Photoelectric co-packaging optical coupling passive alignment packaging structure and method

Abstract

The invention relates to the technical field of semiconductor chip packaging, in particular to a photoelectric co-packaging optical coupling passive alignment packaging structure and method. According to the invention, high-precision automatic alignment of the grating coupler in the optical chip and the through hole of the adapter plate is realized by using the solder ball tension effect in the flip reflow soldering process of the optical chip, and a stable optical limiting structure is formed. The passive coupling of the optical elements (such as bare optical fibers, optical fiber arrays, reflectors and the like) and the grating coupler is realized by placing the optical elements with matched sizes in the via holes of the adapter plate and completing refractive index matching and structure fixing by using curing glue. The whole process does not need additional active alignment equipment, is the same as a traditional chip packaging process, has the advantages of being simple in process, low in cost and high in packaging efficiency, and is a key packaging technology of a photoelectric co-packaging system in the future.

Description

Technical Field

[0001] The present invention relates to the technical field of semiconductor chip packaging, and in particular to an optically coupled passive alignment packaging structure and method for optoelectronic co-packaging. Background Art

[0002] With the rapid growth of demand for high bandwidth, low latency, and high power density in data centers, AI computing centers, and supercomputing, traditional electrical interconnect technologies are gradually facing bottlenecks. Optical interconnect technology, with its advantages in high bandwidth, low power consumption, and long-distance transmission, has become an important development direction for next-generation packaging technology. Co-Packaged Optics (CPO) integrates optical and electrical components into the same package, achieving collaborative interconnection of optoelectronic chips to improve system performance and package integration.

[0003] In optoelectronic co-packaging, achieving high-precision alignment between the optical fiber and the grating coupler is particularly critical. Current fiber coupling technologies mainly use two types of solutions: 1. Active alignment technology; 2. Passive alignment technology.

[0004] 1. Active alignment technology: Using precision alignment equipment, the position of the optical fiber and grating coupler is adjusted in real time during the packaging process. The coupled optical power is measured in real time, and the fiber coupling position is determined based on the coupling efficiency. While this method offers high precision and coupling efficiency, it is highly dependent on equipment, has low packaging efficiency, high manufacturing costs, and is difficult to implement in large-scale automated production.

[0005] 2. Passive alignment technology: Utilizes pre-designed mechanical stop structures to automatically align optical components. However, existing passive alignment technologies often rely on precision machining or custom stop structures, making them incompatible with traditional electrical packaging processes. This is particularly true in multi-chip integrated packaging applications, resulting in high packaging complexity and costs.

[0006] In summary, existing active alignment processes rely on high-precision equipment and complex processes, which not only increases manufacturing cost and time but also suffers from poor process compatibility. Therefore, developing a fiber-coupled packaging structure or method based on passive alignment that can reduce alignment difficulty while maintaining high precision is an important direction for the development of optoelectronic co-packaging technology. Summary of the Invention

[0007] In view of the above-mentioned problems or deficiencies, and to solve the problem of high-precision alignment of existing optical fiber coupling technology, the present invention provides an optically coupled passive alignment packaging structure and method for optoelectronic co-packaging.

[0008] An optoelectronic co-packaged optically coupled passive alignment packaging structure comprises: an adapter plate, an optical chip, a packaging substrate, an electrical chip and an optical element.

[0009] Adapter plate pads are respectively provided on the upper and lower surfaces of the adapter plate, and the distribution of the adapter plate pads corresponds to the distribution of the electric chip pads, the optical chip pads and the packaging substrate pads respectively (that is, after welding and fixing, the sum of the adapter plate pads corresponds to the sum of the electric chip pads, the optical chip pads and the packaging substrate pads, and there is a one-to-one correspondence in the thickness direction between the layers); the adapter plate is also provided with adapter plate vias for placing optical elements, and vertical via conductive columns connecting the upper and lower pads.

[0010] The optical element passes through the adapter plate via hole and contacts the surface of the optical chip, and optical coupling is achieved through the optical element and the grating coupler on the surface of the optical chip; and the size of the adapter plate via hole is adapted to the placement size of the optical element.

