JP4905968B2 - package - Google Patents

Description

  The present invention relates to a solder joint structure in which, for example, solder sandwiched between two pads is melted and solidified again to join both pads, and a sealed package having the solder joint structure.

  2. Description of the Related Art Conventionally, in a technical field such as a low-temperature fired multilayer substrate, a sealed package has been proposed that hermetically seals a circuit or electronic component by bonding a lid to the package body provided with the circuit or electronic component with solder. Yes. The sealed package includes a package body provided with a circuit and an electronic component and a first pad surrounding them, and a lid provided with a second pad disposed to cover the package body and facing the first pad. The package body and the lid are joined to melt the solder sandwiched between the first pad and the second pad and solidify again, thereby sealing the circuit and electronic components. To do.

  According to such a sealed package, the circuit and electronic components are protected from radiation and dew condensation, and the operation of the circuit and electronic components is prevented from being influenced or exerted on the external circuit or electronic components. (For example, refer to Patent Documents 1 and 2).

JP 2004-71938 A Japanese Patent Laid-Open No. 2005-244032

  However, conventionally, in the solder melting step, when the molten solder moves (flows) on the pad, the moving solder may stagnate at a specific location. When the solder is stagnated at a specific location, the amount of solder at this location increases, and conversely, the amount of solder at the location adjacent thereto decreases. If the amount of solder that should be uniform in this way is different in various places in this way, voids may be formed in the solder and the hermetic sealing may be impaired. Therefore, an improvement has been desired to solve this solder non-uniformity.

  The present invention has been made to solve the above-described problems. A solder joint structure that reduces solder stagnation, uniforms the amount of solder and suppresses the generation of voids, and a seal having the solder joint structure. The purpose is to obtain a stop package.

The solder joint structure of the present invention includes a first circuit and a second circuit, a rectangular outer edge surrounding the first and second circuits, a region where the first circuit is provided, and the provision of the second circuit. A flat plate in which a first pad of a Japanese character having a dividing part wider than the outer edge part for dividing the formed region is formed on an upper surface, and the dividing part and the outer edge part intersect in a T-shape. A package main body having a shape, and a concave portion that is disposed so as to cover the package main body and accommodates both in the portion corresponding to the first circuit and the second circuit, and in a portion facing the first pad A lid provided with a second pad as a solder guide portion having a shape substantially symmetrical to the first pad, and the first pad of the package body and the second of the lid. The pads are joined via solder, and the intersection Outside the outer edge at the portion intersecting the T-shape of the first pad and the second pad so as to branch from the dividing portion to the outer edge with the same width as the width of the outer edge. A concave shape is provided.

  According to the solder joint structure and the sealing package according to the present invention, it is reduced that the solder stagnates at a specific location, the amount of solder on the pad becomes uniform, and the generation of voids is suppressed. The reliability of the sealing structure is improved.

Embodiment 1 FIG.
FIG. 1 is a perspective view showing a state in which the lid of the sealed package of Embodiment 1 according to the present invention is opened. 2 is a top view of the package body excluding the lid of the sealed package of FIG. In FIG. 1, a sealed package 40 includes a flat package body 10 having a transmission circuit 11 and a reception circuit 12 provided on the upper surface thereof, and the transmission circuit 11 and the reception circuit 12 covering the upper surface of the package body 10. It has the same rectangular flat lid 20 for sealing.

  1 and 2, the package body 10 is formed in a rectangular flat plate shape using ceramic as a main raw material, and a first surface extending in the form of a line on the same plane as the transmission circuit 11 and the reception circuit 12 is formed on the upper surface. Pads 15 are formed so as to surround the transmission circuit 11 and the reception circuit 12, respectively. Specifically, the first pad 15 includes an outer edge portion formed in a quadrangular shape so as to go around the whole of the rectangular package body 10, an area where the transmission circuit 11 is provided, and a reception circuit. And a dividing portion formed across the package main body 10 so as to divide the region where 12 is provided. A solder 35 is placed on the first pad 15 over the entire length. The solder 35 is formed on the pad 15 by a printing process, and forms a layer having a predetermined thickness and a predetermined width.

  The lid 20 is made of a metal material in a substantially rectangular flat plate shape, and a second pad 25 (solder guide portion) is formed on the lower surface facing the package body 10. The second pad 25 is formed in the same shape as the first pad 15 at a position facing the first pad 15. That is, the second pad 25 is formed symmetrically with respect to the first pad 15. A portion inside the second pad 25 of the lid 20, that is, a portion facing the transmission circuit 11 and the reception circuit 12 is a recess (not shown) so that a predetermined sealed space is formed. This recess is formed by recessing the part other than the second pad 25, or by forming a spacer such as a sealing member in the part of the second pad 25 and making it higher than the other part. Or

  The sealed package 40 having such a configuration is heated by, for example, a reflow process in a state where the lid body 20 is overlapped on the package body 10 to melt the solder 35 on the pad 15, and further cooled to remove the solder 35. After being solidified, the package body 10 and the lid 20 are joined in an airtight state.

