JP2008021873A - Lsi package with interface module - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an LSI package with an interface module which can correspond to miniaturization, which has high material utilization efficiency, in which floating metal does not exist between electric connection terminals, and which has an excellent high frequency characteristic. <P>SOLUTION: An LSI package with an interface module comprises an interposer 10 carrying a signal processing LSI11, and having a connecting electric terminal 14 for a mounting board on a rear surface side and a first electric connection terminal 17 on a front surface side; and an interface module 20 on which a transmission line 21 for a high-speed signal for wiring with an external apparatus is provided, and which has a second electric terminal 26 on a rear surface side and is to be electrically connected with the interposer 10 by mechanical contact between the first and second electric connection terminals 17 and 26, in a state in which the interposer 10 is mounted on a mounting substrate. At least one of the first and second electric connection terminals 17 and 26 comprises a conductive rubber bump. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an LSI package with an interface module in which the structure of an electrical connection between an interface module for signal transmission for external wiring of high-speed signals and an interposer equipped with an LSI is improved.

  In recent years, the clock frequency of LSIs has been increasing, and 4 GHz or higher has been put into practical use in CPUs for personal computers. Furthermore, as multicore processing advances, the processing capability inside the CPU is further improved. However, the pace of improving the throughput of the interface between LSIs is moderate compared to the increase in internal processing capability, and this has become a bottleneck in the performance of personal computers. For this reason, research and development for increasing the throughput of interfaces has been actively conducted.

  In order to improve the throughput of the interface, it is necessary to improve the signal frequency per terminal and increase the number of terminals. However, when the number of terminals is increased in order to increase the parallelism and improve the throughput, the area of the wiring occupying the LSI and the package tends to increase, and the wiring length necessary for connection tends to increase. On the other hand, when the frequency per terminal is increased, the attenuation of the electric signal per unit length is increased and the line length is limited. Therefore, it is necessary to devise such as using a transmission line that suppresses attenuation as much as possible even for high-speed signals.

  It is effective to use an optical transmission line as a transmission line with little influence of signal frequency-dependent signal attenuation. In an optical fiber, signal attenuation due to transmission is almost negligible at about several tens of meters. When an optical waveguide is used, the absolute value of attenuation is a little as large as about 0.2 dB / cm. However, since the signal frequency dependence of attenuation that leads to signal degradation is small, the waveform degradation is small and large in transmission of about several tens of centimeters. Does not affect.

In order to use an optical transmission line, it is more advantageous to perform electrical / optical signal conversion in the immediate vicinity of the LSI. Therefore, a structure in which an optical interface module having a photoelectric conversion function is disposed in the immediate vicinity of the LSI package has been studied. In particular, after assembling the LSI package on the mounting substrate (PWB) using the normal mounting process, the optical interface module is mounted without a thermal process later, so that it is completely compatible with conventional LSI package mounting. An realized LSI package has been proposed (see, for example, Patent Document 1).
JP 2004-253456 A

  However, the example of Patent Document 1 has the following problems. In other words, as LSI throughput further increases, it is necessary to further reduce the pitch of electrical connections and increase the number of connection pins. However, if pins are used, there is a limit to miniaturization, and it is necessary to cope with narrow pitches. Is difficult.

  In addition, when an anisotropic conductive film is used for electrical connection, it can cope with a relatively small size, but the material utilization efficiency of the anisotropic conductive film is low (that is, even in a portion where there is no opposing electrode). Since conductive particles and fine metal wires are disposed), there is a problem that the price increases. Furthermore, since electrically floating conductive particles or fine metal wires exist in a portion very close to a conductive portion used as a signal line, there are problems such as noise sources and difficulty in impedance matching design.

  The present invention has been made in consideration of the above circumstances, and an object of the present invention is to provide an interface module that can easily connect an interposer and an interface module, can cope with miniaturization, and has excellent high-frequency characteristics. It is to provide an attached LSI package.

  In order to solve the above problems, the present invention adopts the following configuration.

  That is, according to one embodiment of the present invention, a signal processing LSI is mounted, an interposer having a mounting board connecting electrical terminal on the back surface side and a first electrical connecting terminal on the front surface side, and wiring with an external device. A high-speed signal transmission line is provided, has a second electrical connection terminal on the back side, and mechanical contact between the first and second electrical connection terminals in a state where the interposer is mounted on a mounting substrate. An interface module electrically connected to the interposer, wherein at least one of the first and second electrical connection terminals is made of a conductive rubber bump. To do.

