Chip glue injection method and semiconductor structure

Abstract

The invention discloses a chip glue injection method and a semiconductor structure, and the method comprises the steps: welding a heat dissipation bonding pad of a packaging chip to a circuit substrate, preheating the heat dissipation bonding pad to a preset temperature, and injecting a structural adhesive at the end corner of the packaging chip; carrying out heat preservation treatment on the packaging chip and the circuit substrate which are injected with the structural adhesive, and carrying out high-temperature curing treatment on a bonding part of the packaging chip and the circuit substrate; wherein the glue injection amount when the structural glue is injected into the end corners of the packaging chip and the time duration of the heat preservation treatment meet the requirement that the preset bonding area between the packaging chip and the circuit substrate is reached, and the structural glue injected into the different end corners does not intersect. According to the method, the flowing direction, the flowing speed and the flow of the structural adhesive between the packaging chip and the conductive substrate can be controlled, so that the bonding effect between the packaging chip and the circuit substrate is effectively guaranteed.

Description

Technical Field

[0001] The present application relates to the field of semiconductor processing technology, and in particular to a chip glue injection method and a semiconductor structure. Background Art

[0002] Chip packaging can be divided into through-hole packaging and surface mount packaging. QFN (Quad Flat No-leads Package) is a surface mount pinless package with a square or rectangular appearance. QFN packaging has the characteristics of small size and light weight, and can provide higher packaging efficiency, so it can be used under conditions where space and weight are limited. Since the conductive path between the internal pins and pads of the QFN packaged chip is short, the self-inductance coefficient and the wiring resistance in the package are very low, so it can provide better electrical performance; and the QFN package adopts a metal carrier design, combined with appropriate surface treatment and plastic packaging materials, it can enhance the bonding force of the various interfaces in the package. Compared with DIP, SOP packaging and other surface mount packaging, QFN packaging has good reliability. At present, chips using QFN packaging are widely used in Bluetooth chips, audio chips, power management chips, power amplifier chips, base station clock chips, video surveillance chips and other fields.

[0003] Currently, most QFN packages use the following packaging process: grinding, thinning the wafer to adapt to the limited packaging space; dicing, cutting the wafer into independent chips for subsequent packaging; mounting, placing the separated chips on the metal carrier, and connecting the chip and the metal carrier with silver paste or adhesive film; wire bonding, using automatic wire bonding equipment to connect the functional pad of the chip to the pin of the metal carrier with wires; encapsulation, using injection molding equipment to wrap and cure the wire-connected chip and metal carrier with epoxy resin to provide physical protection; electroplating, when the back of the metal carrier is copper, in order to prevent the bare copper from oxidizing and ensure good welding, a layer of tin needs to be plated on its surface; printing, using laser printing equipment to print product-related information on the chip for easy traceability; cutting, cutting multiple chips from the strip frame carrier into single chips.

[0004] The existing QFN packaged chips may have cracks between the chip and the circuit substrate during the subsequent manufacturing process. Therefore, how to avoid cracks between the QFN packaged chips and the circuit substrate is a problem that needs to be solved. Summary of the invention

[0005] The technical problem to be solved by the present application is to provide a chip glue injection method to solve the problem of cracking between the existing chip and the circuit substrate.

[0006] According to one aspect of the present invention, a chip glue injection method is provided, the method comprising:

[0007] Soldering the heat dissipation pad of the packaged chip to the circuit substrate and preheating it to a predetermined temperature, and injecting structural glue at the end corners of the packaged chip;

[0008] Performing heat preservation treatment on the packaged chip and the circuit substrate injected with structural adhesive, and performing high temperature curing treatment on the bonding part of the packaged chip and the circuit substrate;

[0009] The amount of structural glue injected at the corners of the packaged chip and the length of time for the heat preservation treatment are such that a predetermined bonding area is achieved between the packaged chip and the circuit substrate and that structural glue injected at different corners does not intersect.

[0010] In one embodiment, the amount of structural glue injected at the end corners of the packaged chip is a preset amount of glue injected, and the duration of the heat preservation treatment is a preset duration.

[0011] In one embodiment, the amount of glue injected at each end corner is 0.3±0.05㎎.

[0012] In one embodiment, the insulation treatment time length is 3±1 minutes.