  FIG. 3 is a cross-sectional view taken along the line AA in FIG. 2, showing how the solder 35 melts between the pad 15 and the pad 25. 3A shows a state in which the solder 35 is in a solid phase, and FIG. 3B shows a state in which the solder 35 has melted into a liquid phase. When the solder 35 melts into a liquid phase, the solder 35 is attracted to the compatible pads 15 and 25 by its wettability, and is repelled from other parts. Furthermore, the solder 35 tries to keep its surface area to a minimum due to its interfacial tension. Therefore, as shown in FIG. 3, the solder 35 in a liquid phase stays between the two pads 15 and 25 and does not flow out. At this time, since the distance between the two pads 15 and 25 becomes very narrow, a capillary phenomenon works, and the solder 35 flows along the pads 15 and 25 to form a flow path. At this time, the solder 35 exhibits the same characteristics as the fluid flowing through the pipeline.

  The fluid flowing through the pipeline has a characteristic that it stagnates at a location where the pressure loss changes when the pressure loss of the fluid is not constant in the pipeline. For example, the pressure loss of the fluid decreases at a position where the pipe cross section expands, and the fluid stagnates at this position.

  In the present embodiment, for the purpose of suppressing the stagnation of the solder 35 at a specific location, the shape of the first pad 15 and the second pad 25 is the same as the pressure loss of the molten solder 35. In such a shape, the pressure loss of the molten solder 35 does not change over the entire length of the flow path. This will be described below.

When the flow rate is constant, the pressure loss ΔP is expressed by the following equation (1) in hydraulics.
ΔP = λ · (L / De) · (ρ / 2) · v ² (1)
ΔP: Pressure loss
Y: Pipe friction coefficient ratio (determined by the aspect ratio of the pipe)
ρ: Fluid density
ν: Fluid dynamic viscosity coefficient
L: Pipe length
V: Flow rate
s: Perimeter of pipe cross section De: Equivalent diameter of pipe cross section Note that the equivalent diameter refers to a pseudo radius of a rectangular parallelepiped cross section approximated to a circular cross section.
Where λ = Y · (64 / Re)
Re = (De · v / ν)
v = V / A
De = (4A) / s
Therefore, the above equation (1) is converted into the following equation (2).
ΔP = 128 Y · ρ · ν · L · V / (s · De ³ ) (2)

  As shown in the equation (2), the pressure loss ΔP is inversely proportional to the cube of the equivalent diameter De of the pipe cross section and the circumferential length s of the pipe cross section. Based on this, the sealed package 30 of the present embodiment is configured such that the shape of the pads 15 and 25 is such that the equalized diameter and circumferential length of the cross section of the flow path are uniform on the flow path.

  4 is a cross-sectional view showing a state in which the distance between the pad 15 and the pad 25 is narrower than that in FIG. 3 in a state where the solder 35 is in a liquid phase. When the solder 35 is in a liquid phase, if the distance between the pad 15 and the pad 25 is narrow, the pad 35 may protrude from the side of the pad. That is, when the solder 35 is in a liquid phase, the side portion is recessed as shown in FIG. 3B due to the relationship between the amount of the solder 35 and the distance between the pads 15 and 25, and conversely, as shown in FIG. The side part swells into a convex shape. However, FIGS. 3 and 4 show the gap between the pads 15 and 25 exaggerated. Actually, the gap H between the pads 15 and 25 is very small compared to the width W of the pad. The cross-sectional area is almost determined by the width W of the pad. Therefore, whether or not the solder 35 protrudes from the pad side portion does not matter.

  As described above, in the sealed package 30 of this embodiment, the first pad 15 and the second pad 25 are formed when the molten solder 35 forms a flow path between them as a fluid. The pressure loss of the fluid is uniform on the flow path. Therefore, it is suppressed that the solder is stagnated at a specific location, the amount of the solder 35 on the pads 15 and 25 becomes uniform, and the generation of voids is suppressed, so that the reliability of the sealing structure is improved. To do.

  The sealed package 30 of the present embodiment seals the transmission circuit 11 and the reception circuit 12, but is not limited to the transmission circuit 11 and the reception circuit 12, and seals other circuits and electronic components. However, the same effect can be obtained.

