Circuit board with embedded heat dissipation structure and its manufacturing method

Abstract

This invention provides a method for manufacturing a circuit board with an embedded heat dissipation structure. The method includes a multilayer circuit board comprising a substrate layer, a first circuit board and a second circuit board formed on opposite sides of the substrate layer; a receiving groove is formed on the multilayer circuit board, the receiving groove penetrating the second circuit board and a portion of the substrate layer; multiple through holes are formed on one side of the first circuit board, the through holes penetrating the first circuit board and the substrate layer, and communicating with the receiving groove; a heat sink is disposed in the receiving groove, with a gap between the heat sink and the side of the receiving groove; an adhesive is disposed in the gap; thermal paste is disposed in the through holes, and the thermal paste is baked to obtain a thermally conductive pillar, the thermally conductive pillar connecting to the heat sink, thus obtaining the circuit board with the embedded heat dissipation structure. This invention also provides a circuit board with an embedded heat dissipation structure.

Description

Technical Field

[0001] This invention relates to a circuit board with an embedded heat dissipation structure and its manufacturing method. Background Technology

[0002] In the 5G era, high frequency and high speed are fundamental requirements for circuit boards (PCBs). PCBs operating under high-frequency, high-power conditions experience significant internal losses and generate substantial heat. Embedded heat sink technology is widely used in high-density integrated circuit (HDI) heat dissipation, and its advantages of strong heat dissipation and small footprint make it particularly suitable for PCBs with embedded components.

[0003] The existing method for manufacturing circuit boards with embedded heat dissipation structures typically includes the following steps: (1) fabricating a bottom circuit layer; (2) slotting the obtained bottom circuit layer and placing a heat dissipation copper block; (3) adding a top circuit layer on the bottom circuit layer in step (2) and laminating it to obtain a multilayer circuit board; (4) fabricating through holes on the obtained top circuit layer so that the bottom of the through hole is connected to the heat dissipation copper block; (5) performing a hole-filling electroplating treatment on the through hole. Although this method can effectively enhance the heat dissipation effect of printed circuit boards, it has the following drawbacks: (1) The heat dissipation copper block is in direct contact with the bottom circuit layer. It cannot be firmly bonded by pressing alone. It is easy to move or deviate during subsequent layer addition. The connection of the buried copper block is prone to cracking during pressing; (2) The surface of the copper pillar formed by electroplating in the through hole is exposed to the outer layer of the circuit board. Because the hardness of the copper pillar is greater than that of the multilayer circuit board itself, the outer layer of the board is easily lifted by the copper pillar during pressing, making the board surface uneven; (3) Because the PCB board material will expand under high temperature, the connection of the through hole and the slot is prone to deformation during the continued layer addition or pressing process; (4) The slot and through hole need to be made in separate processes, which is complicated and long. Summary of the Invention

[0004] In view of this, it is necessary to provide a method for manufacturing a circuit board with an embedded heat dissipation structure that solves the above problems.

[0005] The present invention also provides a circuit board with an embedded heat dissipation structure to solve the above-mentioned problems.

[0006] This invention provides a method for manufacturing a circuit board with an embedded heat dissipation structure, comprising the following steps:

[0007] A multilayer circuit board is provided, including a substrate layer, a first circuit board and a second circuit board formed on opposite sides of the substrate layer;

[0008] An accommodating groove is formed on the multilayer circuit board, and the accommodating groove penetrates the second circuit board and part of the substrate layer;

[0009] Multiple through holes are formed on one side of the first circuit board, the through holes penetrating the first circuit board and the substrate layer, and connecting to the receiving groove;

[0010] A heat dissipation block is provided in the receiving groove, and there is a gap between the heat dissipation block and the side of the receiving groove;

[0011] An adhesive is provided within the gap; and

[0012] Thermal paste is placed inside the through hole, and the thermal paste is baked to obtain a thermally conductive pillar. The thermally conductive pillar is connected to the heat sink to obtain the circuit board with the embedded heat dissipation structure.

[0013] In some embodiments, the thermal paste is copper paste.

