WO2021164607A1 - 封装结构及其形成方法 - Google Patents

封装结构及其形成方法 Download PDF

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Publication number
WO2021164607A1
WO2021164607A1 PCT/CN2021/075944 CN2021075944W WO2021164607A1 WO 2021164607 A1 WO2021164607 A1 WO 2021164607A1 CN 2021075944 W CN2021075944 W CN 2021075944W WO 2021164607 A1 WO2021164607 A1 WO 2021164607A1
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Prior art keywords
substrate
opening
chip
sub
molding compound
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PCT/CN2021/075944
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English (en)
French (fr)
Inventor
刘杰
何军
全昌镐
应战
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长鑫存储技术有限公司
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Priority to US17/373,893 priority Critical patent/US20210343548A1/en
Publication of WO2021164607A1 publication Critical patent/WO2021164607A1/zh

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    • H01L23/00—Details of semiconductor or other solid state devices
    • H01L23/48—Arrangements for conducting electric current to or from the solid state body in operation, e.g. leads, terminal arrangements ; Selection of materials therefor
    • H01L23/488—Arrangements for conducting electric current to or from the solid state body in operation, e.g. leads, terminal arrangements ; Selection of materials therefor consisting of soldered or bonded constructions
    • H01L23/498—Leads, i.e. metallisations or lead-frames on insulating substrates, e.g. chip carriers
    • H01L23/49811—Additional leads joined to the metallisation on the insulating substrate, e.g. pins, bumps, wires, flat leads
    • H01L23/49816—Spherical bumps on the substrate for external connection, e.g. ball grid arrays [BGA]
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    • H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
    • H01L21/02—Manufacture or treatment of semiconductor devices or of parts thereof
    • H01L21/04—Manufacture or treatment of semiconductor devices or of parts thereof the devices having potential barriers, e.g. a PN junction, depletion layer or carrier concentration layer
    • H01L21/50—Assembly of semiconductor devices using processes or apparatus not provided for in a single one of the subgroups H01L21/06 - H01L21/326, e.g. sealing of a cap to a base of a container
    • H01L21/56—Encapsulations, e.g. encapsulation layers, coatings
    • H01L21/563—Encapsulation of active face of flip-chip device, e.g. underfilling or underencapsulation of flip-chip, encapsulation preform on chip or mounting substrate
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Definitions

  • the invention relates to the field of chip packaging, in particular to a packaging structure and a forming method thereof.
  • the packaged chip needs to be wrapped by injection molding to protect the chip.
  • the chip and the substrate are connected to the circuit on the substrate through solder balls.
  • the plastic packaging process it is necessary to wrap the entire chip with a plastic molding compound to fill the gap between the chip and the substrate. Since the chip and the substrate are directly connected by solder balls or other solder bumps, the gap is small, and the distance between the connection points is also small. Therefore, the air is not easily discharged when the plastic compound is filled, and the problem of unreliable packaging structure is likely to occur. .
  • a plurality of pores are provided on the packaging substrate, so that during the injection molding process, as the molding compound is filled, the gas is discharged from the pores on the substrate.
  • multiple air holes are usually formed on the substrate.
  • the area where the air holes can be formed is small and a larger number of air holes are formed. , So that the size of each pore is smaller.
  • the exhaust position can be increased, but because the pore size is small, it will be easily blocked by the plastic encapsulant, and the improvement of the exhaust effect is limited.
  • the reliability of the package structure using the above-mentioned substrate is low, and severe warpage of the substrate often occurs, which causes the electrical connection between the chip and the substrate to be disconnected, resulting in product failure.
  • the technical problem to be solved by the present invention is to provide a packaging structure and a method for forming the packaging structure to improve the reliability of the packaging structure.
  • the present invention provides a package structure including: a substrate having a first surface and a second surface opposite to each other, and the substrate has a first surface to a second surface that penetrates the substrate.
  • the opening is elongated, and the size of both ends is larger than the middle size; the chip, the chip is flip-chip fixed on the first surface of the substrate by solder bumps, and the solder bumps are connected to the An electrical connection is formed between the substrates, the opening is located in the projection of the chip on the substrate; the plastic molding compound wraps the chip and fills the gap between the chip and the first surface of the substrate, and The opening.
  • the opening is arranged along the symmetry axis of the substrate.
  • the opening includes two first sub-openings located at both ends and a second sub-opening located in the middle, and the second sub-opening communicates with the two first sub-openings.
  • the cross section of the first sub-opening is circular, semi-circular, elliptical, rectangular or polygonal, and the second sub-opening is a long strip with uniform width; the first sub-opening is vertical The maximum width in the length direction of the opening is greater than the width of the second sub-opening.
  • the maximum width of the first sub-opening ranges from 1 mm to 5 mm, and the maximum width of the second sub-opening ranges from 500 ⁇ m to 2 mm.
  • the cross-sectional edge of the opening is a smooth line.
  • the substrate includes two or more openings with the same length extending direction and located on the same straight line, and the distance between adjacent openings is greater than 3 mm.
  • the length of the opening ranges from 5 mm to 12 mm.
  • the molding compound fills the opening and overflows to the second surface of the substrate to form a molding compound protruding from the second surface of the substrate.
  • it further includes: solder balls formed on the second surface of the substrate.
