CN112216688A

CN112216688A - Support plate and optical module

Info

Publication number: CN112216688A
Application number: CN201910623034.9A
Authority: CN
Inventors: 方习贵; 孙雨舟; 王祥忠
Original assignee: Innolight Technology Suzhou Ltd
Current assignee: Innolight Technology Suzhou Ltd
Priority date: 2019-07-11
Filing date: 2019-07-11
Publication date: 2021-01-12

Abstract

The application discloses a carrier plate and an optical module, wherein the carrier plate comprises a PCB and a packaging substrate arranged in the PCB, the packaging substrate is provided with a conductive circuit, and the conductive circuit is electrically connected with the PCB; at least part of the packaging substrate is exposed out of the PCB to be used as a packaging area, and the packaging area is used for mounting a bare chip; the thermal expansion coefficient of the packaging substrate is smaller than that of the PCB. The manufacturing method combines the manufacturing processes of the packaging substrate and the PCB, the packaging substrate is pressed into the PCB, a high-precision circuit is arranged locally, the packaging requirement of the photoelectric chip can be met, and the rest part has high peeling strength and high plugging reliability; meanwhile, the method has the shortest high-speed link, effectively improves the high-frequency bandwidth and has lower cost.

Description

Support plate and optical module

Technical Field

The application relates to the technical field of optical communication, in particular to a carrier plate and an optical module.

Background

With the requirements of the 5G era on high bandwidth calculation, transmission and storage and the maturity of silicon optical technology, the optical interconnection era on boards and among boards has also been entered, the number of channels of optical modules has increased greatly, and the work of optical transceiver modules is controlled by an Application Specific Integrated Circuit (ASIC). In order to reduce the volume, the optical module is packaged with an optical chip or an optical module and an ASIC control chip to improve the interconnection density, so that the concept of optical-electrical co-packaging is proposed. Optoelectronic co-packages offer important advantages over traditional board edges and optical modules in boards in terms of bandwidth, size, weight and power consumption.

At present, there are 2 main types of optoelectronic co-package, one is to integrate various optoelectronic chips and/or signal processing chips on a package substrate, and attach them as a whole to a PCB (printed circuit board) of a module in a BGA (Ball Grid Array) form or a wire bonding form. The other method is to manufacture a module-level packaging substrate by using a chip process, a ceramic carrier plate or a packaging substrate process so as to meet the high-precision circuit requirement required by chip inversion, and flip or attach all photoelectric chips, control chips and the like on the packaging substrate. Although the former has been shortened a little compared with the high-speed link of the traditional board edge structure, the radio frequency bandwidth is also improved, but the link from the chip to the package substrate to the PCB still needs to be improved, and the high frequency still has an improved space. The latter, although having a short high speed link, is very limited in technology: 1. the package substrate is made into a module size, so that the cost is high; 2. in order to meet the circuit fineness requirement of the photoelectric chip inversion, a copper layer of a circuit layer is made to be very thin, the peeling strength is small, and the reliability of the mounting of an electronic chip and the plugging and unplugging of a golden finger is poor; 3. as the number of layers of the package substrate at the module level increases, the thickness of the package substrate increases, and the yield of fine lines is low.

Disclosure of Invention

The present application provides a carrier and an optical module, which employ a co-package (co-package) structure, have a shorter high-speed link, and have good high-frequency performance, high reliability and low cost.

In order to achieve one of the above objectives, the present application provides a carrier, including a PCB and a package substrate disposed in the PCB, wherein the package substrate is provided with a conductive circuit, and the conductive circuit is electrically connected to the PCB; at least part of the surface of the packaging substrate is exposed out of the PCB as a packaging area, and the packaging area is used for mounting and installing bare chips; the thermal expansion coefficient of the packaging substrate is smaller than that of the PCB.

As a further improvement of the embodiment, the package region is provided with pads, and the pitch of the pads is matched with the pitch of the pads of the bare chip to be mounted.

As a further improvement of the embodiment, the center-to-center pad-to-center spacing of the pads on the package region is less than or equal to 150 μm.

As a further refinement of an embodiment, the package substrate has a coefficient of thermal expansion in the horizontal direction that is less than or equal to 10 ppm/deg.c.

As a further improvement of the embodiment, the package substrate is a conductive silicon substrate, a conductive ceramic substrate, a conductive glass substrate, or a conductive BT plate.

As a further improvement of the embodiment, the peel strength of the surface circuit layer of the PCB board meets the peel strength requirement of surface mounting.

As a further improvement of the embodiment, the surface of the PCB board is provided with a surface mounting area and an electrical interface; the surface mount area is used for mounting a surface mount component.

As a further improvement of the embodiment, an accommodating space is arranged in the PCB, and the package substrate is arranged in the accommodating space; the accommodating space comprises at least one opening, and the opening penetrates through one surface of the PCB to ensure that at least part of the surface of the packaging substrate is exposed outside the PCB.

As a further improvement of the embodiment, the accommodating space is an open slot, the open slot includes a slot bottom and a side wall, the slot bottom is provided with a conductive hole, and the conductive hole is used for electrically connecting the conductive circuit of the package substrate and the PCB.