  Further, according to another aspect of the present invention, a signal processing LSI is mounted, an interposer having a mounting board connection electric terminal on the back surface side and a first electric connection terminal on the front surface side, and wiring with an external device. A high-speed signal transmission line and a drive element for sending a signal to the transmission line or receiving a signal from the transmission line, and a second electrical connection paired with the first electrical connection terminal on the back side An interface module having a terminal and electrically connected to the interposer by mechanical contact of the first and second electrical connection terminals in a state where the interposer is mounted on a mounting substrate. In the LSI package with a module, at least one of the first and second electrical connection terminals is made of a conductive rubber bump.

  According to the present invention, since at least one of the first and second electrical connection terminals is formed of the conductive rubber bump, unlike the case where the connection is made using the connection pins, the LSI package can be sufficiently miniaturized. . And unlike the case where an anisotropic conductive film is used, since material utilization efficiency is high and there is no floating metal between electrical connection terminals, it is excellent in high frequency characteristics.

  The details of the present invention will be described below with reference to the illustrated embodiments.

(First embodiment)
1 and 2 are sectional views showing a schematic configuration of an LSI package with an interface module according to the first embodiment of the present invention. FIG. 1 shows a state before the interface module and the interposer are connected, and FIG. 2 shows a state after the connection.

  In the figure, reference numeral 10 denotes an interposer, and a signal processing LSI 11 is mounted at the center of the surface side of the interposer 10. Of the input / output of the LSI 11, the high-speed signal is electrically connected to the high-speed electrical wiring 13 formed on the surface of the interposer 10. The interposer 10 has a mounting board connection electrical terminal 14 on the back surface, and is constituted by, for example, a ball grid array (BGA) or the like, and is solder-reflow mounted on a mounting board (not shown). A power supply voltage, a relatively low-speed control signal, and GND are supplied from the mounting board to the LSI 11 through the interposer 10.

  A first electrical connection terminal 17 that is electrically connected to the wiring 13 is provided on the surface of the interposer 10. The surface of the wiring 13 is covered with a resist 15, and an opening is provided in a part of the resist 15. The first electrical connection terminal 17 is defined by the opening of the resist 15. Further, a crushing prevention spacer 16 for preventing crushing of conductive bumps, which will be described later, is provided around the first electrical connection terminal 17.

  20 in the figure is an interface module. This interface module 20 has a transmission line 21 for externally wiring a high-speed signal, and is a pigtail type in which one end is built in the interface module 20 and the other end protrudes to the outside. By adopting the pigtail type, it is not necessary to incorporate a connector for connecting the transmission lines in the interface module 20, and the size can be reduced. For this reason, the interface module 20 can be disposed in the immediate vicinity of the LSI 11 on the interposer 10, which is more advantageous for high-speed operation.

  The interface module 20 includes drive elements 22 and 23 for driving the transmission line 21. These drive elements 22 and 23 are drawn inward (LSI 1 side) by the internal wiring 24 and are connected to a second electrical connection terminal 26 provided on the lower surface of the interface module 20. The drive element 22 is, for example, an optical element composed of a light emitting element or a light receiving element optically coupled to an optical fiber (transmission line 21), and the drive element 23 is an interface (buffer) IC for driving the optical element. When an optical fiber is used for the transmission line 21, the transmission loss is almost negligible for a length of several tens of meters compared to the thin coaxial line, the diameter can be reduced and the size can be reduced, and the ground line is transmitted. There are many advantages such as separation by reception.

  The surface of the internal wiring 24 is covered with a resist 25, and an opening is provided in a part of the resist 25. The second electrical connection terminal 26 is defined by the opening of the resist 25 and is formed by providing conductive bumps on the wiring 24 exposed in the opening.

  The second electrical connection terminal 26 is electrically connected by mechanical contact with the first electrical connection terminal 17 connected to the electrical wiring 13 formed on the interposer 10. As described above, the interposer 10 is reflow-mounted in advance on the mounting board together with other components and connector members (not shown) by the mounting board connecting electrical terminals 14. After that, the first electrical connection terminal 17 and the second electrical connection terminal 26 are electrically connected only by mechanical contact without undergoing a thermal process, so that the insulator of the coaxial line used for the transmission line 21 There is an advantage that the interface module 20 containing a heat-sensitive material such as an optical fiber coating film can be mounted without being exposed to high temperature.

