Substrate stack-up preparation method, mold and substrate

Abstract

The invention discloses a preparation method of a substrate stack structure, a mold and a substrate, the preparation method of the substrate stack structure comprises the following steps: providing a bottom substrate, the first surface of the bottom substrate is provided with a first bonding pad structure, and the second surface of the bottom substrate is provided with a second bonding pad structure; a first plastic package mold and a second plastic package mold are provided, the first plastic package mold and the second plastic package mold comprise mold bases and a plurality of protruding structures located on the surfaces of the mold bases, and the parts, close to the mold bases, of the protruding structures are of hollow structures; the part, away from the mold base, of the protruding structure is of a non-hollowed-out structure. Closing the mold and carrying out injection molding and plastic packaging on the first surface and the second surface of the bottom substrate; and molding compound solder mask layers are formed on the first surface and the second surface of the bottom substrate. According to the technical scheme, the problems that an existing substrate dissipates heat and is prone to short circuit are effectively solved.

Description

Technical Field

[0001] The present invention belongs to the field of semiconductor technology, and in particular relates to a method for preparing a substrate stack structure, a mold and a substrate. Background Art

[0002] At present, the solder mask layer of the PCB substrate mainly uses ink for protection, and the window is opened through exposure and development, so that the exposed pad structure can be welded with the solder ball of the chip. However, as the exposure energy gradually weakens, it will cause side corrosion of the development, resulting in side corrosion of the solder mask ink around the exposed pad structure, posing the risk of short circuit. At the same time, the thermal conductivity of the ink is not high and cannot meet the high heat dissipation requirements. Ink is also prone to abnormalities such as cracks, and reliability performance needs to be improved. Summary of the invention

[0003] In view of the existing problems, the present invention proposes a method for preparing a substrate stack structure, a mold and a substrate.

[0004] A method for preparing a substrate stack structure, comprising: Providing a base substrate, wherein a first surface of the base substrate has a first pad structure, and a second surface of the base substrate has a second pad structure; A first plastic encapsulation mold and a second plastic encapsulation mold are provided, wherein the first plastic encapsulation mold comprises a mold base and a plurality of first protruding structures located on a surface of the mold base, and the second plastic encapsulation mold comprises a mold base and a plurality of second protruding structures located on a surface of the mold base, wherein the position of the first protruding structure of the first plastic encapsulation mold matches the position of the first pad structure of the base substrate, and the size of the first protruding structure matches the size of the first pad structure, and the position of the second protruding structure of the second plastic encapsulation mold matches the position of the second pad structure of the base substrate, and the size of the second protruding structure matches the size of the second pad structure; The first plastic encapsulation mold is arranged opposite to the first surface of the base substrate, so that the first protrusion structure of the first plastic encapsulation mold is aligned and attached to the first pad structure of the base substrate, and a gap exists between the first surface of the base substrate and the surface of the mold base of the first plastic encapsulation mold; the second plastic encapsulation mold is arranged opposite to the second surface of the base substrate, so that the second protrusion structure of the second plastic encapsulation mold is aligned and attached to the second pad structure of the base substrate, and a gap exists between the second surface of the base substrate and the surface of the mold base of the second plastic encapsulation mold; Closing the mold and performing injection molding to seal the gap between the first surface and the second surface of the base substrate; The first and second molding molds are removed, and except for the positions covered by the first protruding structure and the second protruding structure, a molding compound solder resist layer is formed on the first and second surfaces of the base substrate, and the molding compound solder resist layer exposes the surface of the first pad structure covered by the first protruding structure and the surface of the second pad structure covered by the second protruding structure.

[0005] As an optional embodiment, portions of the first protruding structure and the second protruding structure close to the mold base are hollow structures, and portions of the first protruding structure and the second protruding structure away from the mold base are non-hollow structures.

[0006] As an optional embodiment, the height of the hollow structure corresponds to the process requirements during injection molding.

[0007] As an optional embodiment, before the formed plastic encapsulation material solder resist layer is completely cured, the first plastic encapsulation mold and the second plastic encapsulation mold are removed.

[0008] As an optional embodiment, the size of the first protrusion structure is equal to or slightly smaller than the size of the first pad structure, and the size of the second protrusion structure is equal to or slightly smaller than the size of the second pad structure.

[0009] As an optional embodiment, the heights of the first protruding structure and the second protruding structure correspond to the thickness of the solder resist layer of the plastic encapsulation material.