As a further improvement of the embodiment, a connecting portion is disposed at an opening of the accommodating space, and the connecting portion is press-fitted on a part of the surface of the package substrate;

the connecting portion is provided with a conductive hole, and the conductive hole is used for electrically connecting the conductive circuit of the packaging substrate and the PCB.

As a further improvement of the embodiment, the accommodating space includes an upper opening and a lower opening respectively penetrating through the upper surface and the lower surface of the PCB, the upper opening and/or the lower opening is provided with a connecting portion, and the connecting portion is press-fitted on a part of the surface of the package substrate;

As a further improvement of the embodiment, the side wall of the package substrate is provided with a side conductive layer; the conducting circuit of the packaging substrate is electrically connected with the side conducting layer, and the side conducting layer is electrically connected with the conducting layer of the PCB.

As a further improvement of the embodiment, the surface of the package substrate is a plane; or the surface of the packaging substrate is provided with a step surface.

As a further refinement of the embodiment, the surface of the package substrate has at least a first step face and a second step face;

the first step surface is exposed outside the PCB and serves as the packaging area;

the connecting part is pressed on the second step surface.

The beneficial effect of this application: the packaging substrate is laminated into the PCB by combining the manufacturing process of the packaging substrate and the PCB, the local part of the packaging substrate is provided with a high-precision circuit and a thermal expansion coefficient matched with the bare chip, the requirement of packaging the photoelectric bare chip can be met, and the rest part of the packaging substrate is provided with high peel strength and high plugging reliability; meanwhile, the shortest high-speed link is provided, the high-frequency bandwidth is effectively improved, the overall height of the assembly is reduced, and the cost is lower.

Drawings

FIG. 1 is a schematic diagram of an optical module according to the present application;

fig. 2 is a schematic diagram illustrating an assembly of a carrier and a chip of an optical module according to the present application; (ii) a

FIG. 3 is a schematic diagram illustrating an assembly of a carrier and a chip according to another embodiment of an optical module of the present application;

FIG. 4 is a schematic diagram of a carrier board in an optical module employing an on-board optical structure according to the present application;

fig. 5 is a schematic structural diagram of embodiment 1 of a hybrid carrier for optoelectronic co-package according to the present application;

fig. 6-9 are schematic diagrams illustrating a method for manufacturing a hybrid carrier for optoelectronic co-package according to the present application;

fig. 10 is a schematic structural diagram of a carrier board for optoelectronic co-package according to an embodiment 2 of the present application;

fig. 11 is a schematic diagram of another variation of the carrier structure according to embodiment 2 of the present application;

fig. 12 is a schematic diagram of another variation of the carrier structure in embodiment 2 of the present application.

Detailed Description

The present application will now be described in detail with reference to specific embodiments thereof as illustrated in the accompanying drawings. These embodiments are not intended to limit the present application, and structural, methodological, or functional changes made by those skilled in the art according to these embodiments are included in the scope of the present application.

In the various illustrations of the present application, certain dimensions of structures or portions may be exaggerated relative to other structures or portions for ease of illustration and, thus, are provided to illustrate only the basic structure of the subject matter of the present application.

Also, terms used herein such as "upper," "above," "lower," "below," and the like, denote relative spatial positions of one element or feature with respect to another element or feature as illustrated in the figures for ease of description. The spatially relative positional terms may be intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. For example, if the device in the figures is turned over, elements described as "below" or "beneath" other elements or features would then be oriented "above" the other elements or features. Thus, the exemplary term "below" can encompass both an orientation of above and below. The device may be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein interpreted accordingly. When an element or layer is referred to as being "on," or "connected" to another element or layer, it can be directly on, connected to, or intervening elements or layers may be present.

The present application provides a novel optical module packaged together with optical and electrical components, as shown in fig. 1 and 2, including a housing, an optical interface 200 disposed at one end of the housing, a bare chip 30 disposed in the housing, a surface mount component 40, and a carrier 100. The housing includes an upper housing 202 and a lower housing 201, and the carrier board 100 includes a PCB board, on which a package region 11, a surface mount region 27 and an electrical interface 26 are disposed. The bare chip 30 is flip-chip Mounted on the package region 11, and the Surface mount component 40 (SMT component for short) is Mounted on the Surface Mount Technology (SMT) region 27, where the Surface mount component 40 generally employs a packaged electronic chip or a resistor capacitor, and when the bare chip is employed, the bare chip needs to be processed to adapt to actual needs, and the mounting manner of the packaged Surface mount component 40 and the Surface mount region 27 is a common mounting Technology, and is not described herein again. The electrical interface 26 of the PCB is used as an electrical interface for plugging and unplugging the optical module, and generally a gold finger is used, and the gold finger is disposed on the upper and lower surfaces of one end of the carrier board 100. Of course, the electrical interface of the PCB may also be an interface for interfacing with other circuit boards, such as a flexible circuit board. The bare chip 30 includes a Photonic Integrated Circuit (PIC), and one or more of a Digital Signal Processor (DSP), a Driver (DRV), a trans-impedance amplifier (TIA), and the like. Here, the photonic integrated chip may be an integrated chip in which a laser, a detector, a modulator, and a waveguide are integrated, or may be an integrated chip in which a waveguide and a modulator are integrated, and the laser and the detector are separately provided from the photonic integrated chip. The laser and the detector which are separately arranged can be the laser and the detector which are commonly used in the traditional optical module, and can also be made into a bare chip which is reversely arranged on the packaging area. The surface mount component 40 may be a microprocessor, a memory, an application specific integrated circuit, or the like. The package region is provided with pads having a pitch (pitch) matching the pitch (pitch) of the pads of the bare chip 30. Generally, the distance between the center and the center of the pad on the packaging area is less than or equal to 150 μm, and the fineness is high. The surface mount area 27 and the electrical interface 26 are formed by a conventional PCB process, and have high peel strength and high insertion and extraction reliability.