  • the technical solution of the present invention also provides a method for forming a package structure, including: providing a packaged chip, the packaged chip comprising a substrate and a chip fixed on the substrate; the substrate has a first surface and a second surface opposite to each other , The substrate is formed with an opening as described above penetrating the first surface and the second surface; the chip is fixed on the first surface of the substrate by solder bumps of the flip chip process, the An electrical connection is formed between the solder bumps and the substrate, and the opening in the substrate is located in the projection of the chip on the substrate; injection molding is performed on the packaged chip, and the plastic package is wrapped around the chip, and Fill the gap between the chip and the first surface of the substrate and the opening.
  • the gas inside the packaging structure is exhausted through at least part of the openings.
  • the method for injection molding the packaged chip includes: providing an injection mold, the injection mold including a chassis and a cover, the cover is used to cover the chassis, and the chassis Forming a cavity; placing the packaged chip in the cavity, and placing the substrate on the surface of the chassis; injecting liquid molding compound into the cavity until the liquid molding compound fills the cavity Heat treatment to solidify the liquid molding compound; take out the packaged chip wrapped by the solidified molding compound from the cavity.
  • the cover is provided with at least one opening, and the opening communicates with the cavity and the outside; and the liquid molding compound is injected into the cavity through the at least one opening.
  • the cover has at least two openings, and further includes: during the injection molding process, exhausting the gas in the cavity to the outside through at least one of the openings.
  • the molding compound fills the opening and overflows to the second surface of the substrate to form a molding compound protruding from the second surface of the substrate.
  • the method further includes: forming solder balls on the second surface of the substrate.
  • the packaging structure of the present invention has elongated openings formed in the substrate, and the size of the two ends of the opening is larger than the size of the middle part, which can avoid premature blockage by the molding compound during injection molding and improve the efficiency of exhaust gas; and the opening is The elongated shape can improve the uniformity of the internal stress distribution of the substrate, avoid warping and deformation of the substrate in a high-temperature environment, keep the substrate flat, and ensure the reliability of the electrical connection between the chip and the substrate.
  • FIG. 1 is a schematic diagram of stress distribution when there are multiple pores on the substrate
  • FIGS. 2A to 2C are schematic structural diagrams of a package structure according to a specific embodiment of the present invention.
  • FIG. 3 is a schematic diagram of a substrate of a package structure according to a specific embodiment of the present invention.
  • FIG. 4 is a schematic structural diagram of the formation process of the packaging structure according to a specific embodiment of the present invention.
  • the plastic molding compound in order to facilitate the discharge of gas inside the package structure during the injection molding process, the plastic molding compound can fill the space between the chip and the substrate, and usually multiple air holes are formed on the substrate. .
  • the problem of uneven stress distribution in the substrate is prone to occur.
  • the substrate After the plastic molding compound fills the pores, due to the large difference in thermal expansion coefficient between the molding compound and the substrate material, the substrate is susceptible to the stress applied by the molding compound under the condition of temperature changes. In the case of multiple pores, the substrates between adjacent pores and the substrates around the pores are subjected to different types of stress, which may easily cause deformation of the substrate and result in product failure.
  • FIG. 1 is a schematic diagram of the stress distribution when there are multiple air holes 101 on the substrate 100.
  • the substrate 101 between the adjacent pores 101 is subjected to tensile stress, and the substrate 100 on the periphery of the area where the pore 101 is located is subjected to tensile stress.
  • the substrate 100 is warped due to the uneven stress distribution in the substrate 100, which damages the bond between the substrate 100 and the solder bumps of the chip, resulting in product failure.
  • the inventor proposes a new packaging structure, so that the substrate can discharge gas during the injection molding process, and at the same time, the stress distribution is more uniform.
  • FIGS. 2A to 2C are structural schematic diagrams of a package structure according to a specific embodiment of the present invention.
  • FIG. 2A is a schematic top view of a substrate of the package structure
  • FIG. 2B is a schematic cross-sectional view of the package structure along the AA' direction
  • FIG. 2C It is a schematic cross-sectional view of the package structure along the B-B' direction.
  • the packaging structure includes: a substrate 210, a chip 220, and a molding compound 230.
  • the substrate 210 has a first surface 201 and a second surface 202 opposite to each other.
  • the substrate 210 also has an opening 211 passing through the first surface 201 to the second surface 202, and the opening 210 is elongated, and The size of the two ends is larger than the size of the middle.
  • the substrate 210 is a circuit board, and electrical connection structures such as interconnecting circuits and solder pads are formed on the surface and/or inside of the substrate 210, which are used to form electrical connections with the chip 220, and input electrical signals or The electrical signal generated by the chip 220 is output.
  • the chip 220 is flip-chip fixed on the first surface 201 of the substrate 210 through solder bumps 221, and an electrical connection is formed between the solder bumps 221 and the substrate 210.
  • the solder bumps 221 may be conductive bumps such as metal pillars, solder balls, etc., which are in contact with the electrical connection structure on the first surface of the substrate 210, so that the chip 220 is fixed on the surface of the substrate 210 and is in contact with the An electrical connection is formed between the substrates 210.
  • the structure in FIG. 2 is only an example. Those skilled in the art can adopt a suitable flip-chip connection according to the specific chip and substrate connection structure. Way.
  • the opening 211 is located in the projection of the chip 220 on the substrate 210, so that when the molding compound 230 fills the gap between the chip 220 and the substrate 210, air can be discharged from the opening 211.
  • the molding compound 230 wraps the chip 220 and fills the gap between the chip 220 and the first surface 201 of the substrate 210 and the opening 211.
  • the molding compound 230 protects the chip 220 and the connection between the chip 220 and the substrate 210, and prevents the chip 220, the chip 210 and the substrate from being impacted by the packaging structure. The connection between 210 is damaged.
