JPS63187906A - Press-in type airtight holder for piezoelectric vibrator - Google Patents

Abstract

PURPOSE:To prevent the generation of lead vapor, and also, to prevent the deterioration of airtightness between a base and a cap by further forming thinly a silver plating layer on the surface of a lead compound plating layer formed on the inside surface of the cap. CONSTITUTION:On the part A being the inside surface of a cap 1 and a junction part to a base, a lead compound plating layer 7 is formed, and also, on its surface, a silver plating layer 6 is formed. The lead compound plating layer 7 consists of lead or a lead alloy whose melting start temperature under one atmospheric pressure is at least >=230 deg.C, and above a temperature at which a press-in type airtight holder is heated at the time of soldering, and formed to thickness of about 10mu. On the other hand, the silver plating layer 6 is formed to thin plating of about 3mu. In such a way, at the time of soldering, etc., the lead compound plating layer does not melt, and airtightness between the base and the cap is held surely. Also, the silver plating layer 6 prevents the generation and scattering of lead compound vapor, and it is prevented that the lead compound vapor adheres to a piezoelectric vibration element.

Description

DETAILED DESCRIPTION OF THE INVENTION A. Field of Industrial Application The present invention relates to a press-fit type airtight retainer for a piezoelectric vibrator that prevents the airtightness and characteristics of the piezoelectric vibrating element from being impaired.

B0 Summary of the Invention The present invention provides a press-fit type airtight retainer for a piezoelectric vibrator in which a cap is press-fitted to cover a space on which a piezoelectric vibrating element is attached, in which lead or a lead alloy is used at least in the inner surface of the cap at the joint with the base. In order to form a lead-based plating layer consisting of a lead-based plating layer, and further to form a silver plating layer on at least the surface of the lead-based plating layer, the plating is melted in the reflow oven and the paper becomes airtight. This prevents it from adhering to the piezoelectric vibrating element.

C1 Prior Art An airtight holder for airtightly enclosing a piezoelectric vibrating element is composed of a paste that holds the piezoelectric vibrating element, and a cap that is placed over the piezoelectric vibrating element and the paste.

As the airtight keeper, press-fit type airtight holders are currently widely used, in which the seal between the paste and the cap is achieved by a soft metal plating layer being fitted together.

This press-fit type airtight retainer has a soft metal layer formed by plating on at least the inner surface of the cap at the joint surface between the base and the cap, and maintains the airtightness inside the cap simply by press-fitting the cap into the base. The following are conventional press-fit airtight retainers:

As shown in FIG. 4 (al), the piezoelectric vibrating element 3 is attached to the inner end of a pair of leads 5 that are provided directly to the pace 4 or insulated and airtightly penetrated through the pace 4. is attached, and a pair of electrodes provided on both sides of the piezoelectric vibrating element 3 are connected to the pair of glueds 5.A solder plating layer 2 is formed on the outer peripheral surface of the base 4.And For example, a cap 1 made of nickel silver as an l:u, Ni alloy and having a solder plating layer 2 formed on its inner and outer surfaces is press-fitted onto a base 4 and covered with a cap 1, as shown in FIG. As shown in the figure, there is a solder plating layer 2 between the base 4 and the cap 1.
sealed through. As the components of this solder plating layer 2, those having a ratio of Sn to PB of 9=1 are generally used.

