shell, and metal lead terminals 11 and 12 that are fixedly penetrated to the insulating glass 13. The shell 10 uses, for example, Kovar as a base and has a cylindrical shape penetrating vertically. The lead terminals 11 and 12 are processed into a linear shape using, for example, Kovar as a base, and are disposed through the shell 10 at a predetermined interval. The insulating glass 13 is made of, for example, borosilicate glass, and the shell 10 and the lead terminals 11 and 12 are filled in the shell in an electrically independent state. The shell 10, the lead terminals 11 and 12, and the insulating glass 13 are integrally formed by a glass baking technique. Note that the metal material of the shell 10 or the lead terminals 11 and 12 is not limited to the above materials, and for example, an iron nickel alloy such as 42 alloy may be used for the shell.

  This integrally formed base 1 is degreased, acid cleaned, etc., to clean the metal surface and remove the carburized portion, and then the next metal film is formed. On the base surface, that is, the Kovar surfaces of the shell 10 and the lead terminals 11 and 12, a base plating layer 100 made of, for example, a copper layer having a thickness of about 1 to 7 μm is formed by electrolytic plating or the like. The underlying plating layer 100 is not limited to a copper layer, and may be a nickel layer having a thickness of about 1.5 to 5 μm.

  Next, a tin-copper alloy layer (first layer) 101 having a thickness of 5 to 20 μm and having a copper weight percentage of 10 to 20 wt% is formed on the base plating layer 100. A copper layer (second layer) 102 having a thickness of 0.5 to 2 μm is formed on the upper surface, and a nickel layer (third layer) 103 having a thickness of 0.05 to 5 μm is formed on the upper surface. A gold layer or silver layer (fourth layer) 104 having a thickness of 0.01 to 0.5 μm is formed on the upper surface. As shown in FIGS. 2 and 3, the metal film of each layer is formed on the surface of the shell 10 and the lead terminals 11 and 12 of the base 1 by plating.

  Next, the tuning fork type crystal resonator element 2 which is an electronic element is mounted on the inner sides 11a and 12a of the lead terminals, and is joined by a brazing material such as high temperature solder or lead-free high temperature solder. More specifically, a pair of excitation electrodes (not shown) are formed on the main surface and side surfaces of the tuning fork type quartz resonator piece, and each electrode is drawn out to the base 21 below the tuning fork type quartz vibration piece. . The base 21 of the tuning fork type crystal resonator element is mounted in a state of being upright on and in contact with the lead terminal inner side 11a, 12a of the base, and the brazing material (not shown) supplied in advance to the lead terminal. ) To electrically and mechanically connect the base electrode and the lead terminal. Since the gold layer and the silver layer (fourth layer) 104 are formed on the inner side 11a, 12a and the outer side 11b, 12b of the lead terminal, the bondability with the brazing material is improved.

  The cap 3 is made of a metal material such as white (Cu—Ni—Zn alloy) or phosphor bronze, and has a bottomed cylindrical shape. Although not shown, a nickel layer having a thickness of 1 to 10 μm is formed on the outer and inner peripheral surfaces of the cap 3 by means such as plating.

  The metal layer formed on the cap may use silver or gold instead of nickel, or may have a multilayer structure in which nickel, copper, silver, and gold are appropriately combined. It is also possible to use the base material (white and white) as it is. The inner diameter of the cap is designed to be slightly smaller than the outer diameter of the shell portion of the base. For example, the inner diameter is set to be 2 to 5% smaller. Such a cap covers the tuning-fork type crystal resonator piece, which is the electronic element, in a vacuum atmosphere, and press-fits the cap opening into the base. By press-fitting, the base and the cap are tightly adhered to each other and hermetically sealed, and the inside of the cap is kept in a vacuum state. Thus, the electronic component according to the embodiment of the present invention is completed.

  The present invention is not limited to the above embodiment, and the third layer 103 made of silver may be formed instead of the third layer 103 made of nickel. That is, according to this configuration, the first tin-copper alloy layer (first layer) 101 having a thickness of 5 to 20 μm and having a copper weight percentage of 10 to 20 wt% is formed in the upper layer of the base plating layer 100. . A copper layer (second layer) 102 having a thickness of 0.5 to 2 μm is formed on the upper surface, and a silver layer (third layer) 103 having a thickness of 0.05 to 5 μm is formed on the upper surface. A gold layer (fourth layer) 104 having a thickness of 0.01 to 0.5 μm may be formed on the upper surface of the third layer as necessary. The above metal layers are formed on the surface of the shell 10 and the lead terminals 11 and 12 of the base 1 by plating, as shown in FIGS.