  • the molding compound 230 only covers the first surface 210 of the substrate 210 and exposes the second surface 202 of the substrate 210.
  • the second surface 202 is formed with pins or solder pads as the package structure and A contact point for electrical connection between other components.
  • solder balls 203 are also formed on the second surface 202 of the substrate 210, and the solder balls 203 are formed on the pins or pads on the second surface 202 of the substrate 210, and the The electrical connection structures in the substrate 210 form electrical connections.
  • the solder balls 203 may be leaded tin balls or lead-free tin balls.
  • the package structure can be mounted on other electronic components such as other circuit boards through the solder balls 203 through a reflow soldering process.
  • only one opening 211 is formed in the substrate 210, the opening 211 is elongated, and the width of both ends of the opening 211 is greater than the width of the middle of the opening 211.
  • the opening 211 includes two first sub-openings 2111 and a second sub-opening 2112. Mentioned first sub-opening 2111.
  • the first sub-opening 2111 has a circular cross-section in a direction parallel to the surface of the substrate 210
  • the second sub-opening 2112 has a strip shape with a uniform width and a uniform cross-section parallel to the surface of the substrate 210.
  • the diameter of the first sub-opening 2111 ranges from 1 mm to 5 mm
  • the width of the second sub-opening 2112 ranges from 500 ⁇ m to 2 mm.
  • the length of the opening 211 ranges from 5 mm to 12 mm, which facilitates rapid gas discharge and prevents the opening 211 from being prematurely blocked by the plastic compound during the injection molding process, so that the opening 211 has a better exhaust effect.
  • the first sub-opening 2111 has a larger caliber, which is conducive to rapid gas discharge; while the second sub-opening 2112 has a longer length, smaller and uniform width, and is conducive to dispersing the molding compound in the opening 211 and applying it to the substrate 210
  • the stress increases the uniformity of the stress distribution throughout the substrate 210.
  • the edge junction of the first sub-opening 2111 and the second sub-opening 2112 is an arc, forming an arc-shaped corner, so that the cross-sectional edge lines of the opening 211 are smooth. Lines, no sharp corner structure, to avoid stress gathering at corners.
  • the opening 211 is arranged along the axis of symmetry (A-A') of the substrate 210, and is symmetrical about the axis of symmetry, so that the opening 211 and the plastic molding compound 230 filled therein exert stress on both sides of the substrate 210 Symmetrical distribution.
  • the soldering area of the substrate 210 is located on both sides of the opening 211, and the soldering bumps 221 of the chip 220 are soldered to the soldering area of the substrate 210.
  • the cross-section of the first sub-opening may also be at least one of a semicircle, an ellipse, a rectangle, or a polygon;
  • the width may be different, but preferably, the width of the second sub-opening is the same at all positions; the maximum width of the first sub-opening in the direction perpendicular to the length of the opening is greater than the width of the second sub-opening .
  • the second sub-opening has a small width, a relatively large length and width, and is connected to the first sub-opening as a whole.
  • the stress applied to the substrate can be reduced, and Improve the uniformity of the internal stress distribution of the substrate, so that the substrate remains flat in a high-temperature environment, and ensure that the electrical connection between the flip chip and the substrate is intact.
  • the first sub-opening has a larger caliber, which facilitates the rapid discharge of gas, makes the opening difficult to be blocked during the injection molding process, and improves the exhaust effect.
  • the width of the second sub-opening is the same at all positions, and the cross-section of the first sub-opening is circular, the uniformity of the stress distribution can be further improved.
  • the maximum width of the first sub-opening ranges from 1 mm to 5 mm
  • the maximum width of the second sub-opening ranges from 500 ⁇ m to 2 mm.
  • the length of the opening is larger, which will affect the strength of the substrate.
  • FIG. 3 is a schematic top view of a substrate according to another embodiment of the present invention.
  • two openings 301 with the same length extending direction are formed in the substrate 300 and located on the same straight line.
  • the spacing between the two openings 301 is relatively large.
  • the spacing d between the two openings 301 is greater than 3 mm. .
  • the number of openings in the substrate corresponding to each chip can also be set reasonably according to the size of the chip and the substrate; under the premise of meeting the substrate strength, only one opening can be formed on the substrate corresponding to each chip. Minimize the stress applied to the substrate and improve the uniformity of the stress distribution.
  • the molding compound 230 not only fills the opening 211, but can also overflow to the second surface 202 of the substrate 210 to form a plastic package protruding from the second surface 202 of the substrate 210
  • the plastic protruding strips 231 also cover part of the second surface of the substrate 210 to ensure that the opening 211 is completely closed.
  • the molding compound protruding strips 231 are connected to the molding compound 230 on the first surface of the substrate 210 to further improve the bonding strength between the molding compound 230 and the substrate 210.
  • the packaging structure of the present invention has elongated openings formed in the substrate, and the size of the two ends of the opening is larger than the size of the middle part, which can avoid premature blockage by the molding compound during injection molding and improve the efficiency of exhaust gas; and the opening is The elongated shape can improve the uniformity of the internal stress distribution of the substrate, avoid warping and deformation of the substrate in a high-temperature environment, keep the substrate flat, and ensure the reliability of the electrical connection between the chip and the substrate.
  • the specific embodiment of the present invention also provides a method for forming the above-mentioned package structure.
  • FIG. 4 is a flowchart of a process of forming a package structure according to a specific embodiment of the present invention.
