Multi-layer PCB stacking and potting method and multi-layer PCB stacking structure

Abstract

The invention discloses a multi-layer PCB (Printed Circuit Board) stacking and encapsulating method and a multi-layer PCB stacking structure, and relates to an integrated circuit packaging technology. The multi-layer PCB stacking and potting method comprises the following steps that a, a first PCB layer is used for bearing a core component, the core component and a bonding wire of the first PCB layer are covered with high-heat-conduction or high-pressure-resistant potting glue, and the core component is a high-heating or high-pressure component; b, the second PCB layer bears the low-heating component, the second PCB layer and the first PCB layer are overlapped and fixed to form a low-layer PCB structural body, and the low-heating component and the bonding wire of the second PCB layer are covered with low-stress pouring sealant; and c, carrying a power supply or a passive device by using a third PCB layer, overlapping the third PCB layer to the low-layer PCB structural body to form a composite PCB structural body, and carrying out potting on the composite PCB structural body by using a conventional potting adhesive. The method is simple in process, high in effectiveness and low in cost, and can be widely applied to potting of multi-layer PCB stacked products including power chips, bare chips, passive elements and the like.

Description

Technical Field

[0001] The invention relates to integrated circuit packaging technology. Background Art

[0002] Multi-layer PCB stacked products are often composed of ground layers, power consumption layers, signal layers, and power supply layers, and the electrical interconnection between the multiple layers is achieved through metal columns. In order to protect the internal components of the product, the product will be potted after assembly. The power consumption layer generates a lot of heat, requiring the powder potting glue to have fast thermal conductivity. The signal layer has more bare chips and many bonding wires, requiring the potting glue to have low stress and good moisture-proof effect. The power supply layer is mostly composed of components such as resistors, capacitors, and inductors, and the requirements for the potting glue are relatively low. It is difficult to meet the requirements between the layers using a single potting glue. Even if there is a potting glue that takes into account the above characteristics, the cost of potting the entire product is very high, making the product lose its competitive advantage.

[0003] Chinese patent application CN110602865B discloses a circuit device with multi-layer glue potting and a glue potting method, including a base, a printed circuit board (PCB), a colloid and a separator, electronic components of different heights are arranged on the printed circuit board, and the electronic components are distributed in the lowest area or other areas according to different heights, a first colloid layer is arranged on the printed circuit board, the height of the first colloid layer is the same as the glue sealing height of the lowest area, and the separator and the first colloid layer separate the other areas to form a separation cavity, and also includes a glue potting method for a circuit device with multi-layer glue potting. This scheme arranges components of different heights on the same base, but all components are spread out on the same PCB board in a plane, and the separators used occupy space, which is not conducive to reducing the overall volume of the product; and the first colloid layer will coat the height of all components, and the separation cavity is subsequently filled with glue, resulting in the high components being coated with two kinds of glue, which is not as good as the product performance of similar components completely coated with the same required potting glue. Summary of the invention

[0004] The technical problem to be solved by the present invention is to provide a multi-layer PCB stacking potting method and a multi-layer PCB stacking structure to achieve good thermal conductivity and bare core packaging compatibility at low cost.

[0005] The technical solution adopted by the present invention to solve the technical problem is:

[0006] The multi-layer PCB stacking potting method is characterized by comprising the following steps:

[0007] a. The first PCB layer carries the core components, and the core components and bonding wires of the first PCB layer are covered with high thermal conductivity or high-voltage potting glue, wherein the core components are high-heat generating or high-voltage components;

[0008] b. Use the second PCB layer to carry the low-heat generating components, overlap and fix the second PCB layer with the first PCB layer to form a low-layer PCB structure, and cover the low-heat generating components and bonding wires of the second PCB layer with a low-stress potting glue;

[0009] c. Use the third PCB layer to carry the power supply or passive components, overlap the third PCB layer to the lower PCB structure to form a composite PCB structure, and pot the composite PCB structure with conventional potting glue.

[0010] Furthermore, the core component includes a power chip, and the low-heat generating component includes an MCU chip.

[0011] The step a comprises:

[0012] (a1) Use screen printing solder paste on the front and back of the first PCB layer, then place the first PCB layer on the heat sink, attach the MOS tube to the first PCB layer, and solder the first PCB layer to the heat sink by reflow soldering; after cleaning the flux, connect the MOS tube and the first PCB layer with bonding wires;

[0013] (a2) After the MOS tube is surrounded by dam glue, it is partially filled with high thermal conductivity or high pressure resistant potting glue to cover the MOS tube and the bonded wires, and then cured in an oven.

