Fabrication method of package substrate

Abstract

A method of fabricating a package substrate includes forming a circuit structure having a plurality of electrical contact pads on a carrier, fabricating a flexible substrate configured with a plurality of solder bumps according to positions of the plurality of electrical contact pads, and pressing the flexible substrate onto the circuit structure to bond the solder bumps onto the electrical contact pads. The flexible substrate is then removed, and finally the solder bumps are reflow to form solder balls. Therefore, the soldering tin bump is formed on the flexible substrate, so that the ball mounting operation is carried out on the warped circuit structure.

Description

Technical Field

[0001] The present invention relates to a semiconductor packaging process, and more particularly to a method for manufacturing a packaging substrate that can improve the yield rate. Background Art

[0002] With the booming development of the electronics industry, electronic products tend to be thinner, lighter, shorter and smaller in form, and in terms of functions, they are developed towards high performance, high functionality and high speed. Therefore, in order to meet the requirements of high integration and miniaturization of semiconductor devices, in the packaging process, packaging substrates with high-density and fine-pitch circuits are often used.

[0003] Figures 1A to 1E It is a schematic cross-sectional view of a method for manufacturing an existing packaging substrate.

[0004] As Figures 1A to 1B shown, a carrier 9 is provided, and a first metal layer 91 is formed on opposite surfaces of the plate body 90 thereof, and a second metal layer 92 is formed on the first metal layer 91, so as to form a circuit structure 11 on each of the second metal layers 92, which includes at least one dielectric layer 110 formed on the second metal layer 92, a circuit layer 111 formed on the dielectric layer 110, and a plurality of conductive blind vias 112 formed in the dielectric layer 110, so that the plurality of conductive blind vias 112 electrically connect the circuit layer 111 and the metal layer 92, and the outermost circuit layer 111 has a plurality of electrical contact pads 12. Then, a solder mask layer 13 is formed on the circuit structure 11, and a plurality of openings 130 exposing the plurality of electrical contact pads 12 are formed on each of the solder mask layers 13.

[0005] As Figure 1C shown, a flux 14 is formed on the electrical contact pads 12 in the plurality of openings 130.

[0006] As Figure 1D shown, solder bumps 15 are formed on the electrical contact pads 12 in the plurality of openings 130 by means of the positioning holes 70 of the carrier 7.

[0007] As Figure 1E shown, the solder bumps 15 are reflowed by the flux 14 to form solder balls 16.

[0008] However, in the method for manufacturing an existing packaging substrate, when performing an interlayer build-up operation in a process with a regular whole layout, it is easy to cause warping, bending or other deformation conditions of the carrier 9 and the overall structure thereon due to factors such as uneven stress distribution of the circuit layer 111 and thermal stress concentration of the solder mask layer 13 (such as Figure 1CAs shown by the dashed line, the electrical contact pad 12 is displaced, so that during the subsequent ball mounting operation, the positioning hole 70 cannot be aligned with the electrical contact pad 12, and the solder bumps 15 cannot be effectively formed on the electrical contact pad 12. Therefore, after reflow soldering the solder bumps 15, the solder balls 16 will fall off, resulting in the problem of no ball on the electrical contact pad 12.

[0009] Therefore, how to overcome the above problems of the prior art has actually become an urgent issue to be solved currently. Summary of the Invention

[0010] The object of the present invention is to provide a method for manufacturing a packaging substrate to solve at least one of the above problems.

[0011] In view of the above-mentioned various defects of the prior art, the present invention provides a method for manufacturing a packaging substrate, including: forming a circuit structure with a plurality of electrical contact pads on a carrier; manufacturing a flexible substrate configured with a plurality of solder bumps according to the positions of the plurality of electrical contact pads; pressing the flexible substrate onto the circuit structure so that the solder bumps are bonded to the electrical contact pads; removing the flexible substrate; and reflow soldering the solder bumps to form solder balls.

[0012] In the above-mentioned manufacturing method, the circuit structure includes a dielectric layer formed on the carrier, a circuit layer formed on the dielectric layer, and a plurality of conductive blind vias formed in the dielectric layer to electrically connect the plurality of conductive blind vias to the circuit layer, and the outermost circuit layer has the plurality of electrical contact pads. Further, a solder mask layer is formed on the circuit structure, and a plurality of openings exposing the electrical contact pads are formed on the solder mask layer.

