JPH10340980A - BGA connection structure - Google Patents

Abstract

(57) [Summary] When a component larger than an LSI or a module board and a circuit board are connected by a BGA, if the module board and the circuit board have different coefficients of thermal expansion, the BGA is subjected to a thermal history. A stress is repeatedly applied to the connection portion, thereby preventing the solder from being broken by fatigue and causing disconnection. A plastic ball is included in a solder, a gap is formed at an interface between the ball and a nickel film as a base layer of the solder, and a cross section of the solder is shaped like a drum. . Strain applied to solder is gap 6
And the stress is relieved. Also, since the cross section of the solder 3 is drum-shaped, it is difficult for stress to concentrate. When the planar shape of the electrodes 2A and 2B of the module board and the circuit board is a shape having a projection stretched in the direction of the tensile stress, the life of the connection portion against repeated temperature changes is not affected by the variation in the amount of solder. I can do it.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a BGA for electronic parts.
(Ball Grid Array: Ball Grid A
(rray) connection structure, and more particularly, to a BGA connection structure for connecting a circuit board or a component or board larger than an LSI, such as a module board on which a plurality of LSI packaged components or electronic components are mounted. .

[0002]

2. Description of the Related Art BGA connection is known as one of the techniques for packaging a multi-pin semiconductor device represented by an LSI. The connection structure (BGA connection structure) according to this technique is as follows.
The present invention can also be used for connection between a circuit board and a component or board larger than the LSI, such as a module board on which a plurality of LSI packaged components or electronic components are mounted. BG used for connection between such large parts or circuit board and circuit board
The A connection structure is basically the same as the BGA connection structure practically used for packaging of LSI. That is, as shown in an enlarged cross-sectional view of the connection portion in FIG. 10, the electrodes on the connection side (hereinafter, referred to as the module substrate) 1 and the connection side (same circuit board) 4 are connected to the respective substrate. Are arranged in the form of a lattice at the same pitch, the electrode forming surface of the module substrate 1 and the electrode forming surface of the circuit board 4 are opposed to each other, and the corresponding electrodes 2A and 2B are connected by solder 3. .

In this BGA connection structure, when the connection is made only by the solder 3, the cross-sectional shape of the solder 3 after the connection is determined by the balance between the surface tension of the molten solder and the force applied between the substrates 1 and 4, and the height of the solder 3 in the height direction. The central part overhangs laterally,
It is known to be drum-shaped. Here, a case where a temperature change occurs in the whole including the module substrate and the circuit substrate will be considered. At this time, if the coefficient of thermal expansion of the module substrate 1 is different from the coefficient of thermal expansion of the circuit board 4, stress in a direction parallel to the substrate surface as shown by an arrow pointing right or left in FIG. . Then, a tensile stress is applied to a joint portion where the solder 3 is connected to the electrode 2A at an obtuse angle, such as a portion E indicated by a dashed circle in the drawing, and stress concentration occurs. In severe cases, the solder at the joint E is cracked. Such cracks grow due to repeated temperature changes, and may eventually lead to fracture of the joint.

[0004] One method for preventing the breakage of a joint portion due to the difference in the coefficient of thermal expansion between the two substrates when the module board and the circuit board are BGA-connected is to reduce the difference in the coefficient of thermal expansion itself. Therefore, it is to reduce the generated stress. JP-A-8-64711 discloses an LSI.
The present invention relates to the packaging of the present invention, and is not directly related to the connection between a component or module board and a circuit board larger than an LSI, which is a main object of the present invention,
There is disclosed a connection technique (conventional example 1) in which a third material layer having a different coefficient of thermal expansion from the two substrates to be connected is sandwiched between the two substrates to reduce stress.
That is, FIG. 1 showing a cross section of a connection structure in Conventional Example 1
1, a resin substrate 103 having a thickness of 1 mm is attached to a ceramic substrate 102 as a matching layer during thermal expansion and contraction, and solder balls 108 are provided on the resin substrate 103. The material of the resin substrate 103 is selected so that its coefficient of thermal expansion is intermediate between the coefficient of thermal expansion of the circuit board (not shown) and the coefficient of thermal expansion of the ceramic substrate 102. The thermal expansion coefficient of the typical ceramic substrate 102 is made close to the thermal expansion coefficient of the circuit board, so that the stress at the connection portion is reduced. Such a technique of Conventional Example 1 will have an effect of stress relaxation even for connection of a large component or a substrate mainly targeted by the present invention.