[0011] The transfer board pad is packaged on the packaging substrate through solder balls, and the bottom filler is filled between the two; a groove for placing the optical chip is provided in the middle of the packaging substrate, and the optical chip is in thermal contact with the packaging substrate.

[0012] The optical chip, electrical chip and packaging substrate are respectively welded to the upper and lower surfaces of the adapter board with their respective pads through solder balls and their corresponding adapter board pads; wherein the optical chip pads are symmetrically distributed about the center of the grating coupler of the optical chip, and after the optical chip pads and all corresponding adapter board pads are aligned in the vertical direction between layers, the grating of the grating coupler is aligned with the relative position between the layers of the adapter board via.

[0013] Furthermore, the gap between the optical element and the grating coupler is filled with a refractive index matching liquid to improve the light coupling efficiency and fix the optical element (such as optical fiber).

[0014] Furthermore, the included angle between the adapter plate via hole and the vertical direction, that is, the tilt angle, is any angle between 0 and 90 degrees.

[0015] Furthermore, the number of the through hole of the adapter plate is one, or ranges from 1 to n, where n is the number of optical elements, and the shape thereof is any shape (such as a rectangle, a circle, etc.).

[0016] Furthermore, the optical element is a single-mode optical fiber, an optical fiber array, a lens, a reflector or a laser.

[0017] Furthermore, the optical chip is a silicon chip, a silicon nitride chip, a III-V compound chip, a silicon oxide chip or a lithium niobate chip.

[0018] Furthermore, the adapter board is also provided with an optical waveguide and a multi-layer redistribution circuit.

[0019] Furthermore, the packaging process of the optically coupled passive alignment packaging structure of the above-mentioned optoelectronic co-packaging is as follows: the optical chip is first packaged on the surface of the adapter board. During the packaging process, the adapter board is placed under the optical chip. The optical chip adopts a solder ball high-temperature reflow soldering process, and the tension effect during the melting and solidification of the solder is used to align the optical chip pads with the corresponding adapter board pads, so as to synchronously achieve the inter-layer relative position alignment of the optical chip grating and the adapter board via; after this process, the underfill is filled to fix the optical chip; then the flip-chip packaging of the electrical chip and the corresponding underfill filling are completed; finally, the flip-chip packaging between the adapter board and the packaging substrate and the corresponding underfill filling are completed.

[0020] The principle of the packaging structure of the present invention: In optoelectronic co-packaging applications, it is hoped that electrical interconnection and optical fiber packaging can be achieved simultaneously. The adapter plate is a commonly used technical solution for traditional electrical chip packaging. For this reason, it is an extremely attractive solution to use the adapter plate vias as an optical element alignment limit structure to achieve passive optical fiber alignment coupling packaging. To achieve high-precision passive alignment of optical elements (such as optical fibers) and grating couplers, the prerequisite is that the adapter plate vias can be passively aligned with the grating couplers with high precision. To this end, the present invention innovatively proposes to use the tension effect during solder ball solidification to passively align the grating coupler of the flip-chip optical chip with the adapter plate vias, and then insert the optical element into the adapter plate vias to achieve passive alignment coupling packaging.

[0021] The present invention has the following beneficial effects:

[0022] 1. Compatible packaging of multiple types of optical devices: Using solder ball tension-assisted alignment technology, it supports passive alignment packaging of multiple optical devices, such as fiber arrays, single-mode optical fibers, lenses, mirrors, and lasers, providing more flexible optical device integration options. In addition, due to the passive alignment packaging technology, it can improve packaging efficiency and reduce packaging costs.

[0023] 2. Strong packaging process compatibility: The slotting, via-hole and chip reflow processes of the adapter board are all mature electrical packaging technologies. No additional process steps are required. Co-packaging of optoelectronic chips can be achieved based on existing packaging technologies, meeting the technical specifications of the existing packaging industry chain, and having significant cost advantages and process compatibility.

[0024] 3. Support for large-scale optoelectronic integration: Traditional active optical chip adapters require TSV and backside thinning processes on the optical chip, which are more complex and costly, and the adapter board size is limited by the size of the mask. The high-efficiency passive alignment optical coupling packaging solution of this invention is suitable for large-scale integration of wafer-level and panel-level optoelectronic chips, supporting optical and electrical interconnection on the adapter board.

