Connecting a chip to a circuit board

Abstract

A system (210) comprises a chip (215); an interposer (220); a circuit board (225) comprising a first optical fiber (230); and an optoelectrical converter (260). The chip (215) is connected to the circuit board (225) by means of the interposer (220); and the optoelectrical converter (260) is configured to convert an electrical signal from the chip (215) into an optical signal and to feed the optical signal into the first optical fiber (225).

Description

[0001] The present invention relates to a system comprising a chip connected to a circuit board by means of an interposer. Furthermore, the present invention relates to a control unit comprising such a system and a vehicle having such a control unit.

[0002] Systems are known from the prior art in which an interposer electrically connects a chip to a circuit board. The chip comprises pins for electrical contact, which are regularly arranged at predetermined intervals, where the spacing is also called pitch. The interposer is used in particular to fan out the connections of the chips and to lead them to pins with a larger pitch, which can be more easily connected to the circuit board. Due to the increased spacing between adjacent pins, interference at the interface between the interposer and the circuit board is less easily coupled in or out. Electromagnetic compatibility (EMC), in particular interference immunity, can be increased, and the signal quality of a signal transmitted between the chips and the circuit board can be improved.

[0003] The ever-increasing density of pin connections between the chip and the interposer, and between the interposer and the circuit board, can make it difficult to integrate the chip and the interposer into the system without compromising the quality of the transmitted signals between the chip and the circuit board or worsening EMC. Another problem is that the higher density of pin connections can result in higher energy density, causing the connections to heat up. This can cause thermal management issues in the system.

[0004] The present invention is based on the object of providing an improved system of the type mentioned above. The invention achieves this object by means of the subject matter of the independent claims. Subclaims specify preferred embodiments.

[0005] According to a first aspect of the present invention, a system is proposed comprising a chip, an interposer, a circuit board, and an optoelectrical converter. The circuit board comprises a first optical fiber, and the chip is connected to the circuit board by means of the interposer. The optoelectrical converter is configured to convert an electrical signal from the chip into an optical signal and to feed the optical signal into the first optical fiber.

[0006] By using the first optoelectrical converter, it is possible to eliminate one or more electrical lines between the chip and the circuit board. This can reduce the number of electrical connections in the system. The energy density in the transition region between the circuit board and the interposer or between the interposer and the chip can be lowered. Heating of the system in this region can thus be reduced. The signal integrity of a signal routed via the optoelectrical converter can be increased compared to an electrically transmitted signal. The bandwidth of the optical signal can be larger than that of an electrical signal. EMC immunity can be improved.

[0007] For the purposes of the present invention, a chip is an electronic element comprising one or more semiconductors. The chip may comprise a single semiconductor, an integrated circuit comprising multiple semiconductors, or a chiplet. The chip may be embodied naked or with a package. A chip or chiplet typically comprises a semiconductor structure formed on a semiconductor crystal, for example, a silicon crystal.

[0008] In a first variant, the optoelectric converter is integrated into the chip. This allows for a particularly compact system design. The optoelectric converter can comprise a semiconductor, in particular a light emitter, for example in the form of an LED, and / or a light receptor, for example in the form of a photodiode. The semiconductor can be easily integrated into the semiconductor structure of the chip, thus reducing overall system costs.

[0009] In a second variant, the optoelectric converter is integrated into the interposer. Such an interposer can be used with various chips, allowing the system to be more flexible.

[0010] The interposer can comprise an optical fiber. This can be particularly advantageous if the first optoelectrical converter is integrated into the chip. Two optical fibers can also be provided in the interposer, with a first optical fiber in the interposer conducting optical signals to the first optoelectrical converter and a second optical fiber in the interposer conducting optical signals away from the optoelectrical converter. This allows two separate optical fibers to be used for communication between the first optoelectrical converter and the circuit board. A communication rate can be increased because optical signals can be received and transmitted by the optical converter simultaneously. The risk of mutual interference between a transmitting and receiving direction can be minimized.

[0011] A light guide in the interposer can be designed in the form of an optical via. An optical via comprises a transparent element that typically extends vertically between the circuit board and the chip and passes through a material of the interposer. A via can be made of glass or a transparent plastic, for example. Alternatively, an optical waveguide structure can be used, for example a glass fiber or a similar optical fiber. A via can be inserted into a corresponding recess in the interposer in the manner of a cylindrical insert, for example.

[0012] The system can further comprise a ball grid array with at least one optical connection, wherein the chip is connected to the interposer or the interposer is connected to the circuit board by means of the ball grid array. The optical connection is configured to transmit the optical signal between the chip and the interposer or between the interposer and the chip. This allows both electrical and optical signals to be transmitted and forwarded particularly easily.

