Thick copper FCBGA packaging substrate

Abstract

Provided is a thick copper FCBGA package substrate, comprising: a resin substrate including a central resin substrate and side resin substrates, a plurality of side resin substrates being symmetrically attached to both sides of a single central resin substrate in the thickness direction, the thickness of the single central resin substrate being greater than the thickness of the single side resin substrate; the copper layer is in contact with the resin substrate, and the copper thickness value of the copper layer ranges from 15 microns to 50 microns; wherein the resin substrate is made of a bismaleimide triazine resin material or an epoxy resin material; the thermal expansion coefficient of the resin substrate ranges from 0.1 PPM / DEG C to 20 PPM / DEG C; the copper layer comprises a plated hole copper layer; the plated hole copper layer comprises tubular plated copper and annular copper layers, and the annular copper layers extend outwards in the radial direction at the two ends of the tubular plated copper; and the tubular plated copper penetrates through the central resin substrate. The prepared FCBGA substrate is high in rigidity, not prone to warping and good in size stability.

Description

Technical Field

[0001] This application relates to the field of printed circuit boards, and particularly to a thick copper FCBGA packaging substrate. Background Art

[0002] A flip chip ball grid array packaging substrate can be referred to as an FCBGA board (Flip Chip Ball Grid Array). The FCBGA board is the substrate used in the most advanced chip packaging method in the current semiconductor packaging field. Currently, to meet the rapidly increasing demand for chip input / output (I / O), the size of the FCBGA board is getting larger and larger to meet the need to simultaneously carry multiple heterogeneous bare chips or a single larger-sized bare chip.

[0003] Currently, the FCBGA board mainly uses bismaleimide triazine resin (full English name: Bismaleimide Triazine, abbreviation: BT) to make the core layer (Core) and Ajinomoto build-up film (full English name: Ajinomoto Build-up Film, abbreviation: ABF) to make the build-up (abbreviation: BU). Due to the different coefficients of thermal expansion (CTE) and Young's moduli of each material (the CTE of the ABF material is large and the Young's modulus is small), after the thermal processing, the substrate is prone to warping. This problem becomes more prominent when the packaging size becomes larger. When the warping is too large, it will lead to poor soldering during the packaging of the bare chip and the FCBGA substrate or during the mounting of the FCBGA substrate and the PCB board, resulting in poor reliability after chip packaging or after the chip is mounted on the PCB board.

[0004] Limited by the thickness of the ABF material, when the copper thickness is relatively thick, more materials are needed to fill the gaps between the circuit patterns of the FCBGA packaging substrate. Moreover, due to the relatively large CTE of the ABF material, there are also concerns about the reliability of the connection of the conductive vias when the thickness is relatively thick, which limits the production of FCBGA products with a copper thickness of more than 25um using the semi-additive process (SAP) with the ABF material. Such vias are treated with fully filled solid copper. By controlling the laser drilling conditions to control the hole shape (open hole roundness, size, hole bottom-hole top ratio) and then adapting the electroplating parameters to achieve the fully filled solid copper treatment of such vias. And some high-current and high-voltage chips precisely require the BU copper thickness of the FCBGA substrate to reach more than 25um to ensure that the chips can achieve the designed performance. Summary of the Utility Model

[0005] This application is made in view of the state of the above-mentioned prior art. The purpose of this application is to provide a thick copper FCBGA packaging substrate, including: a resin substrate, including a central resin substrate and side resin substrates, several of the side resin substrates are symmetrically attached to both sides of a single central resin substrate in the thickness direction, and the thickness of a single central resin substrate is greater than that of a single side resin substrate; a copper layer, the copper layer is in contact with the resin substrate, and the copper thickness value of the copper layer ranges from 15um to 50um; wherein, the resin substrate is made of bismaleimide triazine resin or epoxy resin; the coefficient of thermal expansion of the resin substrate ranges from 0.1PPM / °C to 20PPM / °C; the copper layer includes a plated through-hole copper layer; the plated through-hole copper layer includes a tubular copper plating and an annular copper layer, and the annular copper layer extends radially outward at both ends of the tubular copper plating; the tubular copper plating penetrates through the central resin substrate.

[0006] As a further improvement of this application, the resin substrate contains glass fibers.

[0007] As a further improvement of this application, the copper thickness value of the copper layer ranges from 25um to 50um.

[0008] As a further improvement of this application, the hollow part of the tubular copper plating is filled with a sealing glue, and the sealing glue connects two adjacent side resin substrates on both sides of the central resin substrate.

