Circuit board with heat dissipation function and manufacturing method thereof

Abstract

The invention provides a circuit board which comprises a circuit substrate and a heat dissipation block. The heat dissipation block is embedded in the circuit substrate and comprises a metal block and a bonding material. The bonding material is located on the metal block and distributed between the metal block and the circuit substrate. The two end faces of the heat dissipation block are exposed on the two opposite surfaces of the circuit substrate respectively. In addition, because the bonding material contains the interpenetrating network polymer, the bonding strength between the circuit substrate and the metal block can be improved.

Description

Technical Field

[0001] The invention relates to a circuit board, in particular to a circuit board with an embedded heat dissipation metal block. Background Art

[0002] As the number of electronic components installed on circuit boards continues to increase and circuit design becomes more complex, the need for heat dissipation in circuit boards has also increased. Generally speaking, a copper block is set in the circuit board as a heat conduction medium, and the high heat conduction rate of the copper block quickly conducts the heat energy generated by the components in the circuit board to the outside of the circuit board.

[0003] However, due to the insufficient bonding strength between the copper block and the circuit board, when the circuit board is subjected to external force during the process, cracks are easily generated between the copper block and the circuit board. As a result, the outer layer of electroplated copper covering the junction between the copper block and the circuit board will also have cracks, thereby affecting the electrical performance of the circuit board. Summary of the invention

[0004] Therefore, the present invention provides a circuit board with heat dissipation function and a manufacturing method thereof, so as to improve the manufacturing yield of the circuit board.

[0005] The present invention provides a circuit board, comprising a circuit substrate and a heat sink embedded in the circuit substrate. The heat sink comprises a metal block and a bonding material on the metal block, and the bonding material is distributed between the metal block and the circuit substrate. Two end surfaces of the heat sink are respectively exposed to two opposite surfaces of the circuit substrate, and the bonding material comprises an interpenetrating network polymer.

[0006] In at least one embodiment of the present invention, the interpenetrating polymer network comprises polystyrene segments and polybutadiene segments.

[0007] In at least one embodiment of the present invention, the circuit substrate further comprises two circuit layers and an insulating layer between the two circuit layers. A bonding material is present between the circuit layer and the metal block, and a bonding material is present between the insulating layer and the metal block.

[0008] In at least one embodiment of the present invention, the thickness of the bonding material is between 30 μm and 150 μm.

[0009] In at least one embodiment of the present invention, one end surface of the heat dissipation block is recessed into one surface of the circuit substrate.

[0010] In at least one embodiment of the present invention, a metal layer is further included, which is located on the circuit substrate and covers the surface of the circuit substrate and the end surface of the heat dissipation block.

[0011] The present invention also provides a method for manufacturing a circuit board with heat dissipation function, comprising providing a circuit substrate; removing a portion of the circuit substrate to form an opening, wherein the opening connects two opposite sides of the circuit substrate; providing a metal block; forming a bonding material on the metal block to form a heat dissipation block, wherein the bonding material comprises an interpenetrating network polymer; and after forming the opening, placing the heat dissipation block in the opening.

[0012] In at least one embodiment of the present invention, forming a bonding material on a metal block includes setting a solution on the metal block so that the solution covers the surface of the metal block, and the solution includes a thermoplastic elastomer and a resin; and after setting the solution on the surface of the metal block, baking the solution to form a bonding material.

[0013] In at least one embodiment of the present invention, the thermoplastic elastomer is selected from the group consisting of polystyrene elastomer or polyurethane.

[0014] In at least one embodiment of the present invention, the method further includes removing a portion of the bonding material after forming the bonding material on the metal block to expose a portion of the surface of the metal block.

[0015] Based on the above, the bonding material on the surface of the heat sink block is used to improve the bonding strength between the circuit substrate and the metal block, so as to avoid cracks at the junction of the heat sink block and the circuit substrate caused by external force during the process. In this way, it is helpful to improve the manufacturing yield of the circuit board while increasing the heat dissipation efficiency by using the metal block. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The present invention will be understood from the following detailed description and the accompanying drawings. It should be noted that various features are not drawn to the standard scale in industry practice. In fact, the size of various features may be arbitrarily increased or decreased for clarity of discussion.

