JP2009141455A - Crystal device for surface mounting - Google Patents

Abstract

A surface mount device that prevents solder cracks during surface mounting is provided.
A container main body having a rectangular shape in which at least a pair of external terminals 3 are mounted on an outer bottom surface, and the external terminals 3 are fixed to a set substrate by soldering. 1, the external terminal 3 includes a plurality of first divided terminals 10 (a, b, c, d) divided into a plurality of first divided terminals 10 (a, b, Between c and d), the substrate body 1 is exposed.
[Selection] Figure 1

Description

  The present invention relates to a surface mount crystal device (hereinafter referred to as a surface mount device) in the technical field, and more particularly to an external terminal that prevents solder cracks after surface mount.

(Background of the Invention)
Surface mount devices, such as surface mount resonators, are small and light, so they are taken into an oscillation circuit as a frequency and time reference source and incorporated in various electronic devices. In recent years, in particular for in-vehicle use, which has a large change in temperature environment, it is required to prevent solder cracking due to a difference in thermal expansion coefficient accompanying a change with time (heat cycle).

(Example of conventional technology)
FIG. 6 and FIG. 7 are diagrams of a surface-mounted vibrator for explaining a conventional example. Each figure (a) is a sectional view, (b) is a bottom view, and (c) is a plan view of a crystal piece. FIG.

  Surface-mounted vibrators are generally of two-terminal type (FIG. 6) and four-terminal type (FIG. 7). In this example, a quartz container body 1 is formed in a rectangular container body 1 made of a laminated ceramic. The piece 2 is accommodated. In the case of the two-terminal type, the inner bottom surface of the container body 1 has crystal terminals (not shown) at both end portions in the length direction, and is connected to the external terminals 3 on the outer bottom surface through through holes (end surface electrodes) on the laminated surface and side surfaces. Connecting. And the cover 4 which consists of ceramics etc. is joined to the opening end surface of the container main body 1 by glass sealing, and the crystal piece 2 is sealed and sealed.

  In the case of the 4-terminal type, the inner bottom surface of the container body 1 has crystal terminals (not shown) on both sides of one end in the length direction, and extends as, for example, a pair of diagonal portions as external terminals 3 through the laminated surface. . Then, a cover 4 made of metal by seam welding, for example, is joined to the opening end surface of the container body 1 to hermetically enclose the crystal piece 2. The other pair of diagonal portions of the container body 1 have external terminals 3 as ground terminals electrically connected to the cover 4.

  The quartz crystal piece 2 has excitation electrodes 5a on both main surfaces. In the case of the two-terminal type, the extraction electrodes 5b are extended at both ends, and in the case of the four-terminal type, the extraction electrodes 5b are extended on both sides of the one end. Then, the outer peripheral portion of the crystal piece 2 where the extraction electrode 5 b extends is fixed to the crystal terminals on both ends of the container body 1 or on both sides of the one end by the conductive adhesive 6.

These two-terminal and four-terminal surface mount vibrators are solders using, for example, cream solder by printing or the like on a set substrate 7 (not shown) of an electronic device for automobiles as shown in FIG. Mounted (fixed) by reflow. Reference numeral 7 in the figure includes molten solder by heating, and the solder includes not only cream solder but also normal solder and lead-free solder.
Japanese Patent No. 3685683 (Japanese Patent Laid-Open No. 2001-308490)

(Problems of conventional technology)
However, the surface-mounted vibrator having the above-described configuration has a problem of causing a solder crack based on a change with time due to a thermal expansion coefficient difference between the container body (ceramic) 1 of the surface-mounted vibrator and the set substrate 7. In these cases, for example, in the case of the two-terminal type, as indicated by arrows AA and BB in FIG. 9A, solder cracks are formed from the outer periphery in the diagonal direction of the external terminals 3 on the opposite ends. Arise.

  In the four-terminal type, solder cracks are generated from the outer periphery in each diagonal direction arranged in two diagonal directions (four corners) (FIG. 9B). These are all due to the fact that the stress in the diagonal direction is the largest, and usually the stress concentrates on any one of the external terminals 3 and causes solder cracks from the outer periphery. As a result, for example, the external terminals 3 are peeled off from the set substrate 7 or poorly connected.

