JP2013187347A - Substrate connection structure and substrate module - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve the problem that a required circuit scale cannot be formed on a ceramic substrate in a BGA structure where the ceramic substrate is connected with a resin substrate with a number of bumps because when the ceramic substrate is enlarged, thermal stress acting on the bumps positioned at an outer edge part becomes large and a connection part is damaged.SOLUTION: Bumps placed in a size area where thermal stress breakage does not occur are fixed by solder joint. As for bumps in other regions, spring contact terminals are attached to a ceramic substrate and are placed in slidable contact with electrodes of a resin substrate by crimping.

Description

  The present invention relates to a substrate connection structure for connecting different types of substrates having different linear expansion coefficients with a plurality of bumps, and a substrate module.

  Conventionally, a structure in which a ceramic substrate on which an electronic circuit is formed and a resin substrate are connected to each other has a structure in which leads and pins are attached to the ceramic substrate and the leads and pins are connected to the resin substrate, and a plurality of bumps (protrusions) are arranged. There is a BGA (Ball Grid Array) type mounting structure in which the surface connection is made with the electrode terminals). The BGA type mounting structure is capable of collectively connecting multiple electrodes with a minimum area.

  The BGA type mounting structure is called BGA because the ball-shaped electrodes are arranged in a plane as a bump in a predetermined arrangement or lattice shape, but the electrode shape of the bump is not limited to the ball type, and various shapes and materials are used. The entire configuration in which the bumps are arranged in a plane is called BGA. As the bump, a metal ball, a plastic ball plated with conductivity, a solder ball or the like is used. Any of the bumps is bonded to the ceramic substrate or the resin substrate by soldering or bonding, and is electrically connected and fixed at the same time as the ceramic substrate and the resin substrate are electrically connected.

  On the other hand, since there is a difference of two or more in the linear expansion coefficient between the ceramic substrate and the resin substrate, in the BGA type mounting structure, the stress breakdown of the bump joint portion due to the temperature environment change is likely to occur. Further, the thermal stress is greater at the outer edge portion of the ceramic substrate, and the thermal stress breakdown proceeds from the outer edge portion and gradually reaches the inner bump joint portion.

  As a method for preventing stress breakdown of the bump joint in this BGA type mounting structure, even if an underfill agent such as a resin is filled between the substrates and fixed, and thermal stress due to a difference in linear expansion occurs due to a change in temperature environment There is a technique for suppressing the transition in the bump portion (see, for example, Patent Document 1). In addition, a technique is known in which stress distribution is performed at a bump joint by providing a hierarchical structure in which an intermediate layer having an intermediate value of linear expansion coefficient is provided between a ceramic substrate and a resin substrate (for example, Patent Document 2). ).

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

  By applying the method for preventing stress destruction at the bump joint as disclosed in Patent Documents 1 and 2, the size of the ceramic substrate can be made larger than when no thermal stress suppression measures are taken. However, since two types of components having a large difference in linear expansion are joined, there is a problem that the outer dimensions of the ceramic substrate still remain limited. For this reason, the degree of freedom in selecting the size of the ceramic substrate remains low.

  In addition, since the underfill shown in Patent Document 1 is a dielectric material, deterioration of electrical characteristics is inevitable in a high-frequency circuit in which a high-frequency current flows through a bump, and since it is a liquid resin, it is difficult to control the filling amount during manufacturing. There is a problem. Furthermore, since the entire ceramic substrate is bonded with resin, the ceramic substrate cannot be replaced.

  In addition, since a linear expansion intermediate layer is provided as in Patent Document 2, the structure becomes complicated, so that not only the deterioration of the high frequency characteristics is unavoidable, but also the high frequency circuit design becomes very complicated. There is also a problem that the number of assembling steps increases and becomes expensive.

  As described above, in the BGA type mounting structure of the high-frequency circuit, the actual situation is that the size of the ceramic substrate is limited to a dimension that does not cause thermal stress destruction without using an underfill or a stacked structure.

  In addition, since the BGA type mounting structure allows three-dimensional circuit connection, it is a very effective mounting configuration for miniaturization of circuit boards and circuit modules. However, since it must be limited to a size that can withstand the BGA type mounting structure, the required circuit scale cannot be configured, or in order to divide the circuit into several BGA type mounting structures. However, the design is complicated and the manufacturing cost is increased.

  The present invention has been made to solve the above-described problems. For example, in a substrate connection structure between different types of substrates such as a ceramic substrate and a resin substrate, a high-frequency circuit of a scale necessary for one substrate, for example, a ceramic substrate, is provided. Even if it forms, it aims at suppressing the thermal-stress destruction of a bump connection part, without using an underfill or a stacked structure.