[0009] As a further improvement of this application, the side of the copper layer facing away from the central resin substrate has a rough surface, and the rough surface is in concave-convex mating connection with the contacted resin substrate.

[0010] As a further improvement of this application, the total number of layers of the resin substrate and the copper layer ranges from four to thirty layers.

[0011] As a further improvement of this application, the copper layers are arranged in mirror symmetry on both sides of the central resin substrate in the thickness direction.

[0012] As a further improvement of this application, the resin substrate is a material with a flame retardant material grade code of FR-4.

[0013] As a further improvement of this application, the opposite surfaces of the two side resin substrates that are farthest apart are covered with a solder mask ink layer.

[0014] As a further improvement of this application, the solder mask ink layer is penetrated by prefabricated solder bumps, and the prefabricated solder bumps are in contact connection with the copper layer.

[0015] The beneficial effects of the thick copper FCBGA packaging substrate of the present application include: using a bismaleimide triazine resin material (BT material) as the resin substrate. Since the coefficient of thermal expansion (CTE) of the BT material is smaller than that of the Ajinomoto build-up film (ABF) material and the Young's modulus is larger than that of the Ajinomoto build-up film (ABF) material, and combined with the thick copper line technology, the FCBGA substrate prepared in this way has stronger rigidity than the substrate with an ABF structure. The whole is not easy to warp, has good dimensional stability and high reliability. It has good high-temperature performance, thus improving the yield of bare die packaging or chip mounting. In addition, the thickness range of the thick copper is applicable to the field of high-current and high-voltage chips. Description of the Drawings

[0016] In order to more clearly illustrate the technical solutions in the embodiments, the drawings of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0017] Figure 1 It is a diagram of the front-half operation state of an embodiment of the thick copper FCBGA packaging substrate of the present application;

[0018] Figure 2 It is a diagram of the rear-half operation state of an embodiment of the thick copper FCBGA packaging substrate of the present application;

[0019] Figure 3 It is a schematic structural diagram of an embodiment of the thick copper FCBGA packaging substrate of the present application;

[0020] Figure 4 is Figure 3 The partial enlarged view of part A of

[0021] Description of the Reference Numerals

[0022] 1 - Preformed solder bump; 2 - Solder mask ink layer; 31 - First copper layer; 32 - Second copper layer; 33 - Third copper layer; 34 - Fourth copper layer; 35 - Fifth copper layer; 36 - Sixth copper layer; 37 - Trapezoidal copper layer; 38 - Tubular copper plating; 39 - Rough surface; 41 - First resin substrate; 42 - Second resin substrate; 43 - Third resin substrate; 44 - Fourth resin substrate; 45 - Fifth resin substrate; 5 - Sealing glue. Detailed Embodiments

[0023] The following describes the exemplary embodiments of the present application with reference to the drawings. It should be understood that these specific descriptions are only used to teach those skilled in the art how to implement the present application, and are not used to exhaust all possible ways of the present application, nor to limit the scope of the present application.

[0024] Refer toFigure 3 , embodiments of the present application provide a thick copper FCBGA packaging substrate. The thick copper FCBGA packaging substrate includes a plurality of resin substrates and a plurality of copper layers. The resin substrates include a central resin substrate and side resin substrates. A plurality of side resin substrates are symmetrically attached to both sides in the thickness direction of a single central resin substrate. The thickness of a single central resin substrate is greater than the thickness of a single side resin substrate. The resin substrate is made of bismaleimide triazine resin material or epoxy resin material. The bismaleimide triazine resin material is the BT material. The BT material usually refers to a high-performance substrate material used in the manufacturing of PCB boards. In practical applications, the BT material has a resin system with a triazine ring structure, and this structure endows the BT material with higher heat resistance, moisture resistance, and dimensional stability. From another perspective, the BT material is also synthesized from bismaleimide (full English name: Bismaleimide, abbreviation: BMI) and cyanate ester (full English name: cyanate ester, abbreviation: CE). The resin substrate can also use a BT-like material, that is, a material that is thermally stable and similar to the BT material in electrical properties. The thermal expansion coefficient (CTE) of the BT material or BT-like material of the resin substrate is between 0.1 PPM / °C and 20 PPM / °C. The copper layer is in contact with the resin substrate, and the copper thickness value range of the copper layer is from 15 μm to 50 μm.

[0025] The resin substrate can also use an FR-4 flame-retardant material with a thermal expansion coefficient (CTE) and elastic modulus performance similar to that of the bismaleimide triazine resin material. What FR-4 represents is a material specification in which the resin material must be able to extinguish itself after being in a combustion state. It is a composite material formed by adding a filler and glass fiber to epoxy resin. Most bismaleimide triazine resin materials and epoxy resin materials meet the FR-4 specification.

