Substrate preparation method, substrate, flip chip packaging method and packaging structure

Abstract

The disclosed embodiment provides a substrate preparation method and a substrate, flip chip packaging method and packaging structure, the substrate preparation method includes: providing a substrate body, the substrate body is provided with a plurality of pads; forming solder balls corresponding to the pads; forming filling holes by opening holes in the solder balls, and filling the filling holes with a preset dose of flux; stamping and sealing the filling holes after the flux filling, to form solder joints with embedded flux. A preset dose of flux is filled in the solder joints of the substrate, and when the substrate and the chip are flip-chip soldered, the flux is released from the solder joints to play a role of flux. While ensuring the flux dose, there is no need to spray flux on the substrate, which simplifies the process flow, increases product reliability, and improves product production quality. In addition, no additional detection equipment is required to detect the flux spraying condition, which further simplifies the process flow, improves productivity, and saves production costs.

Description

Technical Field

[0001] The embodiments of the present disclosure belong to the field of semiconductor packaging technology, and specifically relate to a substrate preparation method and a substrate, flip chip packaging method and packaging structure. Background Art

[0002] The conventional flip chip packaging method is to immerse the chip bumps in flux so that the flux is set on the chip bumps, then place the chip bumps on the substrate for flip-chip soldering, and then reflow in a reflow furnace to flip the chip on the substrate. When a large-sized or complex-structured chip is flip-chip soldered to the substrate, a sufficient amount of flux is required for soldering. Therefore, in addition to dipping the chip bumps in flux, it is also necessary to spray flux on the pads of the substrate, and then solder the chip bumps to the pads of the substrate to flip the chip on the substrate.

[0003] Among them, the method of using chip bumps to dip soldering flux and spraying soldering flux on the substrate has the following problems:

[0004] 1) The dosage of flux sprayed on the substrate is unstable, and there is a problem of too much or too little spraying, which affects the quality of flip-chip soldering of the chip and further affects the reliability of the chip;

[0005] 2) After the flux is sprayed on the substrate, corresponding flux detection equipment is required to detect the spraying condition of the flux, which adds additional process flow, additional detection equipment, and increases production costs.

[0006] In view of the above problems, it is necessary to propose a substrate preparation method and a substrate, flip chip packaging method and packaging structure that are reasonably designed and effectively solve the above problems. Summary of the invention

[0007] The embodiments of the present disclosure aim to solve at least one of the technical problems existing in the prior art, and provide a substrate preparation method and a substrate, a flip chip packaging method and a packaging structure.

[0008] An aspect of an embodiment of the present disclosure provides a method for preparing a substrate, the method comprising:

[0009] Providing a substrate body, wherein the substrate body is provided with a plurality of pads;

[0010] forming a solder ball corresponding to the solder pad on the solder pad;

[0011] Opening a hole in the solder ball to form a filling hole, and filling a preset dose of soldering flux into the filling hole, wherein the melting point and density of the soldering flux are lower than the melting point and density of the solder ball;

[0012] The filling hole after the soldering flux filling is stamped and sealed to form a soldering point with embedded soldering flux.

[0013] Optionally, forming a solder ball corresponding to the solder pad on the solder pad includes:

[0014] Solder paste is printed on the solder pad, and reflow forming is performed to form solder balls corresponding to the solder pad.

[0015] Optionally, the step of opening a hole in the solder ball to form a filling hole includes:

[0016] A hole is opened along the end of the solder ball away from the solder pad by laser drilling to form the filling hole.

[0017] Optionally, the formed filling hole passes through the solder ball.

[0018] Another aspect of the present disclosure provides a substrate, which is prepared by the substrate preparation method described above, wherein the substrate includes a substrate body, the substrate body is provided with a plurality of pads, and each of the pads is provided with a corresponding solder point; wherein:

[0019] A receiving cavity is arranged in the soldering point, and a preset dosage of soldering flux is arranged in the receiving cavity.

[0020] Optionally, the accommodating cavity is arranged close to the pad.

[0021] Another aspect of the present disclosure provides a flip chip packaging method, the method comprising:

[0022] A substrate and a chip are provided, wherein the functional surface of the chip is provided with chip bumps, and the substrate is the substrate described above;

[0023] Dipping the chip bumps into soldering flux to obtain the soldering flux, and flip-chip mounting the chip on the substrate so that the chip bumps are aligned with the corresponding solder joints;

[0024] The chip and the substrate that have been mounted are subjected to reflow heating, wherein when the solder joint begins to melt, the soldering flux inside the solder joint is released and comes into contact with the soldering flux of the chip bump;

[0025] The chip bumps and the solder joints are completely melted and cooled to solidify, thereby completing the welding of the chip bumps and the solder joints, and then the chip is flip-chip welded to the substrate.

