Connecting an integrated circuit to a printed circuit board

Abstract

A system (200, 400) comprising: an integrated circuit (205); a printed circuit board (215); and a ball grid array (210); wherein the integrated circuit (205) is mounted on the printed circuit board (215) by means of the ball grid array (210); and wherein the ball grid array (210) comprises at least one optical connection (235) configured to transmit optical signals (240).

Description

[0001] The present invention relates to a system comprising an integrated circuit, a printed circuit board, and a ball grid arrangement by means of which the integrated circuit is arranged on the printed circuit board. In particular, the present invention relates to a control unit comprising such a system and a vehicle comprising such a control unit.

[0002] Systems are known from the prior art in which integrated circuits (ICs) or packages containing integrated circuits are arranged on printed circuit boards using ball grid arrays (BGAs). The ball grid array electrically, mechanically, and thermally connects the integrated circuit or a surface-mounted device (SMD) arranged therein to the printed circuit board. For this purpose, the ball grid array comprises a large number of solder balls, which are usually arranged in a grid and which are melted during the so-called reflow soldering process. After cooling, they form a permanent connection between the integrated circuit and the printed circuit board or the contact pads of the printed circuit board.

[0003] Ball grid arrays can achieve a high density of connections per unit area, making them advantageous over traditional pin grid arrays (PGAs). The ever-increasing density of connections between an integrated circuit and a printed circuit board (PCB) also increases the requirements for signal integrity, EMC suppression, and increasing data rates between the integrated circuit and the printed circuit board.

[0004] The present invention is based on the object of further developing a connection between the integrated circuit and the printed circuit board in such a way that the above-mentioned requirements can be met in an improved manner.

[0005] According to a first aspect of the present invention, a system is proposed comprising an integrated circuit, a printed circuit board, and a ball grid array. The integrated circuit is mounted on the printed circuit board by means of the ball grid array. The ball grid array comprises at least one optical connection configured to transmit optical signals.

[0006] The integrated circuit can comprise an interposer or be mounted on an interposer, so that the proposed mixed electrical and optical ball grid arrangement is located between the interposer and the circuit board. In this case, the integrated circuit can be connected to the interposer using microbumps, particularly copper pillars.

[0007] The present invention is therefore primarily directed to ball grid arrays comprising at least one optical connection or one optical connecting element. The use of an optical connection in the ball grid array for transmitting optical signals between the integrated circuit and the printed circuit board makes it possible to connect an optical component in the integrated circuit to a corresponding optical component via the printed circuit board.

[0008] This enables the use of an optical communication system that can be less susceptible to EMC (electromagnetic compatibility) interference than conventional electrical circuits. Signal integrity can be improved compared to electrical transmission. Furthermore, the inventors have recognized that the use of optical communication systems allows for higher bandwidth transmission and reduces the power consumption of the integrated circuit. The use of optical components also enables a higher packing density of the integrated circuit.

[0009] According to a second aspect of the present invention, a method for connecting an integrated circuit to a printed circuit board using a ball grid array is shown, wherein the ball grid array comprises at least one optical connection. The method comprises the following steps: placing the integrated circuit on the printed circuit board such that solder balls of the ball grid arrays and the optical connection are each located in predetermined positions relative to the printed circuit board; and heating the ball grid array such that the solder balls are soldered to the printed circuit board and the optical connection is integrally connected to the printed circuit board.

[0010] The method according to the invention offers the particular advantage that the electrical connections can be made simultaneously by the solder balls and the optical connection, allowing for more efficient packaging. Manufacturing a control unit with such a system can be simple and reliable. Manufacturing costs can be kept lower.

[0011] According to a third aspect, the present invention relates to a control unit having a system according to the first aspect of the present invention. According to a fourth aspect, the present invention relates to a vehicle, in particular a motor vehicle, having a control unit according to the third aspect of the present invention.

[0012] Although at least one optical connection is mentioned according to the first aspect, the ball grid arrangement can comprise multiple optical connections that optically connect the integrated circuit to different locations on the circuit board. This makes it possible for the integrated circuit to be optically connected to and communicate with, for example, at least two other integrated circuits.