[0010] As an optional embodiment, the height of the first protruding structure and the height of the second protruding structure are the same or different.

[0011] As an optional embodiment, the first protruding structure and the second protruding structure are made of metal.

[0012] As an optional embodiment, the first protruding structure and the second protruding structure are elastic columns.

[0013] As an optional embodiment, the first protruding structure and the second protruding structure are composed of a metal column and an elastic layer located on top of the metal column.

[0014] As an optional embodiment, the thickness of the plastic encapsulation material solder resist layer ranges from 15 to 30 um.

[0015] As an optional embodiment, the base substrate includes a core board, a prepreg board located on both side surfaces of the core board, and a pad structure located on the surface of the prepreg board.

[0016] A mold comprises: a first plastic encapsulation mold and a second plastic encapsulation mold, wherein the first plastic encapsulation mold comprises a mold base and a plurality of first protruding structures located on the surface of the mold base, and the second plastic encapsulation mold comprises a mold base and a plurality of second protruding structures located on the surface of the mold base, wherein the position of the first protruding structure of the first plastic encapsulation mold matches the position of the first pad structure of a bottom substrate for forming a substrate stack, and the size of the first protruding structure matches the size of the first pad structure, and the position of the second protruding structure of the second plastic encapsulation mold matches the position of the second pad structure of the bottom substrate for forming a substrate stack, and the size of the second protruding structure matches the size of the second pad structure.

[0017] As an optional embodiment, portions of the first protruding structure and the second protruding structure close to the mold base are hollow structures, and portions of the first protruding structure and the second protruding structure away from the mold base are non-hollow structures.

[0018] As an optional embodiment, the height of the hollow structure corresponds to the process requirements during injection molding.

[0019] As an optional embodiment, the size of the first protrusion structure is equal to or slightly smaller than the size of the first pad structure, and the size of the second protrusion structure is equal to or slightly smaller than the size of the second pad structure.

[0020] As an optional embodiment, the height of the first protruding structure and the height of the second protruding structure are the same or different.

[0021] As an optional embodiment, the first protruding structure and the second protruding structure are made of metal.

[0022] As an optional embodiment, the first protruding structure and the second protruding structure are elastic columns.

[0023] As an optional embodiment, the first protruding structure and the second protruding structure are composed of a metal column and an elastic layer located on top of the metal column.

[0024] A substrate prepared by the substrate stacking method includes: a base substrate, a plastic encapsulation material solder resist layer on the first surface and the second surface of the base substrate, wherein the plastic encapsulation material solder resist layer exposes the surface of the first pad structure and the surface of the second pad structure.

[0025] Beneficial effects: The technical solution of the present invention utilizes a first plastic encapsulation mold and a second plastic encapsulation mold to form a plastic encapsulation material solder resist layer on the first surface and the second surface of the base substrate, and the plastic encapsulation material solder resist layer exposes the surface of the first pad structure and the surface of the second pad structure. Since the plastic encapsulation material solder resist layer has better heat dissipation performance than the graphite solder resist layer and is not prone to cracking, the corrosion resistance of the solder resist layer of the substrate is enhanced and the probability of short circuit is reduced. And because the present invention uses the first protruding structure of the first plastic encapsulation mold to fit the first pad structure, and the second protruding structure of the second plastic encapsulation mold to fit the second pad structure, the plastic encapsulation material solder resist layer is directly formed on the two surfaces of the base substrate when the injection molding process is used, and the solder resist layer on the surface of the pad structure does not need to be removed by a photolithography process, and the problem of side etching by development similar to that in the prior art will not occur, thereby reducing the probability of short circuit.