  The second electrical connection terminal 26 is made of a conductive rubber bump. The conductive rubber bump is made of, for example, Ag or C filler mixed in silicone rubber, and has elasticity. For this reason, when the electrical connection is configured in a state where it is mechanically pressed and pressure is applied, when the transmission line 21 is pulled upward with respect to the mounting board, the vertical movement due to the force applied to the electrical connection portion is increased. It is possible to maintain an electrical connection by expanding and contracting corresponding to the distortion of the direction. Therefore, even for a structure in which a large number of fine electrical connection portions are arranged, it is possible to absorb the variation and the difference in deformation size depending on the location.

  Specific examples of the conductive rubber bump material include (DA6524 manufactured by Toray Dow Corning). The conductive rubber bump is formed by applying it to a portion corresponding to the electrical connection portion by dispenser or screen printing and then thermosetting. For this reason, patterning is easy, material utilization efficiency is high, and it is also easy to form bumps with a height of several hundreds μm. Therefore, it is possible to cope with a large warp or deformation of several tens to several hundreds μm with its elasticity, and it is possible to realize an electrical connection part capable of maintaining electrical connection.

  As described above, the insulating portion and the opening are formed by the resist 15 on the electric wiring 13, and the opening may be formed so as to define the first electric connection terminal 17. The crush prevention spacer 16 is formed so as to surround the first electrical connection terminal 17. Here, the thickness of the crushing prevention spacer 16 is set so that the conductive rubber bumps 26 are appropriately crushed into a good shape in a state where the interface module 20 and the interposer 10 are finally connected. .

  In other words, the distance between the interface module 20 and the interposer 10 in the state where the interposer 10 is finally connected at the installation position of the conductive rubber bump 26 determined by the thickness of the crushing prevention spacer 16 is the distance between the conductive rubber bump 26 and the conductive rubber bump 26. It is set to be shorter than the initial height and longer than the height exceeding the elastic limit when the conductive rubber bump 20 is compressed.

  The effect of inserting the spacer 16 is as follows. It is assumed that the conductive rubber bumps 26 maintain electrical connection in a state where they are compressed within the elastic limit by pressing. However, if the conductive rubber bumps 26 are greatly strained due to deformation of the interposer 10 or the interface module 20 due to heat, the conductive rubber bumps 26 are electrically conductive. The elastic rubber bump 26 may be destroyed by being compressed beyond the elastic limit. Therefore, when compressed to a certain height or less, the amount of collapse can be controlled by the contact of the spacer 16. In this example, the spacer 16 is formed on the interposer 10 side. However, the spacer 16 may be formed so as to surround the periphery of the conductive rubber bump 26 on the interface module 20 side, and as shown in FIG. And the interposer 10 may be formed so as to be positioned around the conductive rubber bump 26 in a state of being electrically connected.

  As described above, according to the present embodiment, the conductive rubber bumps are used as the second electrical connection terminals 26 on the interface module 20 side, and the first electrical on the interposer 10 is mounted on the mounting substrate. By bringing the conductive rubber bumps 26 into contact with the connection terminals 17, the interposer 10 and the interface module 20 can be electrically connected without exposing the interface module 20 to a high temperature.

  In this case, as compared with the case where pins are used for electrical connection between the interposer 10 and the interface module 20, it is possible to sufficiently cope with further miniaturization of the LSI package. Furthermore, unlike the case of using an anisotropic conductive film, there is no inconvenience such as the presence of electrically floating conductive particles or fine metal wires in the vicinity of the conductive parts used as signal lines, and the speed is increased. Better. Further, by providing the spacer 16, it is possible to prevent the conductive bump 26 from being damaged due to excessive crushing, and to improve the connection reliability.

(Second Embodiment)
FIG. 3 and FIG. 4 are cross-sectional views showing the main configuration of an LSI package with an interface module according to the second embodiment of the present invention. FIG. 3 shows a state before the interface module and the interposer are connected, and FIG. 4 shows a state after the connection. 1 and 2 are denoted by the same reference numerals, and detailed description thereof is omitted.

  This embodiment is different from the first embodiment described above in that a connection holding portion for increasing the mechanical connection strength between the interposer 10 and the interface module 20 is provided. That is, a guide hole 18 penetrating from the front surface to the back surface is provided near the end of the interposer 10. On the other hand, the interface module 20 is provided with a fixing pin 28 to be inserted into the guide hole 18. The fixing pin 28 is disposed between the conductive rubber bump 26 and the transmission line 21 and is mechanically connected between the interface module 20 and the interposer 10 by being inserted into the guide hole 18 formed in the interposer 10. It is formed for the purpose of increasing strength.