[0013] In one embodiment, the ball grid arrangement comprises a plurality of solder bumps for soldering to the circuit board, wherein the optical connection is configured to melt under similar conditions to a solder bump. If the optical connection has a similar or the same thermal behavior as a solder bump, both the electrical contact via the solder bumps and the optical contact via the optical connection between the integrated circuit and the circuit board can be established simultaneously. As a result, the reflow process for soldering the solder bumps or for optically contacting the optical connection only needs to be performed once. Furthermore, reflow processes known from the prior art can also be used in this case. The optical connection can be used in conjunction with an electrical connection with lead-free or lead-containing solder.

[0014] The optical connection can be configured to form a material bond with the circuit board upon melting. The bond can, in particular, involve gluing or welding. This allows the use of molten materials that can be bonded using a simple reflow process known from the prior art. In this case, it can be advantageous if the material for the optical connection is already bonded to a corresponding location on the integrated circuit prior to the reflow process. This allows the material to already be applied in the correct location to be bonded to the circuit board during the reflow process.

[0015] The optical connection may comprise a plastic. This may be a plastic with a melting temperature similar to that of the solder materials used for the solder balls. For example, a plastic with a melting temperature of approximately 180°C for leaded solder or approximately 194°C for lead-free solder may be used.

[0016] In a preferred embodiment, polycarbonate can be used as the plastic for the connection. Polycarbonate is an amorphous plastic that has no melting point, but at approximately 150°C, it can transform into a soft, rubbery state, in which it can be bonded to the circuit board. Alternatively, a thermoplastic polymer can be used, for example, of the type known as hot melt adhesive. The material can be based on polyamide, for example.

[0017] The integrated circuit may include an electronic component for emitting and / or receiving light in the region of the optical element. For example, the optical element may be an LED or a photodiode.

[0018] The optical connection can be connected to a light guide that extends in the circuit board, particularly in a horizontal direction, i.e., along or parallel to the surface of the circuit board facing the integrated circuit. This allows an optical signal to be guided into the circuit board in a horizontal direction, allowing the use of a compact integrated circuit with a small footprint. This also enables communication between the integrated circuit and another integrated circuit that is also connected to the circuit board. The circuits can be attached to the same or opposite surfaces of the circuit board. The packing density of the circuits on the circuit board can be high.

[0019] According to yet another embodiment, the optical connection is held captive on the integrated circuit. For the purposes of the present invention, captive means that the optical connection is arranged permanently or irreversibly on a surface of the integrated circuit facing the circuit board, so that the integrated circuit and the optical connection form a separately manageable unit. In particular, the optical connection can be held firmly on the circuit, for example by gluing or welding. This allows the optical connection to be connected to the integrated circuit before the integrated circuit is placed on the circuit board, similar to the solder balls of the ball grid arrangement.

[0020] The optical connection can be configured to prevent light from entering or exiting in a lateral direction. For example, the optical connection can be made of a material with a high refractive index. Preferably, the refractive index is greater than approximately 1.5 and can be up to 2 or even higher. This can effectively prevent light from being coupled in or out. This can result in improved signal integrity.

[0021] The optical connection can comprise a tube running between a semiconductor housing of the integrated circuit and the printed circuit board, through whose interior light can be transmitted. This allows the optical signal to be transmitted without interference even over long distances. An interior of the tube is preferably filled with a material that creates the optical connection. The tube can be made of a flexible material so that it securely seals the interior, while the distance between the circuit and the printed circuit board decreases when the solder balls melt. In another embodiment, the tube is easily deformable and can, for example, comprise a film. In both cases, it is possible to prevent the material of the optical connection from flowing unintentionally or from forming an undesired connection, for example with a neighboring solder ball.

[0022] The ball grid arrangement can comprise equally sized solder balls, with the optical connection preferably occupying the same area as a solder ball. This allows the optical connection to be integrated into a grid of solder balls. The solder balls are arranged, for example, in columns and rows in a checkerboard-like grid. The grid can be square or rectangular, for example. For example, the grid can comprise 2, 3, 4, or more rows and 2, 3, 4, or more columns. In some embodiments, a ball grid arrangement comprises a large number of elements, for example, more than 100 or several hundred.