  • the method of forming the packaging structure includes the following steps:
  • Step S401 Provide a substrate, the substrate has a first surface and a second surface opposite to each other, an opening penetrating the first surface and the second surface is formed in the substrate, and the opening is elongated, and The size of the two ends is larger than the size of the middle.
  • the substrate may be a circuit board, and electrical connection structures such as interconnecting circuits and solder pads are formed inside and/or on the surface.
  • the opening in the substrate is elongated and penetrates the substrate.
  • the opening is arranged along the symmetry axis of the substrate, and is arranged symmetrically about the symmetry axis.
  • the length of the opening ranges from 5 mm to 12 mm, so that the opening has a higher exhaust efficiency.
  • the opening includes a first sub-opening at both ends and a second sub-opening connecting the two first sub-openings, and the cross-section of the first sub-opening is circular, semicircular, elliptical, rectangular or polygonal
  • the second sub-opening is a long strip with uniform width; the maximum width of the first sub-opening in a direction perpendicular to the length of the opening is greater than the width of the second sub-opening.
  • the maximum width of the first sub-opening ranges from 1 mm to 5 mm, and the maximum width of the second sub-opening ranges from 500 ⁇ m to 2 mm.
  • the cross-sectional edge of the opening is a smooth line to prevent stress from accumulating at the sharp topography of the edge of the opening.
  • the substrate corresponding to a single chip is formed with more than two openings with the same length extending direction and located on the same straight line, and the distance between adjacent openings is greater than 3 mm.
  • Step S402 Through the flip-chip process, the chip is flip-chip fixed on the first surface of the substrate through solder bumps, an electrical connection is formed between the solder bumps and the substrate, and the opening in the substrate is located on the first surface of the substrate. The chip is in the projection on the substrate.
  • Step S403 Perform injection processing on the chip flipped on the substrate, wrap the chip with a plastic molding compound, and fill the gap between the chip and the first surface of the substrate and the opening.
  • a substrate with a flip chip on the surface can be placed in the cavity of an injection mold, and the second surface of the substrate is located on the bottom surface of the cavity; then a liquid molding compound is injected into the cavity and then cured, and the molding compound fills the cavity. Body, wrapping the chip and filling the gap between the chip and the surface of the substrate.
  • the method of injection molding the packaged chip includes: providing an injection mold, the injection mold including a chassis and a cover, the cover is used to cover the chassis, A cavity is formed with the chassis; the packaged chip is placed in the cavity, and the substrate is placed on the surface of the chassis; liquid molding compound is injected into the cavity until the liquid molding compound The cavity is filled; heat treatment is performed to solidify the liquid molding compound; and the packaged chip wrapped by the solidified molding compound is taken out of the cavity.
  • the surface of the chassis at the bottom of the cavity may have a groove communicating with the opening in the substrate, and the groove communicating with the outside of the packaging mold.
  • the gas in the cavity is discharged through at least part of the openings.
  • the molding compound fills the opening and overflows to the second surface of the substrate to form a molding compound protruding from the second surface of the substrate.
  • the molding compound can continue to serve as a gas discharge channel before the cavity is completely filled with the molding compound.
  • the diameter of the two ports is larger than that in the middle, which can maintain a faster exhaust speed.
  • the cover is provided with at least one opening, and the opening communicates the cavity with the outside; and the liquid molding compound is injected into the cavity through the at least one opening.
  • the cover has at least two openings, and further includes: in the injection molding process, injecting the liquid molding compound through at least one of the openings, and discharging to the outside through at least one of the openings The gas in the cavity.
  • Step S404 forming solder balls on the second surface of the substrate.
  • solder balls are formed on the second surface of the substrate.
  • the solder balls may be lead solder balls or lead-free solder balls.
  • the package structure can be mounted on other electronic components such as other circuit boards through the solder balls 203 through a reflow soldering process.
  • the gas inside the packaging structure can be discharged through the opening on the substrate, and the opening has a large diameter and a long strip shape, which can maintain a high exhaust efficiency. Further, the opening is elongated, which can improve the uniformity of the stress distribution in the substrate, avoid warping and deformation of the substrate in a high temperature environment, keep the substrate flat, and ensure the reliability of the electrical connection between the chip and the substrate, thereby Improve the reliability of the package structure.