  The board connection structure according to the present invention includes a first board on which a plurality of lands are arranged, a second board on which a plurality of lands are arranged, and having a linear expansion coefficient different from that of the first board, and the first board A plurality of bumps that connect the land of the substrate and the land of the second substrate and constitute a ball grid array, and a part of the bumps is wider than the width of the first and second substrates. Are soldered and joined to the lands of the first substrate and the lands of the second substrate within a small predetermined solder joint region, and the other part of the bumps is composed of spring contact terminals, It is soldered and joined to the land of the first substrate outside the predetermined solder joint region, and is pressed against the land of the second substrate.

  According to the present invention, the first substrate is fixed to the second substrate by the solder connection bumps, and at the same time, the spring contact is pressed against the second substrate at a portion other than the solder connection portion. A connection structure is obtained in which the electrodes on the entire first substrate constituting the substrate can be electrically connected to, for example, the second substrate constituting the resin substrate, and thermal stress breakdown does not occur even if the first substrate is made larger. It is done.

3 is a cross-sectional view showing a substrate connection structure between a ceramic substrate and a resin substrate according to Embodiment 1. FIG. 4 is a side view showing a bump forming portion of the ceramic substrate according to Embodiment 1. FIG. 6 is a cross-sectional view showing a substrate connection structure of a ceramic substrate and a resin substrate according to Embodiment 2. FIG.

Embodiment 1 FIG.
1 is a cross-sectional view showing a substrate connection structure of a ceramic substrate and a resin substrate according to Embodiment 1 of the present invention. 2A and 2B are diagrams showing a bump forming portion of the ceramic substrate according to the first embodiment, wherein FIG. 2A is a rear view showing the bump forming surface, and FIG. 2B is a side view showing the bump forming portion. 1 and 2, a substrate module having a BGA type mounting structure in which a ceramic substrate 1 as a first substrate and a resin substrate 5 as a second substrate are joined together via bumps 7 for solder connection. 10 is constituted. The substrate module 10 is formed by integrally connecting dissimilar substrates (ceramic substrate 1 and resin substrate 5) having different linear expansion coefficients by a factor of two or more. Further, a spring contact terminal 9 is provided between the ceramic substrate 1 and the resin substrate 5 so that the ceramic substrate 1 and the resin substrate 5 are electrically connected. A component 3 is mounted on the front surface (upper surface) of the ceramic substrate 1, and a bump forming portion is provided on the rear surface (lower surface) of the ceramic substrate 1. Solder connection bumps 7 and spring contact terminals 9 are joined to the bump forming portion as bumps. The ceramic substrate 1 is mounted with a component such as an electronic component or an electrical component, and a wiring pattern constituting an electrical circuit is formed.

  The solder connection bumps 7 are formed of ball-shaped electrodes, and the shape of the electrodes is not limited to the ball shape, and may be formed of bumps of various shapes and materials. The solder connection bumps 7 may be metal balls, plastic balls plated with conductivity, solder balls, or the like.

  The spring contact terminal 9 is a kind of bump made of a metal material having a spring property. The shape of the spring-like contact terminal 9 may be any shape as long as it is slidable in a spiral shape, a coil shape, a laterally U-shaped shape, an S-shaped shape, or the like, and a repulsive force is generated by isopressing. However, in order to minimize the transmission loss of the high-frequency signal, the spring contact terminal 9 is preferably of a shape that can shorten the path, for example, an S-shape and a lateral U-shape as shown in FIGS. .

  A circuit pattern 2 made of a conductor is formed on one surface (upper surface) of the ceramic substrate 1. The plurality of components 3 are mounted on a part of the circuit pattern 2 and are electrically connected to a part of the circuit pattern 2. Each component 3 includes a high-frequency element that performs processing such as amplification, modulation, frequency mixing, signal shaping, and oscillation on microwave and millimeter-wave high-frequency signals, a coupler, a divider, a resonator, a terminator, a filter, and a matching It consists of passive elements such as elements. A plurality of bump lands (hereinafter simply referred to as lands) 4 made of metal thin film conductors are two-dimensionally arranged for bump bonding over the entire other surface (lower surface) of the ceramic substrate 1. In the example of FIG. 2, 63 rectangular lands 4 of 7 rows × 9 columns are formed, but the number, arrangement, and shape of the lands 4 are not limited to this. The land 4 is connected to the circuit pattern 2 via a via (VIA) (not shown) that penetrates the front and back of the ceramic substrate 1. The land 4 is fed with a microwave or millimeter wave high frequency signal. The land 4 is supplied with a low-frequency signal, a bias signal, and a control signal transmitted to and from the component 3. Alternatively, the land 4 is connected to the ground.

