JP4254911B2 - Socket for land grid array type package - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a socket technique that is suitably used when a land grid array type package having arrayed terminal electrodes is mounted on a substrate.
[0002]
[Prior art]
In general, it is known that it is difficult to reliably connect electrode groups formed on two substrates having different thermal expansion coefficients so as to face each other. For this reason, the following method has been conventionally employed in the operation of mounting a semiconductor on a printed wiring board.
[0003]
That is, when a semiconductor package is mounted on a printed wiring board and electrically connected, for example, a semiconductor chip is formed into a QFP (quad flat package) with long leads and the package is mounted on the printed wiring board. It was done. According to this method, a dimensional difference between the semiconductor and the printed wiring board due to a change in ambient temperature can be absorbed by the leads.
[0004]
Further, for the purpose of downsizing and high-speed operation of electronic devices, it has been conventionally performed to form semiconductor packages such as BGA (ball grid array) and LGA (land grid array). . In this example, a grid array terminal electrode is provided on the back side of the package instead of the lead.
[0005]
However, when a package having a long lead is used, the package becomes large, and since the lead is long, a signal is delayed and high-speed signal processing cannot be performed. Also, when a package such as BGA or LGA is mounted on a printed wiring board and soldered, the stress generated by the difference in thermal expansion between the printed wiring board and the package cannot be absorbed, and connection reliability cannot be obtained. Had a problem.
[0006]
As a solution of this point, a technique using an LGA type package socket has been developed.
FIG. 7 is an exploded perspective view showing an example of a socket used when an LGA type package is mounted on a printed wiring board. The socket 301 includes a socket main body 302 and a cover 303. The socket body 302 is provided with a mounting portion 305 to which the semiconductor package 304 is mounted.
[0007]
The mounting portion 305 is provided with contacts 310 (see FIG. 8) for electrically connecting the grid array-like terminal electrode group on the back side of the package 304 and the electrodes on the printed wiring board 306. A contact force of the contact 310 is obtained by a force that presses the package 304 against the socket body 302 with the cover 303. The force for pressing the package 304 with the cover 303 is obtained by the repulsive force of the spring 308 acting in a state where the cover 303 is attached to the socket main body 302 with the bolt 307. Reference numeral 309 denotes a stiffener for backing the printed wiring board 306.
[0008]
[Problems to be solved by the invention]
However, such a conventional LGA type package socket has problems to be solved in the following points.
[0009]
First, there is a problem of the distribution of force that presses the package 304 toward the socket body 302 by the spring 308 of the cover 303. The spring 308 is disposed near the periphery of the cover 303. Accordingly, the force pressing the package 304 acts on the periphery of the package 304. Therefore, a biased force that curves so that the central portion swells upward acts on the package 304 due to the repulsive force of the contact 310. As a result, there arises a problem that the contact strength between the terminal electrode group of the package 304 and the electrode group of the printed wiring board 306 is different between the central portion and the peripheral portion of the package 304. This problem becomes more prominent as the package 304 is made thinner. This is because the thinner the package 304 is, the easier it is to bend.
[0010]
Secondly, in the socket 301 having a configuration in which a large number of elastically deforming contacts 310 are provided in the socket main body 302, the presence of the contacts 310 hinders the miniaturization of the socket 301. Considering this point, a technique of connecting electrodes by interposing a flexible printed wiring board (FPC) for electrode connection between the terminal electrode group of the package 304 and the electrode on the printed wiring board 306 is also considered. Yes. Since this technique uses a flexible printed wiring board, it can be configured as a package socket corresponding to miniaturization and high density of semiconductors by miniaturizing the connection electrodes and increasing the density. However, since this technology only adopts the idea of providing connection electrodes at opposite positions on both sides of the flexible printed wiring board, this alone is not sufficient to obtain high connection reliability. There was a need to make improvements.
[0011]
Therefore, the object of the present invention is to obtain high connection reliability between the terminal electrode group of the land grid array type package and the electrode group on the substrate, and also to reduce the thickness, size and density of the semiconductor package. Another object is to provide a socket for a land grid array type package.