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Abstract

一种封装结构及其形成方法，封装结构包括：基板（210），基板具有相对的第一表面（201）和第二表面（202），基板内具有贯穿基板第一表面至第二表面的开口（211），开口呈长条状，且两端尺寸大于中部尺寸；芯片（220），芯片通过焊接凸点（221）倒装固定于基板的第一表面上，通过焊接凸点与基板之间形成电连接，开口位于芯片在基板上的投影内；塑封料（230），包裹芯片，并填充满芯片与基板的第一表面之间的间隙以及开口。封装结构的可靠性得到提高。

Description

封装结构及其形成方法
相关申请引用说明
本申请要求于2020年02月19日递交的中国专利申请号202010102446.0，申请名为“封装结构及其形成方法”的优先权，其全部内容以引用的形式附录于此。
技术领域
本发明涉及芯片封装领域，尤其涉及一种封装结构及其形成方法。
背景技术
芯片在封装完成后，需要通过注塑将封装完成后的芯片进行包裹，从而对芯片进行保护。
对于通过倒装工艺(Flip chip)封装的芯片，芯片与基板之间通过焊球与基板上的电路连接。塑封过程，需要将塑封料包裹整个芯片，填充满芯片与基板之间的间隙。由于芯片与基板之间直接通过焊球或其他焊接凸点连接，间隙较小，连接点之间间隔距离也较小，因此，塑封料在填充时空气不易排出，容易出现封装结构不可靠的问题。
现有技术中，为了便于在注塑过程中有利于气体的排出，会在封装基板上设置多个气孔，从而在注塑过程中，随着塑封料的填充，气体自基板上的气孔排出。为了具有较好的排气效果，通常会在基板上形成多个气孔，但是由于基板上大部分区域都要用于与芯片连接，因此，能够形成气孔的面积较小，形成较多数量的气孔，使得每个气孔的尺寸都较小，虽然气孔数量增多，可以增加排气位置，但是由于气孔尺寸小又会很容易被塑封料堵住，对排气效果的改善有限。
而且，采用上述基板的封装结构的可靠性较低，经常会出现基板发生剧烈的翘曲形变，使得芯片与基板之间的电连接断开，导致产品失效。
因此，如何在注塑过程中，避免封装结构内气体残留的同时，避免基板发生翘曲，提高封装结构的可靠性，是目前亟待解决的问题。
发明内容
本发明所要解决的技术问题是，提供一种封装结构及其形成方法，提高封装结构的可靠性。
为了解决上述问题，本发明提供了一种封装结构，包括：包括：基板，所述基板具有相对的第一表面和第二表面，所述基板内具有贯穿所述基板第一表面至第二表面的开口，所述开口呈长条状，且两端尺寸大于中部尺寸；芯片，所述芯片通过焊接凸点倒装固定于所述基板的第一表面上，通过所述焊接凸点与所述基板之间形成电连接，所述开口位于所述芯片在所述基板上的投影内；塑封料，包裹所述芯片，并填充满所述芯片与所述基板的第一表面之间的间隙以及所述开口。
可选的，所述开口沿所述基板的对称轴设置。
可选的，所述开口包括位于两端的两个第一子开口和位于中部的第二子开口，所述第二子开口连通所述两个第一子开口。
可选的，所述第一子开口的横截面为圆形、半圆形、椭圆形、矩形或多边形，所述第二子开口为宽度均匀的长条形；所述第一子开口在垂直所述开口长度方向上的最大宽度大于所述第二子开口的宽度。
可选的，所述第一子开口的最大宽度范围为1mm～5mm，所述第二子开口的最大宽度范围为500μm～2mm。
可选的，所述开口的横截面边缘为平滑的线条。
可选的，所述基板包括长度延伸方向一致，且位于同一直线的两个以上的所述开口，且相邻开口之间的距离大于3mm。
可选的，所述开口的长度范围为5mm～12mm。
可选的，所述塑封料填充满所述开口，并溢出至所述基板的第二表面，形成凸出于所述基板第二表面的塑封料凸条。
可选的，还包括：焊球，形成于所述基板的第二表面。
本发明的技术方案还提供一种封装结构的形成方法，包括：提供封装芯片，所述封装芯片包括基板和固定于所述基板上的芯片；所述基板具有相对的第一表面和第二表面，所述基板内形成有贯穿所述第一表面和所述第二表面的如上所述的开口；所述芯片通过倒装工艺的焊接凸点固定于所述基板的第一表面上，所述焊接凸点与所述基板之间形成电连接，所述基板内的开口位于所述芯片在所述基板上的投影内；对所述封装芯片进行注塑处理，将塑封料包裹所述芯片，并填充满所述芯片与基板第一表面之间的间隙以及所述开口。
可选的，在注塑处理过程中，通过至少部分所述开口排出封装结构内部的气体。
可选的，对所述封装芯片进行注塑处理的方法包括：提供注塑模具，所述注塑模具包括底盘和封盖，所述封盖用于盖合于所述底盘上，与所述底盘之间形成空腔；将所述封装芯片置于所述空腔内，所述基板放置于所述底盘表面；向所述空腔内注入液态塑封料，直至所述液态塑封料填充满所述空腔；进行热处理，使所述液态塑封料固化；将被固化的塑封料包裹的封装芯片自所述空腔内取出。
可选的，所述封盖上具有至少一个开孔，所述开孔连通所述空腔与外界；通过至少一个所述开孔向所述空腔内注入液态塑封料。
可选的，所述封盖上具有至少两个开孔，还包括：在注塑处理过程中，通过其中至少一个开孔向外界排出所述空腔内的气体。
可选的，所述塑封料填充满所述开口，并溢出至所述基板的第二表面，形成凸出于所述基板第二表面的塑封料凸条。
可选的，还包括：在所述基板的第二表面形成焊球。
