JP2011146625A - High-frequency circuit board device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problem that a necessary circuit scale can not be formed on a ceramic substrate with a BGA connection structure having the ceramic substrate and a resin substrate connected by many bumps since thermal stress operating on bumps positioned at an outer edge portion becomes larger as the ceramic substrate becomes larger in size so that a connection portion is broken. <P>SOLUTION: When the ceramic substrate 1 is bump-joined with the resin substrate 6, a BGA formation region is defined as a size range wherein the bump connection portion is not broken, and bumps are gathered only at a part of the ceramic substrate to form the BGA formation region. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a high-frequency circuit board device in which a ceramic substrate and a resin substrate are connected by bumps.

  Conventionally, in BGA (Ball Grid Array) mounting, in which a large number of ceramic substrates and resin substrates are bonded together, there is a difference of two or more in the linear expansion coefficient between the two. By filling and fixing an underfill agent such as a resin, thermal stress caused by a change in ambient temperature is suppressed, and damage to the bump joint is prevented (for example, see Patent Document 1). Also known is a bump mounting technique in which a linear expansion intermediate layer (laminate) having an intermediate value of linear expansion coefficient is inserted between a ceramic substrate and a resin substrate to form a two-storied stacked structure to disperse stress. (For example, refer to Patent Document 2).

JP-A-11-17044 JP 2002-237553 A

  However, when such conventional bump mounting is performed, the ceramic substrate dimensions can be increased as compared with the case where no thermal stress suppression measures are taken, but two types of components having a large difference in linear expansion coefficient are used. As long as they are joined, the ceramic substrate size still remains a limitation.

  As for Patent Document 1, since the underfill is a dielectric material, if it is used in a high-frequency circuit in which a high-frequency current flows through the bumps, the electrical characteristics are inevitably deteriorated, and a liquid resin is poured as a manufacturing method. It was very difficult and complicated to control the filling position and amount of the resin.

  In addition, as for Patent Document 2, in a complicated stacked structure with a linear expansion intermediate layer, not only is the deterioration of the high frequency characteristics unavoidable, but also the high frequency circuit design becomes very complicated and the number of assembly steps increases. It was expensive.

  Therefore, in BGA mounting of high-frequency circuits, the actual situation is that the size of the ceramic substrate is limited to dimensions that do not cause thermal stress breakdown without using an underfill or a linear expansion intermediate layer. As described above, since BGA mounting can connect circuits three-dimensionally, it is a very effective mounting configuration for miniaturization of circuit boards and circuit modules, but it must be limited to dimensions that can withstand the strength degradation associated with BGA mounting. Therefore, there is a problem in that it is often impossible to make a necessary circuit scale large.

  In the high frequency circuit board device according to the present invention, when the ceramic substrate and the resin substrate are bump-connected, even if a high frequency circuit of a required scale is formed on the ceramic substrate, the bump bonding is performed without using an underfill or a linear expansion intermediate layer. An object of the present invention is to obtain a substrate bonding structure that can prevent thermal stress destruction of a portion.

  A high frequency circuit board device according to the present invention includes a ceramic substrate on which a plurality of lands are arranged, a resin substrate on which a plurality of lands are arranged, a land between the lands of the resin substrate and the lands of the ceramic substrate, and a ball grid A plurality of bumps constituting the array, wherein an outer width of the ceramic substrate is larger than a formation region of the ball grid array, and the ball grid array is formed only at a central portion of the ceramic substrate. .

  Also, a ceramic substrate on which a plurality of lands are arranged, a resin substrate on which a plurality of lands are arranged, and a plurality of bumps that are bonded between the lands on the resin substrate and the lands on the ceramic substrate to form a ball grid array The ball grid array may be formed only on a part of the ceramic substrate, and a support member made of an elastic resin may be provided at a position where the ceramic substrate is not supported by the bumps.

  According to the present invention, the BGA mounting area formed by arranging the bumps can be limited to a size area that does not cause the thermal stress breakdown of the bump bonding portion. In addition, a BGA mounting structure with a required circuit scale can be obtained.

Sectional drawing of the connection structure of the ceramic substrate and resin substrate by Embodiment 1 which concerns on this invention is shown. It is a figure which shows the bump formation surface of the ceramic substrate by Embodiment 1 which concerns on this invention. Sectional drawing of the connection structure of the ceramic substrate and resin substrate by Embodiment 2 which concerns on this invention is shown. It is a figure which shows the bump formation surface of the ceramic substrate by Embodiment 2 which concerns on this invention. It is a figure which shows the bump formation surface of the ceramic substrate by the other aspect of Embodiment 2 which concerns on this invention.