[0013] In the above-mentioned manufacturing method, the flexible substrate includes at least one insulating layer and a plurality of positioning pads formed on the insulating layer, and a first soldering aid is bonded to the positioning pads so that the solder bumps are formed on the first soldering aid. Further, the solder bumps are bonded to the electrical contact pads by the second soldering aid. For example, the viscosity of the first soldering aid is greater than that of the second soldering aid.

[0014] In the above-mentioned manufacturing method, it further includes removing the first soldering aid together when removing the flexible substrate.

[0015] In the above-mentioned manufacturing method, it further includes first forming a second soldering aid on the electrical contact pad and then bonding the solder bump to the second soldering aid on the electrical contact pad. Or, first forming a second soldering aid on the solder bump and then bonding the solder bump to the electrical contact pad with the second soldering aid thereon.

[0016] In the above-mentioned manufacturing method, it further includes that before manufacturing the flexible substrate, the carrier and the circuit structure thereon are in a warped state.

[0017] As can be seen from the above, the manufacturing method of the packaging substrate of the present invention mainly forms the solder bumps on the flexible substrate to achieve the ball planting operation on the warped circuit structure, and can avoid the problem of incorrect ball planting position caused by the warping of the circuit structure. Therefore, compared with the prior art, even if the carrier and the overall structure thereon are warped, bent or otherwise deformed, the solder bumps can still be effectively combined with the respective electrical contact pads to avoid the problems of no ball or incorrect ball planting position, thereby improving the production yield of the packaging substrate. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figures 1A to 1E It is a cross-sectional schematic view of the manufacturing method of the existing packaging substrate.

[0019] Figures 2A to 2E It is a cross-sectional schematic view of the first embodiment of the manufacturing method of the packaging substrate of the present invention.

[0020] Figures 3A to 3B It is a cross-sectional schematic view of the second embodiment of the manufacturing method of the packaging substrate of the present invention.

[0021] The reference numerals are as follows:

[0022] 11, 21 Circuit structure

[0023] 110, 210 Dielectric layer

[0024] 111, 211 Circuit layer

[0025] 112, 212 Conductive blind hole

[0026] 12, 22 Electrical contact pad

[0027] 13, 23 Solder mask layer

[0028] 130, 230 Opening

[0029] 14 Flux

[0030] 15, 25 Solder bump

[0031] 16, 26 Solder ball

[0032] 24, 34 Second flux

[0033] 7 Carrier

[0034] 70 Locating hole

[0035] 8 Flexible substrate

[0036] 81 Insulating layer

[0037] 82 Locating pad

[0038] 83 Insulation protection layer

[0039] 830 Target point

[0040] 831 Opening

[0041] 84 First solder material

[0042] 9 Carrier

[0043] 90 Plate body

[0044] 91 First metal layer

[0045] 92 Second metal layer. Detailed implementation manners

[0046] The following describes the implementation manners of the present invention through specific embodiments. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification.

[0047] It should be noted that the structures, ratios, sizes, etc. shown in the attached drawings of this specification are only used to cooperate with the content disclosed in the specification for the understanding and reading of those skilled in the art, and are not used to limit the limiting conditions for the implementation of the present invention. Therefore, they do not have technical essential significance. Any modification of the structure, change of the proportional relationship, or adjustment of the size, without affecting the effects that the present invention can produce and the purposes that can be achieved, should still fall within the scope that can be covered by the technical content disclosed in the present invention. At the same time, the terms such as "upper", "first", "second", "one", etc. cited in this specification are only for the convenience of clear narration, and are not used to limit the scope for the implementation of the present invention. The change or adjustment of their relative relationships, without substantial change in the technical content, should also be regarded as the scope that the present invention can implement.

[0048] Figures 2A to 2E It is a cross-sectional schematic diagram of the first embodiment of the manufacturing method of the packaging substrate of the present invention.

