CN-115767887-B - Interconnection structure of PCB and chip, preparation method of interconnection structure and optical module

CN115767887BCN 115767887 BCN115767887 BCN 115767887BCN-115767887-B

Abstract

The invention discloses an interconnection structure of a PCB (printed circuit board) and a chip, a preparation method of the interconnection structure and an optical module, wherein the interconnection structure of the PCB and the chip comprises the PCB and a plurality of chips arranged on the PCB, the PCB is formed by sequentially stacking a first copper foil layer, a second dielectric layer, a third copper foil layer, a high-speed wiring positioned on the third layer, a fourth dielectric layer and a fifth copper foil layer, all the first copper foil layer and the second dielectric layer which are positioned under chip high-speed pins of a DSP chip and a driver chip are hollowed on the PCB to form a hollowed groove, the bottom of the hollowed groove is exposed out of a bonding pad on the third layer high-speed wiring, and the chip high-speed pins are connected with the bonding pad of the third layer high-speed wiring. The electromagnetic shielding device has the advantages of good electromagnetic shielding effect and strong crosstalk inhibition capability, and meanwhile, high-speed radio frequency signal degradation caused by the via hole is avoided.

Inventors

BAO KANGSHENG
HAN YE
CHENG JIN
CHEN TAO
WANG YANG
WANG CHENGHUA
HAN LIBIAO

Assignees

希烽光电科技(南京)有限公司

Dates

Publication Date: 20260512
Application Date: 20221109

Claims (7)

1. The interconnection structure of the PCB and the chips comprises a PCB (2) and a plurality of chips arranged on the PCB, and is characterized in that the PCB (2) is formed by sequentially stacking a first copper foil layer (201), a second dielectric layer (202), a third copper foil layer (203), a high-speed wiring (4) positioned on the third layer, a fourth dielectric layer (204) and a fifth copper foil layer (205), wherein the first copper foil layer (201) and the second dielectric layer (202) which are positioned under chip high-speed pins of a DSP chip (1) and a driver chip (3) are completely hollowed to form a hollowed groove, the bottom of the hollowed groove is exposed out of a bonding pad on the third high-speed wiring (4), a chip high-speed pin is connected with the bonding pad on the third high-speed wiring (4), the bonding pad is positioned under the chip high-speed pin, and the tail end of the high-speed wiring (4) of the third layer is provided with the bonding pad; The hollowed-out area comprises a first copper foil layer (201) and a second dielectric layer (202) of the PCB (2), the depth of the hollowed-out groove is equal to the sum of the thicknesses of the first copper foil layer (201) and the second dielectric layer (202) of the PCB (2), copper foils are electroplated on the groove walls of the hollowed-out groove, copper foils are arranged on the groove walls of the hollowed-out groove, and the copper foils realize the up-down interconnection of the first copper foil layer (201) and the third copper foil layer (203) of the PCB (2) to form a semi-closed side wall shielding structure.
2. The interconnecting structure of the PCB and the chip as set forth in claim 1, wherein the high-speed wiring (4) of the third layer is a strip line.
3. The method for manufacturing the interconnection structure of the PCB board and the chip according to any one of claims 1 to 2, comprising the steps of: S1, stacking and pressing all layers of the PCB sequentially, and hollowing out the PCB after the pressing is finished, wherein the bottom of the hollowing out groove exposes a bonding pad on a third layer of high-speed wiring (4); S2, electroplating copper foil on the wall of the hollowed groove, wherein the electroplated copper foil realizes up-down interconnection of the first copper foil layer (201) and the third copper foil layer (203); S3, soldering tin is planted on a bonding pad on the PCB; s4, heating the PCB, placing the chip, and connecting high-speed pins of the chip with soldering tin.
4. The method of manufacturing a PCB according to claim 3, wherein S1, the hollowed-out position on the PCB is marked, and the marked position on the PCB (2) is hollowed out by using a laser drill or a mechanical drill, wherein the hollowed-out depth is equal to the sum of the thicknesses of the first copper foil layer (201) and the second dielectric layer (202).
5. The method for manufacturing a high-speed wiring board according to claim 3, wherein in S3, first soldering tin is planted on the bonding pads of the high-speed wiring board (4) of the third layer, the first soldering tin is higher than the first copper foil layer (201), the upper surfaces of the first soldering tin on all the bonding pads are in the same plane, second soldering tin is planted on other bonding pads on the upper surface of the first copper foil layer (201), and the upper surface of the second soldering tin is in the same plane with the upper surface of the first soldering tin planted on the high-speed wiring board of the third layer.
6. An optical module comprises a PCB, a DSP chip and a driver chip, and is characterized in that the DSP chip and the driver chip which are arranged on the PCB are electrically connected by adopting the interconnection structure of any one of claims 1-2.
7. The optical module of claim 6, further comprising at least one light emitting sub-module and at least one light receiving sub-module arranged in parallel, wherein the light emitting sub-module is of a BOX packaging structure and is electrically connected with the PCB through a soft belt, and the light receiving sub-module is of a BOX packaging structure and is electrically connected with the PCB through a soft belt.