Another method for preventing the breakage of the connection portion due to the difference in the coefficient of thermal expansion between the two substrates in the BGA connection structure is as follows.
The difference in the coefficient of thermal expansion due to the difference in the substrate material is tolerate and reduce the rigidity of the solder at the connection portion to absorb the strain applied to the solder. JP-A-8-213400 discloses an electronic component (conventional example 2) to which such a strain absorption technique is applied. That is, referring to FIG. 12 showing a cross section of a connection part in an electronic component described in the above publication,
The connection structure shown in this figure includes a ball 281 made of polyimide resin and having elasticity inside a solder bump 280. The ball 281 has its own elasticity, and absorbs a strain caused by a difference in a thermal expansion coefficient at the time of heating or pressing when connecting an electronic component to a circuit board (not shown). This alleviates the stress applied to the solder bumps 280 and prevents breakage at the connection. Conventional example 2
Although the present invention is not directly related to the connection between a large component or a substrate and a circuit board, which is the main object of the present invention, the effect of stress relaxation by strain absorption is expected even when applied to the connection of a large component or a substrate. I can do it.

[0006]

When two types of substrates having different coefficients of thermal expansion are connected by a BGA connection structure using only solder, when a thermal history is received, a solder crack is generated near the joint between the solder and the electrode on the substrate side. And finally breaks.
Since the thermal expansion coefficients of each substrate are different, the stress is repeatedly concentrated on a part because the shearing force and the pulling force are applied to the BGA connection and the cross-sectional shape of the solder after connection is drum-shaped. It is.

In order to prevent the breakage of the connection portion due to such a reason, it is necessary to relieve the stress generated in the joint portion by a temperature change by some method. The technique of reducing the magnitude of the generated stress itself by doing the above, and the technique of relaxing the stress by absorbing the strain generated in the solder by the elastic ball included in the solder in the conventional example 2 would be effective.

However, in the case of Conventional Example 1, the formation of the resin substrate 103 (see FIG. 11) has a side effect of increasing the cost. Also, the resin substrate 103
, The volume of the connection portion (original volume between the ceramic substrate 102 and the circuit board) is increased. According to the embodiment described in the above-mentioned JP-A-8-6471, the thickness increases by as much as 1 mm. Such an increase in the volume of the connection portion directly leads to an increase in the size of an electronic device mounted by the BGA, and is not recognized at all at present when there is a strong demand for a small and lightweight electronic device.

On the other hand, in the case of the conventional example 2, the solder bump 2
Depending on the rigidity of the balls 281 included in the solder bumps 80 (see FIG. 12), the stress applied to the solder bumps cannot be absorbed. That is, a main application object of the present invention is a connection between a circuit board and a component or board much larger than an LSI, such as a module board on which a plurality of LSI components or electronic components are mounted. In such a large module substrate, since the distance between the electrodes in the substrate surface is large and the distance between the connection points is long, the amount of strain applied to the solder itself is much larger than in the case of a small component such as a simple LSI. Become. On the other hand, if the ball 281 in the solder bump 280 is made of, for example, a polyimide resin as used in Conventional Example 2, the rigidity is too large, and the solder 280 in the joint portion of the solder bump 280 with the substrate-side electrode is too large. The deformation is not large enough to absorb the stress. After all,
A large stress is applied to the circuit board or the module board, and the module board, the circuit board, or the solder near the joint is destroyed.

Therefore, according to the present invention, when a component larger than an LSI or a module board and a circuit board are connected by a BGA structure, a distortion applied to a component arranged near a joint portion due to a difference in thermal expansion coefficient between the two boards. Is to reduce the

Another object of the present invention is to extend the life of the BGA connection structure against thermal history without increasing the volume of the connection.

[0012]

According to the BGA connection structure of the present invention, an electrode provided on an electronic component or a module substrate on which a plurality of electronic components are mounted and an electrode on a circuit board surface to be connected to the electrode are soldered to the BGA connection structure. In the connected BGA connection structure, a nucleus made of plastic covered with an underlayer for the solder is included in the solder of the BGA connection structure, and a gap is provided at an interface between the nucleus and the underlayer covering the nucleus. Features.

In addition, the BGA connection structure of the present invention
In the GA connection structure, a protruding electrode extending in a direction in which a shear stress is applied is added to a pair of electrodes connected by the BGA connection.

