JP2008103380A - Hermetically sealed electronic component - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a hermetically sealed electronic component which is lead-free and excellent in heat resistance, and to provide a hermetically sealed electronic component without causing the deterioration of airtightness and connectivity after press-fitting. <P>SOLUTION: The electronic component is composed of a base 1 having insulating glass 13 filled in a metallic shell 10 and lead terminals 11, 12 piercing and fixed to the insulating glass; an electronic element 2 mounted to the base; and a cap 3 for hermetically sealing the electronic element by being press-fitted into the base, wherein a copper layer is formed on at least the metallic shell and the lead terminals, a nickel layer is formed on the copper layer and an ultra-thin gold layer is formed on the nickel layer. The nickel layer is formed on at least a fitting region with the base in the cap, and a soft metal layer is formed on only the fitting region with the base on the nickel layer. <P>COPYRIGHT: (C)2008,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 can cope with lead-free and has heat resistance.

  A hermetic seal configuration in which a metal shell is filled with insulating glass, and a lead terminal is fixed to the insulating glass with a lead terminal penetrated, and a cylindrical cap is press-fitted into the hermetic base is, for example, a cylinder type container. It is commonly used for housed tuning fork crystal units. 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 42 alloy or Kovar, a nickel or copper layer is formed on the surface by means such as plating, and a tin layer is further formed on the surface. is there. Further, the cap was made of a copper-nickel alloy such as white and white, and solder of a lead 1: tin 9 ratio was formed at least in a region pressed against the base. With the above configuration, the tin on the base side and the solder layer on the cap side are soft and excellent in ductility. Therefore, when the two metals are press-fitted in a tightly adhered state, they are plastically deformed to facilitate press-fitting.

  By the way, in recent years, it has become necessary to cope with a reflow soldering environment. That is, in reflow soldering, mounting on a mounting board is performed in a high-temperature environment such as 240 to 270 ° C., so that the metal structure of the press-fitted portion is also required to have heat resistance.

  In order to meet such demands, for example, lead 9: tin 1 and solder having a higher melting point and a higher melting point have 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. It was.

  A configuration taking such lead-free into consideration is disclosed in Japanese Patent Laid-Open No. 2005-191558 (Patent Document 1). In Patent Document 1, the surfaces of a base (airtight terminal) including a lead terminal and a cap (sealing tube) are each plated with copper, a nickel layer is formed on the copper layer, and the nickel layer is further formed. An ultrathin gold layer is formed on top. With this configuration, since the melting temperature of copper is high, the hermetic terminal and the sealing tube after plating can be processed at a high temperature, and can be applied to a so-called heat-resistant specification product, corresponding to the above-described reflow soldering environment. be able to. In addition, a configuration that suppresses the harmful effects of copper oxidation has been proposed.

  However, in such a configuration, the hardness of the entire plating is high, and if the fitting is loose when press-fitting and sealing, the base glass may be cracked and the base glass may be cracked. There was a risk of problems such as lowering of the temperature.

JP-A-2005-191558

  The present invention has been made in order to solve the above-described problems. It is an object of the present invention to provide an electronic component that can be lead-free and perform hermetic sealing with excellent heat resistance. Another object of the present invention is to provide an electronic component that performs hermetic sealing without deteriorating performance and connectivity.

  In order to achieve the above object, as shown in claim 1, a base made of a metal shell filled with insulating glass and lead terminals penetrated and fixed to the insulating glass, and an electronic device mounted on the base And a cap that hermetically seals the electronic element by being press-fitted into the base, a copper layer is formed on at least the metal shell and the lead terminal, and a nickel layer is formed on the copper layer, Further, in an electronic component in which an ultrathin gold layer is formed on the nickel layer, a nickel layer is formed at least on a fitting region of the inner surface of the cap with the base, and the base on the nickel layer is formed. A soft metal layer is formed only in the fitting region.

  Since the copper layer is excellent in ductility, it is possible to improve the hermetic sealing performance (hermetic sealing performance) when the cap is hermetically sealed by press fitting. The nickel layer formed on the copper layer has a function of a barrier layer. That is, the nickel layer suppresses copper oxidation and suppresses diffusion between the gold layer formed in the upper layer and the copper layer located in the lower layer. If an alloy layer of gold and copper is formed, copper may diffuse to the surface and form an oxide film. In such a case, the airtightness and external connectivity deteriorated as pointed out in the conventional problems. However, the occurrence of such a problem can be suppressed by the presence of the nickel layer. In addition, the gold layer improves the bondability when brazing the inside and outside of the base. That is, in the base, the electronic element is joined with a brazing material such as solder or lead-free solder, but this joining property is improved. Also, in connection with the outside of the base, for example, in brazing to a mounting substrate, the bondability is improved, and the bonding strength and the bonding reliability are improved.