[0026] Furthermore, the first convex structure and the second convex structure are partially hollowed out near the mold base, and the first convex structure and the second convex structure are partially non-hollowed out far from the mold base. When the gap between the first surface and the second surface of the base substrate is encapsulated by the injection molding process, the encapsulation material may enter between the fitting surfaces of the first convex structure, the second convex structure and the pad structure through capillary action. When the first convex structure and the second convex structure are partially hollowed out near the mold base, due to the pressure difference, the encapsulation material preferentially passes through the hollowed out structure and the side of the convex structure to cover the gap between the first surface and the second surface of the entire base substrate, so that the fitting surfaces of the first convex structure, the second convex structure and the pad structure will not be formed with the encapsulation material, thereby avoiding the subsequent use of an additional removal process to remove the encapsulation material on the surface of the pad structure. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 is a flow chart of a method for preparing a substrate stack structure according to an embodiment of the present invention; Figure 2 It is a schematic diagram of the structure of chip packaging using a substrate in the prior art; Figure 3 It is a schematic diagram of the ink solder mask layer being eroded during the exposure and development process in the prior art; Figure 4 It is a schematic diagram of a short circuit caused by abnormal tin infiltration in the prior art; Figure 5 is a schematic structural diagram of a bottom substrate according to an embodiment of the present invention; Figure 6 is a schematic structural diagram of a mold according to an embodiment of the present invention; Figure 7 is a structural schematic diagram of a mold according to another embodiment of the present invention; Figure 8 Schematic diagram of the injection molding process after mold closing according to an embodiment of the present invention; Fig. 9 It is a schematic diagram of the enlarged structure of the embodiment of the present invention after mold closing; Fig.10 is a schematic structural diagram of a substrate after injection molding according to an embodiment of the present invention; Fig.11 It is a schematic structural diagram of chip packaging using the substrate stacking structure of an embodiment of the present invention. DETAILED DESCRIPTION

[0028] The specific implementation methods of the present application are described in detail below in conjunction with the accompanying drawings. When describing the embodiments of the present application in detail, for the sake of convenience, the schematic diagrams will not be partially enlarged according to the general proportion, and the schematic diagrams are only examples, which should not limit the scope of protection of the present application. In addition, in actual production, the three-dimensional dimensions of length, width and depth should be included.

[0029] like Figure 2 and Figure 3 As shown, the current solder resist layer of the substrate is mainly an ink solder resist layer 10, which is exposed and developed through a photolithography process to open a window to expose the solder structure so that it can be welded to the solder balls of the packaged chip. During the exposure process, as the exposure energy gradually weakens, it will cause side corrosion, and the ink solder resist layer 10 will be eroded 101. In the subsequent welding process, the solder balls on the surface of the welding structure are prone to short circuits with the metal interconnection structure at adjacent positions. In addition, Figure 4 As shown, the thermal conductivity of the ink is not high, and the heat cannot be dissipated, which cannot meet the needs of certain high heat dissipation packaging structures. In addition, the ink solder mask layer 10 often cracks and other abnormalities, causing tin penetration 102. Therefore, the reliability performance of the existing substrate needs to be improved.

[0030] For this reason, Figure 1 As shown, the present invention provides a method for preparing a substrate stack structure, comprising: Step S10, providing a base substrate, wherein a first surface of the base substrate has a first pad structure, and a second surface of the base substrate has a second pad structure; Step S20, providing a first plastic encapsulation mold and a second plastic encapsulation mold, wherein the first plastic encapsulation mold includes a mold base and a plurality of first protrusion structures located on a surface of the mold base, and the second plastic encapsulation mold includes a mold base and a plurality of second protrusion structures located on a surface of the mold base, wherein the position of the first protrusion structure of the first plastic encapsulation mold matches the position of the first pad structure of the base substrate, and the size of the first protrusion structure matches the size of the first pad structure, and the position of the second protrusion structure of the second plastic encapsulation mold matches the position of the second pad structure of the base substrate, and the size of the second protrusion structure matches the size of the second pad structure; Step S30, the first plastic encapsulation mold is arranged opposite to the first surface of the base substrate, so that the first protrusion structure of the first plastic encapsulation mold is aligned and attached to the first pad structure of the base substrate, and a gap is formed between the first surface of the base substrate and the surface of the mold base of the first plastic encapsulation mold; the second plastic encapsulation mold is arranged opposite to the second surface of the base substrate, so that the second protrusion structure of the second plastic encapsulation mold is aligned and attached to the second pad structure of the base substrate, and a gap is formed between the second surface of the base substrate and the surface of the mold base of the second plastic encapsulation mold; Step S40, closing the mold and performing injection molding to seal the gap between the first surface and the second surface of the base substrate; Step S50, removing the first plastic encapsulation mold and the second plastic encapsulation mold, except for the positions covered by the first protruding structure and the second protruding structure, the first surface and the second surface of the base substrate are formed with a plastic encapsulation material solder resist layer, and the plastic encapsulation material solder resist layer exposes the surface of the first pad structure covered by the first protruding structure and the surface of the second pad structure covered by the second protruding structure.