In the present invention, in order to prevent stress from being concentrated on a part of the solder of the connection portion, a plastic ball covered with a solder base layer different from the connection solder is included in the connection portion. Further, a material having a coefficient of linear thermal expansion larger than that of the solder base layer is used for the ball. Then, utilizing the difference in the coefficient of thermal expansion between the ball and the solder underlayer, the plastic ball and the solder underlayer are peeled off at the interface between them in a heat step at the time of connection, and a gap is formed between the ball and the solder underlayer. Is provided. The distortion applied to the connection due to the temperature change is absorbed by the deformation of the solder by the size of the gap. Also, by including balls in the solder,
The cross section of the solder in the vicinity of the electrode is made to have a hollow shape with no stress concentration to prevent solder destruction.

Further, the planar shape of each of the electrode on the module substrate and the electrode on the circuit substrate to be connected to the BGA has a shape obtained by adding a protruding electrode extending in the direction in which shear stress is applied in addition to the original electrode. Thus, the life of the solder with respect to the repetition of the temperature change is not affected by the fluctuation of the solder amount.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The embodiments of the present invention will be described below with reference to the drawings using examples.

(Embodiment 1) FIG. 1 shows an enlarged cross section of a BGA connection portion between a module board and a circuit board in a first embodiment (Embodiment 1) of the present invention. Referring to FIG. 1, electrodes 2A on module substrate 1 and electrodes 2B on circuit board 4 are connected by solder 3. Solder 3
The cross-sectional shape is such that the center in the height direction is concave, and the electrode 2 on the substrate surface is concave.
It has a drum-like shape that spreads toward the joint surface with A and 2B. Inside the solder 3, a plastic ball 7 wrapped in a nickel film 5 which is a solder base layer (described later) is arranged. A gap 6 is formed between the nickel film 5 and the ball 7. In the case of this embodiment, the diameter of the ball 7 is 500 μmφ, and the gap 6 between the ball and the nickel film is
Is 2-3 μm.

The right half of FIG. 1 shows a state in which a displacement in the shearing direction is applied to the connection portion due to a temperature change in this embodiment. Referring to the drawing, the connection portion is thinner in the solder near the center in the height direction (portion surrounded by a long circle A in the broken line in the drawing).
Further, since there is a gap 6 between the ball 7 and the nickel film 5, the solder 3 is easily deformed in the shearing direction until the displacement is about 4 μm. Larger displacements are absorbed by the warpage of the module board 1 and the circuit board 4 and the extension of the circuit board 4. In the present invention, when the solder 3 is deformed, it is the portion A in FIG. In the part A, as shown in FIG. 1, the solder is thinner than other parts such as the vicinity of the electrode. In addition, the portion A where the solder is thin extends over a wide range of about 100 μm in the vertical direction. Therefore, unlike the connection structure according to the related art shown in FIG. 10, the connection is made in a narrow range (only one point in the extreme case) such as a joint portion E (same) between the board-side electrode 2A (see FIG. 10) and the solder 3. The distortion is not concentrated. In the connection structure of the conventional example, the cross-sectional shape of the solder is a shape in which stress concentrates on a joint (E portion in FIG. 10) between the electrode and the solder. For this reason, stress concentrates in a very narrow range of the interface between the solder and the electrode, cracks are generated in the solder, and the connection portion is broken by repeated stress. On the other hand, in this embodiment, the maximum stress applied to portion A of the solder is
Since it can be smaller than the portion E in the conventional connection structure, the generation and progress of cracks caused by repeated displacement can be delayed, and the life of the connection portion can be extended.

The inventor manufactured the above-described embodiment according to the following manufacturing process. FIG. 2 shows the manufacturing process of this embodiment in order. Referring to FIG. 2, first, a module substrate 1 is prepared (FIG. 2A). FIG. 3 is a plan view of the module substrate. Referring to FIG. 3, module substrate 1 is made of glass ceramic (linear thermal expansion coefficient 6 ppm /
C), a 30 mm square package with a thickness of 1 mm. The electrodes 2A are arranged in four rows around the substrate. The electrodes 2A are circles having a diameter of 700 μmφ and are arranged at a pitch of 2.54 mm. Electronic components are mounted on the surface of the module substrate 1 opposite to the surface on which the electrodes are formed, although they are hidden and invisible.

