A method for rapidly embedding conductive adhesive

Abstract

This invention discloses a method for rapidly embedding conductive adhesive, comprising the following steps: material preparation – inner layer circuitry – PP groove routing and drilling PP positioning holes – placing conductive adhesive in the PP groove – hot pressing with medium temperature – pre-lamination – lamination – drilling – PPTH groove routing – PPTH electroplating – outer layer circuitry – solder resist – lettering – controlled-depth PP routing – surface treatment – ​​PP routing – electrical testing – FQC – FQA. This invention fixes a pre-cut prepreg to a substrate using rivets according to a laminated structure, then applies conductive adhesive to the PP groove area, and then laminates it, ensuring the conductive adhesive is embedded in the substrate. Then, metallized grooves or holes are created using conventional mechanical PP routing or drilling. Finally, controlled-depth PP routing removes a section of the metal groove, forming a T-shaped semi-metallic groove, thus creating a groove that meets the volume requirements of the component, achieving high thermal conductivity and shielding. It eliminates the need for embedded copper blocks, saving resources, and the conductive adhesive is fixed by a metal layer to prevent it from falling off.

Description

Technical Field

[0001] This invention relates to PCB manufacturing methods, and more particularly to a method for rapidly embedding conductive adhesive. Background Technology

[0002] In the manufacturing of existing PCBs, some PCBs embed T-shaped (or boss) devices within the PCB for purposes such as heat dissipation and interference prevention. The T-shaped devices need to achieve high thermal conductivity with the PA module side of the PCB while not interfering with the TRX side. Therefore, it is necessary to design a conductive PTH slot (or hole) on one side of the PCB and a non-conductive NPTH slot (or hole) on the other side. The PTH slot is connected to the T-shaped device to achieve grounding shielding and heat dissipation functions.

[0003] Existing conductive adhesive embedding methods require attaching to a T-shaped copper base. This involves embedding the T-shaped copper base into a drilled hole, then applying conductive adhesive over the T-shaped base, and finally covering it with an outer circuit board layer exposing the copper base head, as disclosed in CN 113660784 A, which describes a processing and testing method for PCB embedded conductive adhesive. Therefore, this method suffers from significant resource consumption due to the reliance on the copper base for positioning. Furthermore, the conductive adhesive has poor adhesion and tends to detach from the PCB board, causing the copper base to fall off during processing. Therefore, improvements to existing conductive adhesive embedding methods are needed. Summary of the Invention

[0004] This invention discloses a method for rapidly embedding conductive adhesive. This invention achieves both high thermal conductivity and shielding, eliminates the need for copper pads (saving resources), and uses a metal layer to fix the conductive adhesive, preventing it from detaching.

[0005] To solve the above problems, the technical solution adopted by the present invention is as follows:

[0006] A method for rapidly embedding conductive adhesive includes the following steps:

[0007] Step 1: Fabricate an inner layer pattern on the first core board 112 containing conductor lines, and measure the scaling factor of the inner layer pattern after etching. The factor is a.

[0008] Step 2: Based on the expansion and contraction coefficient α of the inner layer pattern, manufacture proportionally stretched positioning hole drill strips and milling grooves using computer-aided manufacturing. First, drill the positioning holes, which are 25µm larger than the rivets; then, open windows on the prepreg at 120mm.

[0009] Step 3: Apply 200g of conductive adhesive to the inside of the window;

[0010] Step 4: Press the second core board 111 containing conductor lines and the first core board 112 containing conductor lines together using the prepreg 120 to form a preliminary PCB board;

[0011] Step 5: Run the slots that need to be metallized, namely PTH slots, on the preliminary PCB board. The PTH slots run through the middle of the conductive adhesive 200 on the entire preliminary PCB board.

[0012] Step 6: Perform copper plating to achieve conductivity between the PTH tank and the inner copper layer;

[0013] Step 7: After completing the outer layer pattern and solder mask, perform mechanical depth control routing. The depth control routing groove forms a non-metallized groove, i.e., an NPTH groove. The diameter of the mechanical depth control router is larger than the diameter of the PTH groove and is coaxial with the PTH groove. The depth control reaches the conductive adhesive but does not exceed the bottom of the conductive adhesive, forming a T-shaped hole structure. The PCB board with the conductive adhesive embedded is obtained.

[0014] In a further improvement, in step three, the conductive adhesive is 500µm larger on one side than the NPTH groove on one side.

[0015] As a further improvement, in step three, after applying the conductive adhesive, air bubbles are removed by pressing the film to prevent the subsequent semi-cured sheet from flowing out.

[0016] In a further improvement, in step three, the thickness of the prepreg is less than or equal to that of the conductive adhesive, and the thickness difference between the prepreg and the conductive adhesive does not exceed 5 μm.