[0014] In some embodiments, the first circuit board includes a plurality of first circuit layers, which are electrically connected to each other through the copper paste.

[0015] In some embodiments, the receiving groove and the through hole are formed by mechanical drilling.

[0016] In some embodiments, the cross-sectional width of the receiving groove is 0.10-0.30 mm larger than the cross-sectional width of the heat sink.

[0017] In some embodiments, the diameter of the through hole is 0.05 to 4.2 mm, and the spacing between adjacent through holes is 0.2 to 3.15 mm.

[0018] In some embodiments, a portion of the adhesive is filled into the through-hole, and before filling the through-hole with thermal grease, the method further includes: using laser ablation to remove residual adhesive from the through-hole.

[0019] In some embodiments, the adhesive is filled into the gap using a vacuum plugging machine, and the thermal paste is filled into the through hole using a vacuum plugging machine.

[0020] In some embodiments, the adhesive is baked at 75°C for 35 minutes; and the thermal paste is baked at 75°C for 35 minutes.

[0021] The present invention also provides a circuit board with an embedded heat dissipation structure, comprising a substrate layer, a first circuit board, a second circuit board, a heat sink, a heat-conducting pillar, and an adhesive; the first circuit board and the second circuit board are disposed on opposite sides of the substrate layer, a receiving groove is formed through the second circuit board and a portion of the substrate layer, and a plurality of through holes are formed through the first circuit board and the substrate layer, the through holes communicating with the receiving groove; the heat sink is disposed in the receiving groove, the heat-conducting pillar is disposed in the through holes, and the heat-conducting pillar is connected to the heat sink; the adhesive fills the gap between the heat sink and the second circuit board or the substrate layer.

[0022] The method for manufacturing a circuit board with an embedded heat dissipation structure provided by this invention involves creating a receiving groove on one side of the second circuit substrate of a multilayer circuit board and creating multiple through holes on one side of the first circuit substrate, using the same process sequentially. This method is simple and allows for easy control of precision. By placing a heat sink in the receiving groove and filling the gap between the receiving groove and the heat sink with adhesive, the heat sink can be well fixed. Filling the through holes with thermal paste prevents protrusions during outer layer lamination, thus maintaining a flat board surface. After the thermal paste cures, the resulting thermal conductive pillars bond to the hole walls, and the bottom of the thermal conductive pillars bonds to the heat sink, effectively preventing the heat sink from moving, shifting, or cracking. Attached Figure Description

[0023] Figure 1 This is a cross-sectional schematic diagram of a multilayer circuit board provided in an embodiment of the present invention.

[0024] Figure 2 Is Figure 1 The diagram shows a cross-sectional view of a multilayer circuit board with recessed slots and through holes.

[0025] Figure 3 Is Figure 2 The diagram shows a three-dimensional structure of a multilayer circuit board with recessed slots and through holes.

[0026] Figure 4 Is Figure 2 The diagram shows a cross-sectional view of the heat sink placed in the accommodating slot.

[0027] Figure 5 Is Figure 3 A schematic diagram of the cross-section of the gap filled with adhesive is shown.

[0028] Figure 6 Yes Figure 4 The diagram shows a cross-sectional view of the through-hole filled with thermal paste.

[0029] Explanation of main component symbols

[0030] 200 circuit boards with embedded heat dissipation structure

[0031] Multilayer circuit board 100

[0032] Substrate layer 10

[0033] First circuit board 11

[0034] First line layer 111

[0035] First adhesive layer 112

[0036] Second circuit board 12

[0037] Second line layer 121

[0038] Second adhesive layer 122

[0039] Reception slot 13

[0040] Inner wall 130

[0041] Gap 131

[0042] Through hole 14

[0043] Heat sink 20

[0044] Adhesive 21

[0045] Heat-conducting column 22

[0046] The following detailed description, in conjunction with the accompanying drawings, will further illustrate the present invention. Detailed Implementation

[0047] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0048] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.

[0049] The following detailed description of some embodiments of the present invention is provided in conjunction with the accompanying drawings. Unless otherwise specified, the following embodiments and features can be combined with each other.