[0025] 4. Compact Horizontal Coupling Design: The fiber stopper of this invention is integrated with the electrical interconnect adapter plate, resulting in a compact package. Furthermore, a reflector converts the vertical beam output by the grating coupler into a horizontal beam, enabling horizontal coupling packaging of the fiber array. This improves package compactness and system integration, facilitating heat dissipation and hermetic packaging. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is a schematic diagram illustrating the principle of automatic alignment between the adapter plate via and the optical chip grating of the present invention.

[0027] Figure 2 It is a schematic diagram of the optoelectronic co-packaging optical coupling passive alignment packaging architecture of the present invention.

[0028] Figure 3 It is a schematic diagram of the optoelectronic co-packaging architecture based on reflectors of the present invention.

[0029] Figure 4 It is a schematic diagram of the multi-channel optical coupling packaging architecture based on single-mode optical fiber of the present invention.

[0030] Figure numerals: (1) adapter plate, (2) optical chip, (3) packaging substrate, (4) electrical chip, (5) bottom filler, (6) refractive index matching liquid, (7) grating coupler, (8) optical element, (9) adapter plate via, (10) vertical via conductive column, (11) adapter plate pad, (12) optical chip pad, (13) solder ball, (14) optical waveguide, (15) metal reflective surface, (16) reflector, (17) adapter plate via center line, (18) grating coupler center line, (19) single-mode optical fiber. DETAILED DESCRIPTION

[0031] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0032] An optoelectronic co-packaged optically coupled passive alignment packaging structure includes: (1) an adapter plate, (2) an optical chip, (3) a packaging substrate, (4) an electrical chip, and (8) an optical element.

[0033] The adapter plate is provided with adapter plate pads on the upper and lower surfaces respectively, and the distribution of the adapter plate pads corresponds to the distribution of the electrical chip pads, the optical chip pads and the packaging substrate pads respectively; the adapter plate is also provided with adapter plate vias for placing optical elements, and vertical via conductive columns connecting the upper and lower pads;

[0034] The optical element passes through the adapter plate via hole and contacts the surface of the optical chip, and optical coupling is achieved through the optical element and the grating coupler on the surface of the optical chip; and the size of the adapter plate via hole is adapted to the placement size of the optical element;

[0035] The transfer board pad is packaged on the package substrate through solder balls, and the underfill is filled between the two; a groove for placing the optical chip is provided in the middle of the package substrate, so that the optical chip is in thermal contact with the package substrate;

[0036] The optical chip, electrical chip and packaging substrate are respectively welded to the upper and lower surfaces of the adapter board with their respective pads through solder balls and their corresponding adapter board pads; the optical chip pads are symmetrically distributed about the center of the grating coupler of the optical chip, and after the optical chip pads and all corresponding adapter board pads are aligned in the vertical direction between layers, the grating of the grating coupler is aligned with the relative position between the layers of the adapter board via.

[0037] like Figure 1 The figure shows a schematic diagram illustrating the principle of the automatic alignment effect based on high-temperature reflow soldering of the present invention. 1. First, solder balls are planted on the surface of the adapter board with vias and conductive columns, and the optical chip is flipped and placed on the solder balls. At this time, the solder pads of the optical chip and the solder pads of the adapter board are seriously misaligned, and the grating coupler is also not aligned with the vias of the adapter board; 2. As the reflow temperature rises and the reflow duration increases, the solder balls gradually melt, and are affected by the lateral tension between the upper and lower solder pads, and the upper and lower solder pads are gradually aligned, and during the reflow soldering cooling process, the solder pads are further aligned and finally fixed; 3. When fixed, the grating coupler of the optical chip is also synchronously aligned with the vias of the adapter board. Since the solder balls have been solidified to connect the optical chip and the adapter board into a whole, the vias of the adapter board can serve as a passive alignment limit structure for the grating coupler of the optical chip.