[0017] Figure 1 A cross-sectional view of a circuit board according to an embodiment of the present invention is shown.

[0018] Figure 2 A partial schematic diagram of a circuit board according to an embodiment of the present invention is shown.

[0019] Figure 3 A cross-sectional view of a circuit board according to another embodiment of the present invention is shown.

[0020] Figure 4 A cross-sectional view of a circuit board according to another embodiment of the present invention is shown.

[0021] Figure 5 A cross-sectional view of a circuit board according to another embodiment of the present invention is shown.

[0022] FIG. 6A to FIG. 6CA cross-sectional view of a circuit board manufacturing method according to an embodiment of the present invention is shown.

[0023] FIG. 7A to FIG. 7B A cross-sectional view of a circuit board manufacturing method according to an embodiment of the present invention is shown. DETAILED DESCRIPTION

[0024] The present invention will be described in detail with the following examples. It should be noted that the following description of the embodiments of the present invention is only for illustration and is not intended to exhaustively disclose all embodiments or to limit the specific embodiments of the present invention. For example, the description of "a first feature formed on a second feature" includes multiple implementations, including the first feature being in direct contact with the second feature, and also including additional features being formed between the first feature and the second feature so that the two are not in direct contact. In addition, the same element symbols used in the drawings and the specification will represent the same or similar elements as much as possible.

[0025] Spatially relative terms, such as "lower," "below," "beneath," "above," and related terms, are used herein to simply describe the relationship of an element or feature as shown in the figures to another element or feature. These spatially relative terms also cover different orientations when using or operating the device in addition to the orientation depicted in the figures. In addition, when the element is rotatable (rotated 90 degrees or other angles), the spatially relative descriptors used herein can also be interpreted accordingly.

[0026] In the following text, in order to clearly present the technical features of the present invention, the dimensions (such as length, width, thickness and depth) of the elements (such as layers, films, substrates and regions, etc.) in the drawings will be enlarged in unequal proportions. Therefore, the description and explanation of the embodiments below are not limited to the dimensions and shapes presented by the elements in the drawings, but should cover the dimensions, shapes and deviations thereof caused by actual processes and / or tolerances. For example, the flat surface shown in the drawings may have rough and / or nonlinear features, while the acute angles shown in the drawings may be rounded. Therefore, the elements presented in the drawings of the present invention are mainly for illustration, and are not intended to accurately depict the actual shape of the elements, nor are they intended to limit the claims of the present invention.

[0027] Furthermore, the words "about", "approximately" or "substantially" used in the present case not only cover the numerical values ​​and numerical ranges clearly recorded, but also cover the permissible deviation range that can be understood by a person skilled in the art, wherein the deviation range can be determined by the error generated during measurement, and the error is caused by, for example, the limitation of the measurement system or process conditions. In addition, "about" can mean within one or more standard deviations of the above numerical values, such as ±30%, ±20%, ±10% or ±5%. The words "about", "approximately" or "substantially" used in the present case can select the acceptable deviation range or standard deviation according to the optical properties, etching properties, mechanical properties or other properties, and not just one standard deviation can be applied to all the above optical properties, etching properties, mechanical properties and other properties.

[0028] Please refer to Figure 1 The circuit board 100 with heat dissipation function includes a circuit substrate 120 and a heat dissipation block 140 embedded in the circuit substrate 120. The circuit substrate 120 includes a circuit layer 122a, a circuit layer 122b and an insulating layer 124, wherein the insulating layer 124 is located between the circuit layer 122a and the circuit layer 122b. The heat dissipation block 140 includes a metal block 142 and a bonding material 144, wherein the bonding material 144 is located on the metal block 142 and distributed between the metal block 142 and the circuit substrate 120.

[0029] In this embodiment, the bonding material 144 fills the gap between the metal block 142 and the circuit substrate 120. Specifically, the bonding material 144 exists between the circuit layer 122a and the metal block 142; the bonding material 144 exists between the circuit layer 122b and the metal block 142; and the bonding material 144 also exists between the insulating layer 124 and the metal block 142.