[0050] Please refer to the following: Figures 1-5 A method for manufacturing a circuit board 200 with an embedded heat dissipation structure according to an embodiment of the present invention includes the following steps:

[0051] Step S1: Please refer to Figure 1 A multilayer circuit board 100 is provided, the multilayer circuit board 100 includes a substrate layer 10, a first circuit board 11 and a second circuit board 12 formed on opposite sides of the substrate layer 10.

[0052] The multilayer circuit board 100 can be a flexible circuit board, a rigid circuit board, or a rigid-flex board. The substrate layer 10 can be made of one of the following materials: polyimide (PI), glass fiber epoxy adhesive (FR4), polyethylene terephthalate (PET) or polyethylene naphthalate (PEN), or polyethylene (PE).

[0053] The first circuit board 11 is formed by alternatingly stacking at least one first circuit layer 111 and at least one first adhesive layer 112 (a first adhesive layer 112 is disposed between every two first circuit layers 111). The second circuit board 12 is formed by alternatingly stacking at least one second circuit layer 121 and at least one second adhesive layer 122 (a second adhesive layer 122 is disposed between every two second circuit layers 121). The first circuit board 11 can have two layers, three layers, or more, and the number of layers in the second circuit board 12 can be the same as or different from the number of layers in the first circuit board 11.

[0054] In this embodiment, the first circuit board 11 has four layers, namely, four first circuit layers 111 and three first adhesive layers 112.

[0055] Both the first adhesive layer 112 and the second adhesive layer 122 are semi-cured sheets, which melt and soften when heated during pressing and solidify upon cooling, thus exhibiting excellent adhesive strength. The multilayer circuit board 100 is formed by pressing and bonding.

[0056] Step S2: Please refer to Figure 2 and Figure 3 A receiving groove 13 is formed on the multilayer circuit board 100 from one side of the second circuit board 12, and the receiving groove 13 penetrates the second circuit board 12 and part of the substrate layer 10. A plurality of through holes 14 are formed on one side of the first circuit board 11, and the through holes 14 penetrate the first circuit board 11 and the substrate layer 10 and communicate with the receiving groove 13.

[0057] The receiving groove 13 is generally rectangular, with a length L of 16–22 mm, a width W1 of 21–27 mm, and a height H of 0.8–1.5 mm. The number of through holes 14 can be set according to requirements. In this embodiment, there are 5 through holes 14.

[0058] The through hole 14 is generally cylindrical, with a diameter R of 0.05 to 4.2 mm, and the spacing W2 between adjacent through holes 14 is 0.2 to 3.15 mm.

[0059] In this application, the receiving groove 13 and the through hole 14 are manufactured sequentially using the same process, resulting in high precision and a simple manufacturing process. Furthermore, the diameter of the through hole 14 can be as small as 0.05 mm, effectively increasing the wiring density of the first circuit board 11.

[0060] The receiving groove 13 and the through hole 14 are formed by mechanical drilling. In this embodiment, the receiving groove 13 and the through hole 14 are formed sequentially by milling. First, the receiving groove 13 is machined with a milling cutter, and then the through hole 14 is machined with a drill bit.

[0061] The parameters for creating the receiving groove 13 using a milling cutter are: cutter diameter 2.0 mm, spindle speed 120 kr / min, feed rate 25 mm / s, retraction speed 320 mm / s, cutter life 1.25 m, and depth control error + / - 50 μm. The parameters for creating the through hole 14 using a drill bit are: drill bit diameter 0.05–4.2 mm, spindle speed 160–180 kr / min, feed rate 28–32 mm / s, retraction speed 350–380 mm / s, drill life 1500 (holes), and a correction value of -0.005 mm.

[0062] Step S3: Please refer to Figure 4 A heat sink 20 is placed in the receiving groove 13, and a gap 131 is formed between the heat sink 20 and one side of the inner wall 130 of the receiving groove 13.

[0063] In this embodiment, the heat sink 20 is formed in the receiving groove 13 using surface mount technology (SMT). The cross-sectional width of the receiving groove 13 is 0.10-0.30 mm larger than the cross-sectional width of the heat sink 20, allowing the heat sink 20 to be smoothly placed into the receiving groove 13 while maintaining a gap 131. The heat sink 20 can be a copper block.