However, when attaching piezoelectric vibrators and other elements to a printed circuit board and connecting them by soldering, the conventional flow-type method in which, for example, melted solder is spouted onto the back side of the circuit board and soldered has recently been replaced. Increasingly, there is a flow-type method in which the piezoelectric vibrator is housed in an airtight holder and is set on the board together with the solder. When the piezoelectric vibrator passes through a reflow oven together with the board during soldering, the melting start temperature (in-phase line temperature) of the solder plating layer in the airtight holder is around 180°C;
As shown in Figure 5(b), which shows the relationship between heating time and temperature in a reflow oven, heating in a reflow oven is generally performed using a substrate, a piezoelectric vibrator or other element mounted on the substrate, etc. After the parts are heated and maintained at a temperature of about 150° C. for uniform heating, the parts are heated to a temperature for soldering. The heating temperature for soldering in a reflow oven is no.
/200 to 260℃ (depending on the temperature constraints of the elements to be soldered and the selection of the type and composition of the solder used)
In many cases, the temperature is set at a temperature between 215 and 260°C. Therefore, when the piezoelectric vibrator is passed through a reflow oven and soldered to the board, the piezoelectric vibrator is also heated, and the solder plating layer formed on the inner peripheral surface of the cap of the airtight holder melts and scatters, causing the piezoelectric vibrator to melt and scatter. If it adheres to the vibrating element, it may change the vibration frequency or make it impossible to maintain airtightness between the pace and the cap.

As a countermeasure to this problem, we considered using a material with a high melting point as the middle layer for sealing.

-1f, gold with a melting point of 1,063°C was used as the material for the plating layer, and the melting point of the plating layer was much higher than the temperature of the reflow oven, so the plating layer not only melted but also paper was generated. However, the characteristics were favorable. Next, we conducted an experiment using lead with a melting point of 327°C or a lead alloy whose melting start temperature (solidus temperature) is higher than the heating temperature for soldering in a reflow oven. The airtightness between the base and the cap, in which the plating layer was melted, did not deteriorate even after passing through the cap.

D0 Problems to be solved by the invention However, using gold as a plating layer is not suitable for mass production because gold is expensive, and using lead or a lead alloy costs 200~200 yen.
There is a drawback that lead or lead alloy paper is generated in the 60°C glue flow furnace and adheres to the surface of the piezoelectric vibrating element, changing the vibration frequency.

Although it is conceivable to use silver, which has a melting point of 961° C., as the plating layer, silver is somewhat hard and therefore unstable in obtaining airtightness, making it unsatisfactory in terms of production and reliability.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a press-fit type hermetic holder for a piezoelectric vibrator which eliminates the above-mentioned drawbacks when connecting the piezoelectric vibrator by passing it through a reflow oven and soldering it to a board.

Means for Solving Problem E4 The structure of the present invention for achieving the above object is to attach a piezoelectric vibrating element and pass through the lead wire connected to the piezoelectric vibrating element in an airtight manner. In a press-fit type airtight holder for a piezoelectric vibrator, which is configured by press-fitting and covering the element with a cap that holds the element airtight, at least the inner surface of the cap and the joint with the pace is filled with lead or - under atmospheric pressure. forming a lead-based plating layer made of a lead alloy having a melting start temperature of at least 230°C or higher and at least the temperature at which the press-fit airtight retainer is heated during soldering; O F0 action characterized by forming a silver plating layer. As a plating layer of lead or lead alloy, depending on the heating setting temperature in the flow furnace, lead or lead alloy with a melting start temperature of 230°C or higher. Since the plating layer is formed by selecting a lead alloy whose melting start temperature is high considering the heating temperature in the flow furnace, airtightness between the paste and the cap is maintained as described in the prior art section. However, there is a drawback that lead-based paper is generated in the reflow oven and adheres to the piezoelectric vibrating element.In the present invention, the plated layer of lead or lead alloy In addition, a silver plating layer is formed on the surface of the piezoelectric vibrating element to prevent lead-based paper from forming and adhering to the piezoelectric vibrating element, even in a reflow oven. This solves both the problems of maintaining airtightness and preventing metal paper from adhering to the piezoelectric vibrating element.

G. Examples Hereinafter, the present invention will be explained in detail based on examples shown in the drawings.

A lead-based plating layer made of lead or a lead alloy is further formed with a thin silver plating layer on the surface of the cap-based plating layer to prevent the generation of lead paper.