[0012]
[Means for Solving the Problems]
In order to solve the above problems, the present invention employs the following means.
A first means of the present invention is a socket for mounting a land grid array type package on a substrate, and a first electrode group connected to the arrayed terminal electrode group of the package is provided on one surface. A flexible wiring board provided with a second electrode group connected to the electrode group on the substrate on the other surface, a socket body on which the flexible wiring board is mounted, and a cover for pressing the package against the socket body side And
Each electrode of the first electrode group and each electrode of the second electrode group are arranged so as not to overlap each other in the thickness direction of the flexible wiring board.
[0013]
According to this means, each electrode of the first electrode group of the flexible wiring board and each electrode of the second electrode group are arranged so as not to overlap each other in the thickness direction of the flexible wiring board. For this reason, when the package and the flexible wiring board are pressed by the cover and pressed, the portion of the flexible wiring board between each electrode of the first electrode group and each electrode of the second electrode group is elastic in the pressing direction. To form a spring. This spring exerts an action of relieving stress due to a difference in thermal expansion between the package and the substrate. Furthermore, the effect which raises the connection strength of electrodes is exhibited. Thereby, high connection reliability between the terminal electrode group of the package and the electrode group on the substrate can be obtained.
[0014]
In the second means of the present invention, each electrode of the second electrode group connected to the electrode group on the substrate in the first means is constituted by a solder ball. If it does in this way, the electrode group on a board | substrate and the 2nd electrode group of a flexible wiring board can be easily connected using a solder flow technique.
[0015]
According to a third means of the present invention, each of the first electrode group and the second electrode group is composed of metal bumps. If it does in this way, each electrode group can be set as a suitable structure for using the flexible printed wiring board manufactured with the printing technique which can be densified and highly accurate.
[0016]
According to a fourth aspect of the present invention, a tension device is provided between the socket main body and the flexible wiring board to provide a force for pulling the flexible wiring board in a direction perpendicular to the direction in which the flexible wiring board is pressed by the cover. . When the tension device is provided in this way, tension is generated on the surface of the flexible wiring board, so that the flatness of the flexible wiring board can be improved. Thereby, the contact state of electrodes can be made more uniform. Further, by adjusting the tensile strength of the tension device, the flexibility and elasticity of the flexible wiring board can be adjusted to an optimum state for connecting the electrodes.
[0017]
According to a fifth aspect of the present invention, a plurality of protrusions that are brought into contact with the surface of the package directly or via rubber are provided on the back surface of the cover that faces the surface of the package. In this way, it is possible to make point contact with the surface of the package directly or indirectly at a plurality of locations with a plurality of protrusions provided on the cover.
[0018]
According to a sixth means of the present invention, the plurality of protrusions are arranged in a lattice pattern along the back surface portion of the cover, and the height of each protrusion is from the protrusion located near the center to the protrusion located near the center. It was set as the structure set so that it might become low as heading to. If it does in this way, the surface of a package can be pressed with uniform force only by setting up the projection length of each projection. Therefore, it is possible to prevent the package from being bent and to improve the uniformity of the contact strength between the electrodes.
[0019]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is an exploded perspective view of a land grid array type package socket 1 according to an embodiment of the present invention. FIG. 2 is a perspective view showing the back surface of the cover, and FIG. 3 is a sectional view of the protrusion. FIG. 4 shows an enlarged perspective view of the first electrode group and the second electrode group of the flexible wiring board.
[0020]
As shown in FIG. 1, the land grid array package socket 1 is used to back a socket body 2 as a positioner, an electrode-connecting flexible wiring board 30 on which the package 4 is mounted, and a substrate (board) 6. A stiffener 9 to be used, a cover 3, and a plurality of set screws 7 used for assembling and fixing the respective members to the substrate 6 are provided. A printed wiring board is used for the substrate 6.