[0030] The two end surfaces of the heat sink 140 are exposed to two opposite surfaces of the circuit substrate 120. Figure 1 As shown, the end surface 145t of the heat dissipation block 140 is exposed to the surface 120f of the circuit substrate 120, and the end surface 145b of the heat dissipation block 140 is exposed to the surface 120s of the circuit substrate 120. It is worth mentioning that the bonding material 144 is not distributed on the end surface 145t and the end surface 145b of the heat dissipation block 140. In other words, the end surface 145t and the end surface 145b of the heat dissipation block 140 are substantially equivalent to the surface of the metal block 142. Although this embodiment includes only one heat dissipation block 140, the present invention is not limited thereto. In other embodiments, the number of heat dissipation blocks 140 may be more than one, for example, two.

[0031] In various embodiments of the present invention, the material of the metal block 142 may include a metal with good thermal conductivity, such as copper, silver, or similar alloy materials. In particular, the bonding material 144 of the present invention includes an interpenetrating polymer network (IPN). In this embodiment, the interpenetrating polymer network includes polystyrene segments and polybutadiene segments. For example, please refer to Figure 2 The interpenetrating polymer network is composed of a plurality of polystyrene segments SS and a plurality of polybutadiene segments BS cross-linked with each other to form a three-dimensional network structure. In addition, in other embodiments, the bonding material 144 can also be a semi-interpenetrating polymer network (Semi-IPN).

[0032] The polystyrene segment SS has high mechanical strength and is relatively hard and brittle, while the polybutadiene segment BS has high toughness and ductility. Therefore, the three-dimensional network structure formed by cross-linking the two can provide better mechanical strength and ductility, so that the bonding material 144 has the properties of an elastomer, that is, it has a lower Young's modulus and higher ductility. For example, the Young's modulus of the bonding material 144 can range from 0.01 to 0.10 GPa, and the elongation can reach about 1000%.

[0033] Based on the above characteristics, when the circuit board 100 is subjected to external force, the bonding material 144 can serve as a buffer layer between the metal block 142 in the heat sink 140 and the circuit substrate 120 to avoid cracks between the two. In other words, the bonding material 144 can enhance the bonding strength between the heat sink 140 and the circuit substrate 120. In this embodiment, the thickness t of the bonding material 144 can be in the range of 30 μm to 150 μm, but the present invention is not limited thereto, and the thickness t of the bonding material 144 can depend on the material or size of the metal block 142. In addition, the bonding material 144 may also include resin additives such as hardeners, flame retardants, and the like.

[0034] Please go back Figure 1The circuit board 100 further includes a plurality of conductive through holes 160, which pass through the circuit layer 122a, the circuit layer 122b and the insulating layer 124, and electrically connect the circuit layer 122a and the circuit layer 122b. In the present embodiment, each conductive through hole 160 further includes a plugging material 165, and the plugging material 165 may be a resin material. In the present embodiment, the circuit board 100 further includes two metal layers 180. The metal layer 180 is located on the circuit substrate 120, and covers the surface 120f and the surface 120s of the circuit substrate 120 respectively. In addition, the metal layer 180 also covers the end surface 145t and the end surface 145b of the heat sink 140.

[0035] Figure 3 The circuit board 300 is another embodiment of the present invention. The circuit board 300 includes a circuit substrate 120, a heat sink 140, and a circuit substrate 330. The circuit substrate 330 includes a circuit layer 332a, a circuit layer 332b, and an insulating layer 334, wherein the circuit layer 332a and the circuit layer 332b are respectively located on opposite sides of the insulating layer 334. On the other hand, the circuit board 300 further includes an insulating material 370, and the insulating material 370 is located between the circuit substrate 120 and the circuit substrate 330.

[0036] The insulating material 370 may be a composite material including glass fiber and resin, such as prepreg. In particular, the insulating layer 124 of the circuit substrate 120 and the insulating layer 334 of the circuit substrate 330 may also be a composite material including glass fiber and resin. In other words, the insulating layer 124, the insulating layer 334 and the insulating material 370 may include the same material.