[0031] like Figure 5 As shown, firstly, a base substrate 1 is provided, wherein a first surface 111 of the base substrate 1 has a first pad structure 11 , and a second surface 121 of the base substrate 1 has a second pad structure 12 .

[0032] In this embodiment, the base substrate 1 is a PCB substrate, which includes a core board, semi-cured boards located on both side surfaces of the core board, and a first pad structure 11 and a second pad structure 12 located on the surface of the semi-cured boards.

[0033] In other embodiments, the base substrate may also be a ceramic substrate, an aluminum substrate, an organic laminate substrate, etc., and the surface of the base substrate has a pad structure.

[0034] Please refer to Figure 6 A first plastic encapsulation mold 210 and a second plastic encapsulation mold 220 are provided, wherein the first plastic encapsulation mold 210 includes a mold base 211 and a plurality of first protruding structures 212 located on the surface of the mold base 211, and the second plastic encapsulation mold 220 includes a mold base 221 and a plurality of second protruding structures 222 located on the surface of the mold base 221, wherein the position and quantity of the first protruding structures 212 of the first plastic encapsulation mold 210 match the position and quantity of the first pad structures 11 of the base substrate 1, and the size of the first protruding structures 212 matches the size of the first pad structures 11, and the position and quantity of the second protruding structures 222 of the second plastic encapsulation mold 220 match the position and quantity of the second pad structures 12 of the base substrate 1, and the size of the second protruding structures 222 matches the size of the second pad structures 12.

[0035] In one embodiment, the first protrusion structure 212 and the second protrusion structure 222 are metal pillars, and the first protrusion structure 212 matches the number and position of the first pad structure 11 of the base substrate 1, and the size of the first protrusion structure 212 is equal to the size of the first pad structure 11, so that when the first plastic encapsulation mold 210 is against the first surface of the base substrate, the first protrusion structure 212 fits the first pad structure 11 of the base substrate 1, and the plastic encapsulation material will not be formed on the surface of the first pad structure 11 covered by the first protrusion structure 212 during the subsequent injection molding process.

[0036] Correspondingly, the second protrusion structure 222 matches the number and position of the second pad structure 12 of the base substrate 1, and the size of the second protrusion structure 222 is equal to the size of the second pad structure 12, so that when the second plastic encapsulation mold 220 is against the second surface of the base substrate, the second protrusion structure 222 fits with the second pad structure 12 of the base substrate 1, and the plastic encapsulation material will not be formed on the surface of the second pad structure 12 covered by the second protrusion structure 222 during the subsequent injection molding process.

[0037] In one embodiment, the size of the first protrusion structure 212 is slightly smaller than the size of the first pad structure 11, and the size of the second protrusion structure 222 is slightly smaller than the size of the second pad structure 12. During the subsequent injection molding process, the molding compound will cover the surface of the edge of the first pad structure 11 that is not covered by the first protrusion structure 212, and the molding compound will cover the surface of the edge of the second pad structure 12 that is not covered by the second protrusion structure 222, so as to strengthen the structural strength of the first pad structure 11 and the second pad structure 12 and avoid stratification between the metal layer of the pad structure and the substrate.

[0038] In one embodiment, the first protruding structure 212 and the second protruding structure 222 are elastic columns made of rubber. On the one hand, when the first protruding structure 212 is attached to the first pad structure 11 of the base substrate 1 and the second protruding structure 222 is attached to the second pad structure 12 of the base substrate 1, the first pad structure 11 and the second pad structure 12 will not be damaged by hard materials. On the other hand, the attachment effect of the protruding structure and the pad structure can be further improved.

[0039] In one embodiment, the first protruding structure 212 and the second protruding structure 222 are a combination of a metal column and an elastic layer located on top of the metal column.

[0040] The heights of the first protruding structure 212 and the second protruding structure 222 correspond to the thickness of the solder resist layer of the plastic encapsulation material to be formed subsequently.

[0041] In one embodiment, the height of the first protrusion structure 212 is the same as or different from the height of the second protrusion structure 222. When the height of the first protrusion structure 212 is different from the height of the second protrusion structure 222, the thickness of the subsequent plastic encapsulation material solder resist layer formed on the two surfaces of the base substrate is also different accordingly.