[0013] In one embodiment, after the structural adhesive is injected at the end corners of the packaged chip, it also includes: real-time monitoring of whether a predetermined bonding area is reached between the packaged chip and the circuit substrate, and whether intersection occurs between the structural adhesives injected at different end corners, and determining the duration of the insulation treatment based on the monitoring results.

[0014] In one embodiment, injecting structural adhesive at the end corners of the packaged chip includes: dispensing adhesive on each end corner of the packaged chip in a clockwise direction.

[0015] In one embodiment, when the fluidity of the structural adhesive is lower than a preset fluidity threshold, the method further comprises: supplementing the edge and corner areas of the packaged chip with glue in an L-shaped glue injection manner.

[0016] In one embodiment, the preheating to a predetermined temperature includes: preheating the packaged chip to 80° C. to 90° C.

[0017] In one embodiment, a high temperature curing treatment is performed on the bonding portion of the packaged chip and the circuit substrate, including: using a temperature of 140° C. to 160° C. for 14 minutes to 18 minutes to perform a high temperature curing treatment on the bonded packaged chip and the circuit substrate.

[0018] According to another aspect of the present invention, there is provided a semiconductor structure, which includes a packaged chip and a circuit substrate, wherein a heat dissipation pad in a middle region of the packaged chip is welded to the circuit substrate, and structural adhesive is injected between each end corner region of the packaged chip and the circuit substrate, so that each end corner of the packaged chip and the circuit substrate reach a predetermined bonding area, and the structural adhesives at different end corners do not intersect.

[0019] Compared with the prior art, this application has the following advantages:

[0020] The chip glue injection method provided by the embodiment of the present application includes: welding the heat dissipation pad of the packaged chip to the circuit substrate, preheating to a predetermined temperature, and injecting structural glue at the end corner of the packaged chip; performing heat preservation treatment on the packaged chip and the circuit substrate injected with the structural glue, and performing high temperature curing treatment on the bonding part of the packaged chip and the circuit substrate; wherein the amount of glue injected and the length of heat preservation treatment when injecting the structural glue at the end corner of the packaged chip meet the predetermined bonding area between the packaged chip and the circuit substrate, and the structural glue injected at different end corners does not intersect. The method coordinately controls the amount of glue injected and the length of heat preservation time, so that the flow direction, flow rate and flow rate of the structural glue between the packaged chip and the conductive substrate are controllable, and the injection effect of reaching the predetermined bonding area between the packaged chip and the circuit substrate and preventing the injection effect of the structural glue injected at different end corners from intersecting is achieved, thereby effectively ensuring the bonding effect between the packaged chip and the circuit substrate, and avoiding the problem that the flow direction of the structural glue is uncontrollable due to the presence of the heat dissipation pad, which affects the bonding stability between the packaged chip and the circuit substrate.

[0021] The above description is only an overview of the technical solution of the present application. In order to more clearly understand the technical means of the present application, it can be implemented in accordance with the contents of the specification. In order to make the above and other purposes, features and advantages of the present application more obvious and easy to understand, the following specifically cites the preferred embodiments and describes them in detail with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a process flow chart of the chip glue injection method provided in the embodiment of the present application;

[0023] Figure 2 It is a schematic diagram of chip glue injection provided in an embodiment of the present application.

[0024] Notes on the attached drawings:

[0025] 1. Packaged chip, 2. Circuit substrate, 3. Heat dissipation pad, 4. Structural adhesive. DETAILED DESCRIPTION

[0026] Many specific details are described in the following description to facilitate a full understanding of the present application. However, the present application can be implemented in many other ways than those described herein, and those skilled in the art can make similar generalizations without violating the connotation of the present application, so the present application is not limited by the specific implementation disclosed below.

[0027] The terms used in one or more embodiments of this specification are only for the purpose of describing specific embodiments, and are not intended to limit one or more embodiments of this specification. The singular forms of "a", "said" and "the" used in one or more embodiments of this specification and the appended claims are also intended to include plural forms, unless the context clearly indicates other meanings. It should also be understood that the term "and / or" used in one or more embodiments of this specification refers to and includes any or all possible combinations of one or more associated listed items.

[0028] It should be understood that although the terms first, second, etc. may be used to describe various information in one or more embodiments of this specification, this information should not be limited to these terms. These terms are only used to distinguish the same type of information from each other. For example, without departing from the scope of one or more embodiments of this specification, the first may also be referred to as the second, and similarly, the second may also be referred to as the first. Depending on the context, the word "if" as used herein may be interpreted as "at the time of" or "when" or "in response to determining".