[0037] In this embodiment, the heat sink 140 is embedded in the circuit substrate 120, the insulating material 370 and the circuit substrate 330. The end surface 145t and the end surface 145b of the heat sink 140 are exposed to the surface of the circuit substrate 120 and the surface of the circuit substrate 330 respectively. Specifically, the end surface 145t is exposed to the surface 120f of the circuit substrate 120, and the end surface 145b is exposed to the surface 330s of the circuit substrate 330. The surface 120f of the circuit substrate 120 faces away from the surface 330s of the circuit substrate 330, that is, the insulating layer 124 and the insulating layer 334 are located between the surface 120f and the surface 330s.

[0038] In this embodiment, the conductive via 160 of the circuit board 300 is electrically connected to the circuit substrate 120 and the circuit substrate 330. Figure 3As shown, the conductive via 160 passes through the insulating layer 124, the insulating material 370 and the insulating layer 334, and electrically connects the circuit layer 122a of the circuit substrate 120 and the circuit layer 332b of the circuit substrate 330. On the other hand, the metal layer 180 in this embodiment is respectively located on the surface 120f of the circuit substrate 120 and the surface 330s of the circuit substrate 330, and respectively covers the end surface 145t and the end surface 145b of the heat sink 140.

[0039] It is worth mentioning that in this embodiment, a portion of the insulating material 370 exists between the bonding material 144 and the circuit substrate 120 (and between the bonding material 144 and the circuit substrate 330). In other words, the bonding material 144 and a portion of the insulating material 370 fill the gap between the metal block 142 and the circuit substrate 120 (and between the metal block 142 and the circuit substrate 330).

[0040] Please refer to Figure 3 In this embodiment, the surface 120f of the circuit substrate 120 is flush with the end surface 145t of the heat sink 140, and the surface 330s of the circuit substrate 330 is also flush with the other end surface 145b of the heat sink 140. However, the present invention is not limited thereto. In other embodiments, one of the end surfaces of the heat sink 140 may be recessed in one of the surfaces of the circuit substrate 120. For example, please refer to Figure 4 In the circuit board 400 , the end surface 145 t of the heat dissipation block 140 is recessed in the surface 120 f of the circuit substrate 120 , while the other end surface 145 b of the heat dissipation block 140 is flush with the surface 330 s of the circuit substrate 330 .

[0041] Although the heat sink 140 in this embodiment is in the shape of a column with a uniform width, the present invention is not limited thereto. Figure 5 , the heat sink 140 in the circuit board 500 is an inverted T-shaped cylinder that is wide at the bottom and narrow at the top. In other words, the heat sink 140 has an end surface 145t and an end surface 145b, and the width Wt of the end surface 145t is smaller than the width Wb of the end surface 145b. On the other hand, although the number of circuit substrates in this embodiment is two, the present invention is not limited thereto. In other embodiments, the number of circuit substrates may be more than two.

[0042] The manufacturing method of the circuit board with heat dissipation function may include the following steps: FIG. 6A to FIG. 6C The steps shown are based on Figure 1 The circuit board 100 in FIG. 1 is used as an example. Please refer to Fig. 6AFirst, a circuit substrate 120 is provided. The circuit substrate 120 is formed as follows: two metal layers (not shown) on a general copper clad laminate (CCL) are patterned to form a circuit layer 122a and a circuit layer 122b located on both sides of an insulating layer 124. Figure 6B , a portion of the circuit substrate 120 is removed to form an opening 110 . The opening 110 extends from the circuit layer 122 a of the circuit substrate 120 through the insulating layer 124 and to the circuit layer 122 b , thereby connecting two opposite sides of the circuit substrate 120 .

[0043] On the other hand, a metal block 142 is provided, and a bonding material 144 is formed on the metal block 142 to form a heat sink 140. Specifically, the step of forming the bonding material 144 on the metal block 142 includes: Fig. 7A As shown, a solution 144 ′ is disposed on the metal block 142 by, for example, spray coating, so that the solution 144 ′ covers the surface 142 s of the metal block 142 .