The light received by the optical module enters the bare chip 30 (such as PIC or photodetector) and is converted into an electrical signal, the electrical signal is directly transmitted to a transimpedance amplifier (TIA) through the internal wiring of the package region 11 by the bare chip 30, and then transmitted to a high-speed line of the surface mounting region 27 and a related surface mounting component 40 through the internal wiring of the package region 11, and then transmitted to a golden finger through the wiring of the PCB board, and then transmitted to an external circuit or processor by the golden finger. Similarly, after receiving an external electrical signal command, the gold finger transmits the electrical signal command to the surface mount device 40 through the PCB board, the surface mount device 40 reads the electrical signal and transmits the electrical signal to the package region 11 through the high-speed line of the surface mount region 27, the package region 11 transmits the electrical signal to the driver, the driver drives the bare chip 30 (such as a laser chip or a photonic integrated chip) to work, and the bare chip 30 converts the electrical signal into an optical signal for output. Of course, the bare chip 30 may also process the optical signal and transmit the optical signal, for example, modulate, amplify, split, combine, etc. the optical signal. Since the bare chip 30 is directly flip-chip mounted on the package region 11 of the carrier 100, the shortest high-speed link between the chip and the carrier, i.e. the Host/line link, is the simplest, which can effectively improve the high-frequency bandwidth and achieve the best high-speed performance. The signal transmission is only described in the above specific embodiment, and in other embodiments, the bare chip on the package area may be one or more of a combination of a photonic integrated chip, a digital signal processor, a driver, a transimpedance amplifier, and the like, or an integrated chip of one or more of the above. In any combination, the signal transmission between the bare chip and the carrier is directly realized through the bonding pads in the packaging area, and the shortest high-speed link is provided. As shown in fig. 2, the package region 11 is disposed on the upper surface or the lower surface of the carrier 100, or as shown in fig. 3, both the upper surface and the lower surface of the carrier 100 may be provided with the package region 11, that is, the bare chips 30 may be totally flip-mounted on the upper surface or the lower surface of the carrier 100, or may be partially flip-mounted on the upper surface of the carrier 100 and partially flip-mounted on the lower surface of the carrier 100. Similarly, the upper and lower surfaces of the carrier 100 may be provided with the surface mounting regions 21 for mounting the surface mounting component 40, or only the upper or lower surface may be provided with the surface mounting regions 21. The optical module integrates the surface mounting component 40 and the bare chip 30 on a carrier 100; the carrier 100 has a high-definition circuit area suitable for the flip-chip mounting of the bare chip 30, i.e., a package area 11, and also has a PCB (printed circuit board) with high peel strength and high insertion and extraction reliability; and the cost is lower, and the whole height (thickness) of the packaging assembly is smaller.

The bare chip 30 is directly mounted on the package region 11 by flip-chip bonding, but in other embodiments, the bare chip 30 may be directly mounted on the package region 11 by Wire bonding.

In this embodiment, the electrical interface of the carrier board used by the optical module is a gold finger, and in other embodiments, other electrical interfaces may also be used. As shown in fig. 4, in an On-board optical (OBO) optical module, the electrical interface 26 of the carrier is an electrical contact pad for electrical connection with an external connector 400. The electrical contact pads (electrical interface 26) may be provided on one surface of the carrier and the surface mount areas 27 are provided on the surface of the carrier opposite the electrical contact pads. Alternatively, the electrical contact pads may be disposed on both the upper and lower surfaces of the carrier.

In the photoelectric co-packaged optical module, bare chips of the optical module can be directly inverted (flip chip) or Wire bonded (Wire bonding) to a PCB (printed circuit board), and the distance between bonding pads of the bare chips is designed to be matched with the distance between bonding pads on the PCB, so that Host/line (Host/line) side links of the optical module are the simplest, the high-speed link performance is optimal, and the overall optical module cost is low. Alternatively, a hybrid carrier board integrating a package substrate and a PCB board may be used, as described below.

In the following embodiments, a hybrid carrier used in the foregoing optical module with opto-electronic co-package will be described in detail, and the hybrid carrier combines the manufacturing processes of a package substrate and a PCB, and presses the package substrate into the PCB, so that a high-definition circuit is locally provided, which can meet the requirements of the package of an opto-electronic chip, and the rest has high peel strength and high plug reliability; meanwhile, the method has the shortest high-speed link, effectively improves the high-frequency bandwidth and has lower cost. Here, the package substrate refers to a substrate manufactured by using an integrated circuit substrate process, where the integrated circuit substrate process includes a carrier-like substrate technology or a ceramic substrate technology, for example, a substrate manufactured by using one or more of a full addition process, a half addition process (SAP), a modified half addition process (MSAP), and the like, and is suitable for an integrated circuit package. The surface of the packaging substrate can form a thinner fine circuit layer by adopting a copper increasing method so as to meet the requirement of bare chip mounting on high precision of the circuit.