[0026] Optionally, after the chip bumps and the solder joints are welded,

[0027] The method further comprises:

[0028] The soldering flux is cleaned and removed, and then baked and dried.

[0029] Optionally, the chip bumps and solder joints are both made of tin-silver-copper alloy.

[0030] Another aspect of the embodiments of the present disclosure provides a flip chip packaging structure, which is formed by packaging using the packaging method described above.

[0031] The present invention discloses a method for preparing a substrate, a method for packaging a substrate and a flip chip, and a packaging structure. The method for preparing a substrate forms a filling hole by opening a hole in the solder ball, and fills a preset dose of flux in the filling hole; the filling hole filled with flux is stamped and sealed to form a solder joint with embedded flux. A preset dose of flux is filled in the solder joint of the substrate, and when the substrate and the chip are flip-chip soldered, the flux is released from the solder joint to play a fluxing role. While ensuring the flux dose, there is no need to spray flux on the substrate, which simplifies the process flow, increases product reliability, and improves product production quality. In addition, no additional testing equipment is required to detect the flux spraying condition, which further simplifies the process flow, improves productivity, and saves production costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 It is a schematic flow chart of a method for preparing a substrate according to an embodiment of the present disclosure;

[0033] Figure 2 A process schematic diagram of a method for preparing a substrate according to another embodiment of the present disclosure;

[0034] Figure 3 This is a schematic structural diagram of a substrate according to another embodiment of the present disclosure;

[0035] Figure 4 A schematic flow chart of a flip chip packaging method according to another embodiment of the present disclosure;

[0036] Figures 5 to 8 The present invention is a process schematic diagram of a flip chip packaging method according to another embodiment of the present disclosure. DETAILED DESCRIPTION

[0037] In order to enable those skilled in the art to better understand the technical solutions of the embodiments of the present disclosure, the embodiments of the present disclosure are further described in detail below in conjunction with the accompanying drawings and specific implementation methods.

[0038] like Figure 1 As shown, one aspect of an embodiment of the present disclosure provides a substrate preparation method S100, the method S100 comprising:

[0039] S110, providing a substrate body, wherein the substrate body is provided with a plurality of pads.

[0040] Specifically, Figure 3 As shown, a substrate body 110 is provided, and a plurality of pads 111 are arranged on the substrate body 110, wherein the pads 111 can be copper pads.

[0041] S120, forming a solder ball corresponding to the solder pad.

[0042] Specifically, a solder ball 120 corresponding to the pad 111 is formed on the pad 111 .

[0043] like Figure 2 As shown, in this embodiment, the process of forming the solder ball 120 can be as follows: solder paste is printed on the pad 111, and reflow is performed to form a solder ball corresponding to the pad 111. That is, in this embodiment, the solder ball 120 formed is a solder ball for example.

[0044] S130, drilling a hole in the solder ball to form a filling hole, and filling a preset dose of soldering flux into the filling hole, wherein the melting point and density of the soldering flux are smaller than the melting point and density of the solder ball.

[0045] Specifically, Figure 2 As shown, a hole is opened along the end of the solder ball 120 away from the pad 111 by laser drilling or the like to form a filling hole 121. After the filling hole 121 is formed, a preset dosage of solder flux is filled into the filling hole 121.

[0046] It should be noted that the melting point and density of the solder flux are lower than those of the solder ball 120. Since the solder flux has a lower melting point and density and can reduce the surface tension of the solder ball, when the chip is flipped onto the substrate and hot-pressed, the solder ball is squeezed to release the solder flux from the solder ball, thereby achieving soldering of the chip and the substrate.

[0047] It should be further explained that the dosage of the filling flux can be selected according to actual needs and is not specifically limited in this embodiment.

[0048] In this embodiment, by filling a preset dose of flux into the filling hole, the dose of flux during the welding process can be ensured. At the same time, there is no need to spray flux on the substrate, which simplifies the process flow, increases product reliability, and improves product production quality.

[0049] For example, Figure 2As shown, preferably, the formed filling hole 121 penetrates the solder ball 120, which can provide more space for filling the flux and better seal the filling hole 121. Of course, the formed filling hole 121 may not completely penetrate the solder ball 120, and the size of the filling hole 121 can be set according to the amount of solder flux filled, which is not specifically limited in this embodiment.

[0050] S140, stamping and sealing the filling hole after the soldering flux is filled to form a soldering point with embedded soldering flux.

[0051] like Figure 2 As shown, the filling hole 121 filled with solder flux is sealed by pressing, forming a solder joint A with embedded solder flux. Specifically, a stamping groove D is provided on the side of the stamping module facing the solder ball 120, so that the end of the solder ball 120 is completely in the stamping groove D during stamping and sealing, thereby ensuring the sealing effect of the filling hole 121.