[0044] Solution 144' includes a thermoplastic elastomer and a resin, and the thermoplastic elastomer of this embodiment is selected from the group consisting of polystyrene elastomers or polyurethane elastomers. For example, solution 144' may include thermoplastic elastomers such as styrene butadiene styrene (SBS), styrene ethylene butylene styrene (SEBS) or similar thermoplastic elastomers, and include resin materials such as polyphenylene oxide (PPO). In addition, solution 144' may also include a hardener such as butadiene, and may also include an organic solvent such as toluene. In detail, PPO can be used as a crosslinking agent for the polystyrene segment SS, and the hardener can be used as a crosslinking agent for the polybutadiene segment BS.

[0045] In the present embodiment, the solution 144' can be a toluene solution containing SEBS (e.g., polystyrene-polyethylene-polybutylene-polystyrene grafted with maleic anhydride), PPO, and a hardener (e.g., butadiene), wherein the proportion of SEBS is approximately 15wt%; the proportion of PPO is approximately 2wt%; and the proportion of the hardener is approximately 0.5wt%. However, the present invention is not limited to this, and the composition ratio of the thermoplastic elastomer, resin, and hardener in the solution 144' can be adjusted according to the requirements of the cross-linking reaction. Although in the present embodiment, the solution 144' is disposed on the metal block 142 by spraying, the present invention is not limited to this. In other embodiments, the solution 144' can also be disposed on the surface 142s of the metal block 142 by immersion.

[0046] After the solution 144' is disposed on the surface 142s of the metal block 142, the solution 144' (located on the metal block 142) is baked to allow the solution 144' to undergo a cross-linking reaction to link the polystyrene segment SS and the polybutadiene segment BS. For example, in this embodiment, the solution 144' attached to the metal block 142 is dried at 100°C for 10 minutes to form a bonding material 144 comprising an interpenetrating network polymer. It is particularly noted that the drying time depends on the thickness of the bonding material 144. Therefore, the drying time is not limited to this embodiment. In other embodiments, the drying time can be adjusted according to the thickness requirement of the bonding material 144.

[0047] Please refer to Figure 7B The steps of this embodiment further include: after forming the bonding material 144 on the metal block 142, removing part of the bonding material 144 by, for example, scrubbing to expose the surface 142s (indicated by Fig. 7A Specifically, a portion of the bonding material 144 located on two opposite end surfaces (not shown) of the metal block 142 is removed, and a portion of the surface 142s of the metal block 142 is exposed to form the heat dissipation block 140, and these exposed surfaces 142s are equivalent to the end surfaces 145t and 145b of the heat dissipation block 140.

[0048] Please refer to Figure 6C After the opening 110 is formed, the heat sink 140 is disposed in the opening 110. In particular, in the present embodiment, the end surface 145t of the heat sink 140 is exposed to the surface 120f of the circuit substrate 120, and the end surface 145b of the heat sink 140 is exposed to the surface 120s of the circuit substrate 120, so that the bonding material 144 is located between the circuit substrate 120 and the metal block 142. Then, by means of, for example, heating and pressing, a link is generated between the bonding material 144 and the insulating layer 124 of the circuit substrate 120, and then they are bonded to each other.

[0049] In the present embodiment, the manufacturing method of the circuit board 100 further includes, after the heating and pressing process, forming at least one conductive through hole 160 electrically connecting the circuit layer 122a and the circuit layer 122b. The formation of the conductive through hole 160 may include forming a plurality of openings (not shown) by drilling or routing, and these openings extend through the circuit layer 122a, the insulating layer 124 and the circuit layer 122b. Then, a conductive material (such as copper) is deposited on the inner wall of the opening. In addition, the formation of the conductive through hole 160 may also include forming a plugging material 165 on the inner wall of the conductive through hole 160 by roller printing and baking.

[0050] In this embodiment, the manufacturing method of the circuit board 100 also includes forming two metal layers 180 on the circuit substrate 120 by electroplating after the heating and pressing process is completed, and the metal layers 180 respectively cover the surface 120f and the surface 120s of the circuit substrate 120, and cover the end surface 145t and the end surface 145b of the heat sink 140.