Example 1

As shown in fig. 2 and 5, in this embodiment, the hybrid carrier for optical electrical co-package includes a PCB and a package substrate 10 laminated together, and the package substrate 10 is electrically connected to the PCB. The PCB includes a first sub-stack 21 and a second sub-stack 22, and the first sub-stack 21 and the second sub-stack 22 are respectively pressed on the upper surface and the lower surface of the package substrate 10. The package substrate 10 includes an insulating medium layer 12 and a conductive layer 13, wherein the insulating medium layer 12 is made of a material different from that of an insulating layer of the PCB. A window is provided on the first sub-stack 21 and/or the second sub-stack 22 of the PCB to expose a portion of the upper surface and/or the lower surface of the package substrate 10 as a package region 11, and the package region 11 is used for mounting a bare chip, such as a photonic integrated chip, a digital signal processor, a driver, a transimpedance amplifier, a laser chip, and/or a photodetector chip. That is, the package region 11 is a part of the surface of the package substrate 10, and is provided with pads, the pitch of the pads matches with the pitch of the pads of the bare chip to be mounted, generally, the center-to-center distance between the pads on the package region 11 is less than or equal to 150 μm, and the fineness is high, so as to meet the requirement of the bare chip mounting on the high precision of the line. The surface mounting area 27 and the electrical interface 26 of the hybrid carrier are disposed on the surface of the PCB, the surface mounting area 27 is used for mounting a surface mounting area, including a microprocessor, a memory or an asic, etc., and the surface circuit layer of a conventional PCB has high peel strength and high plug reliability, so that the peel strength of the circuit layer in the surface mounting area can meet the peel strength requirement of surface mounting.

In this embodiment, the conductive holes 25 are disposed in the first sub-stack 21 and the second sub-stack 22 of the PCB, and the PCB and the package substrate 10 are electrically connected through the conductive holes 25, so that a compact high-speed link is provided, the performance of the high-speed link is optimal, the high-frequency bandwidth is effectively improved, and the cost is low. Considering that the thermal expansion coefficient of the semiconductor material used for each bare chip is smaller than that of the insulating layer of the PCB, in order to match the thermal expansion coefficient of the bare chip and improve the reliability of the mounting and bonding of the bare chip, the insulating medium layer 12 of the package substrate 10 uses a material having a thermal expansion coefficient smaller than that of the insulating layer of the PCB so as to approach the thermal expansion coefficient of the bare chip as much as possible, for example, a material having a thermal expansion coefficient of 10 ppm/deg.c or less in the horizontal direction, including ceramic, glass, BT resin, silicon, or the like.

In this embodiment, as shown in fig. 5, the package substrate 10 is a thin conductive bt (bimoleimide triazine) board, and is manufactured by using an improved Semi-Additive process (MSAP) process, and the package region 11 thereof is provided with a first circuit layer and a pad, and a distance from a hub to a hub of the pad is less than or equal to 150 μm and is matched with a pad distance of a bare chip, so that a requirement of a high-precision circuit required for chip mounting can be satisfied, and the package substrate has a package function. The material of the insulating medium layer 12 is bt (bis (acrylamide) resin, and in other embodiments, the material of the insulating medium layer 12 may also be ceramic, glass, silicon, or the like, and may be made into a conductive ceramic substrate, a glass substrate, a silicon substrate, or the like. The thermal expansion coefficient of a silicon substrate or a BT plate is close to that of bare chips such as a photoelectric chip and a photonic integrated chip, the stability of chip mounting and combination is better, and the reliability of products is higher. When the BT resin is used to fabricate the package substrate, the conductive via 25 between the PCB and the package substrate 10 may directly penetrate through the PCB and the package substrate 10. When the packaging substrate is made of silicon, ceramic or glass, a conductive connecting disc can be arranged on the surface of the packaging substrate pressed in the PCB, and the conductive hole between the PCB and the packaging substrate penetrates through the PCB and is connected with the conductive connecting disc on the surface of the packaging substrate, so that the electrical connection between the PCB and the packaging substrate is realized.

In addition, surface mount components are typically mounted on a PCB board using a Surface Mount Technology (SMT). In this embodiment, the first sub-stack 21 and the second sub-stack 22 of the PCB respectively include a core board 24 and a prepreg 23, only the PCB on the upper layer of the package substrate 10 is marked in fig. 5, and only one core board and one prepreg are shown, and those skilled in the art know that the PCB on the upper layer of the package substrate 10 may have the same or different structure as the upper PCB, and the number of the core boards and the number of the prepregs may also be designed as required. The thickness of the copper layer of the PCB process is thick, the stripping degree between the copper layer of the core board 24 and the board is large, the surface mounting area and the golden finger are arranged on the PCB, the SMT bonding reliability is high, the plugging reliability of the golden finger (electrical interface) is also high, and the problems that the package substrate 10 cannot meet the requirement of the strong stripping degree of the SMT and the plugging reliability of the golden finger is poor are solved.