(Object of invention)
It is an object of the present invention to provide a surface mount device that prevents solder cracks during surface mounting.

(Points of interest)
In the present invention, the occurrence of solder cracks was further considered, and it was found that a liquid flux (not shown) impregnated (mixed) in the solder further increases the solder cracks (cracks). That is, the flux expands due to heat at the time of melting the solder when mounted on the set substrate 7 to form bubbles and the like. And it hardens | cures, without forming a fine void (a defect, a cavity) inside solder, without fully defoaming.

  Therefore, when the voids are uniformly formed in the solder after mounting on the set substrate, the strength of the outer peripheral corner portion itself having the greatest stress is reduced, and cracks due to heat cycles are likely to occur. And the small crack which arose from the outer periphery corner | angular part advances along a void, and enlarges crack itself (solder crack). For this reason, the present invention has focused on reducing voids due to flux.

(Solution)
According to the present invention, as shown in the claims (Claim 1), at least a crystal piece is mounted and hermetically sealed, and at least a pair of external terminals are provided on the outer bottom surface, and the external terminals with respect to the set substrate In the quartz device for surface mounting provided with a rectangular container body fixed by solder, the external terminal comprises a first divided terminal divided into a plurality of parts, and the space between the first divided terminals is between the first divided terminals. The substrate is exposed.

  With such a configuration, when the surface-mounted device is mounted on the set substrate, the solder adheres only on the divided terminals, and the solder does not adhere to the outer bottom surface where the base of the container body between the divided terminals is exposed. Therefore, a gap corresponding to the thickness of the mounting terminal (divided terminal) is generated between the divided terminals between the outer bottom surface of the container body and the set substrate.

  Thereby, bubbles generated during melting of the solder are pushed out into the gap between the divided terminals by, for example, the weight of the surface mount device. And it discharge | releases from the outer periphery of a mounting terminal through the division path used as the gap | interval between division terminals. Therefore, since the amount of voids based on the bubbles is reduced, the occurrence of cracks (solder cracks) can be prevented.

(Embodiment section)
According to a second aspect of the present invention, in the first aspect, a second divided terminal is provided on the first divided terminal which is a central portion of the external terminal. According to this, the bubble at the time of solder melting can be discharged | emitted from an outer peripheral part with the clearance gap between 1st division | segmentation terminals similarly to Claim 1. And here, a 2nd division terminal is provided on the 1st division terminal used as a center part.

  Therefore, when the surface mount vibrator is mounted on the set substrate, the thickness of the molten solder on the second divided terminal is smaller than that on the first divided terminal. Therefore, the pressure applied to the molten solder on the second divided terminal by the dead weight of the surface mount vibrator becomes the largest. Thereby, the bubble by the flux at the time of solder melting is extruded to the molten solder on the second layer with a small applied pressure.

  As the temperature rises, bubbles grow and are discharged (defoamed) from the outer periphery of the second divided terminal into the atmosphere having a low atmospheric pressure. Therefore, after the molten solder is hardened, voids due to the bubbles of the flux in the solder are reduced as a whole, particularly in the central region, so that cracking of the solder can be further prevented.

  In the third aspect of the present invention, in the first aspect, the external terminals are formed at two positions or at four corners on both ends of the outer bottom surface of the container body. As a result, the configuration of the external terminals is clarified and solder cracks (cracks) generated from the outer peripheral corners in the diagonal direction are prevented.

(Relationship with Patent Document 1)
In Patent Document 1, a second layer divided in two dimensions is shown on the first layer of the external terminal in order to increase the connection strength. However, the first layer here is not divided and the entire surface is fixed to the bottom of the container body.

  On the other hand, in the present invention, the mounting terminal corresponding to the first layer of Patent Document 1 is divided into the first divided terminals, and the outer bottom surface of the container body is exposed between the first divided terminals. Therefore, the purpose and configuration in Patent Document 1 that increase the electrode area and increase the fixing strength are essentially different.