[0038] In the subsequent process, the optical chip bottom filling, electrical chip flip-chip welding, and the adapter board as a whole are gradually completed on the packaging substrate through solder balls. The entire process is a traditional electrical ball grid array reflow packaging process with complete process compatibility. In the final link, the passive alignment coupling packaging of optical components (such as optical fiber arrays) is implemented, the optical components are directly inserted into the adapter board vias, and the refractive index matching and structural fixation are completed using UV curing glue, thus completing the entire optoelectronic co-packaging process. Its packaging architecture is as follows Figure 2 shown.

[0039] Example 1:

[0040] like Figure 2As shown, the optical chip (2) is a silicon optical chip, which is first flip-chip mounted on one side of the adapter board (1), and an electrical chip (4) is flip-chip packaged on the other surface of the adapter board. The packaging substrate (3) is a 10-layer organic substrate with a rewiring circuit provided inside. A 750um thick groove is provided in the center of the substrate. The adapter board (1) is packaged on the packaging substrate (3) through a solder ball array, and the optical chip is located in the substrate groove. The bottom filler (5) is made of epoxy resin. The adapter board (1) is 700um thick and contains a large number of vertical via conductive copper pillars with a diameter of 25um. The adapter board via (9) is a rectangular via with a width of 0.6mm and a length of 1mm. The optical element (8) is a 4-channel optical fiber array. The optical fiber array is flush with the surface of the optical chip, and the gap between them is filled and fixed with an external curing glue.

[0041] Passive alignment of fiber arrays: Through high-precision adapter plate vias, innovative passive alignment and coupling of fiber arrays are achieved, significantly improving packaging efficiency.

[0042] Example 2:

[0043] like Figure 3 As shown, the optical chip (2) is a silicon optical chip, which is first flip-chip mounted on one side of the adapter board (1), and an electrical chip (4) is flip-chip packaged on the other surface of the adapter board. The packaging substrate (3) is an 8-layer organic substrate with a redistribution circuit inside and a 300um thick groove in the center of the substrate; the adapter board (1) is packaged on the packaging substrate (3) through a solder ball array, and the optical chip is located in the substrate groove. The bottom filler (5) is made of epoxy resin. The adapter board (1) is 700um thick and contains a large number of vertical via conductive copper pillars with a diameter of 25um, an optical waveguide (14) and an adapter board via (9). The adapter board via (9) is a rectangular via with a width of 0.6mm and a length of 0.6mm. The optical element (8) is a reflector (16), the bevel surface of the reflector is plated with a metal reflective film (15), the bevel angle of the reflector is just enough to couple the light of the grating into the waveguide in the adapter plate, and the gap between the reflector and the optical chip is filled and fixed with an external curing glue.

[0044] Reflector-integrated passive alignment: A 90-degree reflector structure is set in the adapter plate via to achieve passive alignment coupling between the optical chip grating coupler and the glass waveguide. The optical I / O port on the optical chip can be fanned out to any position on the glass adapter plate, and optical path and circuit rewiring can be achieved simultaneously on the glass adapter plate, realizing optoelectronic connections between different chips on the adapter plate.

[0045] Example 3:

[0046] like Figure 4As shown, the optical chip (2) is a silicon photonic chip, which is first flip-chip mounted on one side of the adapter board (1), and an electrical chip (4) is flip-chip packaged on the other surface of the adapter board. The packaging substrate (3) is an 8-layer organic substrate with a rewiring circuit provided inside. A 300um thick groove is provided in the center of the substrate. The adapter board (1) is packaged on the packaging substrate (3) through a solder ball array, and the optical chip is located in the substrate groove. The bottom filler (5) is made of epoxy resin. The adapter board (1) is 700um thick and contains a large number of vertical via conductive copper pillars with a diameter of 25um. The adapter board vias (9) are two rows of inclined vias, each row containing 4 vias, with a pitch of 250um and a via diameter of 126um. The optical element (8) is a single-mode optical fiber with a diameter of 125um. The single-mode optical fiber is inserted into the adapter board via, and the gap between the optical fiber and the optical chip is filled and fixed with an external curing glue.

[0047] Bare fiber passive alignment: Through high-precision adapter plate vias, innovative bare fiber passive alignment coupling is achieved, significantly improving packaging efficiency.