The size and position of the package area may be designed according to actual use requirements, and as shown in fig. 2, one end of the carrier board may be occupied as the package area 11, or as shown in fig. 3, the middle area of one end of the carrier board may be occupied as the package area 11. The package region may be provided on the lower surface of the package substrate, or both the upper surface and the lower surface of the package substrate may be provided with the package region. Correspondingly, the sub-stacks of the PCB board pressed on the upper surface and the lower surface of the packaging substrate are provided with corresponding windows to expose the packaging area.

The hybrid carrier for photoelectric co-packaging of the application utilizes the packaging substrate technology, such as the similar carrier technology or the ceramic substrate technology, i.e. the semi-additive process (SAP) or the improved semi-additive process (MSAP), to manufacture the packaging substrate with thinner thickness and fewer layers according to the precision requirement of bare chip mounting. The packaging substrate is divided into a packaging area and a connecting area, the packaging area is used for mounting bare chips such as photoelectric chips and/or photonic integrated chips, and the connecting area is used for pressing the PCB. Specifically, the manufacturing method of the hybrid carrier board for photoelectric co-encapsulation comprises the following steps:

and manufacturing a packaging substrate, wherein the packaging substrate comprises an insulating medium layer and a conducting layer which are stacked, and the number of the insulating medium layer and the conducting layer can be one or more according to the requirement. When the conducting layers are multiple layers, the conducting layers are electrically connected by adopting the conducting holes, and certainly, in other embodiments, the conducting layers can also be electrically connected by adopting a side wall electroplating mode;

manufacturing a packaging area for mounting a bare chip on the upper surface and/or the lower surface of a packaging substrate, wherein the packaging area is provided with a first circuit layer, and a bonding pad is formed on the first circuit layer;

manufacturing a first sub-stack and a second sub-stack of the PCB;

respectively pressing a first sub-stack and a second sub-stack of the PCB on the upper surface and the lower surface of the packaging substrate, wherein the first sub-stack and/or the second sub-stack of the PCB are/is provided with a window corresponding to the packaging area so as to expose the packaging area;

manufacturing conductive holes between the first sub-stack structure and the second sub-stack structure of the PCB and the packaging substrate, wherein the conductive holes are used for electrically connecting the PCB and the packaging substrate; and manufacturing a second circuit layer and an electrical interface on the surface of the PCB.

The method for manufacturing the package substrate includes a semi-additive process (SAP) or a modified semi-additive process (MSAP), and the package substrate is made into a ceramic substrate, a silicon substrate, a glass substrate or a BT board with a thinner thickness and a smaller number of layers according to the accuracy requirement of bare chip mounting.

In the method for laminating the first sub-stack and the second sub-stack of the PCB on the upper surface and the lower surface of the package substrate, the window on the first sub-stack and/or the second sub-stack may be manufactured after lamination, or the window may be manufactured first and then laminated. Specifically, the following two manufacturing methods are used.

As shown in fig. 6 to 9, the method for respectively pressing the first sub-stack and the second sub-stack of the PCB on the upper surface and the lower surface of the package substrate includes:

providing a prepreg 23, and manufacturing a first window 231 on the prepreg 23, wherein the position and the size of the first window 231 correspond to the packaging area; that is, the first window 231 is located above the package region, and the window size is the same as or slightly larger than the package region;

laminating the prepreg 23 on the upper surface or the lower surface of the package substrate 10, and filling a release film 50 at the first window;

providing a first sub-stack 24 and a second sub-stack 22 of PCB boards;

laminating the sub-stack 24 of the PCB on the prepreg 23, and laminating the second sub-stack 22 on the lower surface of the package substrate 10;

and manufacturing a second windowing on the first sub-stack 24 of the PCB, wherein the position and the size of the second windowing are consistent with those of the first windowing, and taking out the release film to expose the packaging area 11. The method for making the second windowing can adopt a depth-controlled milling technology.

The step of respectively pressing the first sub-stack and the second sub-stack of the PCB on the upper surface and the lower surface of the package substrate may further adopt a method including:

providing a prepreg, and manufacturing a first window on the prepreg, wherein the position and the size of the first window correspond to the packaging area;

superposing the prepreg on the upper surface or the lower surface of the packaging substrate, and filling a release film at the first windowing position;

providing a first sub-stack and a second sub-stack of the PCB, and manufacturing a second window on the sub-stack of the PCB, wherein the position and the size of the second window are consistent with those of the first window;

laminating the sub-stack of the PCB on the prepreg;

and taking out the release film to expose the packaging area.

In the method, a first windowing of the prepreg and a second windowing of the stacked PCB can be prepared in advance, then the prepreg which is prepared with the windowing in advance is stacked on the packaging substrate, the first windowing position is filled with the release film, then the stacked PCB which is prepared with the windowing in advance is pressed on the prepreg, and finally the release film is taken out to expose the packaging area.