  The resin substrate 5 is a printed wiring board composed of a resin such as glass epoxy resin or BT resin. On the surface (upper surface) of the resin substrate 5 facing the ceramic substrate 1, a plurality of lands 6 made of metal thin film conductors are arranged at the same position and pitch corresponding to the lands 4 in the vertical direction. On the back surface (lower surface) of the resin substrate 5 facing the ceramic substrate 1, a ground pattern, a signal pattern, and the like made of a conductor are formed.

A plurality of lands 4 (hereinafter referred to as lands 4a) located at the central portion of the ceramic substrate 1 are formed by a part of the lands 6 of the resin substrate 5 at the facing position and the solder connection bumps 7, respectively. Soldered by soldering or ultrasonic bonding. The solder connection bumps 7 form a BGA by arranging ball electrodes in a predetermined arrangement or lattice shape in a plane. Thus, the solder connection BGA region 8 as the solder joint region located at the center of the ceramic substrate 1 constitutes a joint portion between the ceramic substrate 1 and the resin substrate 5 with the plurality of solder connection bumps 7 interposed therebetween.
The solder connection BGA region 8 may be provided at a peripheral position shifted from the central portion of the ceramic substrate 1.

  Also, some of the lands 4 (hereinafter referred to as lands 4b) located outside the solder connection BGA region 8 are respectively connected to some of the lands 6 of the resin substrate 5 at the opposing positions, respectively, and spring contact terminals. 9 is soldered. Thus, the solder connection BGA region 11 located outside the solder connection BGA region 8 of the ceramic substrate 1 constitutes an electrical connection portion between the ceramic substrate 1 and the resin substrate 5 with the plurality of spring contact terminals 9 interposed therebetween. It becomes.

Next, characteristics of the substrate module 10 having the substrate connection structure of the ceramic substrate and the resin substrate according to the first embodiment will be described.
The linear expansion coefficient of the ceramic substrate 1 is generally about 5 to 7 PPM, whereas the linear expansion coefficient of the resin substrate 5 is around 16 PPM, and the difference is twice or more. For this reason, if heated, the resin substrate 5 greatly progresses, while the ceramic substrate 1 has a small elongation. Therefore, the maximum heat is applied to the joint portion of the solder connection bump 7 located at the outermost edge due to the temperature change of the use environment. Stress is generated. In particular, after the solder bonding step of the solder connection bump 7, a tensile force toward the center direction of the solder connection BGA region 8 remains as a residual stress in each bonding portion of the solder connection bump 7. These thermal stresses are larger at the outer edge of the solder connection 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 solder connection BGA area | region 8 is large. In a normal actual use environment where each substrate is exposed, a heat cycle having a temperature change width of about 70 to 100 ° C. is applied, so that repeated stress due to expansion and contraction is applied. As the area size of the solder connection BGA area 8 is larger, the thermal stress due to the temperature change in the use environment becomes larger.

  For this reason, in a general BGA type mounting structure, the structure deterioration of the solder connection bump connection point proceeds from the outer edge portion of the solder connection BGA region. If the area size of the solder connection BGA region exceeds the limit value, in the worst case, the structure will eventually be broken, resulting in a failure in which the electrical connection between the ceramic substrate and the resin substrate is broken.

  For example, in the case of conventional BGA type mounting structures as shown in Patent Documents 1 and 2, solder connection bumps are arranged on the entire surface of the ceramic substrate, and all the solder connection bumps are soldered to the lands of the resin substrate. The size of the ceramic substrate is substantially the same as the size of the solder connection BGA region, and the larger the size of the ceramic substrate, the larger the tear of the outer edge of the solder connection BGA region. In particular, since the ceramic substrate is made of a brittle material, tearing is likely to occur around the joint with the land, and the land itself may be torn. For this reason, if no countermeasures against thermal stress destruction are taken, the size of the ceramic substrate that does not tear at the outer edge of the solder connection BGA region is, for example, about 20 mm square.