In addition to the above-described steps, a plastic ball 7 (see FIG. 1) to be included in solder is prepared.
This was previously subjected to solder plating. FIG. 4 shows a cross-sectional view of the solder-plated plastic ball. The ball 7 is made of divinylbenzene formed into a 500 μmφ sphere. Nickel 5 having a thickness of 3 μm was formed on the divinylbenzene ball 7 by electroless plating. Further, a solder 3 having a thickness of 15 μm was formed by electroless plating of tin and lead to obtain a solder-plated plastic ball 10. The above nickel film 5
If the ball 7 is directly plated with solder without forming the film 5, when the solder is melted in a later step,
This is to prevent the wettability between the plastic and the molten solder from being deteriorated, and prevent the plastic ball 7 from being repelled from the solder 3 to obtain a desired connection structure.
Since the molten solder is sufficiently wetted by the nickel film 5 and the nickel layer 5 keeps a solid phase, the state in which the ball 7 is included in the solder can be maintained. In the present invention, a metal layer exhibiting such an action is defined as an underlayer for solder plating. Other metals that can be used as the underlayer include, for example, copper and the like. The coefficient of linear thermal expansion of the core divinylbenzene ball 7 is 100
ppm / ° C.

Next, on the electrode 2A on the module substrate surface,
A tin-lead eutectic solder paste was supplied. The solder paste was supplied by screen printing using a 0.2 mm thick metal mask having a hole of 600 μmφ. Further, the above-mentioned solder-plated plastic balls 10 were mounted on the respective electrodes using a jig, and reflowed at 230 ° C. to form solder protrusions 11 having the balls 7 on the module substrate 1 (FIG. 2B). ). FIG. 5 shows a cross-sectional view of the formed solder protrusion 11.

Separately from the above steps, a tin-lead eutectic solder paste 9 was also supplied to the electrode 2B (FIG. 2C) on the circuit board 4 in advance (FIG. 2D). The solder paste was supplied by screen printing using a metal mask as in the module substrate. The circuit board 4
Is a 1 mm thick, 100 mm square, FR-4 glass epoxy square (linear thermal expansion coefficient = 15 ppm / ° C.). An electrode 2B is formed on the module substrate 1 at a position corresponding to the electrode 2A.

Next, the module substrate 1 is placed on the electrode 2B of the circuit substrate 4 while being positioned, and solder reflow is performed at 230 ° C. to connect the two substrates 1 and 4 (FIG. 2).
(E)).

FIG. 1 shows a cross-sectional view of the connection portion after the completion of the solder reflow, with respect to the portion G in FIG. During the cooling process after the reflow, the plastic ball 7 contracts, and separation occurs at the interface between the plastic ball 7 and the nickel film 5. When the cooling is completed, the ball 7 and the nickel film 5
Between 2 and 3 on average from the difference in the coefficient of thermal expansion between the two.
A gap 6 of μm is formed. When the melting point of the solder decreases or the thermal expansion coefficient of the plastic ball decreases, the gap 6 also decreases. Therefore, the melting point of the solder 3 is preferably 183 ° C. or more, and the linear thermal expansion coefficient of the ball 7 is preferably 100 ppm / ° C. or more. .

In the connection structure according to the present invention, the plastic ball 7 is included in the solder 3 of the connection portion, and the interval between the module substrate 1 and the circuit board 4 is always constant. Therefore, by appropriately controlling the amount of solder, A drum-shaped connecting portion shape as shown in FIG. 1 can be stably obtained. When there is no ball 7 inside the solder, a drum-like shape is obtained in which the weight of the module and the surface tension of the molten solder are balanced. On the other hand, in the connection structure according to the present invention, the height of the connection portion becomes the diameter of the ball 7 when the solder is melted. If the amount of supplied solder is not larger than the amount calculated from this shape, a constricted structure around the ball as shown in FIG. 1 can be stably obtained.

A cooling / heating cycle test was performed on 10 samples according to the present embodiment and 10 samples having the conventional structure shown in FIG. The test conditions were as follows: hold at −40 ° C. for 30 minutes;
Hold at 5 ° C for 30 minutes. 300 for conventional samples
All of the wires were disconnected in 500 cycles from the cycle, but in the sample according to the present example, no disconnection occurred up to 1000 cycles.

(Embodiment 2) In a second embodiment (embodiment 2) described below, the cross-sectional shape of the connecting portion and the manufacturing method are the same as those in embodiment 1, and the electrodes on the module board surface and the electrodes on the circuit board surface are used. Is an example in which the planar shape is changed.
FIG. 6A is a perspective plan view of a module board 1 and a circuit board 4 which are BGA-connected in the same manner as in the first embodiment.
Show. FIG. 3 is a diagram viewed from the module substrate 1 side. FIG.
FIG. 6B shows an enlarged plan view of the electrode 2A of the module substrate, and FIG. 6C shows an enlarged plan view of the electrode 2B of the circuit substrate, for a portion B surrounded by a broken circle in FIG. .