  Note that the technical idea of uniforming the amount of solder on the pad according to the present embodiment is not limited to the sealed package as in the present embodiment, but can be applied to other solder joint structures. Since the amount of solder on the pad becomes uniform, the bonding force is improved and the reliability of the bonding portion is improved.

Embodiment 2. FIG.
Figure 5 is a top view of the package body of the sealing package. 5 Te smell, the first pad 16, so that the pressure loss is further uniform, the corners of the outer peripheral portion is rounded in an arc shape in the bent portion B and the branch section (T-shaped intersection) bent portion such as C It has been. That is, the outer peripheral shape of the bent part such as the refracting part B or the branching part C is rounded. Similarly, the second pad formed on the lid (not shown) is rounded into a circular arc at the bent portion, and is formed in a shape that is substantially plane-symmetric with respect to the first pad 16.

  Furthermore, the shape of the solder 36 disposed on the first pad 16 by printing is also rounded in a circular arc shape along with the first pad 16. It should be noted that the amount of the solder 36 disposed in the large portion 16c having a large width of the pad 16 is larger than the amount disposed in the small width portion 16b having a small width so that the flow rate per unit cross section is constant. Are arranged as follows. Other configurations are the same as those of the first embodiment.

  FIG. 6 is an enlarged view showing the pad 16 in the portion of the refracting portion B in FIG. The corner on the outer peripheral side of the portion bent at a right angle of the pad 16 is rounded into an arc shape so that the radius of curvature R = a with respect to the width a of the pad 16. In this way, by rounding the corner on the outer peripheral side of the bent portion with the radius of curvature of the pad width a, the pressure loss of the bent portion can be made more uniform. In order to make the pressure loss uniform more accurately, the outer peripheral side shape of the bent portion may be rounded with a radius of curvature larger than the width a, but in this case, the width of the pad 16 is not narrowed at the bent portion. The inner corner must also be rounded (so that it remains constant) (FIG. 7).

FIG. 8 is a reference diagram, and is an enlarged view of the pad 16 in the portion C of FIG. In FIG. 8, the outer peripheral shape of the portion bent at a right angle in the branch where the large portion 16 c having the width c branches into two small width portions 16 b each having a right width and a half width b is represented by a small width portion. An arc having a radius of curvature R = b with respect to a width b of 16b. Thus, by making the outer peripheral side of the branch part an arc having a radius of curvature of the width b of the narrow part 16b, the pressure loss of the branch part can be made more uniform. As in the case of FIG. 7, the pressure loss can be made uniform more accurately by rounding the outer peripheral shape of the branching portion with a radius of curvature R that is larger than the width b. The corners on the outer peripheral side also need to be rounded so that the width of the outer circumference is not narrower than b (so as to be kept constant) (FIG. 9). FIG. 9 is an enlarged view of the pad 16 according to the second embodiment.

FIG. 10 is a reference view, and shows a branching portion of the second pad 26 (solder guide portion) formed on the lid so as to face the pad 16 of FIG. In the branch portion formed in the lid according to the present embodiment, the tip portion is embedded in the cut portion 26d that is sharply pointed toward the flow path side by connecting the two arc portions formed on the outer periphery. It has been deleted. This is due to the following reason. If a sharp pointed part is formed in the flow path, a large capillary phenomenon may act on this part. Therefore, this capillary action prevents the solder 36 from being sucked (moved) more than expected on the lid side. Note that the capillary phenomenon of the same size occurs in the pad 16 on the package body side, but it has been found by verification and the like that the first pad 16 on which the solder 36 is placed in advance does not need to have such a shape. ing.

This sealing package, a first pad 16 and second pad 26, the bent portion such as a refractive portion and a branch portion, which is shaped to the outer peripheral shape rounded, and more, the outer peripheral shape , Because it is an arc having a radius of curvature greater than the width dimension and rounded, the pressure loss of the fluid becomes even more uniform on the flow path, and it is further suppressed that the solder stagnates at a specific location The

Embodiment 3 FIG.
FIG. 11 is an enlarged view showing a pad at the portion of the refracting portion of the sealed package according to the third embodiment of the present invention. In FIG. 11, the first pad 17 of the present embodiment is rounded so that the outer peripheral corner of the refracting portion that bends at a right angle is removed by a straight cutting line that is inclined 45 degrees with respect to the straight portion. ing. That is, the outer peripheral shape of the refracted portion that bends at right angles is rounded so that the outwardly protruding corners are removed by the straight cutting line. Similarly, the outer peripheral shape of the branch portion (not shown) is rounded so as to be deleted by a straight cutting line inclined by 45 degrees. Other configurations are the same as those of the second embodiment.