  As shown in FIG. 4, when the interface module 20 and the interposer 10 are electrically connected, the transmission line 21 is distorted by a force in the direction in which the transmission line 21 is pulled upward with respect to the mounting board 30 (arrow A in FIG. 4). Tend to be large. This is because, when a force is applied in the downward direction, the transmission line 21 itself contacts the mounting board 30 and no further force is applied to the interface module 20. This is because a large force is applied to the interface module 20.

  FIG. 5 shows an enlarged view of this situation. As in this embodiment, by providing a fixing portion including a fixing pin 28 or the like at an intermediate position between the transmission line 21 and the conductive rubber bump 26, a force is applied to the transmission line 21 in the upward direction (the direction of arrow A in the figure). When it works, the fixing pin 28 serves as a fulcrum, and the left end of the interface module 10 moves downward (in the direction of arrow B in the figure) so that a force in the direction compressed by the conductive rubber bumps 26 acts. Thus, the electrical connection can be maintained within the elastic limit of the conductive rubber bump 26.

  Here, by forming the spacer 16 around the periphery, it is possible to prevent the conductive rubber bump 26 from being crushed beyond the elastic limit, which is more effective. The shape of the spacer 16 can be variously modified.

  6A to 6C show embodiments having different spacer shapes. FIG. 6A shows the spacer 16 having a shape in which a plurality of conductive rubber bumps 26 are collectively surrounded. This example is effective when the pitch of the electrical connection terminals is fine. FIG. 6B is an example showing the spacers 16 that are collectively formed while surrounding the periphery of each conductive rubber bump 26. In this case, since the spacer 16 can be disposed closer to the conductive rubber bump 26, the height can be more strictly limited.

  FIG. 6C shows an example in which the conductive rubber bumps 26 are equivalently surrounded by the plurality of spacers 16. In this example, when the spacer 16 is placed in contact with the electrical wiring 13 or the like and the electrical characteristics such as impedance are affected, the effect can be eliminated as much as possible.

  As described above, according to the present embodiment, the same effect as that of the first embodiment can be obtained, and the connection holding portion for increasing the mechanical connection strength between the interposer 10 and the interface module 20 is provided. As a result, the following effects can be obtained.

  Even when the transmission line 21 is pulled upward, the connection holding portion is positioned between the transmission line 21 and the mechanical contact (electrical connection), so that a force acts in a direction in which the conductive rubber bumps 26 are crushed. It can be configured as follows. Therefore, the collapse preventing spacer 16 is not damaged due to excessive collapse, and an increase in resistance due to a decrease in contact area can be prevented.

(Third embodiment)
FIGS. 7A to 7C are cross-sectional views showing the main configuration of an LSI package with an interface module according to the third embodiment of the present invention. In addition, the same code | symbol is attached | subjected to FIG. 1 and an identical part, and the detailed description is abbreviate | omitted.

  This embodiment is different from the first embodiment in that projections sharper than a flat conductive surface are provided by providing irregularities on a part of the conductive surface of the first electrical connection terminal 17. It is that.

  When the conductive rubber bumps 26 are pressed against the protrusions, the protrusions pierce the surface of the conductive rubber bumps 26 and break through the insulating film formed on the surface of the conductive rubber bumps 26 to maintain a stable electrical connection. There is an effect that can be.

  FIG. 7A shows an example in which a gold stud bump 71 is added to a flat electrical wiring as the first electrical connection terminal 17. As a result, the tip of the stud 71 pierces the conductive rubber bump 26. In FIG. 7B, a protrusion 72 made of an insulating material such as a resist or Cu metal is provided on the back side of a part of the conductive surface of the opening of the first electrical connection terminal 17 to form irregularities on the conductive surface. This is an example. This is a configuration in which a portion corresponding to the edge of the protrusion 72 pierces the conductive rubber bump 26. FIG. 7C shows an example in which unevenness (step) is formed by forming another electrical wiring 73 in the first electrical connection terminal 17 after the electrical wiring 13 is formed in advance.