[0013] A ball grid array can comprise a plurality of contacts arranged in a predetermined configuration. Typically, the contacts are located at predetermined positions in a matrix with rows and columns. The optical connection can take the place of one of the contacts and thus be integrated into the ball grid array. However, the optical connection can also be provided separately from a known electrical ball grid array, for example in the manner of an extension. A distance between the optical connection and an electrical contact can correspond to a distance between adjacent electrical contacts. The optical connection can take up approximately the same amount of space as an electrical contact. Alternatively, the optical connection can take up, for example, 2, 3, or 4 times as much space and replace a corresponding number of electrical connections.

[0014] Solder balls for soldering can be provided on the contacts; these can be heated in a reflow process and soldered to another adjacent contact. This allows an electrical connection to be established between the chip and the interposer, or between the interposer and the circuit board. The optical connection can be configured to be connected using the same process. For example, the optical connection can comprise a transparent terminating element that can form a materially bonded connection with an adjacent element under similar conditions to the solder. The optical connection can thus be established using the reflow process.

[0015] In one embodiment, the optical connection comprises a plastic with a melting temperature similar to that of the solder materials used for the solder bumps. For example, a plastic having a melting temperature of approximately 180°C may be used, which may correspond to a melting temperature of conventional solder. A well-suited plastic includes polyethylene, which may have a melting temperature in the range of approximately 140-200°C and exhibit high transparency. The optical connection may be configured to prevent light from entering or exiting in a lateral direction. For this purpose, an optical element with a high refractive index may be used. This may result in improved signal integrity.

[0016] In a third variant, the optoelectric converter is integrated into the circuit board. This allows the system to have a high degree of flexibility regarding the choice of interposer or chip. Furthermore, it can be easier to attach the interposer to the circuit board. The converter can be electrically connected to the interposer, for example, through contacts in a ball grid array.

[0017] The interposer can comprise or consist of an organic material. Interposers with or made of an organic material can be more resilient than, for example, semiconductor-based interposers. Processing of the material can be easier. An organic interposer can be manufactured cost-effectively. Alternatively, the interposer can comprise or consist of a semiconductor material such as silicon. Silicon provides a wide band bridge for conducting electrical signals, allowing the signals to be transmitted quickly and cleanly.

[0018] The circuit board can also include a second optical fiber. The first optical fiber can be configured to guide optical signals away from the optoelectrical converter; and the second optical fiber can guide optical signals to the optoelectrical converter. This can facilitate simultaneous transmission and reception. Mutual interference can be avoided. The transmission and reception directions can be separated. In some networks, this can be advantageously used to distribute messages in predetermined directions, for example, in a token ring or daisy chaining.

[0019] The system may further comprise another chip connected to the circuit board by means of another optoelectric converter. In conjunction with a system described herein, multiple chips on a circuit board can be optically connected to one another, allowing for improved utilization of the advantages of an optical connection, particularly high interference immunity, high transmission speed, and low sensitivity to interference. A technique described herein can contribute to ensuring that the longest possible portion of a transmission path between the chip and the additional chip is optical.

[0020] According to yet another aspect of the present invention, a control unit comprises a system described herein. The system can, for example, implement a processing device or a control apparatus. In one embodiment, the control apparatus can, for example, be used in a data center for processing information. In another embodiment, the control apparatus is configured to be used on board a motor vehicle. Due to its performance, the control unit can, for example, be configured to process a video data stream from an environment sensor and / or a video camera for object recognition or distance estimation. The control unit can also serve another purpose and, for example, be used in a navigation system or an active driver assistance system, such as a cruise control system or a distance control system.The control unit may also be configured to control an automatic gear change system.

[0021] According to yet another aspect of the present invention, a motor vehicle includes a control system as described herein.

[0022] The invention will now be described in more detail with reference to the accompanying figures, in which: Fig. 1 a motor vehicle with a control unit; Fig. 2 a side view of a system according to a first variant; Fig. 3 a side view of a system according to a second variant; Fig. 4 shows a side view of a system according to a third variant;

[0023] It should be understood that the embodiments described below represent only a limited selection of possible embodiments of the invention. In particular, it is possible to combine the features of individual embodiments or variants in a suitable manner, so that a multitude of different embodiments can be considered as obviously disclosed to those skilled in the art with the embodiments explicitly presented here.

[0024] It should also be noted that spatial terms such as "front" and "back," "top" and "bottom," "left" and "right," etc., are used to describe the relationship of one element to another element or elements as illustrated in the figures. Accordingly, the spatial terms may apply to orientations that are different from the orientations illustrated in the figures. However, it should be understood that all such spatial terms refer to the orientations illustrated in the drawings for convenience of description and are not necessarily limiting, since the particular device, component, etc. illustrated, when in use, may assume orientations that are different from those illustrated in the drawings.