[0023] Various ball grid arrangements are known that can be used with the proposed system. For example, a 10 x 10 arrangement can be used, whereby the optical connection can occupy one field of the known arrangement. Thus, instead of 100 electrical connections, only 99 electrical connections and one optical connection would be realized. In another embodiment, a known arrangement is extended by one field that can be occupied by the optical connection. In the example mentioned, for example, 9 rows of 10 columns and one row with 11 columns could be provided. The ball grid arrangement could thus comprise a total of 101 connections, one of which is optical and the others electrical. The electrical connections can remain in the known arrangement and the optical connection can be adjacent to it.

[0024] The integrated circuit may comprise a processing device, in particular a CPU or a GPU. The processing device may be mechanically, thermally, and / or electrically well connected to the circuit board by means of the ball grid arrangement, wherein communication between the processing device and the circuit board may be improved by means of the proposed optical connection.

[0025] The control unit according to the present invention can be used on board a motor vehicle and, for example, comprise a control unit for processing a video data stream from an environment sensor and / or a video camera for object detection or distance estimation. Furthermore, the control unit can be configured to process a video data stream from a rear-view camera or a control unit for controlling a navigation system.

[0026] 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 embodiment; Fig. 3 a bottom view of a ball grid arrangement; Fig. 4 a system according to a second embodiment; and Fig. 5 shows a flow chart of a procedure.

[0027] It should be noted that in the following detailed description, features or components of different embodiments that are identical or at least functionally identical to the corresponding features or components of another embodiment are provided with the same reference numerals or with reference numerals. To avoid unnecessary repetition, features or components already explained with reference to a previously described embodiment will not be explained in detail later.

[0028] Furthermore, it should be noted 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 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.

[0029] 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.

[0030] Fig. 1 shows a control unit 100 on board a motor vehicle 105. The motor vehicle 105 may, in particular, comprise a motorcycle, a passenger car, a truck, or a bus. Other types of motor vehicles, for example, agricultural vehicles or construction machinery, are also encompassed by the present invention.

[0031] The control unit 100 can be used, for example, to process a video data stream from an environment sensor and / or a video camera for object detection or distance estimation. The control unit can also be configured to process a video data stream from a rearview camera or to control a navigation system or an infotainment system. The control unit 100 comprises at least one system according to the first aspect of the present invention.

[0032] Fig. 2 shows a system 200. The system 200 comprises an integrated circuit 205, a ball grid array 210, and a printed circuit board 215. The integrated circuit 205, which is, for example, a processing unit for processing a video data stream, is electrically and mechanically attached to the printed circuit board 215 by means of the ball grid array 210. The ball grid array 210 is fixedly attached to a surface 225 of the circuit 205 and can be placed together with the circuit 205 onto a surface 230 of the printed circuit board 215, such that the solder balls 220 are located in predetermined positions relative to the printed circuit board 215 or relative to a surface 230 of the printed circuit board 215 facing the integrated circuit. The system 100 is then heated in a reflow soldering process, such that the solder balls 220 are bonded to the printed circuit board 215 orwith the surface 230 of which a material-locking electrical and thermal connection is created between the integrated circuit 205 and the circuit board.

[0033] According to the invention, the ball grid array 210 of the system 200 has at least one optical connection 235 configured to transmit optical signals 240 between the integrated circuit 205 and the printed circuit board 215. An optical connection 235 can replace or extend a solder bump 220 of the ball grid array 210.

[0034] In the embodiment according to Fig. 2, two optical connections 235 are visible, which can transmit optical signals 240 between the integrated circuit 205 and the circuit board 215. The optical signals 240 are emitted and received by an LED 245 and a photodiode 250, respectively, which are integrated in the integrated circuit 205. The optical components 245 and 250 thus enable the integrated circuit 205 to emit or receive light as an optical signal. Light can be used in a visible or invisible wavelength range.