[0051] In summary, in an embodiment of the present invention, a layer of bonding material is formed on the surface of the metal block. This bonding material includes an interpenetrating network polymer, and therefore has the characteristics of low Young's modulus and high ductility. Furthermore, since the bonding material is disposed between the metal block and the circuit substrate, it can serve as a buffer layer between the metal block and the circuit substrate to enhance the bonding strength between the metal block and the circuit substrate. In this way, even if the circuit board is deformed by an external force, cracks between the interfaces (for example, between the bonding material and the metal block or between the bonding material and the circuit substrate) will be avoided because the buffer layer deforms elastically. For example, when the bonding strength between the metal block and the insulating material is improved, cracks caused by squeezing by the electroplating fixture during the electroplating copper plating process can be reduced, thereby improving the yield of the electroplating copper plating process and improving the electrical performance of the circuit board.

[0052] Although the embodiments of the present invention have been disclosed above, they are not intended to limit the embodiments of the present invention. Those skilled in the art may make slight changes and modifications without departing from the spirit and scope of the embodiments of the present invention. Therefore, the protection scope of the embodiments of the present invention shall be determined by the definition of the attached claims.

[0053]

Explanation of symbols

[0054] 100,300,400,500: Circuit board

[0055] 110: Opening

[0056] 120,330: Circuit board

[0057] 120f,120s,142s,330s:Surface

[0058] 122a, 122b, 332a, 332b: circuit layer

[0059] 124,334: Insulation layer

[0060] 140: Heat sink

[0061] 142: Metal Block

[0062] 144:Jointing material

[0063] 144':Solution

[0064] 145t,145b: End face

[0065] 160: Conductive via

[0066] 165: Plug material

[0067] 180:Metal layer

[0068] 370: Insulation material

[0069] BS: Polybutadiene segment

[0070] SS: polystyrene segment.

Claims

1. A circuit board with heat dissipation function, characterized in that: Include: Circuit substrate; The heat sink is embedded in the circuit substrate and comprises: Metal blocks; as well as A bonding material is located on the metal block and distributed between the metal block and the circuit substrate; wherein two end surfaces of the heat dissipation block are respectively exposed to two opposite surfaces of the circuit substrate; The bonding material comprises an interpenetrating polymer network.

2. The circuit board according to claim 1, characterized in that: The interpenetrating network polymer comprises polystyrene segments and polybutadiene segments.

3. The circuit board according to claim 1, characterized in that: The circuit substrate further comprises: two circuit layers, with the bonding material being present between the circuit layers and the metal block; and The insulating layer is located between the circuit layers, wherein the bonding material exists between the insulating layer and the metal block.

4. The circuit board according to claim 1, characterized in that: The thickness of the bonding material is between 30 μm and 150 μm.

5. The circuit board according to claim 1, characterized in that: One of the end surfaces is recessed in one of the surfaces.

6. The circuit board according to claim 1, characterized in that: Also includes: The metal layer is located on the circuit substrate and covers the surface of the circuit substrate and the end surface of the heat dissipation block.

7. A method for manufacturing a circuit board with heat dissipation function, characterized in that: Include: Providing a circuit substrate; Removing a portion of the circuit substrate to form an opening, wherein the opening communicates with two opposite sides of the circuit substrate; Provide metal blocks; forming a bonding material on the metal block to form a heat dissipation block, wherein the bonding material comprises an interpenetrating network polymer; as well as After the opening is formed, the heat dissipation block is disposed in the opening.

8. The method according to claim 7, characterized in that Forming the bonding material on the metal block includes: placing a solution on the metal block so that the solution covers the surface of the metal block, wherein the solution contains a thermoplastic elastomer and a resin; and After the solution is disposed on the surface of the metal block, the solution is baked to form the bonding material.

9. The method according to claim 8, characterized in that The thermoplastic elastomer is selected from the group consisting of polystyrene elastomer or polyurethane.

10. The method according to claim 8, characterized in that Also includes: After forming the bonding material on the metal block, a portion of the bonding material is removed to expose a portion of the surface of the metal block.

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