Embodiment 1 FIG.
FIG. 1 is a cross-sectional view showing a connection structure between a ceramic substrate and a resin substrate in the high-frequency circuit board device according to Embodiment 1 of the present invention. FIG. 2 is a diagram showing a bump forming surface of the ceramic substrate according to the first embodiment of the present invention.
1 and 2, the high-frequency circuit board device 100 according to the first embodiment is configured by connecting a ceramic substrate 1 and a ceramic substrate 6 via conductor bumps 4. A circuit pattern 3 for mounting the component 2 is formed on one surface of the ceramic substrate 1. A plurality of lands 5 for bonding the bumps 4 are arranged on the other surface of the ceramic substrate 1. The land 5 is constituted by a conductor pattern, and is concentrated and arranged at the center of the ceramic substrate 1. The resin substrate 6 is made of a resin such as glass epoxy resin or BT resin, and a plurality of lands 7 are arranged on one surface of the resin substrate 6. The lands 7 are formed of a conductor pattern, are arranged at positions facing the lands 5, and are arranged at the same number and the same pitch as the lands 5.

  The lands 5 of the ceramic substrate 1 and the lands 7 of the resin substrate 6 are joined by the bumps 4 to form the BGA region 8, thereby forming a BGA mounting structure. When the ceramic substrate 1 and the resin substrate 6 are bonded, the bumps are collected only within a dimension that does not cause thermal stress destruction, and a BGA mounting structure is formed. The external dimensions (vertical or horizontal external width) of the ceramic substrate 1 are larger than the dimensions (vertical or horizontal area width) of the BGA region 8, for example, the dimensional difference (vertical or horizontal) is larger than 20 mm. ing.

The BGA mounting structure is a method in which electrical connection between substrates is bonded on a substrate surface-to-substrate surface. Projected electrodes called balls or bumps are arranged in a predetermined arrangement on the substrate surface in a lattice shape in a plane. Because it is arranged, it is called BGA.
In the BGA mounting structure, a circuit block formed by mounting components such as semiconductor elements and passive elements on a ceramic substrate (here, ceramic substrate 1) can be mounted on a mother board (here, resin substrate 6) with a minimum area. . In addition, there is an advantage that all joint points between the ceramic substrate and the mother board can be shortest and collectively joined. There are various types of balls or bumps, such as solder, resin covered with a conductor film, stacked plating, metal balls, and the like, and they are properly used depending on applications and purposes. Here, these are all called bumps.

  The linear expansion coefficient of the ceramic substrate 1 is about 5 to 7 PPM, whereas the linear expansion coefficient of the resin substrate 5 is around 16 PPM, and the difference is more than twice. For this reason, if the high-frequency circuit board device 100 is heated, the resin substrate 6 greatly progresses and the ceramic substrate 1 has a small elongation. Thermal stress is generated. When the bumps 4 are joined by a method such as soldering at a high temperature in the joining process, a tensile force toward the center of the ceramic substrate 1 remains as a residual stress in each joined portion of the bumps 4 after the joining cooling. . These thermal stresses are larger at the outer edge of the BGA region 8 and smaller at the center. Moreover, the thermal stress of an outer edge part increases, so that the area | region dimension of the BGA area | region 8 is large. In an actual use environment where each substrate is exposed, a heat cycle with a temperature change width of about 70 to 100 ° C. is applied, so that repeated stress due to expansion and contraction is applied.

  The larger the area size of the BGA region 8, the greater the thermal stress due to temperature changes in the usage environment. When the size limit is exceeded, the structural deterioration of the bump 4 connection point proceeds from the outer periphery of the BGA region 8 and eventually the fracture occurs. As a result, the electrical connection between the ceramic substrate 1 and the resin substrate 6 is broken.

  In the conventional BGA mounting structure, the bumps 4 are arranged on the entire surface of the ceramic substrate 1, and the entire surface is bonded to the resin substrate 6. For this reason, the dimensions of the ceramic substrate 1 are almost the same as the dimensions of the BGA region 8, and the larger the dimension of the ceramic substrate 1, the easier the tearing of the outer edge of the BGA occurs. The size of the ceramic substrate that does not cause BGA tearing even when the temperature of the operating environment changes varies depending on the linear expansion coefficient of the material and the environmental temperature range, but is generally within 20 mm square (□). It was.