[0014] The step b comprises:

[0015] (b1) Use adhesive to bond the bare chip to the front and back of the second layer PCB, and place it in an oven to complete curing; use bonding wires to complete the connection between the chip and the PCB circuit.

[0016] (b2) Install the second PCB layer onto the connecting column and fix it by welding;

[0017] (b3) After the bare chip is surrounded by dam glue, it is partially potted with low-stress potting glue to cover the bare chip and its bonding wires, and cured in an oven.

[0018] The step c comprises:

[0019] (c1) Use screen printing solder paste on the front and back of the third PCB layer, mount plastic-encapsulated chips or passive components and reflow solder, or manually solder, clean and dry;

[0020] (c2) installing the third PCB layer with components welded on it onto the connecting column and fixing it by welding;

[0021] (c3) Use conventional potting glue to complete the overall potting of the composite PCB structure.

[0022] The present invention also provides a multi-layer PCB stacking structure, characterized in that it includes a shell, and a first PCB layer carrying core components, a second PCB layer carrying low-heat generating components, and a third PCB layer carrying power supplies or passive devices arranged in the shell, the first PCB layer, the second PCB layer, and the third PCB layer are arranged in an overlapping manner; the high-heat generating components and bonding wires arranged on the first PCB layer are covered with high thermal conductivity potting glue, the low-heat generating components and bonding wires arranged on the second PCB layer are covered with low-stress potting glue, and the components and bonding wires arranged on the third PCB layer are covered with conventional potting glue; the core components are high-heat generating or high-voltage components.

[0023] The first PCB layer, the second PCB layer and the third PCB layer are fixedly connected by connecting pillars, and conventional potting glue is filled between the PCB layers.

[0024] Furthermore, the first PCB layer, the second PCB layer and the third PCB layer are fixedly connected by connecting pillars. Conventional potting glue, such as GMX-8152 potting glue, is filled between each PCB layer.

[0025] The low-heat-generating components are bare chips such as MCU, and the passive components are components such as resistors and capacitors.

[0026] The present invention pots different PCB layers with different potting glues, first potting glue with high thermal conductivity and high pressure resistance to wrap the power chip and bonding thick aluminum wire or copper wire, so that the front of the MOS tube can also effectively dissipate heat, and then potting low-stress gel to protect the bare chip and gold wire of the signal layer, to prevent the bonding gold wire from being deformed or the bonding point falling off and failing due to the thermal expansion and contraction of conventional potting glue, and finally potting conventional potting glue to cover resistors, capacitors, inductors or plastic-sealed integrated blocks, etc., to achieve insulation and moisture-proof protection. The method of the present invention has a simple process, strong effectiveness, and low cost, and can be widely used in potting multi-layer PCB stacked products containing power chips, bare chips, passive components, etc. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a flow chart of the method of the present invention.

[0028] Figure 2 It is a schematic diagram of the multi-layer PCB stacking structure of the present invention. DETAILED DESCRIPTION

[0029] In the following text and the accompanying drawings, PCB1 is the first PCB layer, PCB2 is the second PCB layer, and PCB3 is the third PCB layer.

[0030] Example 1

[0031] See also Figure 1 and Figure 2 , the method steps are as follows:

[0032] Step 10. Use screen printing to apply solder paste on both sides of PCB1, place PCB1 on the heat sink, attach power chips such as MOS tubes to PCB1, and solder PCB1 to the heat sink through reflow soldering; after cleaning the flux, bond thick aluminum wire to connect the MOS tube and PCB1.

[0033] Step 20: After the MOS tube is surrounded by the dam glue, the high thermal conductivity potting glue is poured to cover the MOS tube and the bonded thick aluminum wire, and then put into the oven for curing.

[0034] Step 30, solder the connection column, then solder the bonded PCB2 to the column, clean the flux; use dam glue to dam the bare chip, and then use low-stress potting glue to pot the bare chip and bonding wire.

[0035] Step 40, solder the connecting column, solder the PCB3 with components such as resistors and capacitors that have been reflowed into the tube shell through the connecting column, clean the flux and tin beads, dry the entire semi-finished product at 120°C, cool it, and then fill it with silicone rubber.

[0036] In this embodiment, the bare chip of the signal layer has little heat consumption, and a thin gold wire is used to connect the chip and the PCB board. The potting glue is required to have the characteristics of low stress, no ion pollution, good moisture resistance, etc. Wacker 927F or 612AB can be selected.

[0037] Step 20 includes the following after refinement:

[0038] Step 201: Preprocessing:

[0039] Specifically, put the cleaned PCBA semi-finished product into a stainless steel tray, and then put it into a 120±5℃ oven for 1 to 2 hours.