[0052] It should be noted that other methods may also be used to seal the filling hole 121 , which is not specifically limited in this embodiment and can be selected according to actual needs.

[0053] The method for preparing a substrate of the disclosed embodiment is to open a hole in the solder ball to form a filling hole, and fill a preset dose of flux into the filling hole; the filling hole filled with flux is stamped and sealed to form a solder joint with embedded flux. A preset dose of flux is filled in the solder joint of the substrate, and when the substrate and the chip are flip-chip soldered, the flux can be released from the solder joint to play a fluxing role. While ensuring the flux dose, there is no need to spray flux on the substrate, which increases the reliability of the product and improves the product production quality. In addition, no additional testing equipment is required to detect the flux spraying condition, which further simplifies the process flow, improves the yield, and saves production costs.

[0054] like Figure 3 As shown, another aspect of the embodiment of the present disclosure provides a substrate 100, the substrate 100 includes a substrate body 110, the substrate body 110 is provided with a plurality of pads 111, each pad 111 is provided with a corresponding solder point A. The solder point A is provided with a receiving cavity, and a preset dose of solder flux B is provided in the receiving cavity.

[0055] Exemplarily, the accommodating cavity is disposed close to the pad 111, so that the soldering flux B in the solder joint A is disposed close to the pad 111. Figure 3 As shown, preferably, the accommodating cavity is arranged on the soldering pad 111, and the accommodating cavity is arranged on the soldering pad 111, so that the soldering flux B can be better filled in the accommodating cavity.

[0056] The substrate of the disclosed embodiment has a solder joint on the pad of the substrate, and a preset dosage of flux is provided inside the solder joint. When the substrate and the chip are flip-chip soldered, the flux can be released from the solder joint to play a role of flux. While ensuring the dosage of flux, there is no need to spray flux on the substrate, which simplifies the process flow, increases product reliability, and improves product production quality. In addition, no additional testing equipment is required to detect the flux spraying condition, which further simplifies the process flow, improves productivity, and saves production costs.

[0057] like Figure 4 As shown, another aspect of the embodiment of the present disclosure provides a flip chip packaging method S200, the packaging method S200 comprising:

[0058] S210, providing a substrate and a chip, wherein a functional surface of the chip is provided with chip bumps, and the substrate adopts the substrate described above.

[0059] Specifically, Figure 5 As shown, a substrate 100 and a chip 210 are provided, wherein a plurality of chip bumps 220 are provided on the back of the chip 210. The substrate 100 adopts the substrate 100 described above, and a soldering point A with embedded flux is pre-prepared on the soldering pad 111 of the substrate 100. The specific structural features of the substrate 100 have been described in detail above, and will not be repeated here.

[0060] In this embodiment, a pre-prepared substrate is used for flip-chip packaging of the chip, and a preset dose of flux is embedded in the solder joints of the substrate, eliminating the need to spray flux on the substrate, thereby simplifying the process and saving packaging time and cost.

[0061] S220, immersing the chip bumps into soldering flux to obtain the soldering flux, and flip-chip mounting the chip on the substrate so that the chip bumps are aligned with the corresponding solder joints.

[0062] Specifically, the chip bumps 220 are immersed in the soldering flux, so that the ends of the chip bumps 220 facing away from the chip 210 are dipped in the soldering flux C.

[0063] like Figure 5 As shown, the chip 210 is flip-chip mounted on the substrate 100 , and the chip bumps 220 of the chip 210 are aligned and fixed with the corresponding solder joints A of the substrate 100 by means of the soldering flux C.

[0064] It should be noted that, in this embodiment, both the chip bump 220 and the solder joint A are made of a tin-silver-copper alloy material. In other words, the chip bump 220 is a tin ball, and the solder joint A is a tin cap with embedded flux.

[0065] S230, performing reflow heating on the mounted chip and the substrate, wherein when the solder joint begins to melt, the flux inside the solder joint is released and comes into contact with the molten flux of the chip bump.

[0066] Specifically, the chip 210 and the substrate 100 after mounting are placed in a reflow oven for reflow heating. Since the soldering flux has a smaller melting point and density than the solder joint A, and the soldering flux can reduce the surface tension of the solder joint A, Figure 6 As shown, when solder joint A begins to melt, the solder flux inside solder joint A is released and melts and contacts with solder flux C on chip bump 220. In this way, solder flux B and solder flux C begin to work, removing oxides and contaminants on the soldering surface and reducing the surface tension of the solder.

[0067] S240, the chip bumps and the solder joints are completely melted and then cooled and solidified, thereby completing the welding of the chip bumps and the solder joints, and then flip-chip welding the chip to the substrate.