[0042] In one embodiment, the thickness of the first protruding structure 212 and the second protruding structure 222 is in the range of 15 to 30 um, that is, the thickness of the solder resist layer of the plastic encapsulation material is in the range of 15 to 30 um.

[0043] In another embodiment, please refer to Figure 7 The first protrusion structure 212 and the second protrusion structure 222 are hollow structures near the mold base, and the first protrusion structure 212 and the second protrusion structure 222 are non-hollow structures away from the mold base, that is, the first protrusion structure 212 includes a hollow structure 2122 and a non-hollow structure 2121, and the second protrusion structure 222 includes a hollow structure 2222 and a non-hollow structure 2221. The hollow structure facilitates the flow of the molding compound.

[0044] Although the first protruding structure 212 is in contact with the first pad structure 11 of the base substrate 1, and the second protruding structure 222 is in contact with the second pad structure 12 of the base substrate 1, due to differences in process flatness, in the subsequent injection molding process, part of the plastic encapsulation material may still enter between the first protruding structure, the second protruding structure and the contact surface of the pad structure due to capillary action. When the first protruding structure and the second protruding structure are close to the mold base, the plastic encapsulation material preferentially covers the gap between the first surface and the second surface of the entire base substrate through the hollow structure due to the pressure difference, so that the plastic encapsulation material will not be formed on the contact surface of the first protruding structure, the second protruding structure and the pad structure, avoiding the subsequent use of an additional removal process to remove the plastic encapsulation material on the surface of the pad structure.

[0045] In one embodiment, the first protruding structure and the second protruding structure are made of metal, and the hollow structure is a metal column with a through hole to facilitate the flow of molding compound, wherein the height of the hollow structure corresponds to the process requirements during injection molding.

[0046] Please refer to Figure 8 and Fig. 9, the first encapsulation mold 210 is arranged opposite to the first surface 111 of the base substrate 1, so that the first protruding structure 212 of the first encapsulation mold 210 is aligned and fitted with the first pad structure 11 of the base substrate 1, and a first gap 215 is provided between the first surface 111 of the base substrate 1 and the surface of the mold base of the first encapsulation mold 210; the second encapsulation mold 220 is arranged opposite to the second surface 121 of the base substrate 1, so that the second protruding structure 222 of the second encapsulation mold 220 is aligned and fitted with the second pad structure 12 of the base substrate 1, and a second gap 225 is provided between the second surface 121 of the base substrate and the surface of the mold base of the second encapsulation mold 220; the molds are closed and the first gap 215 and the second gap 225 on the first surface and the second surface of the base substrate are injection molded.

[0047] Among them, the first plastic encapsulation mold 210 and the second plastic encapsulation mold 220 are usually configured as a combined mold, and one or more groups of combined molds including the first plastic encapsulation mold and the second plastic encapsulation mold can be configured in the mold structure (two groups of combined molds are used as an example for explanation in the figure).

[0048] The base substrate 1 is placed between the first molding mold 210 and the second molding mold 220, and the second pad structure 12 of the base substrate 1 is aligned with the second protruding structure 222 of the second molding mold 220, and the first protruding structure 212 of the first molding mold 210 is aligned with the first pad structure 11 of the base substrate 1, the first molding mold 210 and the second molding mold 220 are molded together and molded, and the gap between the first surface and the second surface of the base substrate is injection molded.

[0049] In one embodiment, the mold is closed and the first surface and the second surface of the base substrate 1 are injection molded. During the injection molding process, the plastic molding material 5 is injection molded through the hollow structure and the side of the first protruding structure and the second protruding structure. There is a plastic molding material circulation channel in the hollow structure, and the plastic molding material near the first protruding structure and the second protruding structure preferentially flows through the hollow structure and the side, and the plastic molding material will not drill into the gap between the first protruding structure, the second protruding structure and the pad structure. Since a part of the protruding structure is set as a hollow structure, the internal and external pressure difference is balanced, so that the plastic molding material can flow better and complete the injection molding.

[0050] In one embodiment, the material of the plastic encapsulation material solder resist layer is epoxy molding compound. In other embodiments, the material of the plastic encapsulation material solder resist layer may also be polyimide resin, benzocyclobutene resin or polybenzoxazole resin; or may also be polybutylene terephthalate, polycarbonate, polyethylene terephthalate, polyethylene, polypropylene, polyolefin, polyurethane, polyolefin, polyether sulfone, polyamide, polyurethane, ethylene-vinyl acetate copolymer or polyvinyl alcohol containing filler.