  In addition, since a nickel layer is formed at least on the inner surface of the cap with the base and the soft metal layer is formed only on the nickel layer on the fitting region, the soft metal is formed. The adverse effect of the layer due to the molten gas is eliminated, the press-fitting operation can be performed smoothly, and the airtightness can be improved. As a result, the electrical characteristics of the electronic component element are not degraded. When a crystal resonator is used as the electronic component element, the series resonance resistance value is not lowered and the aging characteristics are not lowered.

  Furthermore, the present invention also proposes plating formed on the cap side, and since a nickel layer is formed at least on the fitting area of the inner surface of the cap with the base, the cap is pressed into the base. The hermetic sealing performance can be improved. The gold layer formed on the upper surface of the base improves the slippage during press-fitting, and the nickel layer and soft metal layer of the cap and the gold layer conform to each other, and in combination with the ductility of the copper layer, a good hermetic sealing performance is obtained. Can do.

  In the above configuration, a tin-based metal layer may be formed as the soft metal layer. The tin-based metal layer has a relatively soft property, and coupled with the ductility of the copper layer described above, further improves the hermetic sealing performance (hermetic sealing performance) when the cap is hermetically sealed by press fitting. be able to. The press-fitting work can be performed smoothly (improvement of press-fitting work performance), and the airtightness can be improved.

  Since the tin-based soft metal layer is formed to facilitate press-fitting, the thickness does not need to be increased more than necessary, and may be, for example, about 1 to 10 μm. If it is too thin, the hermetic sealing performance may be reduced, and if it is too thick, the press-fit property is reduced. The tin-based metal layer is more preferably lead-free such as tin or tin copper.

  According to the hermetic sealing type electronic component according to the present invention, lead can be provided without using lead in the base and the cap. In addition, since the metal material used for the base is a material that can sufficiently cope with heating during reflow soldering, an electronic component that performs hermetic sealing with excellent heat resistance can be obtained. In addition, it is a structure that sufficiently acts on the ductility of copper and suppresses oxidation of the surface, so that the airtightness after press-fitting a cap into the base is improved, and the bondability of the lead terminals of the base is reduced. A hermetic sealed electronic component can be obtained. Also, a nickel layer is formed at least on the inner surface of the cap with the base, and a soft metal layer is formed only on the base on the nickel layer. It is possible to obtain a hermetically sealed electronic component that is smoothly performed and has improved hermeticity.

Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.
Embodiments of the present invention will be described with reference to the drawings. FIG. 1 is an exploded internal structure of a tuning fork crystal unit, FIG. 2 is a partially enlarged view of a base portion of FIG. 1, and FIG. 3 is a partially enlarged view of a lead terminal portion. 2 and 3, only one lead terminal portion is shown.

  The base 1 includes a metal shell 10, an insulating glass 13 filled in the shell, and lead terminals 11 and 12 that are fixed to the insulating glass 13 so as to penetrate therethrough. 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. A copper layer 101 is formed on the base surface, that is, the Kovar surfaces of the shell 10 and the lead terminals 11 and 12 by electrolytic plating. The copper plating can be composed of one layer by copper cyanide plating, etc. However, since Kovar is an iron-based alloy, a metal substitution reaction of iron and copper occurs when copper plating is performed, and the adhesion of the plating film Reduction may occur.

  For this reason, as shown in FIG. 3, the film strength can be improved by forming the strike copper plating (thin film copper layer) 101a in the lower layer and the copper sulfate plating (thick film copper layer) 101b in the upper layer. More specifically, the entire base to be plated is immersed in a low-concentration copper cyanide bath or copper pyrophosphate bath, and a large current is applied in a short time. Thereby, a high-density uniform thin film copper layer 101a can be obtained.

  Next, a thick copper layer 101b is formed on the thin copper layer by copper sulfate plating. In copper sulfate plating, the base after strike plating is put into a copper sulfate barrel bath, and the barrel is rotated, so that the opportunities for electrolytic plating can be averaged, and a large number of bases can be plated once. it can. In order not to impair the ductility of the thick copper layer, it is not preferable to add a brightener to the copper sulfate plating bath, and it is preferable to perform plating in an environment in which impurities in the plating bath are removed as much as possible. .