Description

Interconnection structure of PCB and chip, preparation method of interconnection structure and optical module Technical Field The invention relates to the technical field of high-speed PCB design, in particular to an interconnection structure of a PCB and a chip and a preparation method thereof. Background As is well known, the core PCB board of the optical module is a high-speed radio frequency board, and the current optical module is in a stage of rapid development, along with the increasing of the single-channel transmission rate, ensuring that the optical module high-speed radio frequency signal reduces electromagnetic radiation on a certain transmission distance and reducing crosstalk between high-speed channels becomes a key factor of successful design. Due to the limitation of the structure on the layout of the device, the high-speed radio frequency wiring is inevitably adopted for interconnection between the DSP chip and the radio frequency driver chip and between the radio frequency driver chip and the radio frequency modulator chip. Therefore, good electromagnetic shielding is an indispensable component in the design of optical module structures. Because crosstalk between an internal transmitting channel and a receiving channel of an optical module, between multiple transmitting channels and multiple receiving channels seriously interfere with radio frequency performance of a current channel, good crosstalk suppression is also an indispensable part in the design of an optical module PCB. At present, in order to ensure the impedance continuity of high-speed radio frequency signals in the PCB design of an optical module, a surface layer wiring mode is generally adopted aiming at key high-speed radio frequency wiring. The design is characterized in that electromagnetic radiation cannot be effectively controlled, and multichannel crosstalk is difficult to suppress. At present, part of the PCB design of the optical module is to route high-speed wires to the inner layer of the PCB by using a via structure. The design is characterized in that electromagnetic radiation can be restrained, but parasitic parameters and impedance discontinuity caused by the via hole lead to rapid degradation of insertion loss and reflection of the high-speed signal channel, so that the use of the via hole is avoided to the greatest extent by the high-speed radio frequency wiring. Disclosure of Invention The first objective of the present invention is to provide an interconnection structure of a PCB board and a chip, which solves the electromagnetic radiation problem and the serious crosstalk problem between multiple channels caused by the high-speed routing on the surface layer in the PCB design of the optical module in the prior art, and the second objective is to solve the technical problems of parasitic parameter influence and discontinuous impedance caused by the high-speed routing on the inner layer by using the via structure in the prior art. In order to solve the technical problems, the technical scheme adopted by the invention is as follows: the PCB comprises a PCB and a plurality of chips arranged on the PCB, wherein the PCB is formed by sequentially stacking a first copper foil layer, a second dielectric layer, a third copper foil layer, a high-speed wiring positioned on the third layer, a fourth dielectric layer and a fifth copper foil layer, the first copper foil layer and the second dielectric layer which are positioned under chip high-speed pins of a DSP chip and a driver chip are hollowed on the PCB to form a hollowed groove, bonding pads on the third-layer high-speed wiring are exposed at the bottom of the hollowed groove, and the chip high-speed pins are connected with the bonding pads of the third-layer high-speed wiring. According to the interconnection structure, the high-speed bonding pad on the PCB is designed to the third layer of the PCB, and meanwhile, the high-speed radio frequency wiring is designed to the third layer of the PCB, after the first copper foil layer of the PCB and the fifth copper foil layer of the PCB cover Gao Sushe frequency wiring areas, external radiation of signals on the high-speed radio frequency wiring can be shielded, and the electromagnetic shielding performance of the optical module is effectively improved. Under the condition that the multipath radio frequency wires are approximately parallel, crosstalk between the multipath high-speed radio frequency wires is effectively inhibited, and meanwhile, the interconnection technology reduces parasitic parameters of a high-speed link, improves signal integrity and avoids high-speed radio frequency signal degradation caused by a via hole. As a further improvement of the present invention, the high-speed wiring of the third layer is a strip line. As a further improvement of the invention, copper foils are arranged on the groove walls of the digging grooves. The electroplated copper foil enables the first copper foil layer and the t