The prepreg in each manufacturing method is a low-flow adhesive layer, a low-flow adhesive PP layer is generally adopted, the low-flow adhesive layer has low fluidity when heated and pressed, and the release film also plays a role in supporting and protecting, so that the low-flow adhesive is prevented from flowing to a packaging area. The size of the connection area of the packaging substrate is designed according to the PCB process capability, and the surface of the PCB is subjected to surface treatment according to the common PCB manufacturing process, such as green oil laying and the like. The packaging area is used as a bare chip mounting area with fine process, has precise circuits and is used for mounting a photoelectric chip and a photonic integrated chip (bare chip), the PCB has common PCB functions, namely SMT and golden finger functions, and forms a photoelectric co-packaging (co-packaging) carrier plate with local high-precision circuits and high peel strength and high plugging reliability at the rest part. The shortest high-speed link is arranged between the carrier PCB and the packaging substrate, so that the high-frequency bandwidth is effectively improved, and the cost is lower.

Example 2

As shown in fig. 10 to 12, in the optical module of the present application, a carrier may also be used, where the carrier includes a PCB 20 and a package substrate 10 disposed in the PCB 20, and the package substrate 10 is provided with a conductive circuit, and the conductive circuit is electrically connected to the PCB. The surface of the package substrate 10 is at least partially exposed outside the PCB 20 as a package region 11, and the package region 11 is used for mounting a bare chip 30, such as a digital signal processor, a driver, a transimpedance amplifier, an optoelectronic chip and/or a photonic integrated chip. Specifically, the PCB 20 has a receiving space, the package substrate 10 is embedded in the receiving space, and the receiving space includes at least one opening, the opening penetrates through a surface of the PCB, so that at least a portion of the surface of the package substrate 10 is exposed outside the PCB to serve as the package region 11. The thermal expansion coefficient of the package substrate 10 is smaller than that of the PCB 20, and is close to that of semiconductor chips such as photonic integrated chips, wherein the thermal expansion coefficient of the package substrate 10 in the horizontal direction is smaller than 10 ppm/DEG C, and the package substrate 10 is, for example, a conductive silicon substrate, a conductive ceramic substrate, a conductive glass substrate or a conductive BT plate, so that the problem of poor reliability caused by mismatch of the thermal expansion coefficients of the PCB and the bare chip is avoided, the mounting and bonding stability of the bare chip is better, and the product reliability is higher.

In this embodiment, the package substrate 10 is a thin conductive silicon substrate and is manufactured by an improved Semi-Additive process (MSAP) process, the package region 11 is provided with a first circuit layer, the first circuit layer is formed with a pad, and a distance from a hub to a hub of the pad on the package region 11 is less than or equal to 150 μm and is matched with a pad distance of the bare chip 30 to be mounted, so that a high-precision circuit requirement required by the mounting of the bare chip can be satisfied, and the package substrate has a package function. In addition, surface mount component 40 is typically mounted on PCB board 20 using Surface Mount Technology (SMT). In this embodiment, the PCB 20 includes a core board and a prepreg, the thickness of the copper layer of the PCB process is thick, the peeling degree between the copper layer of the core board and the board is very large, the SMT bonding reliability is high, and the gold finger (electrical interface) plugging reliability is also high, i.e., the peeling strength of the circuit layer on the surface of the PCB board meets the peeling strength requirement of surface mounting, and the problems that the package substrate 10 cannot meet the strong peeling degree requirement of SMT and the gold finger plugging reliability is not good are solved.

The package substrate 10 includes a plurality of insulating dielectric layers and conductive layers, and the conductive layers are electrically connected to each other through conductive holes, but in other embodiments, the conductive layers may also be electrically connected to each other through a sidewall electroplating method. The package substrate 10 may be a cuboid or a step, and is embedded in the PCB 20, a part of the PCB 20 is laminated on at least a part of the bottom surface or at least a part of the upper surface of the package substrate 10, and a conductive hole 25 is disposed at a position laminated on the package substrate 10, and the PCB 20 and the package substrate 10 are electrically connected through the conductive hole 25.

Specifically, as shown in fig. 10, the accommodating space of the PCB 20 for embedding the package substrate 10 is an open slot, which may be a blind slot and includes a slot bottom and a slot sidewall, the package substrate 10 and the slot bottom of the open slot are pressed together, and the PCB 20 has a conductive hole 25 at the slot bottom of the open slot and electrically connected to the package substrate 10. Meanwhile, the PCB 20 may further extend a connection portion at the upper surface of the package substrate 10, i.e. at the notch (the opening of the accommodating space), the connection portion is pressed on a portion of the upper surface of the package substrate 10 to expose a portion of the upper surface of the package substrate 10 as the package region 11, and the connection portion is also provided with a second conductive hole for electrically connecting the PCB 20 and the package substrate 10.

As shown in fig. 10, during manufacturing, a package substrate 10 and a PCB 20 are provided; pads are formed on the upper surface of the package substrate 20 as package regions 11, and conductive lands are formed on the lower surface of the package substrate and electrically connected to the conductive lands. Manufacturing an open slot on the PCB 20, and pressing the package substrate 10 into the open slot; and manufacturing a conductive hole 25 at the bottom of the open slot, so that the conductive hole 25 is connected with a conductive connecting disc on the lower surface of the packaging substrate 10, and the electrical connection between the packaging substrate 10 and the PCB 20 is realized. On the PCB board 20, die pads for mounting the surface mount components 40 are fabricated as the surface mount areas 27 and gold fingers are fabricated as the electrical interfaces 26.