  On the other hand, in the high-frequency circuit board 100, the number of lands 5 and lands 7 (number of interfaces or number of connection signals) to be interfaced by exchanging electrical signals and power between the ceramic substrate 1 and the resin substrate 6 is actually the same. There are few. Thus, since the ratio of the number of interfaces or the number of connection signals to the circuit area is small, it is not necessary to form the bumps 4 on the entire surface of the ceramic substrate 1.

  In the first embodiment, by utilizing this property, the bumps 4 that need to be connected to the resin substrate 6 are collected only in the central portion of the ceramic substrate 1, and the bumps 4 may be broken even if the formation area size of the BGA region 8 is the conventional configuration. It is formed within a size range that does not occur. Specifically, the size of the formation area of the BGA area 8 is approximately within 20 mm square.

  In this way, the ceramic substrate 1 is mounted on the resin substrate 6 in a flat roof shape or a flat umbrella shape with the central BGA region 8 as a column, and between the ceramic substrate 1 and the resin substrate 6. The circuit formation region can be enlarged by the size of the hollow portion formed around the BGA region 8.

  Further, although the maximum dimension of the ceramic substrate 1 is determined by restrictions on the weight of components to be mounted and the mechanical environment to be used, it can be increased to at least about 9 times the conventional area ratio. For example, if the formation region size of the BGA region 8 is 20 mm square, the size of the ceramic substrate 1 can be 60 mm square.

As described above, the high frequency circuit board device having the BGA type mounting structure of the ceramic substrate 1 and the resin substrate 6 according to this embodiment has the ceramic substrate 1 on which the plurality of lands 5 are arranged and the resin on which the plurality of lands 7 are arranged. The substrate 6 is provided between a land 7 of the resin substrate 6 and a land 5 of the ceramic substrate 1 and includes a plurality of bumps 4 constituting a ball grid array. The outer width of the ceramic substrate 1 is the same as that of the ball grid array. The ball grid array is larger than the formation region, and is formed only at the center of the ceramic substrate 1.
Further, the difference between the maximum outer width of the ceramic substrate 1 and the maximum width in the same direction as the maximum outer width of the ceramic substrate 1 in the formation region of the ball grid array may be 20 mm or more.
In addition, when the ceramic substrate 1 is bump-bonded, a dimension range in which the bump connection portion is not broken may be used as the formation area of the ball grid array.

  In this way, in the BGA type mounting structure of the ceramic substrate 1 and the resin substrate 6 according to the embodiment, thermal stress failure occurs at the bump joint such as solder crack or ceramic crack in the BGA region formed by arranging the bumps. Since it is limited to a dimensional region having no size, even if no thermal stress destruction prevention structure is provided in the BGA region, thermal stress failure does not occur and the size of the entire ceramic substrate is not limited. It is possible to obtain a BGA mounting structure in which a necessary circuit scale is formed.

  In particular, without taking a complicated two-stage structure using an underfill or a linear expansion intermediate layer, the size of the ceramic substrate can be made about nine times as large as the conventional area ratio, and a high-frequency circuit having a desired circuit scale can be obtained. Can be formed on a ceramic substrate.

  In addition, since no reinforcement is fixed around the joint at the BGA joint between the ceramic substrate 1 and the resin substrate 6, the assembly process of the high-frequency circuit board device can be minimized, and the cost of the high-frequency circuit device can be reduced. An advantageous effect can be obtained.

Embodiment 2. FIG.
3 is a cross-sectional view showing a connection structure between a ceramic substrate and a resin substrate in a high-frequency circuit board device according to Embodiment 2 of the present invention. FIG. 4 is a view showing a bump forming surface of the ceramic substrate according to the second embodiment of the present invention. FIG. 5 shows a bump forming surface of a ceramic substrate according to another embodiment of the second embodiment of the present invention. 3, 4, and 5, the configurations indicated by reference numerals 1 to 7 are similar to those of the first embodiment.