[0048] From the above embodiments, it can be seen that the present invention innovatively utilizes the physical effect of solder ball tension during flip-chip reflow soldering of optical chips to achieve high-precision automatic alignment of the grating coupler in the optical chip and the adapter plate via, forming a stable optical limiting structure; by placing optical elements of appropriate size in the adapter plate via, and using curing glue to complete refractive index matching and structural fixation, passive coupling of optical elements (such as bare optical fibers, optical fiber arrays, reflectors, etc.) and the grating coupler is achieved. The automatic and precise alignment of the grating coupler in the optical chip and the adapter plate via in the entire process does not require additional active alignment equipment, which is the same as the traditional chip packaging process. It has the advantages of simple process, low cost, and high packaging efficiency, simplifies the complex active alignment process, and is a key packaging technology for future optoelectronic co-packaging systems.

Claims

1. An optically coupled passive alignment packaging structure for optoelectronic co-packaging, characterized by: include, Adapter boards, optical chips, packaging substrates, electrical chips and optical components; The adapter plate is provided with adapter plate pads on the upper and lower surfaces respectively, and the distribution of the adapter plate pads corresponds to the distribution of the electrical chip pads, the optical chip pads and the packaging substrate pads respectively; the adapter plate is also provided with adapter plate vias for placing optical elements, and vertical via conductive columns connecting the upper and lower pads; The optical element passes through the adapter plate via hole and contacts the surface of the optical chip, and optical coupling is achieved through the optical element and the grating coupler on the surface of the optical chip; and the size of the adapter plate via hole is adapted to the placement size of the optical element; The transfer board pads are packaged on the package substrate via solder balls, and an underfill is filled between the two; A groove for placing the optical chip is provided in the middle of the packaging substrate, so that the optical chip is in thermal contact with the packaging substrate; The optical chip, electrical chip and packaging substrate are respectively welded to the upper and lower surfaces of the adapter board with their respective pads through solder balls and their corresponding adapter board pads; wherein the optical chip pads are symmetrically distributed about the center of the grating coupler of the optical chip, and after the optical chip pads and all corresponding adapter board pads are aligned in the vertical direction between layers, the grating of the grating coupler is aligned with the relative position between the layers of the adapter board via.

2. The optoelectronic co-package optically coupled passive alignment packaging structure according to claim 1, wherein: The gap between the optical element and the grating coupler is filled with a refractive index matching liquid to improve the light coupling efficiency and fix the optical element at the same time.

3. The optoelectronic co-package optically coupled passive alignment packaging structure according to claim 1, wherein: The angle between the adapter plate via hole and the vertical direction is any angle from 0 to 90 degrees.

4. The optoelectronic co-package optically coupled passive alignment packaging structure according to claim 3, wherein: The number of the through holes in the adapter plate is one, or ranges from 1 to n, where n is the number of optical elements.

5. The optoelectronic co-package optically coupled passive alignment packaging structure according to claim 1, wherein: The optical element is a single-mode optical fiber, an optical fiber array, a lens, a reflector or a laser.

6. The optoelectronic co-package optically coupled passive alignment packaging structure according to claim 1, wherein: The optical chip is a silicon chip, a silicon nitride chip, a III-V compound chip, a silicon oxide chip or a lithium niobate chip.

7. The optoelectronic co-package optically coupled passive alignment packaging structure according to claim 1, wherein: The adapter board is also provided with an optical waveguide and a multi-layer rewiring circuit.

8. The packaging process of the optoelectronic co-package optically coupled passively aligned packaging structure according to claim 1, characterized in that: The optical chip is first packaged on the surface of the adapter board. During the packaging process, the adapter board is placed under the optical chip. The optical chip adopts a solder ball high-temperature reflow soldering process, and the tension effect during the melting and solidification of the solder is used to align the optical chip pad with the corresponding adapter board pad, so as to synchronously achieve the relative position alignment between the optical chip grating and the adapter board via layer; after this process, the underfill is filled to fix the optical chip; then the flip-chip packaging of the electrical chip and the corresponding underfill are completed; finally, the flip-chip packaging between the adapter board and the packaging substrate and the corresponding underfill are completed.

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