[0026] The copper layer includes a plated-through hole copper layer; the plated-through hole copper layer includes a tubular copper plating 38 and an annular copper layer. The annular copper layer extends radially outward at both ends of the tubular copper plating 38; the tubular copper plating 38 penetrates the central resin substrate. Describing from the perspective of shape, the plated-through hole copper layer is in a reel shape, and the English abbreviation of the plated-through hole is PTH.

[0027] In an embodiment, the resin substrate contains glass fiber, and the glass fiber can be arranged in a horizontal and vertical cross-cross form within the resin substrate.

[0028] The copper thickness value range of the copper layer is from 25 um to 50 um; the thickness to which the copper foil is thinned is from 0.3 um to 2 um. The thinning of the copper foil is to control the thickness of the underlying copper of the seed layer, match the etching amount of the flash etching process in the MSAP process, and enable finer and higher-precision circuits. Among them, the flash etching process is to quickly etch away the base copper of the seed layer. Among them, in the industry, there are mainly two processes, MSAP and SAP, in the realization of the fine circuit process of the circuit board. MSAP is the abbreviation of Modified Semi-Additive Process, and SAP is the abbreviation of Semi-Additive Process.

[0029] As Figure 4 shown, one side of the copper layer facing away from the central resin substrate has a rough surface 39, and the rough surface 39 realizes an unevenly-mating butt joint with the contacted resin substrate, and the rough surface 39 realizes sufficient surface contact with the contacted resin substrate.

[0030] In terms of the total number of layers, the range of the total number of layers of the resin substrate and the copper layer is from four to thirty layers, and the copper layers are arranged in mirror symmetry on both sides in the thickness direction of the central resin substrate. In a non-limiting example, the resin substrate has a total of five layers, and the number of side resin substrates is four; there are a total of six copper layers in the copper layer that extend parallel to the plane of the resin substrate. As Figure 3 shown, along the thickness direction, the resin substrate includes a first resin substrate 41, a second resin substrate 42, a third resin substrate 43, a fourth resin substrate 44, and a fifth resin substrate 45 arranged in sequence. Along the thickness direction, according to the position of the actual layer, the copper layer includes a first copper layer 31, a second copper layer 32, a third copper layer 33, a fourth copper layer 34, a fifth copper layer 35, and a sixth copper layer 36 arranged in sequence. The annular copper layer belongs to the category of the third copper layer 33 or the fourth copper layer 34. When observing from a perspective perpendicular to the plane where the resin substrate is located, the contour of the annular copper layer is annular, and the inner circle of the annular copper layer is connected to the axial end of the tubular copper plating 38. At the same time, the third resin substrate 43 is the central resin substrate, and the first resin substrate 41, the second resin substrate 42, the fourth resin substrate 44, and the fifth resin substrate 45 are side resin substrates.

[0031] In one embodiment, the hollow part of the tubular copper plating 38 is filled with a sealing glue 5, and the sealing glue 5 connects two side resin substrates adjacent to the central resin substrate. That is, the sealing glue 5 connects the second resin substrate 42 and the fourth resin substrate 44.

[0032] In one embodiment, the copper layer further includes a king-shaped copper layer combination, which includes three copper layers. The three copper layers are sequentially connected by trapezoidal copper layers 37. The annular copper layer and one of the copper layers in the king-shaped copper layer combination commonly contact the same resin substrate. The first copper layer 31 is connected to the second copper layer 32 by a trapezoidal copper layer 37, and the second copper layer 32 is connected to the third copper layer 33 by another trapezoidal copper layer 37, finally forming a king-shaped copper layer combination. The fourth copper layer 34 is connected to the fifth copper layer 35 by a trapezoidal copper layer 37, and the fifth copper layer 35 is connected to the sixth copper layer 36 by another trapezoidal copper layer 37, finally also forming a king-shaped copper layer combination.

[0033] In one embodiment, several king-shaped copper layer combinations are distributed on both sides of the central resin substrate in a mirror-symmetric layout in the thickness direction.

[0034] In one embodiment, solder mask layers 2 are covered on the opposite surfaces of the two farthest side resin substrates respectively. That is, solder mask layers 2 are covered on the opposite surfaces of the first resin substrate 41 and the fifth resin substrate 45.

[0035] The solder mask layer 2 is penetrated with prefabricated solder bumps 1, and the prefabricated solder bumps 1 contact the king-shaped copper layer combination. That is, the prefabricated solder bumps 1 contact the first copper layer 31. The prefabricated solder bumps 1 facilitate the quick connection of the finished PCB board with other components.