[0040] Step 202: Glue preparation and bubble removal:

[0041] Specifically, take out the high thermal conductivity potting glue from the freezer, and let it stand at room temperature for 1 to 2 hours to wake up the glue; use a glass rod to stir the single-component glue liquid separately, and then use a balance to weigh it according to the proportion, pour it into the glue dispensing syringe, and use a planetary mixer for vacuum stirring and degassing.

[0042] Step 203: dam:

[0043] Specifically, for potting glue with good fluidity, first use an automatic dispensing machine to dam the bonding points on the MOS tube and the surrounding PCB board;

[0044] Step 204: potting and curing:

[0045] Install the de-bubbled syringe on the glue dispenser, and use the automatic glue dispenser to pot the chip and bond the thick aluminum wire. After the glue is potted, put the product in a vacuum oven and let it stand at room temperature for 2 to 10 minutes at a vacuum degree of -0.06 to -0.09. After returning to normal pressure, set the heating temperature to 100 to 150°C and bake for 40 to 90 minutes to cure the potting glue.

[0046] Step 30 includes the following after refinement:

[0047] Step 301, welding connecting column:

[0048] Specifically, install the connecting column into the mounting hole of PCB1 and fix it with a soldering iron; use a cotton swab dipped in anhydrous ethanol to wipe off the flux on the solder joint;

[0049] Step 302: Sticking the film:

[0050] Specifically, a dispensing machine is used to apply conductive glue on the pad of PCB2, and then a chip mounter is used to mount bare chips such as MCU chips, diode cores, etc. onto the conductive glue; the conductive glue is put into an oven to cure, and the bonding is completed;

[0051] Step 303: Bonding:

[0052] Specifically, a gold wire bonder is used to bond the bare chip to the PCB2 circuit;

[0053] Step 304, installing PCB2;

[0054] Specifically, align PCB2 and install it on the connecting column, and then use an electric soldering iron to solder the pads connecting the connecting column and PCB2; after soldering, wipe off the solder flux with a cotton swab dipped in anhydrous ethanol, and put it in a 120±5℃ oven for 1 to 2 hours;

[0055] Step 305: damming:

[0056] Specifically, for potting glue with good fluidity, an automatic glue dispensing machine is first used to dam the bonding points on the bare chip and the surrounding PCB board;

[0057] Step 306: potting and curing:

[0058] Use an automatic dispensing machine to partially encapsulate the chip and bonding wire. After the encapsulation is completed, put the product in a vacuum oven and let it stand at room temperature for 2 to 10 minutes at a vacuum degree of -0.06 to -0.09. After returning to normal pressure, set the heating temperature to 100 to 150°C and bake for 40 to 90 minutes to cure the encapsulation glue.

[0059] Step 40, after refinement, includes:

[0060] Step 401, welding connecting column:

[0061] Specifically, install the connecting column into the mounting hole of PCB2 and fix it with a soldering iron; use a cotton swab dipped in anhydrous ethanol to wipe off the flux on the solder joint;

[0062] Step 402: device welding:

[0063] Specifically, use a screen to print solder paste on the front of PCB3, mount passive components such as resistors and capacitors or plastic-encapsulated integrated blocks; then put it into a reflow oven to complete the soldering; use anhydrous ethanol to clean the solder flux on the board surface, and put it into an oven for drying;

[0064] Step 403, installing PCB3;

[0065] Specifically, align PCB3 and install it on the connecting column, and then use an electric soldering iron to solder the pads connecting the connecting column and PCB3; after soldering, wipe off the solder flux with a cotton swab dipped in anhydrous ethanol, and put it in a 120±5℃ oven for 1 to 2 hours;

[0066] Step 404: potting and curing:

[0067] Install the defoamed syringe on the dispensing machine and fill the entire product with conventional silicone rubber. After filling, place the product in a vacuum oven and let it stand at room temperature for 2 to 10 minutes at a vacuum degree of -0.06 to -0.09. After returning to normal pressure, set the heating temperature to 100 to 150°C and bake for 40 to 90 minutes to cure the filling glue.

[0068] In summary, the present invention provides a potting method for a multi-layer PCB stacked product, comprising the following steps:

[0069] 1. Sinter the power consumption layer onto the heat sink and fill it with high thermal conductivity potting glue RT7612F to cover the power chip and bonding wires;

[0070] 2. Install the signal layer and cover the bare chip and its bonding wires with low stress potting glue 927F;

[0071] 3. Install the top power layer and fill all the gaps inside the product with GMX-8152.