[0029] In view of the cracking problem between the existing QFN chip and the PCB board, this embodiment provides a chip glue injection method, please refer to Figure 1 and Figure 2 To understand this embodiment, Figure 1 is a process flow chart of the chip glue injection method provided in this embodiment; Figure 2 It is a schematic diagram of chip glue injection provided in this embodiment.

[0030] A large-area heat dissipation pad (Exposed Pad or ThermalPad) is provided at the bottom center of the QFN package chip. The heat dissipation pad has a direct heat dissipation channel for effectively conducting the heat generated by the chip in the package. Conductive pads are provided around the package periphery around the large-area heat dissipation pad to achieve electrical connection. By directly soldering the heat dissipation pad to the circuit substrate (PCB board), the QFN package can achieve good heat dissipation performance.

[0031] For another example, the DFN package (Dual Flat No-lead Package) is an extension of the QFN package. The pins of the DFN package are distributed on both sides of the package body, and its overall appearance is rectangular, while the pins of the QFN package are distributed on the four sides of the package body, and its overall appearance is square.

[0032] For the above-mentioned automotive QFN chips, DFN chips and other chip types that use a heat dissipation pad in the middle, the existing technology mostly uses solder paste to solder this type of chip to the circuit substrate (PCB board), and cracks are prone to occur at the peripheral positions of the welding. Therefore, the inventor of the present application proposes to avoid cracks at the peripheral positions of the above-mentioned welding by filling with structural adhesive.

[0033] The existing chip type that needs to be filled with structural adhesive has columnar solder paste arranged at intervals between the chip and the PCB. The filling method is to perform L-shaped glue injection at the edge. The structural adhesive (Underfill) used for filling can flow in the gap between the columnar solder paste. The flow direction of the structural adhesive is controllable, and smooth glue injection can be achieved.

[0034] However, after testing, the inventors of the present application found that if this L-shaped glue injection method is used in the above-mentioned QFN packaged chip, due to the presence of a large-area heat dissipation pad at the central position of the bottom of the chip, the structural glue cannot flow or penetrate into the middle area, and the flow direction of the structural glue cannot be controlled. For example, the structural glues with relative flows may generate eddies due to intersection, and then generate bubbles, affecting the bonding stability.

[0035] Therefore, for chip types such as QFN that use a heat sink pad for heat dissipation at the center of the bottom, the chip injection method provided in this embodiment must be used to avoid the uncontrollable flow direction of the structural adhesive affecting the bonding stability between the packaged chip and the circuit substrate, thereby effectively achieving structural adhesive injection.

[0036] like Figure 1 As shown, the chip glue injection method provided in this embodiment includes the following steps:

[0037] S1, soldering the heat dissipation pad of the packaged chip to the circuit substrate, preheating it to a predetermined temperature, and injecting structural glue at the end corners of the packaged chip.

[0038] In this embodiment, the packaged chip may be a packaged chip such as a QFN packaged chip or a DFN packaged chip, which has a large-area heat dissipation pad at the bottom. The packaging process: for example, the packaged chip is formed after the packaging processes such as grinding, dicing, mounting, wire bonding, encapsulation, electroplating, printing, and cutting. In the subsequent manufacturing process, the packaged chip needs to be further packaged with a circuit substrate (PCB board). The circuit substrate provides physical support and electrical connection for the packaged chip, such as Figure 2As shown, the packaged chip 1 is fixed on the circuit substrate 2, and the heat dissipation pad 3 is welded to the circuit substrate 2 to achieve electrical connection. Then, the packaged chip 1 and the heat dissipation pad 3 are preheated to a predetermined temperature so that the packaged chip is in a state where glue can be injected. Specifically, the packaged chip can be preheated to 80°C to 90°C, for example, 85°C, and then the structural glue 4 is injected into each end corner of the packaged chip 1 in a clockwise direction.

[0039] S2, performing heat preservation treatment on the packaged chip and the circuit substrate injected with the structural adhesive, and performing high temperature curing treatment on the bonding part of the packaged chip and the circuit substrate;

[0040] The amount of glue injected and the duration of heat preservation treatment when injecting structural glue at the corners of the packaged chip meet the requirements of achieving a predetermined bonding area between the packaged chip and the circuit substrate and preventing the structural glue injected at different corners from intersecting.