[0036] The present application also provides a preparation method for a thick copper FCBGA package substrate, which is used to solve the problems that the FCBGA package substrate with an Ajinomoto build-up film (ABF) structure is prone to warping and it is not easy to achieve thick copper. The processes or steps of its preparation method are as follows in sequence:

[0037] (1) Referring to Figure 1 State A therein, prepare a BT material or a BT-like material copper clad laminate with a coefficient of thermal expansion (CTE) between 0.1 PPM / °C and 20 PPM / °C and a thickness between 0.10 mm and 1.50 mm, and perform heat treatment on the copper clad laminate to remove stress and moisture;

[0038] (2) Referring to Figure 1 State B therein, form interconnection holes penetrating the copper clad laminate by laser drilling or mechanical drilling. The interconnection holes can be formed by mechanical drilling or laser pair drilling; among them, necessary pretreatment is carried out before laser drilling, such as selecting a suitable laser source, controlling laser parameters, adjusting the laser focus point, a machine drill bit of appropriate material, controlling the machine drill processing speed, and using a shielding plate;

[0039] (3) Referring to Figure 1 State C therein, metallize the interconnection holes by electroless copper plating or electroplating copper. After copper plating, the interconnection holes form plated through holes (PTH);

[0040] (4) Refer to Figure 1 State D therein, for the plated through holes (PTH), special resin is used to plug the holes, dried and cured, and then ground;

[0041] (5) If necessary, the resin-plugged substrate of the plated through holes (PTH) is electroless copper plated and electroplated with copper again to form a copper cap on the plated through holes (PTH); this process is an optional process. If the conduction micro vias (Via) on the subsequent adjacent layers need to be prepared directly above the plated through holes (PTH), a copper cap needs to be made on the plated through holes (PTH) by copper plating at this time. Otherwise, the conduction micro vias (Via) will be drilled on the resin in the middle of the plated through holes (PTH), and electrical conduction cannot be achieved;

[0042] (6) Refer to Figure 1 State E to I therein, through patterning, conductive circuit patterns are made on the core material; that is, circuit patterns are formed through a series of processing such as applying a photosensitive film, exposure, development, and etching;

[0043] (7) Refer to Figure 1 State J therein, the surface of the copper layer is roughened, and the surface and side of the copper layer contacted by the chemical solution will be roughened to form a rough surface;

[0044] (8) Refer to Figure 2 State K therein, a BT or BT-like prepreg (PP) with a coefficient of thermal expansion (CTE) between 0.1 PPM / °C and 20 PPM / °C and an ultra-thin copper foil are laminated on the surface of the product after roughening treatment. The thickness range of the ultra-thin copper foil is 2 μm to 5 μm;

[0045] (9) Refer to Figure 2 State L therein, pre-treatment for laser drilling on the surface;

[0046] (10) Laser drilling treatment on the surface;

[0047] (11) Refer to Figure 2 State M therein, dry and / or wet desmearing treatment is carried out on the surface. Dry desmearing treatment refers to plasma treatment, and wet desmearing treatment refers to removing the charred resin, debris, etc. caused by laser drilling by soaking in chemical solutions;

[0048] (12) Refer to Figure 2 State N therein, the copper foil is thinned to 0.3 μm to 2 μm;

[0049] (13) Refer to Figure 2In state O, electroless copper plating is carried out to form a seed copper layer on the inner wall of the hole. The seed copper layer is a thin copper film formed on the substrate through a specific process before electroplating. This copper film serves as the "seed" for the subsequent electroplating process, ensuring that the electroplated copper can adhere evenly and firmly to the substrate, improving the adhesion;

[0050] (14) Refer to Figure 2 In states P and Q, apply an anti-plating film and perform pattern exposure;

[0051] (15) Refer to Figure 2 In state R, develop;

[0052] (16) Refer to Figure 2 In states S and T, adjust the electroplating parameters to perform pattern electroplating to form a target copper thickness + α copper thickness, and the value range of α copper thickness can be selected from 1um to 2um;

[0053] (17) Refer to Figure 2 In state U, strip the anti-plating film;

[0054] (18) Refer to Figure 2 In state V, flash etching to form a build-up (BU layer) pattern;

[0055] (19) Refer to Figure 2 In state W, repeat the above processes (7) to (18) until the designed number of build-up (BU layers) is obtained;

[0056] (20) Perform surface roughening treatment on the outermost resin substrate and copper surface to increase the bonding force between the copper surface, resin substrate and solder mask ink;