本发明的封装结构，在基板内形成有长条状的开口，且开口两端的尺寸大于中部尺寸，能够避免在注塑时过早得被塑封料堵塞，提高排出气体的效率；并且所述开口为长条状，能够提高基板内应力分布的均匀性，避免基板在高温环境下发生翘曲形变，使基板保持平整，确保芯片与基板之间电连接的可靠性。
附图说明
图1为基板上具有多个气孔时的应力分布示意图；
图2A至图2C为本发明一具体实施方式的封装结构的结构示意图；
图3为本发明一具体实施方式的封装结构的基板示意图；
图4为本发明一具体实施方式的封装结构的形成过程的结构示意图。
具体实施方式
如背景技术中所述，现有技术在形成倒装工艺(flip chip)封装芯片时，基板容易发生翘曲，导致产品失效。
发明人仔细研究发现，由于现有技术中，为了在注塑过程中，便于排出封 装结构内部的气体，是的塑封料能够填充满芯片与基板之间的空间，通常会在基板上形成多个气孔。而由于基板上多个气孔的存在，导致基板内容易发生应力分布不均匀的问题。塑封料填充气孔后，由于塑封料与基板材料之间的热膨胀系数差异较大，在温度变化情况下，基板容易受到塑封料施加的应力。而在多个气孔的情况下，相邻气孔之间的基板，以及气孔外围的基板所受到的应力类型不同，容易导致基板发生形变，从而使得产品失效。
请参考图1，为基板100上具有多个气孔101时的应力分布示意图。
相邻气孔101之间的基板101受到拉伸应力，而基板100上气孔101所在区域外围的基板则受到拉伸应力。
在封装结构进行贴片组装回流焊的过程中，由于基板100内应力分布不均匀导致基板100发生翘曲，使得基板100与芯片的焊接凸点之间结合受损从而导致产品失效。
为了解决上述问题，发明人提出一种新的封装结构，使得基板能够将在注塑过程中排出气体的同时，应力分布更加均匀。
请参考图2A至图2C为本发明一具体实施方式的封装结构的结构示意图，其中图2A为封装结构的基板的俯视示意图，图2B为封装结构沿A-A’方向的剖面示意图，图2C为封装结构沿B-B’方向的剖面示意图。
该具体实施方式中，所述封装结构包括：基板210、芯片220以及塑封料230。
所述基板210具有相对的第一表面201和第二表面202，所述基板210内还具有贯穿所述第一表面201至第二表面202的开口211，所述开口210呈长条状，且两端尺寸大于中部尺寸。所述基板210为电路板，所述基板210表面和/或内部形成有互连电路、焊垫等电连接结构，用于与所述芯片220形成电连接，向所述芯片220输入电信号或输出所述芯片220产生的电信号。
所述芯片220通过焊接凸点221倒装固定于所述基板210的第一表面201上，通过所述焊接凸点221与所述基板210之间形成电连接。所述焊接凸点221可以为金属柱、焊球等导电凸起，与所述基板210第一表面上的电连接结构接触，使得所述芯片220固定于所述基板210表面，且与所述基板210之间形成电连接。所述芯片220与所述基板210之间为倒装(flip chip)连接结构，图2 中的结构仅作为示例，本领域技术人员可以根据具体的芯片及基板接结构，采用合适的倒装连接方式。
所述开口211位于所述芯片220在所述基板210上的投影内，从而塑封料230填充所述芯片220与基板210之间的间隙时，空气能够从所述开口211被排出。
所述塑封料230包裹所述芯片220，并填充满所述芯片220与所述基板210的第一表面201之间的间隙以及所述开口211。塑封料230对所述芯片220，以及所述芯片220与所述基板210之间的连接处进行保护，避免所述封装结构在受到外部冲击时，芯片220、以及所述芯片210与所述基板210之间的连接受损。
所述塑封料230仅覆盖所述基板210的第一表面210，暴露出所述基板210的第二表面202，所述第二表面202上形成有引脚或焊垫，作为所述封装结构与其他元件之间形成电连接的接触点。
该具体实施方式中，所述基板210的第二表面202上还形成有焊球203，所述焊球203形成于所述基板210的第二表面202上的引脚或焊垫上，与所述基板210内的电连接结构之间形成电连接。所述焊球203可以为含铅锡球或无铅锡球等。可以通过回流焊工艺，通过所述焊球203将封装结构贴装于其他电路板等其他电子元件上。
请参考图2A，该具体实施方式中，所述基板210内仅形成有一个开口211，所述开口211为长条形，且所述开口211的两端宽度大于所述开口211的中部宽度。
该具体实施方式中，所述开口211包括两个第一子开口2111和第二子开口2112，所述两个第一子开口2111分别位于两端，所述第二子开口2112连通两端的所述第一子开口2111。所述第一子开口2111在平行于基板210表面方向的横截面为圆形，所述第二子开口2112在平行于基板210表面的横截面宽距均匀的长条形。所述第一子开口2111的直径范围为1mm～5mm，所述第二子开口2112的宽度范围为500μm～2mm。所述开口211的长度范围为5mm～12mm，有利于快速排出气体，并避免注塑过程中，开口211过早的被塑封料堵住，使得所述开口211具有较好的排气效果。所述第一子开口2111的 口径较大，有利于快速排出气体；而所述第二子开口2112的长度较长，且宽度较小且均匀，有利于分散开口211内塑封料对于基板210施加的应力，提高基板210各处应力分布的均匀性。
并且，该具体实施方式中，所述第一子开口2111与所述第二子开口2112的边缘连接处为弧线，形成弧形拐角，使得所述开口211的横截面边缘线条均为平滑的线条，没有尖角结构，避免应力在拐角位置处聚集。