[0068] Specifically, Figure 7 As shown, as the reflow heating continues in the reflow oven, the chip bumps 220 on the chip 210 and the solder joints A on the substrate 210 are completely melted together, and then cooled and solidified so that the chip bumps 220 and the solder joints A are welded together, and then the chip 210 is flip-chip welded on the substrate 100.

[0069] like Figure 7 As shown, when the chip bump 220 and the solder joint A are soldered together, the soldering flux is distributed on both sides of the chip bump 220 and the solder joint A after soldering.

[0070] Exemplarily, after the chip bumps and the solder joints are welded, the packaging method S200 further includes:

[0071] The flux is cleaned and removed, and then baked and dried. Figure 8 As shown, the flux can be cleaned with a flux remover and then baked and dried.

[0072] It should be noted that after the cleaning of the solder flux is completed, the packaging method S200 further includes:

[0073] An underfill is filled between the chip 210 and the substrate 100 to form an underfill layer that wraps the chip bumps 210 and the solder joints A, thereby further fixing the chip 210 and the substrate 100 .

[0074] The flip chip packaging method of this embodiment adopts the substrate described above, and the soldering pad of the substrate is provided with solder joints, and the soldering joints are provided with flux inside. When the substrate and the chip are flip-chip soldered, the flux can be released from the solder joints to play a role in soldering. Compared with the method of spraying flux on the substrate, there will be no problem of too much or too little flux, which increases the reliability of the product and improves the product production quality. In addition, no additional detection equipment is required to detect the flux spraying condition, which further simplifies the process flow, improves the yield, and saves production costs.

[0075] Another aspect of the present disclosure provides a flip chip packaging structure, which is formed by packaging using the packaging method described above. The chip packaging structure of the present disclosure has good reliability and good production quality.

[0076] It is to be understood that the above embodiments are merely exemplary embodiments used to illustrate the principles of the embodiments of the present disclosure, but the embodiments of the present disclosure are not limited thereto. For those of ordinary skill in the art, various modifications and improvements can be made without departing from the spirit and essence of the embodiments of the present disclosure, and these modifications and improvements are also considered to be within the protection scope of the embodiments of the present disclosure.

Claims

1. A method for preparing a substrate, characterized in that: The method comprises: Providing a substrate body, wherein the substrate body is provided with a plurality of pads; forming a solder ball corresponding to the solder pad on the solder pad; Opening a hole in the solder ball to form a filling hole, and filling a preset dose of soldering flux into the filling hole, wherein the melting point and density of the soldering flux are lower than the melting point and density of the solder ball; The filling hole after the soldering flux filling is stamped and sealed to form a soldering point with embedded soldering flux.

2. The method according to claim 1, characterized in that: The step of forming a solder ball corresponding to the solder pad comprises: Solder paste is printed on the solder pad, and reflow forming is performed to form solder balls corresponding to the solder pad.

3. The method according to claim 1, characterized in that The step of opening a hole in the solder ball to form a filling hole comprises: A hole is opened along the end of the solder ball away from the solder pad by laser drilling to form the filling hole.

4. The method according to claim 3, characterized in that: The formed filling hole penetrates the solder ball.

5. A substrate, characterized in that: The substrate is prepared by the substrate preparation method according to any one of claims 1 to 4; The substrate comprises a substrate body, the substrate body is provided with a plurality of pads, and the pads are provided with corresponding solder points; wherein, A receiving cavity is arranged in the soldering point, and a preset dosage of soldering flux is arranged in the receiving cavity.

6. The substrate according to claim 5, characterized in that The accommodating cavity is arranged close to the pad.

7. A flip chip packaging method, characterized in that: The method comprises: A substrate and a chip are provided, wherein a functional surface of the chip is provided with chip bumps, and the substrate is the substrate according to claim 5 or 6; Dipping the chip bumps into soldering flux to obtain the soldering flux, and flip-chip mounting the chip on the substrate so that the chip bumps are aligned with the corresponding solder joints; The mounted chip and the substrate are subjected to reflow heating, wherein when the solder joint begins to melt, the soldering flux inside the solder joint is released and contacts the soldering flux of the chip bump; The chip bumps and the solder joints are completely melted and cooled to solidify, thereby completing the welding of the chip bumps and the solder joints, and then the chip is flip-chip welded to the substrate.

8. The method according to claim 7, characterized in that After the chip bumps and the solder joints are welded, the method further comprises: The soldering flux is cleaned and removed, and then baked and dried.

9. The method according to claim 8, characterized in that The chip bumps and solder joints are made of tin-silver-copper alloy.

10. A flip chip packaging structure, characterized in that: The packaging is formed by adopting the packaging method described in any one of claims 7 to 9.

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