[0057] (21) Apply a dry film solder mask ink, or coat a liquid solder mask ink by printing, spraying, etc.;

[0058] (22) Level the ink and expose it;

[0059] (23) Develop;

[0060] (24) Perform photothermal curing treatment;

[0061] (25) Perform one of the surface treatments such as electroless nickel gold, electroless nickel palladium gold, electroless tin plating, etc. on the surface;

[0062] (26) Cut the large flat plate of the entire thick copper FCBGA package substrate into small panels;

[0063] (27) Ball mounting or printing solder paste and reflowing to form prefabricated solder bumps;

[0064] (28) Cut into single pieces, that is, further cut the small panel into single PCB board units;

[0065] (29) Pre - flattening of pre - formed solder bumps;

[0066] Figure 3 is Figure 2 an enlarged view of state X in Figure 2 state X in, corresponding to processes (20) to (29).

[0067] The process characteristics of this preparation method are as follows: starting from process (8), BT or BT - like materials are used, and the MSAP process with copper foil is adopted, instead of using ABF film materials and not using the SAP process without copper foil.

[0068] The beneficial effects of the thick - copper FCBGA packaging substrate and its preparation method of this application include: providing an FCBGA packaging substrate with low warpage performance. Using BT and BT - like materials throughout the layer will improve the defect of substrate warpage, thereby improving the packaging yield and enhancing the yield and reliability of bare - die packaging and chip mounting. Realize the preparation of FCBGA with a build - up (BU layer) copper thickness of 15um to 50um, especially realize the preparation of FCBGA with a build - up (BU layer) copper thickness of 25um to 50um, meeting the requirements of high - current and high - voltage high - power chips for FCBGA substrates. The thick copper can improve the heat dissipation, voltage drop, etc. in high - power application scenarios.

[0069] The above - mentioned embodiments are only used to illustrate the technical concept and characteristics of this application. Their purpose is to enable those familiar with this technology to understand the content of this application and implement it, and cannot be used to limit the protection scope of this application. All equivalent changes or modifications made according to the spirit of this application should be covered within the protection scope of this application.

Claims

1. A thick copper FCBGA packaging substrate, characterized in that, Comprising: A resin substrate, including a central resin substrate and side resin substrates. A plurality of the side resin substrates are symmetrically attached to both sides of the single central resin substrate in the thickness direction. The thickness of the single central resin substrate is greater than the thickness of the single side resin substrate. A copper layer, the copper layer being in contact with the resin substrate, and the copper thickness value of the copper layer ranges from 15 μm to 50 μm. Wherein, the resin substrate is made of bismaleimide triazine resin or epoxy resin; the coefficient of thermal expansion of the resin substrate ranges from 0.1 PPM / °C to 20 PPM / °C; the copper layer includes a plated through hole copper layer; the plated through hole copper layer includes a tubular copper plating and an annular copper layer, and the annular copper layer extends radially outward at both ends of the tubular copper plating; the tubular copper plating penetrates through the central resin substrate.

2. The thick copper FCBGA package substrate according to claim 1, wherein: The resin substrate contains glass fibers.

3. The thick copper FCBGA package substrate according to claim 1, characterized in that: The copper thickness value of the copper layer ranges from 25 μm to 50 μm.

4. The thick copper FCBGA package substrate according to claim 1, characterized in that: The hollow part of the tubular copper plating is filled with a sealing glue, and the sealing glue connects two adjacent side resin substrates on both sides of the central resin substrate.

5. The thick copper FCBGA package substrate according to claim 1, wherein: One side of the copper layer facing away from the central resin substrate has a rough surface, and the rough surface is in concave-convex mating connection with the contacted resin substrate.

6. The thick copper FCBGA packaging substrate according to claim 1, wherein: The total number of layers of the resin substrate and the copper layer ranges from four to thirty layers.

7. The thick copper FCBGA package substrate according to claim 1, characterized in that: The copper layers are arranged in mirror symmetry on both sides of the central resin substrate in the thickness direction.

8. The thick copper FCBGA package substrate according to claim 1, wherein: The resin substrate is a material with a flame retardant material grade code of FR-4.

9. The thick copper FCBGA package substrate according to claim 1, wherein: Solder resist ink layers are covered on the opposite surfaces of the two side resin substrates that are farthest apart from each other.

10. The thick copper FCBGA package substrate according to claim 9, wherein: The solder resist ink layer has prefabricated solder bumps passing through, and the prefabricated solder bumps are in contact connection with the copper layer.

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