所述开口211沿所述基板210的对称轴(A-A’)设置，并且关于所述对称轴对称，使得由于所述开口211以及其内部填充的塑封料230对基板210施加的应力两侧对称分布。所述基板210的焊接区域位于所述开口211的两侧，所述芯片220的焊接凸点221焊接于所述基板210的焊接区域上。
在其他具体实施方式中，所述第一子开口的横截面还可以为半圆形、椭圆形、矩形或多边形中的至少一种；所述第二子开口为长条形，不同位置处的宽度可以有一定差异，但是较佳的，所述第二子开口的宽度各位置处一致；所述第一子开口在垂直所述开口长度方向上的最大宽度大于所述第二子开口的宽度。所述第二子开口的宽度较小，长宽比较大，并且与所述第一子开口连通为一整体，与圆孔等尺寸较小的开口相比，可以降低对基板施加的应力，并且提高基板内应力分布的均匀性，使得基板在高温环境下依旧保持平整，确保倒装芯片与基板的电连接完好。
所述第一子开口的口径较大，利于气体快速排出，且使得所述开口在注塑过程中不易被堵住，提高排气效果。所述第二子开口宽度各位置处均相同，且所述第一子开口横截面为圆形时，能够进一步提高应力分布的均匀性。
在一些具体实施方式中，在垂直于所述开口的长度延伸方向上，所述第一子开口的最大宽度的范围为1mm～5mm，所述第二子开口的最大宽度的范围为500μm～2mm。
在另一具体实施方式中，如果芯片的尺寸较大，对应的基板尺寸也较大的情况下，如果仅形成一个开口用于排气，所述开口的长度较大，会影响基板的强度。
请参考图3，为本发明另一具体实施方式的基板的俯视示意图。
该具体实施方式中，所述基板300内形成有两个长度延伸方向一致，且位 于同一直线的开口301。为了避免两个开口301导致基板300不同位置处应力分布不均匀性增大，所述两个开口301之间的间距较大，较佳的，所述两个开口301之间的间距d大于3mm。
在其他具体实施方式中，也可以根据芯片及基板的尺寸大小，合理设置每个芯片对应的基板内的开口数量；在满足基板强度的前提下，每个芯片对应的基板上仅形成一个开口可以最大程度减小对基板施加的应力以及提高应力分布的均匀性。
请继续参考图2B和2C，所述塑封料230不仅填充满所述开口211，而且可以进一步溢出至所述基板210的第二表面202，形成凸出于所述基板210第二表面202的塑封料凸条231，所述塑封料凸条231还覆盖部分基板210的第二表面，以确保将所述开口211完全封闭。所述塑封料凸条231连接至基板210第一表面上的塑封料230，进一步提高所述塑封料230与基板210之间的结合强度。
本发明的封装结构，在基板内形成有长条状的开口，且开口两端的尺寸大于中部尺寸，能够避免在注塑时过早得被塑封料堵塞，提高排出气体的效率；并且所述开口为长条状，能够提高基板内应力分布的均匀性，避免基板在高温环境下发生翘曲形变，使基板保持平整，确保芯片与基板之间电连接的可靠性。
本发明的具体实施方式，还提供一种上述封装结构的形成方法。
请参考图4，为本发明一具体实施方式的封装结构的形成过程的流程图。
所述封装结构的形成方法包括如下步骤：
步骤S401：提供基板，所述基板具有相对的第一表面和第二表面，所述基板内形成有贯穿所述第一表面和所述第二表面的开口，所述开口呈长条状，且两端尺寸大于中部尺寸。
所述基板可以为电路板，内部和/或表面形成有互连电路、焊垫等电连接结构。所述基板内的开口为长条形，贯穿所述基板。
较佳的，所述开口沿所述基板的对称轴设置，关于所述对称轴对称设置。所述开口的长度范围为5mm～12mm，使得所述开口具有较高的排气效率。
所述开口包括位于两端的第一子开口和连接所述两个第一子开口的第二 子开口，所述第一子开口的横截面为圆形、半圆形、椭圆形、矩形或多边形，所述第二子开口为宽度均匀的长条形；所述第一子开口在垂直所述开口长度方向上的最大宽度大于所述第二子开口的宽度。
所述第一子开口的最大宽度范围为1mm～5mm，所述第二子开口的最大宽度范围为500μm～2mm。
所述开口的横截面边缘为平滑的线条，以避免应力在开口边缘的尖锐形貌处聚集。
在其他具体实施方式中，单个芯片对应的所述基板内形成有两个以上长度延伸方向一致，且位于同一直线的两个以上的所述开口，且相邻开口之间的距离大于3mm。
步骤S402：通过倒装工艺，将芯片通过焊接凸点倒装固定于所述基板的第一表面上，所述焊接凸点与所述基板之间形成电连接，所述基板内的开口位于所述芯片在所述基板上的投影内。
步骤S403：对倒装于所述基板上的芯片进行注塑处理，将塑封料包裹所述芯片，并填充满所述芯片与基板第一表面之间的间隙以及所述开口。
可以将表面具有倒装芯片的基板置于注塑模具的腔体内，基板的第二表面位于腔体底部表面上；然后向所述腔体内注入液态塑封料后固化处理，塑封料填充满所述腔体，包裹所述芯片以及填充芯片与基板表面间隙。
具体的，在一个具体实施方式中，对所述封装芯片进行注塑处理的方法包括：提供注塑模具，所述注塑模具包括底盘和封盖，所述封盖用于盖合于所述底盘上，与所述底盘之间形成空腔；将所述封装芯片置于所述空腔内，所述基板放置于所述底盘表面；向所述空腔内注入液态塑封料，直至所述液态塑封料填充满所述空腔；进行热处理，使所述液态塑封料固化；将被固化的塑封料包裹的封装芯片自所述空腔内取出。