Alternatively, the accommodating space includes an upper opening and a lower opening respectively penetrating through the upper surface and the lower surface of the PCB, as shown in fig. 11, the package substrate 10 is embedded in the accommodating space, the PCB 20 further extends to form a connecting portion 28 on the upper surface (corresponding to the upper opening of the accommodating space) and/or the lower surface (corresponding to the lower opening of the accommodating space) of the package substrate 10, the connecting portion 28 of the PCB 20 is pressed on a portion of the upper surface and/or a portion of the lower surface of the package substrate 10 to expose the portion of the upper surface and/or the portion of the lower surface of the package substrate 10 as the package region 11, and the connecting portion 28 is provided with a conductive hole 25 for electrically connecting the PCB 20 and the package substrate 10.

As shown in fig. 11, during manufacturing, a package substrate 10 and a PCB 20 are provided; a pad is formed as a package region 11 in a partial region of the upper surface of the package substrate 10, and a conductive land is formed in another region of the upper surface, and the pad is electrically connected to the conductive land. Manufacturing an accommodating space on the PCB 20, and pressing the package substrate 10 into the accommodating space to make the upper surface of the package substrate 10 flush with the upper surface of the PCB 20; manufacturing a connecting part 28 on the upper opening of the accommodating space, so that the connecting part 28 covers the conductive connecting disc on the surface of the packaging substrate 10; conductive holes 25 are formed in the connection portions 28, and the conductive holes 25 are connected to conductive lands of the package substrate 10, thereby electrically connecting the package substrate 10 and the PCB 20. Of course, in other embodiments, since the accommodating space penetrates through the upper and lower surfaces of the PCB, the package region and/or the conductive land may be formed on the lower surface of the package substrate, and the connecting portion and the conductive hole thereof may be formed in the lower opening of the accommodating space.

The method for manufacturing the connecting part 28 comprises the following steps: providing a low-flow film, and manufacturing a first window on the low-flow film to expose a pad (a packaging area 11) on a packaging substrate 10; superposing the low-flow film on a PCB, and filling a release film at a first window of the PCB so as to protect the bonding pad; providing a PCB board stack 29; pressing the PCB board stack 29 on the low-flow film, and forming a second window on the PCB board stack 29, wherein the position and size of the second window are consistent with those of the first window; the release film is removed to expose the pads of the package substrate 10, and chip pads for mounting the surface mount device 40 and gold fingers are formed on the PCB stack 29. The step of manufacturing the second window on the PCB stack may be manufacturing by a depth-control groove milling method after laminating the PCB stack on the low-flow film, or manufacturing the second window on the PCB stack and laminating the PCB stack on the low-flow film.

In the embodiment shown in fig. 10 and 11, the package substrate is a rectangular parallelepiped, and in other embodiments, the package substrate may also be a step body or other deformation body. As shown in fig. 12, the upper surface of the package substrate 10 has a first step surface 15 and a second step surface 16, and the lower surface is a plane; the first step surface 15 is used as a packaging area 11 and is provided with a bonding pad, and the second step surface 16 is provided with a conductive connecting pad; the accommodating space of the PCB 20 is a blind hole groove, which includes a groove bottom and a groove sidewall, the connecting portion 28 of the PCB 20 is pressed on the second step surface 16 of the package substrate 10, the first step surface 15 is exposed as the package region 11, the connecting portion 28 is provided with a conductive hole 25 for electrically connecting the PCB 20 and the package substrate 10, and the bottom of the groove can also be provided with the conductive hole 25 for electrically connecting the PCB 20 and the package substrate 10. In this embodiment, the first step surface 15 is higher than the second step surface 16, and in other embodiments, the first step surface may be lower than the second step surface. The lower surface of the package substrate can be a plane, and can also be provided with at least two step surfaces, when the lower surface of the package substrate is provided with two step surfaces, the accommodating space is provided with an upper opening and a lower opening which respectively penetrate through the upper surface and the lower surface of the PCB, the PCB can also be provided with a connecting part at the lower surface (the lower opening) of the package substrate, and the connecting part is provided with a conductive hole for electrically connecting the package substrate and the PCB.

As shown in fig. 12, in manufacturing, a package substrate 10 and a PCB 20 are provided, a first step surface 15 and a second step surface 16 are formed on the package substrate 10, a pad is formed on the first step surface as a package region 11, and a conductive land is formed on the second step surface 16, and the pad is electrically connected to the conductive land. A blind hole groove is formed on the PCB 20 as a receiving space, and the package substrate 10 is pressed into the blind hole groove to make the second step surface 16 of the package substrate 10 flush with the upper surface of the PCB 20. Providing a prepreg, and manufacturing a first windowing on the prepreg, wherein the first windowing is larger than or equal to the first step surface; the prepreg is stacked on the PCB 20 and the second step surface 16 of the package substrate 10; providing a PCB (printed circuit board) stacking structure 29, and manufacturing a second windowing on the PCB stacking structure 29, wherein the position and the size of the second windowing are consistent with those of the first windowing; pressing the PCB board stacking structure 29 on the prepreg, and manufacturing a chip bonding pad and a golden finger on the PCB board stacking structure 29, wherein the chip bonding pad is used for mounting a surface mounting component 40; the conductive hole 25 is formed in the portion (i.e., the connection portion 28) of the PCB sub-stack 29 pressed on the second step surface 16 of the package substrate 10, so that the conductive hole 25 is connected to the conductive land on the second step surface 16, thereby achieving the electrical connection between the package substrate 10 and the PCB 20.