Oite above SL is to improve the uniform of the pressure loss by forming the outer peripheral side in an arc shape in the bent portion such as a refractive portion B and bifurcation C. However, if the improvement in the uniformity of pressure loss is sacrificed slightly, it may be rounded by a straight line regardless of the arc. With such a configuration, design and manufacture are facilitated and cost reduction can be achieved.

Embodiment 4 FIG.
FIG. 12 is a cross-sectional view of a solder joint portion of the sealed package according to the fourth embodiment of the present invention. In FIG. 12, in the present embodiment, a protrusion 20 a (solder guide portion) is provided at a position facing the first pad 16 of the lid 20. In the lid 20 made of a metal material, only the top surface of the protrusion 20 a at a position facing the first pad 16 has an affinity for the solder 36. Therefore, the melted solder 36 stays between the pad 16 and the protrusion 20a due to wettability and interfacial tension to form a flow path. Other configurations are the same as described above . By adopting such a configuration, it is not necessary to form a pad on the lid 20 side, so that the manufacturing process is reduced and the cost can be reduced.

Embodiment 5 FIG.
FIG. 13 is a cross-sectional view of a solder joint portion of the sealed package according to the fifth embodiment of the present invention. In FIG. 13, in the present embodiment, a groove 20 b (solder guide portion) is provided at a position facing the first pad 16 of the lid 20. In the lid 20 made of a metal material, only the inner surface of the groove 20 b at a position facing the first pad 16 has affinity with the solder 36. Therefore, the melted solder 36 stays between the pad 16 and the groove 20b due to wettability and interfacial tension to form a flow path. Other configurations are the same as those of the second embodiment. Even with this configuration, the same effects as in the fourth embodiment can be obtained.

  The present invention is suitable for use in a solder joint structure in which, for example, the solder sandwiched between two pads is melted and solidified again to join both pads. Thus, the present invention is optimally applied to a sealed package that hermetically seals a circuit or an electronic component by joining a lid to the package body provided with the circuit or the electronic component with solder.

It is a perspective view which shows a mode that the cover body of the sealing package of Embodiment 1 which concerns on this invention was opened. FIG. 2 is a top view of the package body excluding the lid of the sealed package of FIG. 1. FIG. 3 is a cross-sectional view taken along the line AA in FIG. 2 illustrating a state in which solder melts between the first pad and the second pad. FIG. 4 is a cross-sectional view showing a state in which the distance between the first pad and the second pad is narrower than that in FIG. 3 in a state where the solder is in a liquid phase. It is a top view of the package body of the sealing package. It is a figure which expands and shows the pad of the part of the refractive part B of FIG. It is a figure which shows the example which also made the inner peripheral shape the circular arc when the outer peripheral shape of the bending part is made into the circular arc of a big curvature radius. FIG. 6 is an enlarged reference diagram illustrating a pad at a branching portion C in FIG. 5. It is a figure which shows Embodiment 2, Comprising: When the outer peripheral shape of a branch part is made into the circular arc of a big curvature radius, it is a figure which shows the example which also made the internal peripheral shape the circular arc. FIG. 9 is a reference diagram illustrating a branched portion of the second pad formed on the lid body so as to face the first pad illustrated in FIG. 8. It is a figure which expands and shows the pad of the part of the refractive part of the sealing package of Embodiment 3 which concerns on this invention. It is sectional drawing of the solder joint part of the sealing package of Embodiment 4 which concerns on this invention. It is sectional drawing of the solder joint part of the sealing package of Embodiment 5 which concerns on this invention.

10 Package body 11 Transmission circuit (circuit)
12 Receiver circuit (circuit)
15, 16, 17 First pad 20 Lid 25, 26 Second pad (solder guide)
20a Protrusion (solder guide portion) extending along the opposing first pad
20b Grooves (solder guides) extending along the opposing first pads
35, 36 Solder 40 Sealed package

Claims (1)

The first circuit and the second circuit, a rectangular outer edge that surrounds the first and second circuits, and the outer edge that divides the area where the first circuit is provided and the area where the second circuit is provided A plate-shaped package main body formed on the upper surface with a first pad of a Japanese character having a divided part wider than the part, and the divided part and the outer edge part intersecting the T-shape;
The package body is disposed so as to cover the first circuit and the second circuit, and a recess is formed in the portion corresponding to the first circuit and the second circuit. A lid provided with a second pad as a solder guide having a plane-symmetric shape,
The first pad of the package body and the second pad of the lid are joined via solder,
To branch against the outer edge of the dividing portion has a width and the same width of the outer edge portion other than the crossing portion, said outer edge at a portion intersecting with the T-shape in the first pad and the second pad A package characterized in that a concave shape is provided on the outside of the part.

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