(First embodiment)
FIG. 1 is a view of a quartz crystal device, for example, a surface-mounted vibrator, for explaining an embodiment of the present invention. FIG. 1 (a) is a sectional view and FIG. 1 (b) is a bottom view. In addition, the same number is attached | subjected to the same part as a prior art example, and the description is simplified or abbreviate | omitted.

  In this example, the surface mount vibrator is of a two-terminal type, and as described above, the excitation electrode 5a is connected to a crystal terminal (not shown) on the inner bottom surface on both sides of one end of the rectangular container body 1 made of a laminated ceramic. The outer peripheral portions of both ends of the crystal piece 2 from which the extraction electrode 5 b extends are fixed by the conductive adhesive 6. The outer bottom surface on both ends of the container body 1 has external terminals 3 through a laminated surface connected to a crystal terminal and through holes on the side surfaces, and a cover 4 made of glass sealing is joined to the open end surface.

  In this embodiment, each external terminal 3 on the outer bottom surface of the container body 1 is provided with a cross-shaped dividing path 9 that crosses the center line of the long side and the short side, and is divided into four divided upper, lower, left and right divided terminals. 10 (abcd). These divided terminals 10 are integrally fired together with the container body 1 by using, for example, a base electrode with Cr (chrome) by printing. Then, Ni (nickel) and Au (gold) are formed on the surface of the chromium by electroplating or the like.

  In such a case, when the surface-mounted vibrator is mounted on the set substrate 7, the cream solder 8 previously applied to the set substrate 7 by printing or the like is heated in a high heat path. The cream solder 8 is impregnated with flux (see FIG. 8 above). In this case, the molten solder 8 by heating adheres to each divided terminal 10 of the external terminal 3, but does not adhere to the outer bottom surface where the ceramic base between the divided terminals 10 is exposed. In the molten solder 8, first, in the initial heating state, a gas containing air in the flux expands to generate a large amount of bubbles.

  Next, the molten solder 8 on the external terminal 3 between the set substrate 7 is pressed by the weight of the surface mount vibrator. The bubbles generated in the molten solder 8 are pushed out to the dividing path 9 between the dividing terminals 10 and are discharged from the outer periphery of the external terminal through the dividing path 9. Finally, the molten solder 8 is cured as the temperature decreases, and becomes a solder 8 with few voids based on bubbles.

  For this reason, the surface mount vibrator according to the present embodiment is the solder 8 with few voids even if there is a heat cycle due to a change over time after being mounted on the set substrate 7, so that the external terminal 3 having the greatest stress. The occurrence of cracks from the outer peripheral corners in the diagonal direction is prevented. In addition, even if a crack occurs in the outer peripheral corner, it is suppressed from proceeding to the inside, and as a result, a solder crack can be prevented.

(Second Embodiment)
FIG. 2 is a bottom view of a surface-mounted vibrator for explaining a second embodiment of the present invention. In addition, the same number is given to the same part as 1st Embodiment, The description is abbreviate | omitted or simplified.

  As described above, the surface-mounted vibrator is provided in the central portion on both ends in the long side direction, with the external terminal 3 of the container body 1 being two terminals including the first divided terminal 10 (abcd). In the second embodiment, the second divided terminal 11 (abcd) is provided on the surface of the first divided terminal 10 (abcd) that is the center of the external terminal 3. These form the base electrode of the second split terminal 11 on the base electrode of the first split terminal 10 by printing. And after baking integrally with the container main body 1, Ni and Au are plated in order and formed.

  In such a case, as in the first embodiment, bubbles generated in the molten solder 8 at the time of solder reflow are discharged from the outer periphery of the external terminal 3 through the dividing path 9 between the first dividing terminals 10 (abcd). Is done. Here, the molten solder 8 is pressed from the surface of the second divided terminal 11 by the weight of the surface-mounted vibrator. In this case, the molten solder 8 on the surface of the second divided terminal 11 is smaller in thickness than that on the first divided terminal 10, and the pressure applied by its own weight is large. The molten solder 8 on the first divided terminal 10 is thick, and the applied pressure is suppressed by the second divided terminal 11.