  A nickel layer 102 is formed on the copper layer 101. As described above, the nickel layer 102 has slightly different performance requirements for the nickel layer formed on the shell portion of the base and the lead terminal portion. That is, the base shell portion is required to have a function as a barrier film between the lower copper layer 101 and the gold layer 103 formed thereon, and the lead terminal portion brazed to the mounting substrate has good film strength. Things are required.

Since nickel is basically hard and inferior in ductility, it is preferable that the fitting portion with the cap is formed as thin as possible while ensuring the barrier function as described above. However, since the lead terminal portion is brazed to the external terminal electrode or the like, a film strength that can withstand it is required. Therefore, a thin nickel layer with good film strength is required. In the present embodiment, a strike nickel plating film having a thickness of about 0.5 to 1 μm is formed. More specifically, the base on which the copper layer is formed is immersed in a room temperature wood bath made of nickel chloride (NiCl ₂ · 6H ₂ O) and hydrochloric acid (HCl), and electroplating is performed. On the copper surface of the base, the oxide film is reduced by hydrogen gas and nickel is deposited. As a result, nickel plating can be formed while removing an oxide film such as copper oxide on the surface.

  The nickel layer 102 obtained in this way is a thin film having a barrier function between the copper layer 101 and the gold layer 103 in the shell portion of the base main body. The nickel film is broken by this stress, and the underlying copper layer is exposed relatively smoothly, and the copper ductility necessary for press-fitting can be made to function. Moreover, in the lead terminal portion, film strength corresponding to brazing can be obtained.

  The nickel layer 102 is not limited to strike nickel plating, but may be plated by a commonly used watt bath. In this case, no brightener is used, the amount used is suppressed, or the pH value is set to 2. It is preferable to ensure ductility by devising such as lowering to about 3 or the like.

  An ultrathin gold layer 103 is formed on the upper surface of the nickel layer 102 to a thickness of 0.1 to 0.8 μm by a technique such as flash plating. These ultrathin gold layers may be formed by barrel plating. Barrel plating is excellent in mass productivity because electrolytic plating can be efficiently performed by immersing the barrel into which the film formation target is put in a plating bath and rotating the barrel, and batch processing is possible. ing. It is to be noted that barrel plating is also used in the formation of the thin film copper layer 101a by the strike copper plating and the thick film copper layer 101b by the copper sulfate plating and the formation of the nickel layer 102 by the strike nickel plating, the nickel plating by the watt bath, or the like. From the viewpoint of improving productivity. By forming the gold layer 103, the inner side 11a, 12a of the lead terminal contributes to the improvement of wettability and bondability when an electronic element such as a crystal vibrating piece is joined by a brazing material, and the outer side 11b, 12b Contributes to improvement of wettability and bondability in brazing with a mounting board. By the above plating treatment, the above metal layers are formed on the surface of the shell 10 and the lead terminals 11 and 12 of the base 1.

  In addition, although the above-mentioned nickel layer showed the example using electrolytic plating, such as strike plating, you may apply electroless nickel plating. For example, the electroless nickel plating film may be formed by immersing the base on which the copper layer is formed in a plating bath containing a reducing agent such as nickel ion or sodium hypophosphite. As described above, electroless nickel plating has good plating film coverage and can provide a uniform film thickness. In addition, even if the film thickness is thin, there is an advantage that good film strength can be obtained. Therefore, the electroless nickel layer is a thin film having a barrier function between the copper layer and the gold layer in the shell portion of the base body, so that the nickel film is broken during press-fitting and the exposure of the underlying copper layer is relatively smooth. It is possible to make the copper ductility necessary for press-fitting work. Moreover, in the lead terminal portion, even if it is thin, film strength corresponding to brazing can be obtained. Therefore, the airtightness and the brazing joining ability inside and outside the base can be improved.

  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 solder or lead-free 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 brazing material (not shown) which is mounted in a state where the base 21 of the tuning-fork type crystal vibrating piece is upright on the lead terminal inner side 11a, 12a of the base and in contact with the lead terminal and is supplied to the lead terminal in advance. Thus, the base electrode and the lead terminal are electrically and mechanically connected. Since the inner layer 11a, 12a has a gold layer 103 formed on the surface thereof, the bondability with the brazing material is improved.

  The cap 3 is made of a metal material such as white (Cu—Ni—Zn alloy) and has a bottomed cylindrical shape. A nickel layer 31 is formed on the outer and inner peripheral surfaces of the cap 3 by means such as plating. The nickel layer 31 uses a nickel plating bath based on a watt bath to obtain a nickel film thickness of 1 to 5 μm. As described above, the nickel layer preferably has ductility by suppressing the use of a brightener.