[0049] As Figures 2A to 2B shown, a carrier 9 is provided. A first metal layer 91 is provided on the opposite two surfaces of its plate body 90, and a second metal layer 92 is formed on the first metal layer 91, so as to form a circuit structure 21 on each of the second metal layers 92. The circuit structure 21 includes at least one dielectric layer 210 formed on the second metal layer 92, a circuit layer 211 formed on the dielectric layer 210, and a plurality of conductive blind vias 212 formed in the dielectric layer 210, so that the plurality of conductive blind vias 212 electrically connect the circuit layer 211 and the second metal layer 92, and the outermost circuit layer 211 has a plurality of electrical contact pads 22. Then, a solder mask layer 23 such as green paint is formed on the circuit structure 21, and a plurality of openings 230 exposing the plurality of electrical contact pads 22 are formed on each of the solder mask layers 23.

[0050] In this embodiment, the first metal layer 91 is a thick copper layer such as a copper foil with a thickness of about 18 micrometers (um), making the carrier 9 a copper clad laminate (CCL). For example, the second metal layer 92 is a thin copper layer with a thickness of about 3 micrometers, which is formed on the first metal layer 91 by electroplating or deposition.

[0051] Furthermore, the dielectric layer 210 is an ABF film (Ajinomoto build-up film), polybenzoxazole (PBO), polyimide (PI), prepreg (PP), or other dielectric materials.

[0052] In addition, a build-up process is used to fabricate the circuit layer 211 by electroplating a metal (such as copper) or other methods. For example, multiple holes are first formed on the dielectric layer 210 by a laser method, and then copper is electroplated on the dielectric layer 210 and in the holes to integrally form the circuit layer 211 and the conductive blind vias 212.

[0053] In addition, the circuit layer 211 and the conductive blind vias 212 adopt the Redistribution layer (RDL) specification.

[0054] It should be understood that by using the build-up process, the number of layers of the circuit structure can be designed according to requirements to fabricate the circuit layer with the desired number of layers.

[0055] As Figure 2C shown, first, according to the positions of the plurality of electrical contact pads 22, a flexible substrate 8 with a plurality of solder bumps 25 and a first flux 84 is fabricated, and then a second flux 24 is formed on the electrical contact pads 22 in the plurality of openings 230.

[0056] In this embodiment, the flexible substrate 8 is in a coreless form, which includes at least one insulating layer 81 and a plurality of positioning pads 82 formed on the insulating layer 81 for bonding the first solder material 84, so that the solder bumps 25 are formed on the first solder material 84, and the outermost insulating layer 81 can serve as an insulating protective layer 83, which has a plurality of openings 831 to expose partial surfaces of a plurality of the positioning pads 82. The positioning pads 82 are, for example, copper pads, and the insulating layer 81 is an ABF film (Ajinomoto build-up film), polybenzoxazole (abbreviated as PBO), polyimide (abbreviated as PI), prepreg (abbreviated as PP), or other dielectric materials.

[0057] Furthermore, due to factors such as uneven stress distribution in the circuit layer 211 of the circuit structure 21 and thermal stress concentration in the solder mask layer 23, the carrier 9 and the circuit structure 21 thereon are warped, bent, or deformed in other ways (as shown by the dashed line in Figure 2C ), resulting in displacement of the electrical contact pads 22. Therefore, when designing the flexible substrate 8, target spots 830 are made on the insulating protective layer 83 to align the positions of the positioning pads 82 with the positions of a plurality of displaced electrical contact pads 22.

[0058] In addition, the thinner the thickness of the flexible substrate 8, the easier it is to bend, which is beneficial for the positioning pads 82 to align with the positions of the displaced electrical contact pads 22. Therefore, the fewer the number of layers of the insulating layer 81, the better, such as one layer.

[0059] In addition, the viscosity of the first solder material 84 is greater than that of the second solder material 24 to facilitate the removal of the flexible substrate 8 in subsequent processes.

[0060] As shown in Figure 2D , the flexible substrate 8 is pressed onto the circuit structure 21, so that the solder bumps 25 are bonded to the second solder material 24 on the electrical contact pads 22.

[0061] In this embodiment, when the flexible substrate 8 is pressed onto the circuit structure 21, the flexible substrate 8 and the carrier 9 are positioned by the target spots 830, so that the solder bumps 25 on each of the positioning pads 82 can effectively bond to the second solder material 24 on each of the electrical contact pads 22.

[0062] As shown in Figure 2E , the flexible substrate 8 and the first solder material 84 are removed. Then, the solder bumps 25 are reflowed by the second solder material 24 to form solder balls 26.