[0021]
The socket body 2 is formed in a planar square plate shape, and a mounting portion 21 for mounting the flexible wiring board 30 is provided at the center portion thereof. The mounting portion 21 includes a square opening portion 22 provided in the center and positioning recesses 23 provided on the surface side of the socket body 2 so as to be positioned at the four corners of the opening portion 22. Accordingly, although the positioning recesses 23 are provided at four places, only three places are shown in FIG.
[0022]
The flexible wiring board 30 provides connection reliability when electrically connecting a grid array terminal electrode group (not shown) on the back side of the semiconductor package 4 and an electrode group (not shown) on the substrate 6. Provided to enhance. Therefore, the socket 1 including the flexible wiring board 30 has some special ideas.
[0023]
The first contrivance is that the electrode arrangement of the flexible wiring board 30 is different, the second contrivance is that a tension device that applies tension to the flexible wiring board 30 is provided, and the third contrivance is the cover 3. This is that a plurality of protrusions 3a for uniformly pressing the surface of the package 4 are provided on the back surface.
[0024]
First, the first device will be described. As shown in FIG. 3, a first electrode group 31 is provided on one surface of the flexible wiring board 30, and a second electrode group 32 is provided on the other surface. The first electrode group 31 is connected to the terminal electrode group of the semiconductor package 4, and the second electrode group 32 is connected to the electrode group on the substrate 6. Each electrode of the first electrode group 31 and the second electrode group 32 is connected by a lead 31b passing through a hole 31a penetrating the flexible wiring board 30 in the thickness direction. However, the electrodes of the first electrode group 31 and the electrodes of the second electrode group 32 are arranged so as not to overlap each other in the thickness direction of the flexible wiring board 30.
[0025]
That is, as shown in FIG. 3B, the first electrode group 31 is arranged in a grid pattern on the front surface side of the flexible wiring board 30, and the second electrode group 32 is also arranged in a grid pattern on the back surface side of the flexible wiring board 30. Although they are arranged, they are arranged in a staggered manner so that the electrodes do not overlap each other. 31 c is a reinforcing pattern of the flexible wiring board 30.
[0026]
4 and 5 schematically show examples of electrode arrangement of the flexible wiring board 30 in cross-sectional views. In the example of FIG. 4, the first electrode group 31 is composed of solder bumps, and the second electrode group 32 is composed of solder balls. In the example of FIG. 5, both the first electrode group 31 and the second electrode group 32 are configured by solder bumps. Since the first electrode group 31 and the second electrode group 32 are in a staggered arrangement with each other, an elastic portion 30b that is easily elastically deformed is formed around each electrode due to the difference in the pressing direction indicated by the arrows. Thereby, each electrode of the flexible wiring board 30 becomes a structure as if it had a spring around it.
[0027]
Next, the second device will be described. The tension device for applying tension to the flexible wiring board 30 is mainly composed of a spring member 40 as shown in FIG. The tension device has a pin 41 for providing the spring member 40 between the flexible wiring board 30 and the socket body 2. As shown in FIGS. 1 and 6, the flexible wiring board 30 and the socket body 2 are respectively provided with a hole 35 and a long hole 25 through which the pin 41 passes.
[0028]
The flexible wiring board 30 is formed in substantially the same planar shape as the mounting portion 21 of the socket body 2. The central portion 36 of the flexible wiring board 30 is accommodated in the opening portion 22. The portions of the four protruding pieces 37 extending in a cross shape from the four corners of the central portion 36 are respectively accommodated in the corresponding positioning recesses 23. In this state, the spring member 40 and the pin 41 are set (see FIG. 6). At this time, the spring member 40 is fixed in a state where both ends thereof enter the slit 24 extending from the positioning recess 23. At this time, the tension of pulling the flexible wiring board 30 from four directions is applied by the spring force of the spring member 40.
[0029]
Next, the third device will be described. In recent years, the number of thin semiconductor packages 4 is increasing due to the reduction in size and weight. For this reason, when the package 4 is pressed with a non-uniform force, the package 4 is likely to be slightly bent. For the purpose of eliminating this minute curvature, a plurality of protrusions 3a as shown in FIG. The region where the protrusion 3 a exists is a region corresponding to the flat portion 4 a on the surface of the package 4.