[0025] Fig. 1 shows a motor vehicle 100 with a control unit 105 according to the invention. The motor vehicle 100 can, for example, comprise a motorcycle, a passenger car, a truck, or a bus. Other types of motor vehicles are also encompassed by the present invention.

[0026] The control unit 105 can, for example, be configured to process a video data stream from an environment sensor of a video camera for object detection or distance estimation, for example, for video data from a rearview camera. The control unit 105 can also perform another control task on board the motor vehicle 100, for example that of an ABS system, an entertainment system, or a communication system. The control unit 105 has at least one system described herein.

[0027] Fig. 2 shows a first variant of a system 210. The system 210 comprises a chip 215, an interposer 220, and a circuit board 225 in which a first light guide 230 and a second light guide 235 are provided. The light guides 230, 235 extend essentially horizontally and parallel to a surface of the circuit board 225. In the area of ​​the system 210, a vertically extending section is provided on each of the light guides 230, 235, through which light can be coupled into or out of the horizontal section.

[0028] A first ball grid arrangement 240 with a plurality of solder balls 245 connects the chip 215 to the interposer 220. The interposer 220 is connected to the circuit board 225 by means of a second ball grid arrangement 250, which also includes a plurality of solder balls 245. Electrical signal conductor elements 255, such as conductive traces, through-holes, or vias, can run within the interposer 220 to establish an electrical connection between the chip 215 and the circuit board 225 or between solder balls 245 of the first and second ball grid arrangements 240, 250. Electrical connections between contact elements of the same ball grid arrangement 240, 250 are also optionally implemented.

[0029] Furthermore, the system 210 comprises a first optoelectric converter 260, which is integrated in the interposer 220. In the embodiment according to Fig. 1, the first optoelectric converter 260 is integrated near an interface 265 between the interposer 220 and the circuit board 225. An interface comprises an interface at which two electrical and / or optical components are adjacent to one another and can be mechanically, electrically, and / or optically connected to one another.

[0030] The first optoelectric converter 260 may be attached to a surface of the interposer 220 facing the circuit board 225, as shown in Fig. 1, i.e., on the underside of the interposer 220. Preferably, a surface of the first optoelectrical converter 260 is flush with a surrounding surface of the interposer 220. For this purpose, the interposer can comprise a depression, a recess, or a cutout for the converter 260. Electrical connections of the first optoelectrical converter 260 can be connected by means of electrical signal conductor elements 255.

[0031] The converter 260 is optically connected to the optical fibers 230, 235. For this purpose, an optical connection 270 can be provided between the vertical sections of the optical fibers 230, 235 and the converter, which can preferably be produced in a similar way to a soldered connection between electrical connections of the second ball grid arrangement 250. In particular, an optical connection 270 can comprise a material that, under the influence of heat, can create a material-to-material connection between the interposer 220 and the circuit board 225 in the manner of a hot melt adhesive.

[0032] The first optoelectrical converter 260 can receive electrical signals from an electrical signal guide element 255, convert them into optical signals, and feed the optical signals into the first optical fiber 230 of the circuit board 225. The converter 260 can also receive optical signals from the second optical fiber 235 in the opposite direction, convert them into electrical signals, and transmit them to the chip 215 via an electrical signal element 255 and the first ball grid array 240.

[0033] Even if in the Fig. 2, it is possible that only one optical fiber 230, 235 is present and that optical signals are sent to the optoelectrical converter 260 and received by the optoelectrical converter 260 through this one optical fiber 230, 235.

[0034] The optical signals can be sent to or received from a second optoelectric converter (not shown in detail here) by means of the light guides 230, 235 extending horizontally in the circuit board 225, so that optical communication between the first chip 215 and a second chip (not shown here) is possible.

[0035] Even if it is in the Fig. 2, the first optoelectrical converter 260 can also be integrated into the interposer 220 at an interface 290 between the interposer 220 and the chip 215. In this case, a top side of the optoelectrical converter 260 can be flush with a surface facing the chip 215, so that the first ball grid arrangement 245 is not disturbed. If the interposer 220 is thicker than the converter 260, either sufficiently long optical connections 270 can be used to optically connect the converter 265 to the circuit board 225, or another light-conducting element can be provided for this purpose, for example, an optical via or a light guide.

[0036] The interposer 220 may be made of silicon or an organic material, or may comprise such a material. The material may comprise a resin, in particular polyester or epoxy resin, which may be reinforced, for example, with a fiber material containing glass or paper fibers. The circuit board 225 is preferably made of an electrically insulating material, such as FR4.