[0063] Therefore, the manufacturing method of the present invention mainly forms the solder bump 25 on the first solder material 84 on the positioning pad 82 of the flexible substrate 8, and the positioning pad 82 of the flexible substrate 8 is aligned with the positions of a plurality of displaced electrical contact pads 22 to improve the alignment accuracy of the solder bump 25. Therefore, compared with the prior art, even if the carrier 9 and the overall structure thereon are warped, bent or otherwise deformed, the solder bump 25 can still be effectively combined with each of the electrical contact pads 22 to improve the reliability of the packaging substrate.

[0064] In addition, in the second embodiment of the manufacturing method of the packaging substrate of the present invention, the second solder material 34 can also be formed on the solder bump 25 of the flexible substrate 8 in the Figure 2C process, as shown in Figure 3A . Then, the flexible substrate 8 is pressed onto the circuit structure 21 with its second solder material 34, as shown in Figure 3B , so that the solder bump 25 is combined with the electrical contact pad 22 with the second solder material 34 thereon. After that, as shown in Figure 2E , the flexible substrate 8 and the first solder material 84 are removed, and the solder bump 25 is reflowed with the second solder material 34 to form solder balls 26.

[0065] In summary, the manufacturing method of the packaging substrate of the present invention forms the solder bump on the flexible substrate to achieve the ball mounting operation on the warped circuit structure and can avoid the problem of incorrect ball mounting position caused by the warping of the circuit structure. Therefore, compared with the prior art, even if the carrier and the overall structure thereon are warped, bent or otherwise deformed, the solder bump can still be effectively combined with each of the electrical contact pads to avoid the problems of no ball or incorrect ball mounting position, thereby improving the manufacturing yield of the packaging substrate.

[0066] The above embodiments are only used to illustrate the principle and efficacy of the present invention by way of example, and are not used to limit the present invention. Those skilled in the art can modify the above embodiments without departing from the spirit and scope of the present invention. Therefore, the scope of the rights protection of the present invention should be as listed in the claims.

Claims

1. A method for manufacturing a packaging substrate, comprising: forming a circuit structure having a plurality of electrical contact pads on a carrier; According to the positions of the plurality of electrical contact pads, a flexible substrate is manufactured with a plurality of solder bumps; Pressing the flexible substrate onto the circuit structure so that the solder bump is bonded to the electrical contact pad; removing the flexible substrate; as well as The solder bumps are reflowed to form solder balls.

2. The method for manufacturing a packaging substrate according to claim 1, wherein: The circuit structure includes a dielectric layer formed on the carrier, a circuit layer formed on the dielectric layer and a plurality of conductive blind holes formed in the dielectric layer, so that the plurality of conductive blind holes are electrically connected to the circuit layer, and the outermost circuit layer has the plurality of electrical contact pads.

3. The method for manufacturing a packaging substrate according to claim 2, wherein: A solder mask is formed on the circuit structure, and a plurality of openings for exposing the electrical contact pad are formed on the solder mask.

4. The method for manufacturing a packaging substrate according to claim 1, wherein: The flexible substrate comprises at least one insulating layer and a plurality of positioning pads formed on the insulating layer, and a first soldering material is combined on the positioning pad to form the solder bump on the first soldering material.

5. The method for manufacturing a packaging substrate according to claim 4, wherein: The solder bump is bonded to the electrical contact pad by a second flux material.

6. The method for manufacturing a packaging substrate according to claim 5, wherein: The viscosity of the first flux material is greater than the viscosity of the second flux material.

7. The method for manufacturing a packaging substrate according to claim 4, wherein: The manufacturing method further comprises removing the first soldering material when removing the flexible substrate.

8. The method for manufacturing a packaging substrate according to claim 4, wherein: The manufacturing method also includes first forming a second flux material on the electrical contact pad, and then combining the solder bump onto the second flux material on the electrical contact pad.

9. The method for manufacturing a packaging substrate according to claim 4, wherein: The manufacturing method also includes forming a second flux material on the solder bump first, and then combining the solder bump with the second flux material on the solder bump to the electrical contact pad.

10. The method for manufacturing a packaging substrate according to claim 1, wherein: The manufacturing method also includes that before manufacturing the flexible substrate, the carrier and the circuit structure thereon are in a warped state.

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