[0064] In this application, after the heat sink 20 is placed in the receiving groove 13, there is no pressing process, which can further ensure the flatness of the circuit board 200 with embedded heat dissipation structure.

[0065] Step S4: Please refer to Figure 5 The adhesive is filled into the gap 131 and baked to form an adhesive body 21.

[0066] The adhesive is fluid at room temperature and solidifies after baking. In this embodiment, the adhesive used is IP-6P ink from Sanei Chemicals, Japan, and the baking conditions are 75°C for 35 minutes.

[0067] A fluid adhesive is filled into the gap 131 from one side of the second circuit board 12 using a vacuum plugging machine. After baking, it is cured to form an adhesive body 21, which can bind and fix the heat sink 20 in the multilayer circuit board 100, effectively preventing the heat sink 20 from moving or shifting.

[0068] After the adhesive is baked and cured, the process includes removing any remaining adhesive from the through-holes 14 using laser ablation technology. Because the spacing between adjacent through-holes 14 is sufficient, there are no quality issues such as hole wall deformation during the laser ablation process.

[0069] Step S5: Please refer to Figure 6 Thermal paste is inserted into the through hole 14 and baked at 75°C for 35 minutes to solidify and form a thermally conductive pillar 22, thus obtaining the circuit board 200 with the embedded heat dissipation structure.

[0070] The thermal conductive paste can be a paste with good thermal conductivity, such as copper paste or silver paste.

[0071] In this embodiment, a vacuum plugging machine is used to fill the thermal paste to obtain the thermally conductive pillar 22. There are no air bubbles, and the surface can be brushed without any surface protrusions. After the thermal paste is baked and cured, it bonds to the wall of the through hole 14, and the bottom of the resulting thermally conductive pillar 22 bonds to the heat sink 20, further increasing the stability of the heat sink 20 and effectively preventing deformation or cracking at the connection between the receiving groove 13 and the through hole 14. In this embodiment, the thermal paste used is copper paste from Yunhong Enterprise, model MPA500.

[0072] In this embodiment, the copper paste has good conductivity, which can electrically conduct the multilayer first circuit layer 111, and its surface is connected to the outer layer, which can play a certain role in heat dissipation.

[0073] Compared to existing methods such as electroplating to fill holes and form copper pillars, this invention uses a method of filling with thermal paste. Although the surface of the thermal paste is also exposed on the outer layer, the thermal paste is softer. During subsequent layering or lamination, the thermal paste has a more consistent texture and hardness with the multilayer circuit board, so it is less likely to cause protrusions and thus can keep the board surface flat.

[0074] In addition, considering the aspect ratio (i.e., the ratio of diameter to height) of the through hole 14, electroplating often fails to fill the hole completely, leaving gaps. However, the use of a vacuum plugging machine to fill the hole with thermal paste in this application can effectively avoid this situation.

[0075] The method for manufacturing a circuit board with an embedded heat dissipation structure provided by the present invention involves creating a receiving groove 13 on one side of the second circuit substrate 12 of a multilayer circuit board 100 and creating multiple through holes 14 on one side of the first circuit substrate 11, using the same process sequentially, resulting in a simple manufacturing process. A heat sink 20 is placed in the receiving groove 13, and adhesive is filled into the gaps 131 to form an adhesive body 21, which effectively secures the heat sink 20. Thermal paste is filled into the through holes 14, and after curing, the thermal paste bonds with the hole walls to form thermally conductive pillars 22. The bottom of the thermally conductive pillars 22 is bonded to the heat sink 20, effectively preventing the heat sink 20 from moving, shifting, or cracking.