[0041] That is, the amount of glue injected and the duration of the heat preservation treatment jointly determine the flow direction, flow rate and flow rate between the packaged chip and the circuit substrate. Specifically, the heat preservation time can characterize the flow time of the structural glue, which together with the amount of glue injected affects the protection strength at the chip corners. When the amount of glue injected is determined, if the heat preservation time is too long, the structural glue will flow too long toward the heat dissipation pad and the amount of glue flowing will be too much, which will result in too little glue remaining at the corners and cause the structural glue to be too thin, thereby reducing the bonding performance at the corners; if the heat preservation time is too short, the structural glue will flow too short toward the heat dissipation pad and the amount of glue flowing will be too little, which will result in the glue amount at the corners being more concentrated, and the effective bonding area cannot be guaranteed, affecting the bonding performance.

[0042] When the insulation time is determined, due to the presence of a heat dissipation pad in the middle area of ​​the chip, excessive glue injection will make the flow direction of the structural glue uncontrollable. The structural glue injected at different end corners may intersect and cause eddy currents, which in turn generate bubbles and affect the bonding performance. If the glue injection amount is too small, the effective bonding area cannot be guaranteed.

[0043] This embodiment coordinates the injection amount and the insulation time length to control the flow direction, flow rate and flow rate of the structural adhesive between the packaged chip and the conductive substrate. The two together achieve the injection effect of achieving a predetermined bonding area between the packaged chip and the circuit substrate and preventing the structural adhesives injected at different end corners from intersecting.

[0044] In one embodiment, for structural adhesive with known fluidity, the amount of adhesive injected at the end corners of the packaged chip in the above step S1 can be a preset amount of adhesive, and the duration of the insulation treatment in step S2 can also be a preset duration. Specifically, the amount of adhesive injected at each end corner is 0.3±0.05㎎, and the duration of the insulation treatment is 3±1 minutes. The amount of adhesive injected and the insulation duration can be obtained by summarizing and analyzing historical experimental data.

[0045] In another embodiment, for structural adhesives with uncertain fluidity, the insulation time can also be determined in real time during the current injection process based on the monitoring results of the bonding effect. Specifically, in step S1, after a predetermined amount of structural adhesive is injected at the end corners of the packaged chip, whether a predetermined bonding area is reached between the packaged chip and the circuit substrate, and whether intersection occurs between the structural adhesives injected at different end corners can be monitored in real time, and the insulation treatment time can be determined based on the monitoring results. For example, after a predetermined amount of structural adhesive is injected at the end corners of the packaged chip, while the insulation treatment is performed, real-time monitoring is performed on the bonding area and whether intersection occurs between the structural adhesives injected at different end corners. If the monitoring results show that the predetermined bonding area has been reached at each end corner of the packaged chip, and no intersection occurs between the structural adhesives injected at different end corners, the insulation treatment is stopped. If the monitoring results show that the predetermined bonding area has not been reached at the end corners of the packaged chip, the insulation treatment is continued to allow the structural adhesive to continue to diffuse and flow toward the pad.

[0046] In this embodiment, it can also be determined whether to perform additional glue injection based on the fluidity of the structural adhesive. When the fluidity of the structural adhesive is higher than a preset fluidity threshold, it indicates that its bonding performance to the bonding parts is good, and no additional glue injection is required at this time; when the fluidity of the structural adhesive is lower than the preset fluidity threshold, an L-shaped glue injection method can be used to perform additional glue injection on the edge and corner areas of the packaged chip. For example, a structural adhesive with a length of 3 mm ± 0.3 mm, a width ≥ 1 mm, and a height between 0.4 and 0.7 mm is used to perform additional glue injection on the edge and corner areas of the packaged chip, so as to further improve the bonding performance of the edge and corner areas that are prone to cracking.

[0047] The high temperature curing treatment of the bonding portion of the packaged chip and the circuit substrate may specifically refer to: performing high temperature curing treatment on the bonded packaged chip and the circuit substrate at a temperature of 140° C. to 160° C. for a time of 14 minutes to 18 minutes.