In addition, if a lead-based plating layer is also formed on the surface of the pace, a thin silver plating layer is similarly formed on the surface of the lead-based plating layer, at least in areas other than the outer surface of the press-fit airtight retainer. and prevent the building from becoming contaminated with lead paper.

An enlarged view of part A of the cap 1 shown in FIG.
As shown in Figure 2, only the inner surface of the cap (at least the joint with the base) has a melting start temperature (solidus temperature) of at least 23°C to prevent it from melting even in a flow furnace.
A lead-based plating layer 7 made of a lead alloy having a temperature of 0.06 C or above and above the heating temperature in a reflow oven is formed, and the six sides of the lead-based plating layer 7 are formed, and the silver plating layer 6 has a number of lead paper generation ponds. Since the purpose is to prevent this, a thin plating of about 3 μm is sufficient.

On the other hand, a lead-based plating layer and a silver plating layer may be formed on the outer circumferential surface of the base to which the cap is bonded, in the same manner as on the inner surface of the cap 1.

The lead-based plating layer and the silver plating layer may be formed on the cap at least only on the joint surface with the base, or may be formed on the contact surface of the inner peripheral surface of the cap as shown in FIG. 1 (at). The silver plating layer 6 on the outer circumferential surface of the nail in Figure 1 (bl) may be omitted.

Alternatively, as shown in Fig. 1(C), a piezoelectric vibrator with a piezoelectric vibrating element hermetically housed in an airtight holder configured as described above with a silver plated outer surface may be set on a substrate together with a conductor. , the connection hoop with the circuit on the board is at least 230℃
Since the temperature in the reflow oven is above, the lead or lead-based plating layer 7 does not melt, and the airtightness between the paste and the cap is reliably maintained. Furthermore, since the silver plating layer 6 is formed on the surface of the lead or lead-based plating layer 70, the silver plating layer 6 may become lead-based paper.

This prevents scattering, and the vibration frequency of the piezoelectric vibrating element does not change due to the lead-based paper adhering to the piezoelectric vibrating element.

Next, experimental results using airtight retainers constructed by changing the components of the lead-based plating layer are shown below.

A piezoelectric vibrator in which a piezoelectric vibrating element is housed in an airtight holder with a lead plating layer containing only lead (melting point: 327°C) formed on the inner surface of the cap and a silver plating layer formed on the surface of the lead plating layer. According to the graph of the heating history in the reflow oven shown in FIG. 5, a thermal history of 230°C, 260°C, and 300°C, which exceeds the temperature range in an actual reflow oven, was added. In an actual glue flow furnace, the thermal history is usually only one time, but in the experiment, the thermal history was repeated five times. As a result, the airtightness was completely maintained in all cases, and the vibration frequency was still 300% as shown in Figure 3 K (a).
Obtained with the addition of thermal history in °C. In the figure, the horizontal axis shows the number of times the thermal history is applied, and the vertical axis shows the frequency fluctuation of the piezoelectric vibrating element.Changes in the vibration frequency do not occur until the second time, but only slightly after the third time. I understand that. Similarly, when heat histories of 230°C and 260°C were added, no fluctuations in vibration frequency were observed until the second time, and from the third time onwards, the fluctuation was even more pronounced than when a heat history of 300°C was applied. It was very small.

Next, add approximately 12% by weight of tin (Sn) to the lead.
- melting onset temperature under atmospheric pressure (101,325 pa) (
A piezoelectric vibrator in which a piezoelectric vibrating element is housed in an airtight holder with a lead-based plating layer formed on the inner surface of the cap and a silver plating layer formed on the surface of the lead-based plating layer. 23 according to the graph shown in Figure 5.
After repeating the thermal history at 0° C. 5 times, no abnormality occurred with the same results as above.

Finally, about 14% by weight of tin (Sn) is added to the lead.
A lead-based middle layer of an alloy with a melting start temperature (common phase temperature) of 230°C under atmospheric pressure (0,101 megapascals) is formed on the inner surface of the middle layer, and a silver plating layer is formed on the surface of the lead-based plating layer. 2 according to the graph shown in FIG.
When a thermal history of 00"C was repeatedly applied five times, the same results as above were obtained and no abnormality occurred.