[0051] like Fig.10 and Fig.11 As shown, after forming the plastic encapsulation material solder resist layer 7 of the substrate, after removing the first plastic encapsulation mold and the second plastic encapsulation mold, except for the positions covered by the first convex structure and the second convex structure, the first surface 111 and the second surface 121 of the base substrate 1 are formed with the plastic encapsulation material solder resist layer 7, and the plastic encapsulation material solder resist layer 7 exposes the surface of the first pad structure 11 covered by the first convex structure and the surface of the second pad structure 12 covered by the second convex structure. The plastic encapsulation material solder resist layer 7 formed by the plastic encapsulation material as a resin system has high thermal conductivity and excellent crack resistance, and can be used as a solder resist layer to protect the substrate and reduce solder loss.

[0052] In one embodiment, when the first protruding structure 212 and the second protruding structure 222 are hollow structures near the mold base, the first and second plastic molding molds are removed before the formed plastic molding material solder resist layer 7 is completely cured.

[0053] The present invention also provides a mold, please refer to Figure 6 and Figure 7 , including: a first plastic encapsulation mold 210 and a second plastic encapsulation mold 220, the first plastic encapsulation mold 210 including a mold base 211 and a plurality of first protruding structures 212 located on the surface of the mold base 211, the second plastic encapsulation mold 220 including a mold base 221 and a plurality of second protruding structures 222 located on the surface of the mold base 221, the position and quantity of the first protruding structures 212 of the first plastic encapsulation mold 210 match the position and quantity of the first pad structures 11 of the base substrate 1, and the size of the first protruding structures 212 matches the size of the first pad structures 11, the position and quantity of the second protruding structures 222 of the second plastic encapsulation mold 220 match the position and quantity of the second pad structures 12 of the base substrate 1, and the size of the second protruding structures 222 matches the size of the second pad structures 12.

[0054] In one embodiment, the first protrusion structure 212 and the second protrusion structure 222 are metal pillars, and the first protrusion structure 212 matches the number and position of the first pad structure 11 of the base substrate 1, and the size of the first protrusion structure 212 is equal to the size of the first pad structure 11, so that when the first plastic encapsulation mold 210 is against the first surface of the base substrate, the first protrusion structure 212 fits the first pad structure 11 of the base substrate 1, and the plastic encapsulation material will not be formed on the surface of the first pad structure 11 covered by the first protrusion structure 212 during the subsequent injection molding process.

[0055] Correspondingly, the second protrusion structure 222 matches the number and position of the second pad structure 12 of the base substrate 1, and the size of the second protrusion structure 222 is equal to the size of the second pad structure 12, so that when the second plastic encapsulation mold 220 is against the second surface of the base substrate, the second protrusion structure 222 fits with the second pad structure 12 of the base substrate 1, and the plastic encapsulation material will not be formed on the surface of the second pad structure 12 covered by the second protrusion structure 222 during the subsequent injection molding process.

[0056] In one embodiment, the size of the first protrusion structure 212 is slightly smaller than the size of the first pad structure 11, and the size of the second protrusion structure 222 is slightly smaller than the size of the second pad structure 12. During the subsequent injection molding process, the molding compound will cover the surface of the edge of the first pad structure 11 that is not covered by the first protrusion structure 212, and the molding compound will cover the surface of the edge of the second pad structure 12 that is not covered by the second protrusion structure 222, so as to enhance the structural strength of the first pad structure 11 and the second pad structure 12.

[0057] In one embodiment, the first protruding structure 212 and the second protruding structure 222 are elastic columns made of rubber. On the one hand, when the first protruding structure 212 is attached to the first pad structure 11 of the base substrate 1 and the second protruding structure 222 is attached to the second pad structure 12 of the base substrate 1, the first pad structure 11 and the second pad structure 12 will not be damaged by hard materials. On the other hand, the attachment effect of the protruding structure and the pad structure can be further improved.

[0058] In one embodiment, the first protruding structure 212 and the second protruding structure 222 are a combination of a metal column and an elastic layer located on top of the metal column.