  3 and 4 according to the second embodiment, the BGA region 8 to which the ceramic substrate 1 and the resin substrate 6 are joined is not located at the center of the ceramic substrate 1 but toward the end of the substrate. It is provided at a biased position. Therefore, a rubber-like resin 9 that supports both the weight of the ceramic substrate 1 is provided at the end of the ceramic substrate 1 so that the weight of the ceramic substrate 1 supported by the BGA region 8 is not biased. The substrate 6 is supported by both ends. The rubber-like resin 9 may be an elastic resin, and may be arranged not only in the horizontal direction in FIG. 4 but also in the vertical direction in FIG.

  Next, in the high-frequency circuit board device according to the second embodiment shown in FIG. 5, the BGA region 8 where the ceramic substrate 1 and the resin substrate 6 are joined is provided in the center of the ceramic substrate 1. FIG. 5 shows a case where the size of the ceramic substrate 1 is very long, and the rubber-like resin 9 is provided at both ends of the substrate that need to support the weight of the ceramic substrate 1. Thus, the ceramic substrate 1 is supported by the resin substrate 6 at at least three locations of the BGA region 8 and at least two or more rubber-like resins 9. The rubber-like resin 9 may be arranged not only in the horizontal direction in FIG. 4 but also in the vertical direction in FIG.

  The rubber-like resin 9 may be adhered to both the ceramic substrate 1 and the resin substrate 6 or may be adhered to only one of them. However, when the rubber-like resin 9 is bonded to both the ceramic substrate 1 and the resin substrate 6, it is preferable to select a material that can absorb the transition generated by the difference in linear expansion between the two, for example, Teflon (registered trademark) resin or elastic material. It is preferable to use a resin body made of a nanotube having a carbon nanotube.

  As described above, the high frequency circuit board device having the BGA type mounting structure of the ceramic substrate 1 and the resin substrate 6 according to this embodiment has the ceramic substrate 1 on which the plurality of lands 5 are arranged and the resin on which the plurality of lands 7 are arranged. A substrate 6 and a plurality of bumps 4 which are bonded between a land 7 of the resin substrate 6 and a land 5 of the ceramic substrate 1 and constitute a ball grid array are provided, and the ball grid array is formed only on a part of the ceramic substrate 1. A support member (rubber-like resin 9) made of an elastic resin is provided at a position where the ceramic substrate 1 is formed and not supported by the bumps 4.

  In the BGA type mounting structure of the ceramic substrate 1 and the resin substrate 6 according to the second embodiment, the ceramic substrate 1 can be supported at a plurality of locations by using the rubber-like resin 9 that serves as a support. Can be provided at a desired position in terms of the circuit configuration, and the degree of freedom in the dimensions and the circuit scale of the ceramic substrate 1 are remarkably increased.

  The present invention is particularly effective for bonding a high-frequency circuit board with a small number of connection signals. However, as long as the BGA region size is used within a range that does not exceed the size at which the bump bonding part does not break, the digital circuit board It is also effective for bonding. Further, the present invention can be applied to all structures in which a member having a large difference in linear expansion, such as bonding between a ceramic substrate and a resin substrate, is bonded by a bump.

  DESCRIPTION OF SYMBOLS 1 Ceramic substrate, 2 components, 3 circuit pattern, 4 bump, 5 land, 6 resin substrate, 7 land, 8 BGA area | region, 9 rubber-like resin, 100 high frequency circuit board apparatus.

Claims (4)

A ceramic substrate on which a plurality of lands are arranged; and
A resin substrate on which a plurality of lands are arranged;
A plurality of bumps that are bonded between the land of the resin substrate and the land of the ceramic substrate and constitute a ball grid array,
With
A high frequency circuit board device in which an outer width of the ceramic substrate is larger than a formation region of the ball grid array, and the ball grid array is formed only at a central portion of the ceramic substrate.   The high-frequency circuit board device according to claim 1, wherein a difference between a maximum outer width of the ceramic substrate and a maximum width of a formation region of the ball grid array is 20 mm or more.   2. The high-frequency circuit board device according to claim 1, wherein a dimension range in which the bump connection portion is not destroyed when the ceramic substrate is bump-bonded is defined as a formation area of the ball grid array. A ceramic substrate on which a plurality of lands are arranged; and
A resin substrate on which a plurality of lands are arranged;
A plurality of bumps which are bonded between the land of the resin substrate and the land of the ceramic substrate and constitute a ball grid array,
A high-frequency circuit board device in which the ball grid array is formed only on a part of the ceramic substrate, and a support member made of an elastic resin is provided at a position where the ceramic substrate is not supported by bumps.

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