However, in the BGA type mounting structure of the substrate module 10 according to the first embodiment, the dimension region in which tearing does not occur even when connected by solder while the dimension limit value of about 20 mm square is maintained is the solder connection BGA region 8. . Inside the solder connection BGA region 8, there are provided solder connection bumps 7 for connecting the lands 4a and 6 of the ceramic substrate and the resin substrate. In addition, a peripheral contact position (solder connection BGA region 11) outside the region beyond the solder connection BGA region 8 is provided with a spring contact terminal 9 instead of a solder bump (solder connection bump 7). Are connected between the lands 4b and 6 of the resin substrate.
That is, the solder connection BGA region 8 provided with the solder connection bumps 7 is limited to a rectangular section having a maximum dimension region of 20 mm or less per side, and a spring-like contact is formed around the solder connection BGA region 8. A solder connection BGA region 11 provided with terminals 9 is provided.
The solder connection BGA region 8 is not limited to a rectangular shape, and may be arranged in a circular shape or an elliptical shape. In this case, a circular or elliptical dimension region having a square diagonal length of approximately 20 mm on a side as a diameter or a major axis is a dimension limit value of the solder connection BGA region 8.

  Further, the spring contact terminals 9 are connected and fixed to the lands 4b by soldering, welding, brazing or the like on the ceramic substrate 1 side. On the resin substrate 5 side, the spring contact terminals 9 are not bonded and fixed to the lands 6 but are brought into contact with each other by pressure contact. The ceramic substrate 1 and the resin substrate 5 are electrically connected by the contact between the spring-like contact terminal 9 and the land 6.

  Further, when the substrate module 10 according to the first embodiment is manufactured, before the ceramic substrate 1 is soldered to the resin substrate 5, the solder connection bumps 7 and the spring contact terminals 9 are previously connected to the lands 4 a and the ceramic substrate 1. 4b, respectively. And when soldering and bonding the solder connection bumps 7 of the ceramic substrate 1 to the lands 6 of the resin substrate 5, the entire ceramic substrate 1 is pressed and soldered to the resin substrate 5, and after cooling from the solder temperature, Remove the applied pressure.

  At this time, since the spring-like contact terminal 9 keeps the compressed state, a repulsive force is generated, and the repulsive force ensures that the spring-like contact terminal 9 and the land 6 of the resin substrate 5 are securely connected. Will be able to.

  Even if the resin substrate 1 expands or contracts due to a change in ambient temperature, the portion connected by the spring-like contact terminal 9 is not fixed, so that it slides and the solder connection bumps 7 are broken due to thermal stress. There is nothing.

  Thus, since the BGA type mounting structure of the ceramic substrate 1 and the resin substrate 5 according to the first embodiment does not take an underfill or a complicated two-stage structure, the dimensional freedom of the ceramic substrate 1 is improved as compared with the prior art. It becomes possible to form a high-frequency circuit of the circuit scale on the ceramic substrate 1. Further, the land 4a and the solder connection bump 7 can be selectively used for transmission of a higher frequency signal, and the land 4b and the spring-like contact terminal 9 can be selectively used for transmission of a lower frequency signal. Thus, by using the solder connection bumps 7 fixed between the ceramic substrate 1 and the resin substrate 5, it is possible to stably transmit a high frequency signal.

  Further, since the ceramic substrate 1 is fixed to the resin substrate 5 by solder joint by the solder connection BGA region 8, there is no need for a pressure contact structure or reinforcement for maintaining the contact of the spring-like contact terminal 9. For this reason, the assembly process does not increase so much as the conventional BGA mounting process, and is effective in reducing the cost of the high-frequency circuit device.

  As described above, in the substrate connection structure according to the first embodiment, the ceramic substrate (1), which is the first substrate on which the plurality of lands (4) are arranged, and the plurality of lands (6) are arranged. A resin substrate (5), which is a second substrate having a different linear expansion coefficient from that of the first substrate, is connected between the land of the first substrate and the land of the second substrate to form a ball grid array. A part of the bumps (solder connection bumps 7) within a predetermined solder joint region (solder connection BGA region 8) smaller than the width of the first and second substrates, The bumps are soldered and joined to the lands of the first substrate and the lands of the second substrate, and the other part of the bumps is composed of spring-like contact terminals (9), and is external to the predetermined solder joint region. (Solder connection BGA region 11) While being soldered to the substrate lands, is pressed against the second substrate lands, it is in sliding contact. Further, the solder joint region is characterized in that bumps connected by solder are arranged within a dimension region where thermal stress destruction does not occur (for example, inside a rectangular region having a side length of 20 mm or less). Further, the board module (10) may be configured by having the board connection structure and mounting the component (3) on the first board.

  Thus, the solder connection bumps 7 arranged within the solder joint region (solder connection BGA region 8) having a predetermined dimension that does not cause thermal stress failure are fixed by solder joint, and other portions (solder connection BGA region 11) are fixed. The bumps are configured such that spring contact terminals 9 are attached to the ceramic substrate 1 and are brought into sliding contact with the electrodes of the resin substrate 5 by pressure contact, so that when the solder connection bumps 7 are soldered and joined, the ceramic substrate 1. By pressing the entirety against the resin substrate 5, when the solder connection bumps 7 are completely joined, the spring contact terminals 9 are kept connected by the repulsive force.