[0059] In another embodiment, please refer to Figure 7The first protrusion structure 212 and the second protrusion structure 222 are hollow structures near the mold base, and the first protrusion structure 212 and the second protrusion structure 222 are non-hollow structures away from the mold base, that is, the first protrusion structure 212 includes a hollow structure 2122 and a non-hollow structure 2121, and the second protrusion structure 222 includes a hollow structure 2222 and a non-hollow structure 2221. The hollow structure facilitates the flow of the molding compound.

[0060] Although the first protruding structure 212 is in contact with the first pad structure 11 of the base substrate 1, and the second protruding structure 222 is in contact with the second pad structure 12 of the base substrate 1, due to differences in process flatness, in the subsequent injection molding process, part of the plastic encapsulation material may still enter between the first protruding structure, the second protruding structure and the contact surface of the pad structure due to capillary action. When the first protruding structure and the second protruding structure are close to the mold base, the plastic encapsulation material preferentially covers the gap between the first surface and the second surface of the entire base substrate through the hollow structure due to the pressure difference, so that the plastic encapsulation material will not be formed on the contact surface of the first protruding structure, the second protruding structure and the pad structure, avoiding the subsequent use of an additional removal process to remove the plastic encapsulation material on the surface of the pad structure.

[0061] In one embodiment, the first protruding structure and the second protruding structure are made of metal, and the hollow structure is a metal column with a through hole to facilitate the flow of molding compound, wherein the height of the hollow structure corresponds to the process requirements during injection molding.

[0062] The present invention also provides a substrate manufactured using the above-mentioned method for preparing a substrate stack, comprising: a first surface and a second surface of a base substrate are formed with a plastic encapsulation material solder resist layer, and the plastic encapsulation material solder resist layer exposes the surface of a first pad structure covered by a first protruding structure and the surface of a second pad structure covered by a second protruding structure, forming a molded substrate. The substrate can be manufactured using the above-mentioned mold by the above-mentioned method for preparing a substrate stack.

[0063] In the prior art, as the exposure energy gradually decays, the ink on the semi-cured plate of the substrate is insufficiently cured, and the developer washes away the uncured ink to form side corrosion, which may cause risks such as short circuits. The present invention uses a plastic encapsulation material instead of ink as the solder mask layer of the substrate, does not require an exposure and development process, and can avoid side corrosion of the solder mask layer caused by exposure and development.

[0064] In addition, the thermal conductivity of ink is less than 0.5 W / mK, and the thermal conductivity in the substrate and package is not high, which cannot meet the packaging with high heat dissipation requirements. And the crack resistance is mainly related to the elongation of the material. The greater the elongation, the better the crack resistance. The elongation of commonly used ink is about 3%. After reliability testing, cracks often occur, which leads to abnormal tin infiltration and short circuit risks.

[0065] The technical solution of the present invention changes the solder mask layer of the substrate from ink to plastic encapsulation material, which can effectively avoid side erosion of the solder mask layer. At the same time, the plastic encapsulation material as a resin system has high thermal conductivity. The plastic encapsulation material with high thermal conductivity can provide an effective heat dissipation path for the package body, and the plastic encapsulation material has excellent crack resistance and can be used as a solder mask layer to protect the substrate and reduce solder loss, thereby bringing excellent reliability performance to the substrate.

[0066] Although the present application has been 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 can use the methods and technical contents disclosed above to make possible changes and modifications to the technical solution of the present application without departing from the spirit and scope of the present application. Therefore, any simple modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present application without departing from the content of the technical solution of the present application are within the protection scope of the technical solution of the present application.

Claims

1. A method for preparing a substrate stack structure, characterized in that: include: Providing a base substrate, wherein a first surface of the base substrate has a first pad structure, and a second surface of the base substrate has a second pad structure; A first plastic encapsulation mold and a second plastic encapsulation mold are provided, wherein the first plastic encapsulation mold comprises a mold base and a plurality of first protruding structures located on a surface of the mold base, and the second plastic encapsulation mold comprises a mold base and a plurality of second protruding structures located on a surface of the mold base, wherein the position of the first protruding structure of the first plastic encapsulation mold matches the position of the first pad structure of the base substrate, and the size of the first protruding structure matches the size of the first pad structure, and the position of the second protruding structure of the second plastic encapsulation mold matches the position of the second pad structure of the base substrate, and the size of the second protruding structure matches the size of the second pad structure; The first plastic encapsulation mold is arranged opposite to the first surface of the base substrate, so that the first protrusion structure of the first plastic encapsulation mold is aligned and attached to the first pad structure of the base substrate, and a gap exists between the first surface of the base substrate and the surface of the mold base of the first plastic encapsulation mold; the second plastic encapsulation mold is arranged opposite to the second surface of the base substrate, so that the second protrusion structure of the second plastic encapsulation mold is aligned and attached to the second pad structure of the base substrate, and a gap exists between the second surface of the base substrate and the surface of the mold base of the second plastic encapsulation mold; Closing the mold and performing injection molding to seal the gap between the first surface and the second surface of the base substrate; The first and second molding molds are removed, and except for the positions covered by the first protruding structure and the second protruding structure, a molding compound solder resist layer is formed on the first and second surfaces of the base substrate, and the molding compound solder resist layer exposes the surface of the first pad structure covered by the first protruding structure and the surface of the second pad structure covered by the second protruding structure.