Referring to FIG. 6, in the present embodiment, the patterns of electrodes 2A and 2B on each of substrates 1 and 4 are partially elongated in the direction in which displacement is applied. The direction in which the electrodes are stretched is the direction in which the tensile stress is applied to the solder. That is, in the module substrate 1, the direction is outward from the substrate center (FIG. 6B), and in the case of the circuit substrate, the direction is inward toward the substrate center (FIG. 6C). ). Therefore, the electrodes 2A on the module board and the electrodes 2B on the circuit board are stretched in opposite directions. The size of the extension of the electrode is set so that the width in the direction in which the displacement of the electrode is applied is about 1.2 times the width in the direction perpendicular to the displacement direction. That is, the electrodes 2A, 2B
Referring to FIG. 9A showing an example pattern, the maximum distance L in the direction in which the electrodes are stretched (in this case, the vertical direction on the paper) is set to be 1.2 times the diameter W (L = 1.2 W). ).

The state of the cross section near the electrodes when a stress due to a temperature change is applied to a module substrate having circuit electrodes having the above-mentioned pattern and a circuit board connected by the same manufacturing method as in the first embodiment is shown in FIG. As shown in FIG. FIG.
FIG. 7 is a sectional view of a portion indicated by a straight line F in FIG.
The contact angle of the portion where the tensile stress acts at the joint between the solder 3 and the electrode 2A is further acute than in the first embodiment, so that the solder and the electrode are less likely to be separated.

In the present embodiment, for example, when the supply amount of the solder is varied at the time of manufacture and the amount of the solder is reduced, the cross section of the connection portion has the shape shown in FIG. In this case, when the solder is melted, the solder collects in a portion C where a tensile stress is applied due to surface tension. Therefore, there is a sufficient amount of solder in the portion C where the tensile stress is applied, and even when a tensile force is applied, the solder in this portion does not break. On the other hand, if the amount of solder is large due to variations in the amount of solder supplied,
The cross section of the connecting portion is as shown in FIG. in this case,
The portion deformed by the stress is the portion where the solder around the ball is thinned (near the side surface at the center in the height direction of the ball 7 in FIG. 8B), and the distortion is absorbed in this portion. Therefore, no stress is applied to a portion D surrounded by a broken circle in FIG. 8B, and the portion D is not broken from this portion.

The planar shape of the electrodes 2A and 2B is not particularly limited to the shape shown in FIG. 9A as long as the thickness of the solder can be changed by utilizing the surface tension of the solder. For example, a pattern in which small square protrusions are projected from a square pattern as shown in FIG. 9B, or a pattern in which semicircular protrusions are provided as shown in FIG. 9C may be used. Good. However, depending on the pattern, the plastic ball 7 may not come to the center of the electrode. According to an experiment, regarding the width of the stretched portion (projection portion) and the length of the stretch in the direction of the tensile stress from the electrode, when the width of the electrode in the direction perpendicular to the direction in which the shear stress of the BGA electrode is applied is W, It has been confirmed that it is desirable that the ball is fixed at a predetermined position with a width of 1/3 or less of W, and that if the stretch length d is 0.2 times or more of W, stress concentration does not occur, which is desirable. Was.

The module substrate on which the electrodes of the present embodiment were formed and the circuit substrate were connected in the same manufacturing process as in the first embodiment, and the samples were subjected to a thermal cycle test. The test conditions are the same as those of the test performed in Example 1. The sample has two levels: a metal mask having a hole diameter of 500 μm used when screen printing a tin eutectic solder paste on an electrode, and a hole diameter of 700 μm. The sample according to Example 1 was also subjected to the same test. The sample according to Example 1 also has a metal mask having a hole diameter of 500 μm at the time of solder paste screen printing.
Two levels of 700 μm. The number of samples is 10 for each level. The test results are shown below.

[0033]

[Table 1]

Referring to Table 1, it can be seen that, at any level of the metal mask hole diameter, the life of the connection is longer in the second embodiment than in the first embodiment.

In all of the embodiments described above, a module board larger than an LSI and a circuit board are connected, but the present invention is not limited to this. It will be apparent that the present invention can be applied to the connection between a component or a substrate having a size of about an LSI and another substrate to achieve the same operation and effect as in the embodiment.