[0072] Example 2

[0073] See also Figure 2This embodiment provides a multi-layer PCB stacking structure, including a shell, and a first PCB layer carrying high-heat generating components, a second PCB layer carrying low-heat generating components, and a third PCB layer carrying a power supply or a passive device arranged in the shell, wherein the first PCB layer, the second PCB layer, and the third PCB layer are arranged in an overlapping manner; the high-heat generating components and bonding wires arranged on the first PCB layer are covered by a high-thermal conductive potting glue, the low-heat generating components and bonding wires arranged on the second PCB layer are covered by a low-stress potting glue, and the components and bonding wires arranged on the third PCB layer are covered by a conventional potting glue.

[0074] The first PCB layer, the second PCB layer and the third PCB layer are fixedly connected by connecting pillars. The PCB layers are filled with potting glue GMX-8152.

[0075] The present invention fills the power consumption layer with high thermal conductivity potting glue, and then encapsulates the chip and bonding wires with low stress glue to protect the chip and bonding wires, and then fills the whole with silicone rubber, thereby providing certain structural support and heat dissipation effects on the product. The operation method of the present application is simple to operate, highly effective, and low in cost, and can be widely used in the potting of multi-layer PCB stacked products containing power chips, bare chips, passive components, etc.

Claims

1. A multi-layer PCB stacking and potting method, characterized in that: The steps include: a. The first PCB layer carries the core components, and the core components and bonding wires of the first PCB layer are covered with a high thermal conductivity or high-voltage potting glue, wherein the core components are high-heat generating or high-voltage components; b. Use the second PCB layer to carry the low-heat generating components, overlap and fix the second PCB layer with the first PCB layer to form a low-layer PCB structure, and cover the low-heat generating components and bonding wires of the second PCB layer with a low-stress potting glue; c. Use the third PCB layer to carry the power supply or passive components, overlap the third PCB layer to the lower PCB structure to form a composite PCB structure, and pot the composite PCB structure with conventional potting glue.

2. The multi-layer PCB stacking and potting method according to claim 1, characterized in that: The core component includes a power chip, and the low-heat generating component includes an MCU chip.

3. The multi-layer PCB stacking and potting method according to claim 1, characterized in that: The step a comprises: (a1) Use screen printing solder paste on the front and back of the first PCB layer, then place the first PCB layer on the heat sink, attach the MOS tube to the first PCB layer, and solder the first PCB layer to the heat sink by reflow soldering; after cleaning the flux, connect the MOS tube and the first PCB layer with bonding wires; (a2) After the MOS tube is surrounded by dam glue, it is partially filled with high thermal conductivity or high pressure resistant potting glue to cover the MOS tube and the bonded wires, and then cured in an oven.

4. The multi-layer PCB stacking and potting method according to claim 1, characterized in that: The step b comprises: (b1) Use adhesive to bond the bare chip to the front and back of the second layer PCB, and place it in an oven to complete curing; use bonding wires to complete the connection between the chip and the PCB circuit. (b2) Install the second PCB layer onto the connecting column and fix it by welding; (b3) After the bare chip is surrounded by dam glue, it is partially potted with low-stress potting glue to cover the bare chip and its bonding wires, and cured in an oven.

5. The multi-layer PCB stacking and potting method according to claim 1, characterized in that: The step c comprises: (c1) Use screen printing solder paste on the front and back of the third PCB layer, mount plastic-encapsulated chips or passive components and reflow solder, or manually solder, clean and dry; (c2) installing the third PCB layer with components welded on it onto the connecting column and fixing it by welding; (c3) Use conventional potting glue to complete the overall potting of the composite PCB structure.

6. Multi-layer PCB stacking structure, characterized in that: It comprises a shell, and a first PCB layer carrying core components, a second PCB layer carrying low-heat generating components and a third PCB layer carrying power supplies or passive devices arranged in the shell, wherein the first PCB layer, the second PCB layer and the third PCB layer are arranged in an overlapping manner; the high-heat generating components and bonding wires arranged on the first PCB layer are covered by a high-thermal conductive potting glue, the low-heat generating components and bonding wires arranged on the second PCB layer are covered by a low-stress potting glue, and the components and bonding wires arranged on the third PCB layer are covered by a conventional potting glue; the core components are high-heat generating or high-voltage components.

7. The multi-layer PCB stacking structure according to claim 5, characterized in that: The first PCB layer, the second PCB layer and the third PCB layer are fixedly connected via connecting pillars.

8. The multi-layer PCB stacking structure according to claim 5, characterized in that: Conventional potting glue is filled between each PCB layer.

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