2. The method for preparing a substrate stack structure according to claim 1, wherein: Portions of the first and second protruding structures close to the mold base are hollow structures, and portions of the first and second protruding structures away from the mold base are non-hollow structures.

3. The method for preparing a substrate stack structure according to claim 2, wherein: The height of the hollow structure corresponds to the process requirements during injection molding.

4. The method for preparing a substrate stack structure according to claim 2, wherein: Before the formed plastic encapsulation material solder resist layer is completely solidified, the first plastic encapsulation mold and the second plastic encapsulation mold are removed.

5. The method for preparing a substrate stack structure according to claim 1, wherein: The size of the first protrusion structure is equal to or slightly smaller than the size of the first pad structure, and the size of the second protrusion structure is equal to or slightly smaller than the size of the second pad structure.

6. The method for preparing a substrate stack structure according to claim 1, wherein: The height of the first protruding structure and the second protruding structure corresponds to the thickness of the solder resist layer of the plastic encapsulation material.

7. The method for preparing a substrate stack structure according to claim 1, wherein: The height of the first protruding structure is the same as or different from the height of the second protruding structure.

8. The method for preparing a substrate stack structure according to claim 1, wherein: The first protruding structure and the second protruding structure are made of metal.

9. The method for preparing a substrate stack structure according to claim 1, wherein: The thickness of the plastic encapsulation material solder resist layer ranges from 15 to 30 um.

10. The method for preparing a substrate stack structure according to claim 1, wherein: The bottom substrate comprises a core board, prepreg boards located on both side surfaces of the core board, and a pad structure located on the surface of the prepreg boards.

11. A mold, characterized in that: include: A first molding mold and a second molding mold, the first molding mold includes a mold base and a plurality of first protruding structures located on the surface of the mold base, the second molding mold includes a mold base and a plurality of second protruding structures located on the surface of the mold base, the position of the first protruding structure of the first molding mold matches the position of the first pad structure of the bottom substrate for forming a substrate stack, and the size of the first protruding structure matches the size of the first pad structure, the position of the second protruding structure of the second molding mold matches the position of the second pad structure of the bottom substrate for forming a substrate stack, and the size of the second protruding structure matches the size of the second pad structure.

12. The mold according to claim 11, characterized in that Portions of the first and second protruding structures close to the mold base are hollow structures, and portions of the first and second protruding structures away from the mold base are non-hollow structures.

13. The mold according to claim 11, characterized in that The height of the hollow structure corresponds to the process requirements during injection molding.

14. The mold according to claim 11, characterized in that The size of the first protrusion structure is equal to or slightly smaller than the size of the first pad structure, and the size of the second protrusion structure is equal to or slightly smaller than the size of the second pad structure.

15. The mold according to claim 11, characterized in that The height of the first protruding structure is the same as or different from the height of the second protruding structure.

16. The mold according to claim 11, characterized in that The first protruding structure and the second protruding structure are made of metal.

17. The mold according to claim 11, characterized in that The first protruding structure and the second protruding structure are elastic columns.

18. The mold according to claim 11, characterized in that The first protruding structure and the second protruding structure are composed of a metal column and an elastic layer located on top of the metal column.

19. A substrate prepared by the method for preparing a substrate stack structure according to any one of claims 1 to 10, characterized in that: include: A base substrate, a plastic encapsulation material solder resist layer on the first surface and the second surface of the base substrate, wherein the plastic encapsulation material solder resist layer exposes the surface of the first pad structure and the surface of the second pad structure.

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