[0076] Please see Figure 6 The present invention also provides a circuit board 200 with an embedded heat dissipation structure. The circuit board 200 with the embedded heat dissipation structure includes a substrate layer 10, a first circuit board 11, a second circuit board 12, a heat sink, a heat-conducting pillar, and an adhesive. The first circuit board 11 and the second circuit board 12 are disposed on opposite sides of the substrate layer 10. The first circuit board 11 includes multiple alternating layers of first circuit layers 111 and first adhesive layers 112, and the second circuit board 12 includes multiple alternating layers of second circuit layers 121 and second adhesive layers 122. A receiving groove 13 is formed on one side of the second circuit board 12, and the receiving groove 13 penetrates the second circuit board 12 and part of the substrate layer 10. The heat sink 20 is disposed in the receiving groove 13, and a gap 131 is formed between the inner wall 130 of the receiving groove 13 and the heat sink 20, and the adhesive 21 fills the gap 131. A plurality of through holes 14 are formed on one side of the first circuit board 11. The through holes 14 penetrate the first circuit board 11 and the substrate layer 10 and are connected to the receiving groove 13. The heat-conducting pillar 22 is disposed in the through hole 14, and the bottom of the heat-conducting pillar 22 is connected to the heat sink 20.

[0077] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above as a preferred embodiment, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A method for manufacturing a circuit board with an embedded heat dissipation structure, characterized in that, Includes the following steps: A multilayer circuit board is provided, including a substrate layer, a first circuit board and a second circuit board formed on opposite sides of the substrate layer; An accommodating groove is formed on the multilayer circuit board, and the accommodating groove penetrates the second circuit board and part of the substrate layer; Multiple through holes are formed on one side of the first circuit board, the through holes penetrating the first circuit board and the substrate layer, and connecting to the receiving groove; A heat dissipation block is provided in the receiving groove, and there is a gap between the heat dissipation block and the side of the receiving groove; An adhesive is disposed within the gap, and a portion of the adhesive is filled into the through hole; Laser ablation is used to remove residual adhesive inside the through-hole; as well as Thermal paste is placed inside the through hole, and the thermal paste is baked to obtain a thermally conductive pillar. The thermally conductive pillar is connected to the heat sink to obtain the circuit board with the embedded heat dissipation structure.

2. The method for manufacturing a circuit board with an embedded heat dissipation structure as described in claim 1, characterized in that, The thermal paste is copper paste.

3. The method for manufacturing a circuit board with an embedded heat dissipation structure as described in claim 2, characterized in that, The first circuit board includes a plurality of first circuit layers, which are electrically connected to each other through the copper paste.

4. The method for manufacturing a circuit board with an embedded heat dissipation structure as described in claim 1, characterized in that, The receiving groove and the through hole are formed by mechanical drilling.

5. The method for manufacturing a circuit board with an embedded heat dissipation structure as described in claim 1, characterized in that, The cross-sectional width of the receiving groove is 0.10-0.30 mm larger than the cross-sectional width of the heat sink.

6. The method for manufacturing a circuit board with an embedded heat dissipation structure as described in claim 1, characterized in that, The diameter of the through hole is 0.05~4.2mm.

7. The method for manufacturing a circuit board with an embedded heat dissipation structure as described in claim 1, characterized in that, The adhesive is filled into the gap using a vacuum plugging machine, and The thermal grease is filled into the through hole using a vacuum plugging machine.

8. The method for manufacturing a circuit board with an embedded heat dissipation structure as described in claim 1, characterized in that, It also includes the following steps: The adhesive was baked at 75°C for 35 minutes; and Bake the thermal paste at 75°C for 35 minutes.

9. A circuit board with an embedded heat dissipation structure prepared by a method for manufacturing a circuit board with an embedded heat dissipation structure as described in any one of claims 1 to 8, characterized in that, It includes a substrate layer, a first circuit board, a second circuit board, a heat sink, heat-conducting pillars, and an adhesive. The first circuit board and the second circuit board are disposed on opposite sides of the substrate layer. A receiving groove is formed through the second circuit board and part of the substrate layer. A plurality of through holes are formed through the first circuit board and the substrate layer, and the through holes are connected to the receiving groove. The heat sink is disposed in the receiving groove, the heat-conducting column is disposed in the through hole, and the heat-conducting column is connected to the heat sink; The adhesive fills the gap between the heat sink and the second circuit board or the substrate layer.

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