[0035] Through the optical connection 235, data in the form of optical signals 240 can be exchanged between the integrated circuit 205 and the circuit board 215. A higher transmission rate between the integrated circuit 205 and the circuit board 215 can be achieved than with an electrical connection. Furthermore, through the optical connection 235, the optical signal 240 can be transmitted in an interference-free manner and with very good electromagnetic compatibility (EMC), so that the quality of the transmitted signal can be improved compared to ball grid arrangements known from the prior art.

[0036] Preferably, the optical connection 235 is configured to melt at a temperature similar to a solder ball 220. This allows the optical connection 235 to be connected to the circuit board 215 or to its surface 230 in one operation during the reflow process, using the solder balls 220. It may further be provided that the optical connection 235 comprises a material, such as plastic, which forms a material-to-material bond with the circuit board under the influence of heat.

[0037] Furthermore, it can be provided that the optical connection 235 is applied to the lower surface 225 of the circuit 205 before the integrated circuit 205 is placed on the circuit board 215, so that the optical connection 235 is permanently or captively connected to the surface 225 before the integrated circuit 205 is placed on the circuit board 215. In another embodiment, the optical connection can also be applied to the surface 230 of the circuit board 215 before the circuit 205 is placed. The optical connection 235 can be produced, for example, by means of a thermal process.

[0038] In Fig. 3 is a bottom view of an exemplary ball grid arrangement 210 according to Fig. 2. As shown in the Fig. 3, the ball grid arrangement 210 has two optical connections 235 and consists of a grid which, for example, consists of seven rows 305 and eight columns 310. In the present case, all solder balls 220 and the two optical connections 235 are the same size, so that the optical connections 235 occupy the same area of ​​the solder balls 220. This is particularly advantageous because the solder balls 220 can be replaced by further optical connections 235 without changing the grid of the ball grid arrangement 210, so that the ball grid arrangement 210 has a high degree of flexibility. However, the invention also encompasses the case where the ball grid arrangement 210 has a different structure than an optical connection 235.

[0039] Fig. 4 shows a system 400 which can be regarded as a further embodiment of a system 200. In contrast to the embodiments according to Fig. 2 and Fig. 3, the system 400 according to the Fig. 4 has a light guide 405 which extends horizontally in the circuit board 215. The light guide 405 is configured to transmit an optical signal between the integrated circuit 205, for example between an LED 245 of the integrated circuit 205 and a further integrated circuit 410. As a result, it can be provided, for example, that the further circuit 410 is arranged on the circuit board 215 by means of a further ball grid arrangement 415, preferably on a surface 420 of the circuit board 215 opposite the integrated circuit 215. As an alternative to the further circuit 410, a further circuit board 215 can also be used. Grid spacings of the ball grid arrangements 210 and 415 can be different.

[0040] However, it can also be provided that the further circuit 410 is arranged on the same surface 230 as the integrated circuit 205 by means of the further ball grid arrangement 415. The further ball grid arrangement 415 is constructed similarly to the ball grid arrangement 210 and has solder balls 230 and at least one optical connection 430, which is configured to transmit an optical signal between the light guide 405 and the further integrated circuit 410. Thus, the light guide 405 allows several integrated circuits 205, 410 arranged on the circuit board 215 to communicate with each other via optical signals.

[0041] According to the embodiment in the Fig. 4, it is further provided that the optical connection 235 has a vertically extending tube 425 between a semiconductor housing 406 of the integrated circuit 205 and the circuit board 215. The tube 425 can be filled with a transparent material. Preferably, the tube 425 is made of an opaque material so that light cannot enter or exit the tube 425 laterally. This allows for better optical signal quality. The signal can be transmitted with less loss. The interference immunity of the optical connection can be improved.

[0042] In Fig. 5 is a schematic representation of a method 500 according to the invention for connecting an integrated circuit 205 to a printed circuit board 215 by means of a ball grid arrangement 210, which can be used to form a system 200, 400 as in the embodiments according to the Fig.2 to 4 to train.

[0043] In a first step 505, the ball grid arrangement 210 can be connected to the integrated circuit 205 or to its surface 225, preferably in such a way that both the solder balls 220 and the optical connections 235 are permanently or captively connected to the surface 225. For this purpose, for example, a thermal process can be used, which results in a materially bonded connection between the solder balls 220 and the optical connections 235, on the one hand, and the surface 225 of the integrated circuit 205, on the other.