  A tin layer as the soft metal layer 321 is formed with a thickness of about 1 to 10 μm, for example, only on the upper surface of the nickel layer 31 on the inner peripheral surface of the cap 3 and only in the fitting region 32 with the base 1. . The tin layer as the soft metal layer can be formed by electroless plating. Moreover, it can also form by apply | coating a tin paste (resin paste containing tin), forming by the method of printing, and baking. By the above plating treatment, the metal layers are formed on the outer periphery and the inner peripheral surface of the cap 3.

In addition, by forming the thickness of the gold plating 103 of the above embodiment and the thickness of the tin layer as the soft metal layer 321 (thickness of about 1 to 10 μm), melting the tin after hermetic sealing, Since the gold of the base and the tin layer of the cap are made of a gold-tin alloy, the heat resistance of the sealing portion can be dramatically improved. Moreover, although the said nickel layer was formed in the outer periphery and inner peripheral surface of the said cap, you may form only in the fitting area | region with the said base at least on the inner surface of the said cap. In this case, gas generation can be minimized. Further, as the soft metal layer 321 in the fitting region of the inner peripheral surface of the cap, a tin copper layer (tin: copper = 99: 1) may be formed with a thickness of about 1 to 10 μm instead of the tin layer. Good. Further, a tin-gold layer (tin: gold = 7: 3), a tin-silver layer (tin: silver = 24: 1), or zinc may be used, or tin, tin-copper, tin-gold, tin-silver, copper, zinc A multilayer structure in which these are appropriately combined may be used. These soft metal layers 321 are tin-based metal layers that are soft and optimal for airtight sealing, and are preferably lead-free. 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. The base and the cap are brought into tight contact with each other by the press-fitting and hermetically sealed, and the inside of the cap is kept in a vacuum state.

  As described above, an electronic component in which the surfaces of the inner side and the outer side of the base 1 and the lead terminals 11 and 12 are formed in the order of the copper layer 101, the nickel layer 102, and the ultrathin gold layer 103 can be obtained. As a result, smooth mounting can be performed without lowering the solderability to the mounting substrate by solder or lead-free solder. The brazing material that joins the electronic element to the lead terminal and the brazing material that joins the electronic component to the mounting board are also lead-free, and by using a material with excellent heat resistance, lead-free and heat-resistant as a total of the electronic component. The electronic component corresponding to sex can be obtained. Further, a nickel layer 31 is formed in at least the fitting region 32 of the inner surface of the cap 3 with the base 1, and a tin layer as the soft metal layer 321 is formed only in the fitting region 32 with the base on the nickel layer. Therefore, it is possible to obtain a hermetic-sealed electronic component in which the press-fitting operation is smoothly performed and the hermeticity is improved.

  The present invention is not limited to the above embodiment, and various modifications can be given. For example, in the above configuration, a tin layer may be formed instead of the gold layer formed on the uppermost surface of the base. The tin layer may be formed on the entire exposed metal surface of the base on which the nickel layer is formed, or may be formed only on the fitting surface with the base cap. When forming the whole, the film formation method by plating is suitable, and the film formation of only the fitting surface is formed by applying tin paste (resin paste containing tin) or printing, and firing It is sufficient to adopt a method to do this. A gold tin layer may be used instead of the tin layer.

  In the above embodiment, the tuning fork type crystal resonator that performs vacuum sealing is exemplified. However, the tuning fork type crystal resonator can be applied to a crystal resonator of another vibration mode in an inert gas atmosphere. It is also possible to apply to hermetic sealing.

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 of FIG. The elements on larger scale of the lead terminal part of FIG.

Explanation of symbols

1 Base 10 Shell 11, 12 Lead Terminal 13 Insulating Glass 101 Copper Layer 102 Nickel Layer 103, 106 Gold Layer 31 Nickel Layer 321 Soft Metal Layer

Claims (1)

A metal shell is filled with insulating glass, and a lead terminal is fixed through the insulating glass, an electronic element mounted on the base, and the electronic element is hermetically sealed by being press-fitted into the base. An electron in which a copper layer is formed on at least the metal shell and the lead terminal, a nickel layer is formed on the copper layer, and an ultrathin gold layer is formed on the nickel layer. In the component, a nickel layer is formed in at least a fitting region of the inner surface of the cap with the base, and a soft metal layer is formed only in the fitting region with the base on the nickel layer. Airtight sealed electronic components.

Images