所述腔体底部的底盘表面可以有与所述基板内开口连通的凹槽，所述凹槽与封装模具外部连通。在注入塑封料的过程中，腔体内的气体通过至少部分所述开口排出。在塑封料填充完成后，所述塑封料填充满所述开口，并溢出至所述基板的第二表面，形成凸出于所述基板第二表面的塑封料凸条。
由于所述开口长度较大，不易完全被塑封料堵塞，因此，在塑封料完全填 充满腔体之前，可以持续作为气体排出通道。且，两端口径较中部更大，能够保持较快的排气速度。
在一个具体实施方式中，所述封盖上具有至少一个开孔，所述开孔连通所述空腔与外界；通过至少一个所述开孔向所述空腔内注入液态塑封料。在另一具体实施方式中，所述封盖上具有至少两个开孔，还包括：在注塑处理过程中，通过其中至少一个开孔注入液态塑封料，并且通过其中至少一个开孔向外界排出所述空腔内的气体。
步骤S404:在所述基板的第二表面形成焊球。
完成注塑处理后，再在所述基板的第二表面上形成焊球，所述焊球可以为焊铅锡球或无铅锡球等。后续可以通过回流焊工艺，通过所述焊球203将封装结构贴装于其他电路板等其他电子元件上。
上述封装结构的形成方法，在注塑过程中，可以通过基板上的开口排出封装结构内部的气体，且开口口径较大，为长条状，能够保持较高的排气效率。进一步的，所述开口为长条状，能够提高基板内应力分布的均匀性，避免基板在高温环境下发生翘曲形变，使基板保持平整，确保芯片与基板之间电连接的可靠性，从而提高所述封装结构的可靠性。
以上所述仅是本发明的优选实施方式，应当指出，对于本技术领域的普通技术人员，在不脱离本发明原理的前提下，还可以做出若干改进和润饰，这些改进和润饰也应视为本发明的保护范围。

Claims (17)

  1. 一种封装结构，其中，包括：
    基板，所述基板具有相对的第一表面和第二表面，所述基板内具有贯穿所述基板第一表面至第二表面的开口，所述开口呈长条状，且两端尺寸大于中部尺寸；
    芯片，所述芯片通过焊接凸点倒装固定于所述基板的第一表面上，通过所述焊接凸点与所述基板之间形成电连接，所述开口位于所述芯片在所述基板上的投影内；
    塑封料，包裹所述芯片，并填充满所述芯片与所述基板的第一表面之间的间隙以及所述开口。
  2. 根据权利要求1所述的封装结构，其中，所述开口沿所述基板的对称轴设置。
  3. 根据权利要求1所述的封装结构，其中，所述开口包括位于两端的两个第一子开口和位于中部的第二子开口，所述第二子开口连通所述两个第一子开口。
  4. 根据权利要求3所述的封装结构，其中，所述第一子开口的横截面为圆形、半圆形、椭圆形、矩形或多边形，所述第二子开口为宽度均匀的长条形；所述第一子开口在垂直所述开口长度方向上的最大宽度大于所述第二子开口的宽度。
  5. 根据权利要求4所述的封装结构，其中，所述第一子开口的最大宽度范围为1mm～5mm，所述第二子开口的最大宽度范围为500μm～2mm。
  6. 根据权利要求1所述的封装结构，其中，所述开口的横截面边缘为平滑的线条。
  7. 根据权利要求1所述的封装结构，其中，所述基板包括长度延伸方向一致，且位于同一直线的两个以上的所述开口，且相邻开口之间的距离大于3mm。
  8. 根据权利要求1所述的封装结构，其中，所述开口的长度范围为5mm～12mm。
  9. 根据权利要求1所述的封装结构，其中，所述塑封料填充满所述开口，并 溢出至所述基板的第二表面，形成凸出于所述基板第二表面的塑封料凸条。
  10. 根据权利要求1所述的封装结构，其中，还包括：焊球，形成于所述基板的第二表面。
  11. 一种封装结构的形成方法，其中，包括：
    提供封装芯片，所述封装芯片包括基板和固定于所述基板上的芯片；所述基板具有相对的第一表面和第二表面，所述基板内形成有贯穿所述第一表面和所述第二表面的如权利要求1中所述的开口；所述芯片通过倒装工艺的焊接凸点固定于所述基板的第一表面上，所述焊接凸点与所述基板之间形成电连接，所述基板内的开口位于所述芯片在所述基板上的投影内；
    对所述封装芯片进行注塑处理，将塑封料包裹所述芯片，并填充满所述芯片与基板第一表面之间的间隙以及所述开口。
  12. 根据权利要求11所述的形成方法，其中，在注塑处理过程中，通过至少部分所述开口排出封装结构内部的气体。
  13. 根据权利要求12所述的形成方法，其中，对所述封装芯片进行注塑处理的方法包括：提供注塑模具，所述注塑模具包括底盘和封盖，所述封盖用于盖合于所述底盘上，与所述底盘之间形成空腔；将所述封装芯片置于所述空腔内，所述基板放置于所述底盘表面；向所述空腔内注入液态塑封料，直至所述液态塑封料填充满所述空腔；进行热处理，使所述液态塑封料固化；将被固化的塑封料包裹的封装芯片自所述空腔内取出。
  14. 根据权利要求13所述的形成方法，其中，所述封盖上具有至少一个开孔，所述开孔连通所述空腔与外界；通过至少一个所述开孔向所述空腔内注入液态塑封料。
  15. 根据权利要求14所述的形成方法，其中，所述封盖上具有至少两个开孔，还包括：在注塑处理过程中，通过其中至少一个开孔向外界排出所述空腔内的气体。
  16. 根据权利要求11所述的形成方法，其中，所述塑封料填充满所述开口，并溢出至所述基板的第二表面，形成凸出于所述基板第二表面的塑封料凸条。
  17. 根据权利要求11所述的形成方法，其中，还包括：在所述基板的第二表面 形成焊球。
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