In the above embodiments, the electrical connection between the package substrate and the PCB board may also be implemented by a conductive layer on a sidewall of the package substrate. Specifically, the side wall of the packaging substrate is provided with a side conducting layer, the conducting circuit of the packaging substrate is electrically connected with the side conducting layer, and meanwhile, the side conducting layer is also electrically connected with the conducting layer of the PCB, so that the electrical connection between the packaging substrate and the PCB is realized.

In other embodiments, the accommodating space may also have a side opening penetrating through the side wall of the PCB; the cross-section of the package substrate (the plane parallel to the surface of the PCB board) may be rectangular, square, triangular, "T" -shaped, "L" -shaped, "+" -shaped, or other irregular deformations, etc.

In the carrier plate or the manufacturing method of the carrier plate, the number of the layers of the packaging substrate and the number of the layers of the PCB can be designed into a single layer or multiple layers according to the actual circuit and thickness requirements; the number of the first conductive holes and the second conductive holes can be one or more according to the actual laminated design.

The above list of details is only for the concrete description of the feasible embodiments of the present application, they are not intended to limit the scope of the present application, and all equivalent embodiments or modifications that do not depart from the technical spirit of the present application are intended to be included within the scope of the present application.

Claims

1. A carrier plate, its characterized in that: the packaging structure comprises a PCB and a packaging substrate arranged in the PCB, wherein the packaging substrate is provided with a conductive circuit, and the conductive circuit is electrically connected with the PCB; at least part of the surface of the packaging substrate is exposed out of the PCB as a packaging area, and the packaging area is used for mounting and installing bare chips; the thermal expansion coefficient of the packaging substrate is smaller than that of the PCB.

2. The carrier plate of claim 1, wherein: and the packaging area is provided with bonding pads, and the spacing of the bonding pads is matched with the spacing of the bonding pads of the bare chip to be mounted.

3. The carrier plate of claim 2, wherein: and the distance between the centers of the pads on the packaging area and the center of the pad is less than or equal to 150 mu m.

4. The carrier plate of claim 1, wherein: the thermal expansion coefficient of the packaging substrate in the horizontal direction is less than or equal to 10 ppm/DEG C.

5. The carrier plate of claim 4, wherein: the packaging substrate is a conductive silicon substrate, a conductive ceramic substrate, a conductive glass substrate or a conductive BT plate.

6. The carrier plate of claim 1, wherein: the peeling strength of the surface circuit layer of the PCB meets the peeling strength requirement of surface mounting.

7. The carrier plate of claim 6, wherein: the surface of the PCB is provided with a surface mounting area and an electrical interface; the surface mount area is used for mounting a surface mount component.

8. The carrier plate according to any one of claims 1 to 7, wherein: the PCB is internally provided with an accommodating space, and the packaging substrate is arranged in the accommodating space; the accommodating space comprises at least one opening, and the opening penetrates through one surface of the PCB to ensure that at least part of the surface of the packaging substrate is exposed outside the PCB.

9. The carrier plate of claim 8, wherein: the accommodating space is an open slot, the open slot includes tank bottom and lateral wall, the tank bottom is equipped with electrically conductive hole, electrically conductive hole is used for the electric connection the conducting wire of packaging substrate with the PCB board.

10. The carrier plate of claim 8, wherein:

the opening of the accommodating space is provided with a connecting part which is pressed on part of the surface of the packaging substrate;

11. The carrier plate of claim 8, wherein:

the accommodating space comprises an upper opening and a lower opening which respectively penetrate through the upper surface and the lower surface of the PCB, the upper opening and/or the lower opening is/are provided with a connecting part, and the connecting part is pressed on part of the surface of the packaging substrate;

12. The carrier plate of claim 8, wherein: the side wall of the packaging substrate is provided with a side conducting layer; the conducting circuit of the packaging substrate is electrically connected with the side conducting layer, and the side conducting layer is electrically connected with the conducting layer of the PCB.

13. The carrier plate according to any one of claims 9-12, wherein: the surface of the packaging substrate is a plane; or the surface of the packaging substrate is provided with a step surface.

14. The carrier plate according to any one of claims 10 or 11, wherein:

the surface of the packaging substrate is provided with at least a first step surface and a second step surface;

the connecting part is pressed on the second step surface.

15. An optical module comprising a bare chip and a surface mount component, characterized in that: further comprising a carrier plate according to any of claims 1-14; the bare chip is arranged on the packaging area of the carrier plate; the surface mounting element is arranged on the PCB of the carrier plate.

16. The light module of claim 15, wherein: the bare chip is mounted on the packaging area of the carrier plate in a flip chip and/or wire bonding mode.