[0036]

According to the present invention, a plastic ball is included in the solder of the BGA connection structure, and by appropriately selecting the linear thermal expansion coefficient of the plastic ball, a gap is formed between the ball and the solder underlayer. In this case, the cross-sectional shape of the solder is in the shape of a drum with a hollow central portion in the height direction.

Thus, according to the present invention, when two substrates having different coefficients of thermal expansion are connected by BGA, distortion applied to components mounted near the connection portion can be reduced. This is because, by absorbing the relative displacement of the electrodes caused by the temperature change in the gap around the ball included in the connection portion, the strain applied to each substrate can be reduced.

Also, without increasing the volume of the connecting portion,
The life of the BGA connection with respect to the temperature cycle can be extended. No special parts such as a matching layer for thermal expansion and contraction that increase the volume of the connection are required.Moreover, since the cross section of the solder is shaped like a drum, when a shear stress is applied to the connection, the connection This is because it is possible to disperse the stress and strain and to delay the generation of cracks in the solder.

According to the present invention, the planar shapes of the electrodes of the module substrate and the circuit substrate are formed to have projections elongated in the direction of tensile stress.

Thus, according to the present invention, it is possible to prevent the life of the connection portion from being affected by the variation in the amount of solder supplied to the electrodes. By expanding the shape of the electrode in the direction in which tensile stress is applied, the cross-sectional shape of the solder is such that the stress does not concentrate even if the amount of supplied solder increases, and even if the amount of supplied solder decreases, the stress will be the most. This is because the thickness of the solder to be applied strongly is ensured.

The present invention has a particularly remarkable effect when applied to a case where a component or module board larger than an LSI or a circuit board is connected by a BGA.

[Brief description of the drawings]

FIG. 1 is a sectional view of a connecting portion according to a first embodiment of the present invention.

FIGS. 2A and 2B are diagrams sequentially illustrating the manufacturing process of Example 1. FIGS.

FIG. 3 is a plan view of a module substrate used in Example 1.

FIG. 4 is a sectional view of a solder-plated plastic ball used in Example 1.

FIG. 5 is a cross-sectional view of a solder protrusion including a plastic ball formed on an electrode of a module substrate in the first embodiment.

FIG. 6 is a perspective plan view of a module board and a circuit board of Example 2 mounted thereon, an enlarged plan view of an electrode on the module board, and an enlarged plan view of an electrode on the circuit board.

FIG. 7 is a cross-sectional view of a connection portion according to the second embodiment.

8A and 8B are a cross-sectional view of a connection part when the amount of solder is small and a cross-sectional view when a lot of solder is used in the second embodiment.

FIG. 9 is a plan view showing another example of the planar shape of the electrode in the second embodiment.

FIG. 10 is a cross-sectional view of an example of a conventional BGA connection structure.

FIG. 11 is a cross-sectional view of another example of a BGA connection structure according to the related art.

FIG. 12 is a sectional view of still another example of the BGA connection structure according to the related art.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Module board 2A, 2B electrode 3 Solder 4 Circuit board 5 Nickel film 6 Gap 7 Plastic ball 9 Solder paste 10 Solder plating plastic ball 11 Solder projection

Claims (5)

[Claims] 1. A BG in which electrodes provided on an electronic component or a module substrate on which a plurality of electronic components are mounted and electrodes on a circuit board surface to be connected to the electrodes are BGA-connected by soldering.
In the A connection structure, a nucleus made of plastic covered with an underlayer for the solder is included in the solder of the BGA connection structure, and a gap is provided at an interface between the nucleus and the underlayer covering the nucleus. BGA connection structure. 2. The BGA connection structure according to claim 1, wherein the melting point of the solder is 183 ° C. or higher. 3. The B according to claim 1, wherein the underlayer covering the nucleus is a nickel film, and the nucleus has a linear thermal expansion coefficient of 100 ppm / ° C. or more.
GA connection structure. 4. A B-type electrode according to claim 1, wherein a protruding electrode extending in a direction in which a shear stress is applied is added to a pair of electrodes connected by the BGA connection.
GA connection structure. 5. The protruding electrode has a width of not more than 1/3 of W and a length of 0.2 W of W when a distance in a direction perpendicular to a direction in which shear stress of the original electrode is applied is W. The BGA connection structure according to claim 4, wherein the BGA connection structure is twice or more.