[0017] In a further improvement, in step two, the window is 50-200µm larger on one side than the conductive adhesive on one side.

[0018] A further improvement is that the prepreg is a PP prepreg.

[0019] In a further improvement, in step four, the pressing temperature is 90-105℃ and the pressure is 0.5-2 kgf.

[0020] In a further improvement, the thickness of the conductive adhesive 200 is 100-300 μm.

[0021] As a further improvement, in step four, the pressing temperature is 90-105℃ and the pressure is 0.5-2 kgf.

[0022] A PCB board manufactured by the above-described method for rapidly embedding conductive adhesive is characterized in that it includes a first core board 112 containing conductor lines and a second core board 111 containing conductor lines, which are fixed together by a prepreg 120; conductive adhesive 200 is adhered to the first core board 112 containing conductor lines, and the prepreg 120 has a window that mates with the conductive adhesive 200; the first core board 112 containing conductor lines, the second core board 111 containing conductor lines, and the prepreg 120 form a press-fit structure, and a T-shaped hole structure is formed on the press-fit structure that extends to the location of the conductive adhesive; wherein the inner sidewall of the conductive adhesive 200 and the inner sidewall of the first core board 112 containing conductor lines are plated with a PTH metallized copper layer 311, the PTH metallized copper layer 311 contains a PTH metallized slot 310, and the PTH metallized slot 310 is above an NPTH non-metallized slot 320.

[0023] Advantages of this invention:

[0024] This invention uses a pre-cut prepreg with pre-drilled windows to fix the substrate to the substrate in a laminated structure via rivets. Conductive adhesive is then applied to the PP milled area, followed by pressing to ensure the conductive adhesive is embedded within the substrate. Metallized slots or holes are then created using conventional mechanical milling or drilling. Finally, a section of the metal slot is milled off using controlled-depth mechanical milling, forming a T-shaped semi-metallic, semi-non-metallic slot. This process creates a slot that meets the volume requirements of the component, thus achieving high thermal conductivity and shielding. It eliminates the need for embedded copper blocks, saving resources, and the metal layer secures the conductive adhesive, preventing it from detaching. Attached Figure Description

[0025] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0026] Figure 1 A schematic diagram of a windowed structure for a prepreg;

[0027] Figure 2 This is a schematic diagram of a structure with pre-applied conductive adhesive.

[0028] Figure 3 This is a schematic diagram of the structure after applying conductive adhesive.

[0029] Figure 4 A schematic diagram of the pre-stacked core board containing conductor lines;

[0030] Figure 5 This is a schematic diagram of the borehole structure;

[0031] Figure 6 A schematic diagram of the hole metallization structure;

[0032] Figure 7 This is a schematic diagram of the structure after mechanical control of the deep mill.

[0033] Among them, 111-second core board containing conductor lines, 112-core board with slot containing conductor lines, 120-prepreg; 200-conductive adhesive; 310-PTH metallized slot; 311-PTH metallized copper layer; 320-NPTH non-metallized slot. Detailed Implementation

[0034] To make the objectives, technical solutions, and advantages of the present invention clearer, the invention will be described clearly and completely below in conjunction with specific embodiments. It should be understood that the terms "center," "vertical," "horizontal," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the present invention. Example

[0035] Product design features: The product is manufactured on a four-layer PCB using a core-plus-core stack. Core 1 (L1 / L2 layers) is 0.6mm thick, and Core 2 (L3 / L4 layers) is 0.6mm thick, with a 180µm prepreg sandwiched between them, ensuring a finished board thickness of 1.4±0.2mm. A conductive adhesive is pre-placed within the graphic unit, ensuring tight bonding between the copper traces of layers L2 and L3 to guarantee circuit continuity at that location. NPTH (non-metallized) slots with a length x width of 60mm x 40mm are designed at the L1 / L2 positions on the substrate, with a slot depth of 0.65±0.01µm. Conductive adhesive with dimensions of 62×42mm is embedded in the middle of the stack.

[0036] The method of the present invention is:

[0037] Material cutting - inner layer circuitry - PP groove and PP positioning hole drilling - placing conductive adhesive in PP groove - medium temperature hot pressing adhesive - pre-lamination - pressing - drilling - PPTH groove routing - PPTH electroplating - outer layer circuitry - solder resist - characters - depth control routing - surface treatment - routing board - electrical testing - FQC - FQA.

[0038] Further explanation:

[0039] 1. Create the inner layer pattern and measure the scaling factor 'a' of the inner layer pattern after etching. The warp and weft factors are 1.0009 and 1.0006, respectively.