[0044] In a second step 510, the integrated circuit 205 can be placed on the circuit board 215, more preferably in such a way that the solder balls 220 and the optical connection 235 are located at predetermined positions relative to the circuit board 215. For example, it can be provided that the integrated circuit 205 is placed on the circuit board 215 in such a way that the optical connection 235 is located opposite the light guide 405 of the circuit board 215.

[0045] In a third step 515, the ball grid arrangement 210 can be heated such that the solder balls 220 are soldered to the circuit board 215 and the optical connection 235 is integrally bonded to the circuit board 215. For this purpose, the entire system 100, 400 is typically heated. For this purpose, a reflow process, for example, can be used, particularly if the solder balls 220 and the optical connections 235 have similar or identical thermal behavior with respect to establishing a connection to the circuit board 215.

[0046] The method 500 described above can also be used for connecting further integrated circuits 410 to the circuit board 215 by means of a ball grid arrangement 210 according to the invention. Reference symbol 100 control unit 105 Motor vehicle 200 systems 205 integrated circuit 210 ball grid arrangement 215 circuit board 220 solder beads 225 Surface 230 surface 235 optical connection 240 optical signal 245 LED 250 photodiode 305 series 310 column 400 system 405 light guides 410 additional integrated circuits 415 additional ball grid arrangement 420 surface 425 pipe 430 optical connection 500 procedures 505 Connect ball grid array to circuit 510 Place circuit on circuit board 515 Heat ball grid arrangement

Claims

[1] A system (200, 400) comprising an integrated circuit (205); a printed circuit board (215); and a ball grid array (210); wherein the integrated circuit (205) is mounted on the printed circuit board (215) by means of the ball grid array (210); and wherein the ball grid array (210) comprises at least one optical connection (235) configured to transmit optical signals (240). [2] The system (200, 400) of claim 1, wherein the ball grid array (210) comprises a plurality of solder balls (220) for soldering to the circuit board (215); and wherein the optical interconnect (235) is configured to melt under similar conditions as a solder ball (220). [3] The system (200, 400) of claim 2, wherein the optical connection (235) is configured to form a material connection with the circuit board (215) upon melting. [4] System (200, 400) according to one of the preceding claims, wherein the optical connection (235) comprises a plastic. [5] System according to (200, 400) any one of the preceding claims, wherein the integrated circuit (205) comprises an electronic component (245, 250) for emitting or receiving light in the region of the optical connection (235). [6] System (400) according to one of the preceding claims, wherein the optical connection (235) connects to a light guide (405) which extends horizontally in the circuit board (215). [7] System (200, 400) according to one of the preceding claims, wherein the optical connection (235) is held captively on the integrated circuit (205). [8] System (200, 400) according to one of the preceding claims, wherein the optical connection (235) is arranged to prevent light from entering or exiting in a lateral direction. [9] The system (400) of claim 8, wherein the optical connection (235) comprises a tube (425) extending between a semiconductor package (406) of the integrated circuit (205) and the circuit board (215), through the interior of which light can be transmitted. [10] The system (200, 400) of any preceding claim, wherein the ball grid array (210) comprises equally sized solder balls (220); and wherein the optical interconnect (235) occupies the same area as a solder ball (220). [11] System (200, 400) according to one of the preceding claims, wherein the integrated circuit (205) comprises a processing device. [12] A method for connecting an integrated circuit (205) to a printed circuit board (215) by means of a ball grid arrangement (210); wherein the ball grid arrangement (210) comprises at least one optical connection (235); wherein the method comprises the following steps: placing the integrated circuit (205) on the printed circuit board (215) such that solder balls (220) of the ball grid arrangement (210) and the optical connection (235) are each located in predetermined positions relative to the printed circuit board (215); and heating the ball grid arrangement (210) such that the solder balls (220) are soldered to the printed circuit board (215) and the optical connection (235) is integrally connected to the printed circuit board (215). [13] Control device (100) comprising a system (200, 400) according to one of claims 1 to 11. [14] Vehicle (105), in particular motor vehicle, comprising at least one control unit (100) according to claim 13.

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