  Therefore, the bubbles of the molten solder 8 on the surface of the first divided terminal 10 move to the molten solder 8 on the surface of the second divided terminal 11 and are further discharged from the first divided terminal 10 to the outside air with a low pressure. Is done. From these, the amount of bubbles to be discharged can be increased together with the bubbles to be discharged through the dividing path 9 of the first divided terminal 10. Therefore, since voids based on bubbles are reduced, the occurrence and expansion of cracks can be prevented and the occurrence of solder cracks can be suppressed.

(Other matters)
In the above embodiment, since the divided terminals 10 (abcd) are separated by the dividing path 9, for example, when Ni or Au is provided by electroplating, it is necessary to connect the divided terminals 10 (abcd) in common. . Therefore, for example, taking the first embodiment (FIG. 1) as an example, as shown in FIG. 5 (partial bottom view), the divided terminals 10 (ab) are connected in common by end face electrodes by through holes.

  The divided terminals 10 (ad) and 10 (bc) are commonly connected by a conductive path 12 outside the area of the external terminal 3. This facilitates electroplating. In addition, although connected by the conductive path 12 on the outer bottom surface, the connection is not limited to this, and for example, a common connection can be made on a laminated surface by a through hole.

  Although the surface mount vibrator as the crystal device has been described as a two-terminal type, the present invention can be similarly applied to a four-terminal type as shown in FIG. 3 (bottom view). In this case, for example, as shown in FIG. 4, the through hole from the laminated surface is the same not only for the side surface described above but also for the corner portion.

  Further, the quartz device is not limited to the surface mount vibrator, but can be applied to a surface mount oscillator in which the IC chip and the quartz piece 2 are integrally accommodated. In this case, the external terminals 3 are four terminals such as a power source, a ground, and an output, and the bottom view is the same as those shown in FIGS.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1A is a cross-sectional view and FIG. 1B is a bottom view of a quartz crystal device, for example, a surface-mounted oscillator, for explaining a first embodiment of the present invention. It is a bottom view of the surface mount vibrator explaining the second embodiment of the present invention. It is a bottom view of the surface mount vibrator explaining another example of the present invention. FIG. 10 is a bottom view of a surface-mounted vibrator for explaining still another example of the present invention. It is a partial bottom view of the surface mount vibrator for supplementarily explaining the embodiment of the present invention. 1A and 1B are diagrams of a surface-mount resonator for explaining a conventional example, in which FIG. 1A is a sectional view, FIG. 1B is a bottom view, and FIG. 1C is a plan view of a crystal piece. 1A and 1B are diagrams of a surface-mount resonator for explaining a conventional example, in which FIG. 1A is a sectional view, FIG. 1B is a bottom view, and FIG. 1C is a plan view of a crystal piece. It is the attachment side view of the surface mount moving element with respect to the set board | substrate explaining a prior art example. It is a figure explaining one prior art example, and the same figure (ab) is a bottom view of the surface mount vibrator | oscillator in the state to which the solder was applied.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 Container body, 2 Crystal piece, 3 External terminal, 4 Cover, 5 Excitation and extraction electrode, 6 Conductive adhesive, 7 Set board, 8 Solder, 9 Dividing path, 10 1st dividing terminal, 11 2nd dividing terminal, 12 Conductive path.

Claims (3)

  At least a crystal piece is mounted and hermetically sealed, and has at least a pair of external terminals on the outer bottom surface, and includes a rectangular container body in which the external terminals are fixed to a set substrate by soldering. In the crystal device, the external terminal includes a plurality of first divided terminals, and the base body of the container body is exposed between the first divided terminals.   2. The surface-mount crystal device according to claim 1, wherein a second divided terminal is provided on the first divided terminal which is a central portion of the external terminal.   2. The surface-mount crystal device according to claim 1, wherein the external terminals are formed at two positions or at four corners on both ends of the outer bottom surface of the container body.