[0037] Fig. 3 shows a system 210 in a second variant. In contrast to the system shown in Fig. In the variant shown in Figure 2, the first optoelectric converter 260 is integrated into the chip 215, specifically in the vicinity of an interface 275 between the chip 215 and the interposer 220. The interposer 220 can comprise a first and a second optical fiber 280, 285, which are each optically connected to the first and second optical fibers 225, 230 of the circuit board 225, so that optical signals can be transmitted between the interposer 220 and the circuit board 225. A optical fiber 280, 285 can be designed as an optical via. Such a via can comprise a transparent body that is guided in the vertical direction through a corresponding hole in the material of the interposer 220, so that the interposer 220 is transparent in the vertical direction in the region of the via.

[0038] The second ball grid arrangement 250 comprises, as in the variant according to Fig. 2, optical connections 270, which serve to transmit optical signals between the first and second optical fibers 280, 285 of the interposer 220 and the first and second optical fibers 225, 235 of the circuit board.

[0039] An optical connection of a light guide 280, 285 toward the converter 265 can be made in the same way as toward a light guide 230, 235 in the circuit board 220. For this purpose, optical connections 270 can be used, which can establish a cohesive optical connection under the influence of heat. The heat exposure can be caused by a reflow process for soldering a ball grid arrangement 240, 250.

[0040] Fig. 4 shows a further variant of a system 210 described herein. In contrast to the systems described with reference to Fig. 2 and Fig. In the variants described in Figure 3, the first optoelectric converter 260 is integrated into the circuit board 220. Both the first ball grid arrangement 240 and the second ball grid arrangement 250 can have only solder balls 245 but no optical connections 270.

[0041] In all three versions of the Fig. 2, Fig. 3 and Fig. 4, it is possible for the system 210 to comprise a second chip (not shown), which is connected to the circuit board 225 or to its first and / or second optical fibers 230, 235 via a second optoelectrical converter (also not shown). This makes it possible to integrate multiple chips in a system 210 according to the invention by means of multiple optoelectrical converters 260 and to interconnect them for data purposes. Reference symbol 100 motor vehicles 105 Control unit 210 System 215 Chip 220 interposers 225 circuit board 230 first light guide of the circuit board 235 second light guide of the circuit board 240 first ball grid arrangement 245 solder bead 250 second ball grid arrangement 255 electrical signal conductor element 260 first optoelectric converter 265 Interface between the interposer and the circuit board 270 optical connection 275 Interface between the chip and the interposer 280 first light guide of the interposer 285 second light guide of the interposer 290 Interface between the interposer and the chip

Claims

[1] System (210) comprising: a chip (215); an interposer (220); a circuit board (225) comprising a first light guide (230); and an optoelectrical converter (260); wherein the chip (215) is connected to the circuit board (225) by means of the interposer (220); and wherein the optoelectrical converter (260) is configured to convert an electrical signal of the chip (215) into an optical signal and to feed the optical signal into the first light guide (230). [2] The system (210) of claim 1, wherein the optoelectric converter (260) is integrated in the chip (215). [3] The system (210) of claim 1, wherein the optoelectric converter (260) is integrated in the interposer (220). [4] The system (210) of claim 2 or 3, wherein the interposer (220) comprises a light guide (280, 285). [5] The system (210) of any one of claims 2 to 4, further comprising a ball grid array (240, 250) having at least one optical connection (270), wherein the chip (215) is connected to the interposer (220) or the interposer (220) is connected to the circuit board (225) by means of the ball grid array (240, 250); and wherein the optical connection (270) is configured to transmit the optical signal between the chip (215) and the interposer (220) or between the interposer (220) and the circuit board (225). [6] The system (210) of claim 1, wherein the optoelectric converter (260) is integrated into the circuit board (225). [7] System (210) according to one of the preceding claims, wherein the interposer (220) consists of or comprises an organic material. [8] The system (210) of any one of claims 1 to 6, wherein the interposer (220) is made of or comprises silicon. [9] The system (210) of any preceding claim, wherein the circuit board (225) comprises a second optical fiber (235); wherein the first optical fiber (230) is configured to guide optical signals away from the optoelectrical converter (260); and the second optical fiber (235) is configured to guide optical signals to the optoelectrical converter (260). [10] System (210) according to one of the preceding claims; further comprising a further chip connected to the circuit board (225) by means of a further optoelectric converter. [11] Control unit (105) with at least one system (210) according to one of claims 1 to 10. [12] Vehicle (100), in particular a motor vehicle, with a control unit (105) according to claim 11.

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