  According to the embodiment, by forming the first layer 101 made of a tin-copper alloy having a copper weight percentage of 10 to 20 wt% as a metal film for sealing, it is effective to ensure airtightness during press-fitting due to the softness of tin-copper. Without functioning and reducing the airtightness after press-fitting, the heat resistance can be further increased and lead-free can be handled. In particular, since the liquid phase temperature of the first layer, which is a metal film for sealing, is 300 ° C. or higher, the liquid phase temperature is higher than that of the heat resistant solder, and alloying with the heat resistant solder is less likely to occur. Moreover, by using a tin copper alloy layer with copper of 20 wt% or less, it is possible to suppress the base from becoming hard and to be less affected by the tightening stress that the press-fit base receives from the cap. That is, a heat-resistant lead-free seal material having excellent insertability and fitting characteristics when the base 1 is press-fitted into the cap 3 is obtained. Since the underlayer 100 of copper or nickel is formed on the lower surface of the first layer 101 made of such a tin-copper alloy, the first layer 101 made of a tin-copper alloy that is easy to control the thickness is formed in a stable state. Not only can this be done, but also the familiarity with the base matrix and the lead terminal matrix can be improved and the adhesion strength can be improved. Solderability to the tuning fork type crystal resonator element 3 or the mounting board can also be improved.

  As the bonding metal film, the third layer 103 made of nickel or silver is formed on the upper surface of the first layer 101 made of a tin-copper alloy, so that the bonding solder and the tin-copper that is the first layer 101 are made. Heat resistance can be improved while preventing alloying with the alloy, and generation of molten gas from the first layer 101 can also be suppressed when reflow soldering is performed.

  In addition, since the second layer 102 made of copper is formed between the first layer 101 made of a tin-copper alloy and the third layer 103 made of nickel or silver which is an alloying prevention layer, the first layer 102 Since the second layer 102 made of copper that is softer than the third layer 103 is formed between the third layer 103 and the third layer 103, the alloying between the solder for joining and the first layer 102 is prevented, and the cap 3 is made of the base 1 The effect of stress when press-fitting into the tube is alleviated, and a smoother hermetic sealing can be achieved. In addition, the adhesion strength between the layers from the first layer 102 to the third layer 103 can be further improved. That is, even if it corresponds to a reflow soldering environment, it does not peel off at the boundary between these metal layers. Further, since diffusion occurs between the first layer 102 and the second layer 102 made of copper, a second tin-copper alloy layer having a higher copper weight percentage than the first layer 102 can be formed. It can also contribute to further improvement in adhesion strength between the first layer and the second layer.

  In addition, since the third layer 103 such as silver or the fourth layer 104 such as gold or silver is formed on the uppermost surface of the bonding metal film, the solder wettability at the time of solder bonding is improved. Soldering quality can be improved.

  The present invention can be implemented in various other forms without departing from the spirit or main features thereof. Therefore, the above-described embodiment is merely an example in all respects and should not be interpreted in a limited manner. The scope of the present invention is indicated by the claims, and is not restricted 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 figure which shows the decomposition | disassembly internal structure of a tuning fork type crystal resonator. The elements on larger scale of the base part which shows embodiment of this invention. FIG. 3 is an enlarged view of a round portion in FIG. 2. The elements on larger scale of the base part which shows other embodiment of this invention. The enlarged view of the round part of FIG.

Explanation of symbols

1 Base 2 Tuning fork type crystal unit (electronic element)
3 Cap 10 Shell 11, 12 Lead terminal 13 Insulating glass 100 Base plating layer 101 1st layer 102 2nd layer 103 3rd layer 104 4th layer

Claims (3)

A base made of a metal shell filled with insulating glass, and a metal lead terminal penetrated and fixed to the insulating glass, an electronic element mounted on the base, and the electronic element by being press-fitted into the base A hermetically sealed electronic component comprising a metal cap that is hermetically sealed,
A first layer made of a tin-copper alloy is formed on the metal shell and the metal lead terminal via a copper or nickel underlayer, and a second layer made of copper is formed on the upper surface thereof, A hermetically sealed electronic component comprising a third layer made of nickel or silver.   2. The hermetically sealed electronic component according to claim 1, wherein the first layer comprises a tin-copper alloy layer containing 10 to 20 wt% copper.   3. The hermetic sealed electronic component according to claim 1, wherein a fourth layer of gold or silver is formed on an upper surface of the third layer.

Images