  In this way, the solder connection bumps 7 within the dimension area where thermal stress failure does not occur are joined by soldering, and the other bumps are slidably contacted with the electrodes of the resin substrate 5 by spring contact as the spring-like contact terminals 9. Therefore, the ceramic substrate 1 is fixed to the resin substrate 5 by the solder connection bumps 7 and, at the same time, the spring contact 9 is pressed against the resin substrate 5 at a portion other than the solder connection portion. It is possible to obtain a surface connection structure that can be electrically connected to the resin substrate 5 and that does not cause thermal stress breakdown even with a large ceramic substrate.

Embodiment 2. FIG.
FIG. 3 is a sectional view showing a substrate connection structure between a ceramic substrate and a resin substrate according to the second embodiment. In FIG. 3, a ceramic substrate 1 and a resin substrate 5 are joined via solder connection bumps 7 to constitute a substrate module 10 having a BGA type mounting structure. The substrate module 10 composed of a ceramic substrate and a resin substrate is formed by integrally connecting different types of substrates having different linear expansion coefficients more than twice. Further, a spring contact terminal 9 is provided between the ceramic substrate 1 and the resin substrate 5 so that the ceramic substrate 1 and the resin substrate 5 are electrically connected. A component 3 is mounted on the front surface (upper surface) of the ceramic substrate 1, and a bump forming portion is provided on the rear surface (lower surface) of the ceramic substrate 1. Solder connection bumps 7 and spring contact terminals 9 are joined to the bump forming portion as bumps. In FIG. 3, reference numerals 1 to 9 are the same as or equivalent to those in the first embodiment.

  On the other hand, the board module 10 of the second embodiment is different in position of the solder connection BGA region 8 from that shown in FIG. 1 of the first embodiment. The solder connection BGA region 8 according to the second embodiment is provided at a predetermined position arbitrarily deviated from the central position from the central portion of the ceramic substrate 1 toward the substrate end (side surface). The solder connection bumps 7 are provided inside the solder connection BGA region 8 at the biased position, and fix the ceramic substrate 1 and the resin substrate 5 by solder connection.

  The substrate module 10 according to the second embodiment is provided with the spring-like contact terminals 9 in the entire region other than the solder connection BGA region 8 or in a desired position, so that the electrode (land 4) in the entire ceramic substrate 1 is replaced with the resin substrate 5. Therefore, the electrical connection can be effectively performed, and there is an effect that a high-frequency circuit having a desired circuit scale can be formed and the degree of freedom in designing the device can be increased.

  In addition, in an electronic device configured by surface-connecting a resin substrate 5 having a linear expansion coefficient different from that of the ceramic substrate 1 on which the electronic circuit is formed, it is effective for improving reliability and enlarging the ceramic substrate size.

  Note that the substrate connection structures described in the first and second embodiments are electrically connected by bump bonding between different types of substrates having a large difference in linear expansion coefficient (for example, twice or more), such as bonding between the ceramic substrate 1 and the resin substrate 5. The present invention can be applied to all components that are connected to each other.

  DESCRIPTION OF SYMBOLS 1 Ceramic substrate, 2 Circuit pattern, 3 Components, 4 land, 5 Resin board, 6 land, 7 Solder connection bump, 8 Solder connection BGA area, 9 Spring-like contact terminal, 110 Board module, 11 Solder connection BGA area.

Claims (4)

A first substrate on which a plurality of lands are arranged;
A plurality of lands arranged, a second substrate having a different linear expansion coefficient from the first substrate;
A plurality of bumps connecting the lands of the first substrate and the lands of the second substrate and constituting a ball grid array;
With
A part of the bump is soldered and joined to the land of the first substrate and the land of the second substrate within a predetermined solder joint region smaller than the width of the first and second substrates,
The other part of the bump is formed of a spring-like contact terminal, and is soldered to the land of the first substrate outside the predetermined solder joint region, and the land of the second substrate. Pressed against
Board connection structure.   2. The board connection structure according to claim 1, wherein the solder joint region includes bumps connected by solder within a size region in which thermal stress failure does not occur.   3. The substrate connection structure according to claim 1, wherein the first substrate is a ceramic substrate, and the second substrate is a resin substrate.   A board module comprising the board connection structure according to claim 1, wherein a component is mounted on the first board.

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