[0030]
These protrusions 3a are formed by pressing or the like when the cover 3 is made of a metal plate, and can be formed when the cover 3 is made of resin. It is preferable that the projections 3a have different heights when forming such projections 3a. In FIG. 2, the height of each protrusion 3 a is formed so as to gradually decrease from the protrusion 3 a located in the center toward the protrusion 3 a located in the periphery. The difference in height between the central projection 3a and the peripheral projection 3a depends on the curvature of the package 4 due to the type, size, material, and the like of the package 4. Furthermore, since the cover 3 may be curved, the curvature rate of the cover 3 is also taken into consideration. In any case, it is set so that the region of the flat portion 4a on the surface of the package 4 can be evenly pressurized.
[0031]
On the flat portion 4a of the package 4, a rubber 5 made of synthetic rubber or synthetic resin is disposed. The rubber 5 has a function of protecting the flat portion 4 a of the package 5. The rubber 5 further exhibits a function of evenly distributing the force for pressing the flat portion 4a by the plurality of protrusions 3a.
[0032]
In FIG. 1, 3 b, 2 b, 6 b are through holes for the set screw 7, and 9 b is a screw hole into which the set screw 7 is screwed. Reference numeral 6 c denotes an escape hole provided in the substrate 6 for the pin 41.
[0033]
According to the socket 1 having such a configuration, the flexible wiring board 30 is mounted on the socket body 2 by the spring member 40, and the package 4 and the rubber 5 are mounted on the flexible wiring board 30. The cover 3 is placed thereon, and the cover 3, the socket body 2, and the stiffener 9 are fixed to the substrate 6 with a set screw 7. The force for pressing the package 4 with the cover 3 is adjusted by the screwing strength of the set screw 7. The terminal electrode group of the package 4 and the first electrode group 31, and the second electrode group 32 and the electrode group on the substrate 6 are connected by a solder flow technique or the like.
[0034]
In a state where the package 4 is mounted on the substrate 6, the package 4 and the flexible wiring board 30 are pressed by the cover 3. Since each electrode of the first electrode group 31 of the flexible wiring board 30 and each electrode of the second electrode group 32 are arranged so as not to overlap each other in the thickness direction of the flexible wiring board 30, the first electrode group The elastic portion 30b of the flexible wiring board 30 between each electrode 31 and each electrode of the second electrode group 32 is elastically curved in the pressurizing direction to form a spring. This spring exerts an action of relieving stress due to a difference in thermal expansion between the package 4 and the substrate 6. Furthermore, the effect which raises the connection strength of electrodes is exhibited. Thereby, high connection reliability between the terminal electrode group of the package and the electrode group on the substrate can be obtained.
[0035]
Further, by providing a tension device mainly composed of the spring member 40, tension is generated on the surface of the flexible wiring board 30. As a result, the flatness of the flexible wiring board 30 is improved. Thereby, the contact state of electrodes can be made more uniform. Further, by adjusting the tensile strength of the tension device, it is possible to adjust the flexibility and elasticity of the flexible wiring board 30 to an optimum state for the connection between the electrodes.
[0036]
Further, by providing a plurality of protrusions 3a that are in contact with the flat portion 4a of the package 4 via the rubber 5 on the back surface portion of the cover 3 that faces the flat portion 4a of the front surface of the package 4, the plurality of protrusions 3a can be used to It is possible to make point contact with the surface of 4 indirectly at a plurality of locations. Of course, the protrusion 3a can be brought into direct contact with the flat surface 4a without using the rubber 5.
[0037]
A plurality of protrusions 3a are arranged in a lattice pattern along the back surface portion of the cover 3, and the height of each protrusion 3a increases from the protrusion 3a located near the center toward the protrusion 3a located near the periphery. By setting it to be low, the surface of the package 4 can be pressed with a uniform force only by setting the protrusion length of each protrusion 3a. Therefore, it is possible to prevent the package 4 from being bent and improve the uniformity of the contact strength between the electrodes.