  As described above, according to the present embodiment, the same effects as those of the first embodiment can be obtained, and a protrusion can be provided on the conductive surface of the electrical connection terminal facing the conductive rubber bump 26. Further, it is possible to obtain a more stable low contact resistance connection by breaking the insulating film formed on the bump 26 by the protruding portion during mechanical contact.

(Modification)
In addition, this invention is not limited to each embodiment mentioned above. The material of the conductive rubber bump is not limited to a material in which Ag or C filler is mixed in the silicone rubber, and may be any material having low resistance and sufficient elasticity. In the embodiment, the conductive rubber bumps are formed on the second electrical connection terminals on the interface module 20 side, but conversely, the conductive rubber bumps may be formed on the first electrical connection terminals on the interposer side. . Further, conductive rubber may be formed on both the first and second electrical connection terminals.

  In the embodiment, an example in which an optical fiber is used as the transmission line has been described. However, the same applies to the case where an electric transmission line such as a coaxial cable, a semi-rigid cable, or a flexible wiring board is used as the transmission line. The effect is obtained. That is, instead of the optical interface module, a line driver IC for driving the line and an electric transmission line, means for connecting them (for example, solder bumps and wire bonding), input / output terminals of the signal processing LSI outside the interface module, An interface module having a built-in input / output electrical terminal may be used.

  In addition, various modifications can be made without departing from the scope of the present invention.

Sectional drawing which shows schematic structure of the LSI package with an optical interface module concerning 1st Embodiment (state before a connection). Sectional drawing which shows schematic structure of the LSI package with an optical interface module concerning 1st Embodiment (state after a connection). Sectional drawing which shows the principal part structure of the LSI package with an optical interface module concerning 2nd Embodiment (state before a connection). Sectional drawing which shows the principal part structure of the LSI package with an optical interface module concerning 2nd Embodiment (state after a connection). Sectional drawing which is for demonstrating 2nd Embodiment, and shows the state where force was added to the A direction after the connection to the optical interface module. The top view which shows the example of arrangement | positioning of the spacer for collapsing prevention for demonstrating 2nd Embodiment. Sectional drawing which shows schematic structure of the LSI package with an optical interface module concerning 3rd Embodiment.

Explanation of symbols

10 ... Interposer 11 ... Signal processing LSI
DESCRIPTION OF SYMBOLS 13 ... Electric wiring 14 ... Electrical terminal for mounting board connection 15 ... Resist 16 ... Crush prevention spacer 17 ... 1st electrical connection terminal 18 ... Guide hole 20 ... Interface module 21 ... Transmission line 22, 23 ... Drive element 26 ... Conductivity Rubber bumps 28 ... Fixing pins 30 ... Mounting board

Claims (6)

A signal processing LSI, an interposer having a mounting board connecting electrical terminal on the back side and a first electrical connecting terminal on the front side;
A high-speed signal transmission line for wiring with an external device is provided, the second electrical connection terminal is provided on the back side, and the interposer is mounted on a mounting board, and the first and second An interface module electrically connected to the interposer by mechanical contact of electrical connection terminals;
Comprising
An LSI package with an interface module, wherein at least one of the first and second electrical connection terminals comprises a conductive rubber bump. A signal processing LSI, an interposer having a mounting board connecting electrical terminal on the back side and a first electrical connecting terminal on the front side;
A high-speed signal transmission line for wiring with an external device and a drive element for sending a signal to the transmission line or receiving a signal from the transmission line are provided, and is paired with the first electrical connection terminal on the back surface side. An interface module having a second electrical connection terminal and electrically connected to the interposer by mechanical contact of the first and second electrical connection terminals in a state where the interposer is mounted on a mounting substrate; ,
Comprising
An LSI package with an interface module, wherein at least one of the first and second electrical connection terminals comprises a conductive rubber bump.   3. The LSI package with an interface module according to claim 1, wherein a spacer is provided around the conductive rubber bump to prevent the bump from being crushed.   The connection holding part for increasing the mechanical connection strength between the interposer and the interface module is provided between the transmission line and the second electrical connection terminal. An LSI package with an interface module as described above.   One of the said 1st and 2nd electrical connection terminals consists of conductive rubber bumps, and the other has a projection part in the conductive surface which the said conductive rubber bumps contact, The one in any one of Claims 1-4 characterized by the above-mentioned. LSI package with interface module.   The said transmission line is an optical transmission line, It has at least one optical element of a light emitting element or a light receiving element, and the interface IC which drives this optical element as said drive element. An LSI package with an interface module according to any one of the above.

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