[0048] The chip glue injection method provided in the present embodiment coordinates the glue injection amount and the insulation time length, so that the flow direction, flow rate and flow rate of the structural glue between the packaged chip and the conductive substrate are controllable, thereby achieving an injection effect of achieving a predetermined bonding area between the packaged chip and the circuit substrate and preventing the structural glue injected at different end angles from intersecting, thereby effectively ensuring the bonding effect between the packaged chip and the circuit substrate, and avoiding the problem of the bonding stability between the packaged chip and the circuit substrate being affected by the presence of the heat dissipation pad, which makes the flow direction of the structural glue uncontrollable (for example, the heat dissipation pad prevents the structural glue from flowing or penetrating to the middle area, so the structural glues with relative flows may generate eddies due to intersection and then generate bubbles).

[0049] Corresponding to the above-mentioned chip injection method embodiment, another embodiment of the present application also provides a semiconductor structure, which includes the packaged chip 1 and the circuit substrate 2 described in the above-mentioned method embodiment, the heat dissipation pad 3 in the middle area of ​​the packaged chip 1 is welded to the circuit substrate 2, and structural glue 4 is injected between the end corner areas of the packaged chip 1 and the circuit substrate 2. The structural glue 4 enables the end corners of the packaged chip 1 to reach a predetermined bonding area with the circuit substrate 2, and the structural glue 4 injected at different end corners does not intersect.

[0050] It should be noted that although the present application is disclosed as above in the form of a preferred embodiment, it is not intended to limit the present application. Any technical personnel in this field may make possible changes and modifications without departing from the spirit and scope of the present application. Therefore, the scope of protection of the present application shall be based on the scope defined by the claims of the present application.

Claims

1. A chip glue injection method, characterized in that: The method comprises: Soldering the heat dissipation pad of the packaged chip to the circuit substrate and preheating it to a predetermined temperature, and injecting structural glue at the end corners of the packaged chip; Performing heat preservation treatment on the packaged chip and the circuit substrate injected with structural adhesive, and performing high temperature curing treatment on the bonding part of the packaged chip and the circuit substrate; The amount of structural glue injected at the corners of the packaged chip and the length of time for the heat preservation treatment are such that a predetermined bonding area is achieved between the packaged chip and the circuit substrate and that structural glue injected at different corners does not intersect.

2. The chip glue injection method according to claim 1, characterized in that: The amount of structural glue injected at the end corners of the packaged chip is a preset amount of glue injected, and the duration of the heat preservation treatment is a preset duration.

3. The chip glue injection method according to claim 1 or 2, characterized in that: The amount of glue injected at each end corner is 0.3±0.05㎎.

4. The chip glue injection method according to claim 3, characterized in that: The duration of the heat preservation treatment is 3±1 minutes.

5. The chip glue injection method according to claim 1, characterized in that: After the structural adhesive is injected at the end corners of the packaged chip, the method further includes: real-time monitoring of whether a predetermined bonding area is reached between the packaged chip and the circuit substrate, and whether intersection occurs between the structural adhesives injected at different end corners, and determining the duration of the heat preservation treatment based on the monitoring results.

6. The chip glue injection method according to claim 1, characterized in that: The injecting of structural adhesive at the end corners of the packaged chip comprises: dispensing adhesive on each end corner of the packaged chip in a clockwise direction.

7. The chip glue injection method according to claim 1, characterized in that: When the fluidity of the structural adhesive is lower than a preset fluidity threshold, the method further comprises: supplementing the edge and corner areas of the packaged chip with glue in an L-shaped glue injection manner.

8. The chip glue injection method according to claim 1, characterized in that: The preheating to a predetermined temperature includes: preheating the packaged chip to 80° C. to 90° C.

9. The chip glue injection method according to claim 1, characterized in that: The bonding portion between the packaged chip and the circuit substrate is subjected to a high temperature curing process, comprising: The bonded packaged chip and the circuit substrate are subjected to a high temperature curing treatment at a temperature of 140° C. to 160° C. for a time of 14 minutes to 18 minutes.

10. A semiconductor structure, characterized in that: It includes a packaging chip and a circuit substrate, wherein the heat dissipation pad in the middle area of ​​the packaging chip is welded to the circuit substrate, and structural glue is injected between the end corners of the packaging chip and the circuit substrate. The structural glue ensures that the end corners of the packaging chip and the circuit substrate reach a predetermined bonding area, and the structural glues at different end corners do not intersect.

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