[0038]
【The invention's effect】
As described above, according to the land grid array type package socket of the present invention, high connection reliability between the terminal electrode group of the package and the electrode on the substrate can be obtained, and the semiconductor package can be made thin and small. It is possible to cope with the increase in density and density.
[Brief description of the drawings]
FIG. 1 is an exploded perspective view of a land grid array type package socket according to the present invention.
2A and 2B show a cover of a socket according to the present invention, in which FIG. 2A is a perspective view showing a back surface of the cover, and FIG. 2B is a sectional view of a protrusion of the cover.
3A and 3B show a main part of the socket according to the present invention, in which FIG. 3A is a perspective view showing a relation between a flexible wiring board and its upper and lower members, and FIG. 3B is a circle of FIG. The expansion perspective view of the part enclosed with i.
FIG. 4 is a schematic view showing the electrode arrangement of the flexible wiring board according to the present invention in cross section.
FIG. 5 is a schematic view showing the electrode arrangement of the flexible wiring board according to the present invention in cross section.
FIG. 6 is an enlarged perspective view showing the relationship between a spring member and a positioning recess of the tension device according to the present invention.
FIG. 7 is an exploded perspective view showing a conventional socket for an RGA type package.
FIG. 8 is an enlarged partial cross-sectional view of a contact mounting portion of a conventional socket.
[Explanation of symbols]
1 Socket 2 Socket body 3 Cover 3a Protrusion 4 Package 5 Rubber 6 Board (Printed wiring board)
7 Set screw 9 Stiffener 21 Mounting portion 22 Opening portion 23 Positioning recess 24 Slit 25 Long hole 30 Flexible wiring board 30b Elastic portion 31 First electrode group 31a Hole 31b Lead 32 Second electrode group 35 Hole 36 Central portion 37 Projecting piece 40 Spring Member 41 pin

Claims (7)

A socket for mounting a land grid array type package on a substrate,
The first electrode group connected to the arrayed terminal electrode group of the package is provided on one surface, the second electrode group connected to the electrode group on the substrate is provided on the other surface, and the other flexible wiring board ,
A socket body to which the flexible wiring board is attached;
A cover for pressing the package against the socket body side;
Each electrode of the first electrode group and each electrode of the second electrode group are arranged so as not to overlap each other in the thickness direction of the flexible wiring board, and are holes that penetrate in the thickness direction of the flexible wiring board Socket for land grid array type package connected by lead passing through .   2. The land grid array type package socket according to claim 1, wherein each electrode of the second electrode group connected to the substrate-side electrode is formed of a solder ball.   The land grid array type package socket according to claim 1 or 2, wherein each of the first electrode group and the second electrode group is formed of a metal bump.   The land grid array type package socket according to any one of claims 1 to 3, wherein the flexible wiring board is constituted by a flexible printed wiring board in which the first electrode group and the second electrode group are formed by printing. . A tension device is provided between the socket body and the flexible wiring board in a direction perpendicular to the direction in which the flexible wiring board is pressed by the cover , and applies force to pull the flexible wiring board in four directions. The land grid array type package socket according to any one of claims 1 to 4. The flexible wiring board has a substantially rectangular central portion and four projecting pieces extending in a cross shape from the four corners of the central portion,
The land grid array type package socket according to claim 5, wherein the tension device is provided on the projecting piece, and the tension device is set to apply tension to pull the flexible wiring board from four directions. . A plurality of protrusions that are brought into contact with the surface of the package directly or via rubber are provided on the back surface portion of the cover that faces the surface of the package, and the plurality of protrusions are arranged in a lattice pattern along the back surface portion of the cover. 2. The height of each of the protrusions is set so as to decrease from a protrusion located near the center toward a protrusion located near the center to reduce a curvature generated in the package. Socket for land grid array type package.

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