[0040] 2. Select 180um thick PP. Based on the expansion and contraction coefficient of the inner layer pattern, use computer-aided manufacturing to stretch the positioning hole drill strip and the grooved strip in the same proportion. First, drill the positioning hole, which is 25um larger than the rivet. Then, open the PP window, with a window size of 63mm×43mm. Under the preset size, the strip material is stretched synchronously according to the expansion and contraction coefficient.

[0041] 3. Apply conductive adhesive to the PP groove. The size of the conductive adhesive is set to 62×42mm and the thickness is 182um. After application, it needs to be pressed with an 80℃ molding rod to remove air bubbles until there are no visible air bubbles.

[0042] Furthermore, the pre-compression is applicable to PP and the underlying substrate at 90-105℃ and 0.5-2kgf pressure.

[0043] 4. After pressing at a heating rate of 3.0℃ / min, a high temperature of 190℃, a duration of 3 hours, and a pressure of 350psi.

[0044] 5. After pre-stacking and lamination, the PTH groove needs to run through the entire board.

[0045] 6. Then perform copper plating to achieve conductivity between the PTH tank and the inner copper layer.

[0046] 7. After completing the outer layer pattern and solder mask, perform mechanical depth control drilling. The depth control needs to reach the conductive adhesive area. It can drill through the L2 layer, but not through the L3 layer.

[0047] This method of quickly embedding conductive adhesive in slots allows the conductive adhesive to interconnect with the components after installation, ensuring high thermal conductivity and rapidly dissipating heat from the power amplifier. The conductive adhesive also provides connectivity with the inner copper layer and the PTH section, isolating the components from other components below the shielding layer and achieving a shielding effect.

[0048] By first slotting the PP substrate and pre-overlaying it with the substrate before placing the conductive adhesive, conductive adhesive of a specific size can be placed simply according to the PP slot, reducing the difficulty of conductive adhesive alignment and enabling rapid and efficient manufacturing, facilitating mass production. Adding a medium-temperature hot-pressing pretreatment ensures product reliability.

[0049] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for rapidly embedding conductive adhesive, characterized in that, Includes the following steps: Step 1: Fabricate an inner layer pattern on the first core board (112) containing conductor lines, and measure the scaling factor of the inner layer pattern after etching. The factor is a. Step 2: Based on the expansion and contraction coefficient α of the inner layer pattern, use computer-aided manufacturing to produce proportionally stretched positioning hole drill strips and milling groove strips. First, drill the positioning holes, which are 25µm larger than the rivets; then open windows on the prepreg (120). Step 3: Apply conductive adhesive (200) inside the window. Step 4: Press the second core board (111) containing conductor lines with the first core board (112) containing conductor lines using a prepreg (120) to form a preliminary PCB board; Step 5: Run the slots that need to be metallized, namely PTH slots, on the preliminary PCB board. The PTH slots run through the middle of the conductive adhesive (200) of the entire preliminary PCB board. Step 6: Perform copper plating to achieve conductivity between the PTH tank and the inner copper layer; Step 7: After completing the outer layer pattern and solder mask, perform mechanical depth control soldering. The depth control soldering groove forms a non-metallized groove, i.e., NPTH groove. The diameter of the mechanical depth control soldering is larger than the diameter of the PTH groove and is coaxial with the PTH groove. The depth control reaches the conductive adhesive (200) and does not exceed the bottom of the conductive adhesive (200), forming a T-shaped hole structure. The PCB board with the conductive adhesive (200) embedded is obtained.

2. The method for rapidly embedding conductive adhesive as described in claim 1, characterized in that, In step three, the conductive adhesive (200) is 500µm larger on one side than the NPTH groove on one side.

3. The method for rapidly embedding conductive adhesive as described in claim 1, characterized in that, In step three, after applying the conductive adhesive (200), the air bubbles are removed by pressing the film to prevent the subsequent semi-cured film (120) from flowing out.

4. The method for rapidly embedding conductive adhesive as described in claim 1, characterized in that, In step three, the thickness of the prepreg (120) is less than or equal to the thickness of the conductive adhesive (200), and the thickness difference between the prepreg (120) and the conductive adhesive (200) does not exceed 5 μm.

5. The method for rapidly embedding conductive adhesive as described in claim 1, characterized in that, In step two, one side of the window is 50-200µm larger than one side of the conductive adhesive (200).

6. The method for rapidly embedding conductive adhesive as described in claim 1, characterized in that, The semi-cured sheet (120) is made of epoxy resin.

7. The method for rapidly embedding conductive adhesive as described in claim 1, characterized in that, In step four, the pressing temperature is 90-105℃ and the pressure is 0.5-2 kgf.

8. The method for rapidly embedding conductive adhesive as described in claim 1, characterized in that, The thickness of the conductive adhesive (200) is 100-300um.

Images