A piezoelectric vibrator containing a piezoelectric vibrating element in an airtight holder with only a plating layer of lead or lead alloy formed inside the cap as shown in the prior art section was repeatedly heated five times at various temperatures from 200 to 260°C. When given a thermal history of As shown, it fluctuates greatly.

In this way, by forming at least a lead-based plating layer and a silver plating layer on the joint surface of the cap with the Kel base, a lead-based plating layer and a silver plating layer are not necessarily formed on the outer peripheral surface of the υ base. Even if this is not done, the airtightness of the airtight holder can be maintained and the paper can be prevented from scattering. On the other hand, if a lead-based plating layer and a silver plating layer are formed only on the outer circumferential surface of the base, but not on the inner surface of the cap, it is difficult to maintain stable airtightness through press-fitting. .

As a component of the lead alloy forming the plating layer, in addition to the above-mentioned alloy of lead and tin, an alloy of lead and tin (Sb) or the like may be used.

As described in detail of the H0 invention, according to the present invention, at least the inner surface of the cap and the joint with the base in the airtight holder for sealingly housing a piezoelectric vibrating element therein to form a piezoelectric vibrator. Lead or melting onset temperature (phase line temperature) at -atmospheric pressure (0,101 megapascals) of at least 230°C
As described above, a lead-based plating layer made of a lead alloy is formed at a temperature higher than the temperature at which the press-fit airtight retainer is heated during soldering 7, and a silver plating layer is further formed on at least the surface of the lead-based plating layer. Even if the piezoelectric vibrator assembled on the board passes through a soldering furnace for soldering, metal paper is generated from the plating eyebrows and adheres to the piezoelectric vibrator, changing the vibration frequency. Do not let the airtightness between the parts become poor.

[Brief explanation of the drawing]

Figures 1 and 2 show an embodiment of the airtight holder for a piezoelectric vibrator according to the present invention. The cross-sectional view, Figure 1g3, is a graph showing the relationship between the number of times given to the airtight retainer and the frequency fluctuation, and Figure 4 relates to the hermetic retainer of a conventional piezoelectric vibrator, and Figure flX4 (Al is a graph with a cap on The previous configuration diagram, Figure 4 (bl is the configuration diagram after the cap is covered, Figure 4)
Figure (ci is an enlarged view of part B of Figure 4 (BL), Figure 5 is a graph showing the relationship between heating time and temperature in a flow furnace.]... Cap, 3... Piezoelectric vibrating element , 4...Base, 5...Lead wire, 6...Silver plating, 7...
Lead-based plating. Figure 1 Figure 2 Part A Hirodaiyo (Fubiuchi) Figure 2 Figure 3 Yai, 7-7° cross-sectional view 豐#! 1 for each turn 1 table for the number of Sken Hi's Seki I 1 Ho 4 Graph 4 Figure 2 Enclosure greeting Figure 5: Kiri (paulownia)

Claims (1)

[Claims] A press-fit type airtight piezoelectric vibrator consisting of a base on which a piezoelectric vibrating element is attached and a lead wire connected to the piezoelectric vibrating element hermetically passes through, and a cap that holds the piezoelectric vibrating element airtightly fitted and covered. In the retainer, at least the inner surface of the cap and the joint with the base include lead or a material having a melting start temperature of at least 23°C under one atmospheric pressure.
A lead-based plating layer made of a lead alloy is formed at a temperature of 0° C. or higher and at a temperature higher than the temperature at which the press-fit airtight retainer is heated during soldering, and at least a portion other than the outer surface side of the press-fit hermetic retainer is formed. A press-fit type airtight holder for a piezoelectric vibrator, characterized in that a silver plating layer is further formed on the surface of the lead-based plating layer.