WO2018018847A1 - Intelligent power module and method for manufacturing same - Google Patents

Abstract

An intelligent power module and a method for manufacturing same. The intelligent power module comprises: a substrate (16) serving as a carrier and having a first surface and a second surface opposite to the first surface; an insulating layer (17) provided at a first surface of the substrate (16); a circuit wiring layer (18) formed at the surface of the insulating layer (17); circuit elements (14) reversely mounted and welded at predetermined locations on an upper surface of the circuit wiring layer (18); a radiator (15) surface-mounted on a power element in the circuit elements (14); and a sealing layer (12) coated at the surface of the insulating layer (17), covering the circuit wiring layer (18) and the circuit elements (14), and exposing part of the surface of the radiator (15). The circuit elements are electrically connected in a reverse mounting mode, no metal wire is needed any more, and the cost is saved. A radiating fin and an aluminum substrate are fully exposed outside resin, and the radiating effect is maximized. Even if external moisture invades, it is hard to cause corrosion because there is no metal wire.

Description

Intelligent power module and manufacturing method thereof

The present application claims priority to Chinese Patent Application No. 201610624890.2, entitled "A Smart Power Module and Its Manufacturing Method", filed on July 29, 2016, the entire contents of which are incorporated herein by reference. In the application.

Technical field

The invention belongs to the field of electronic device manufacturing processes, and in particular relates to an intelligent power module and a manufacturing method thereof.

Background technique

The Intelligent Power Module (IPM) is a power-driven product that combines power electronics and integrated circuit technology. The IPM integrates a power switching device and a high voltage driving circuit, and has built-in fault detection circuits such as overvoltage, overcurrent, and overheating. On the one hand, the IPM receives the control signal of the MCU, drives the subsequent circuit to work, and on the other hand sends the status detection signal of the system back to the MCU. Compared with traditional discrete solutions, IPM has won more and more large markets with its high integration and high reliability. It is especially suitable for inverters and various inverter power supplies for driving motors. It is frequency control and metallurgical machinery. An ideal power electronic device for electric traction, servo drive, and frequency conversion appliances.

The intelligent power module generally works in harsh working conditions, such as the outdoor unit of the inverter air conditioner. Under high temperature and high humidity, the high temperature will increase the internal temperature of the intelligent power module, and the current intelligent power module is completely sealed by the sealing resin. The structure of the smart power module is very easy to generate heat accumulation, and high humidity causes water vapor to enter the internal circuit of the intelligent power module through the gap between the sealing resin and the lead, and the high temperature inside the smart power module makes Ions, especially chloride and bromide, migrate under the action of moisture, causing corrosion to metal lines, which often occur in metal lines and circuit components or The combination of the metal wire and the circuit wiring leads to an open circuit, which causes fatal damage to the intelligent power module, and in serious cases, the intelligent power module may be out of control explosion accident, which damages the application environment and causes significant economic loss.

In addition, the intelligent power module has different power devices. For different power devices, the material and thickness of the metal wires are different, which increases the processing difficulty of the intelligent power module. The purchase of different state-of-the-line devices also increases the processing cost, and The combination of various bonding processes makes the manufacturing pass-through rate of the intelligent power module low, and the production yield is difficult to increase. As a result, the cost of the intelligent power module is high, which affects the popular application of the intelligent power module.

Summary of the invention

The invention aims to solve the deficiencies of the prior art, and provides a high-reliability intelligent power module and a process flow adapted to the structure as a manufacturing method, which can reduce the intelligence while ensuring better contact reliability of the intelligent power module. The cost of the power module.

The present invention is achieved by an intelligent power module comprising: a substrate having a first surface and a second surface opposite to the first surface as a carrier; an insulating layer disposed on the first surface of the substrate; forming a circuit wiring layer on a surface of the insulating layer; a circuit component that is reversed and soldered to a predetermined position on an upper surface of the circuit wiring layer; a heat sink mounted on the power component of the circuit component; The surface of the insulating layer covers the circuit wiring layer and the circuit component, and exposes the surface of the heat sink portion to a sealing layer.

Further, a pin is further included, the circuit wiring layer including a pin pad adjacent to the edge, the pin being connected to the pin pad and extending outside the circuit wiring.

Further, the surface of the lead is covered with a plating layer.

Further, the power component is a planar power device.

Further, the heat sink is a heat sink.

Further, the sealing layer is a resin layer.

The beneficial effect of the above intelligent power module is that the circuit components are electrically connected by flip-chip method. The metal bonding line is no longer needed, which saves the cost; the heat sink and the aluminum substrate are completely exposed outside the resin to maximize the heat dissipation effect; even if the external moisture is invaded, it is difficult to form corrosion because there is no metal wire.

Another object of the present invention is to provide a method for manufacturing an intelligent power module, comprising the following steps:

a substrate as a carrier, the first surface of the substrate is covered with an insulating layer; wherein the substrate further has a second surface opposite to the first surface; a circuit wiring layer is disposed on the surface of the insulating layer; The surface mounting circuit component of the circuit wiring layer, wherein the circuit component is assembled in an inverted manner; a heat sink is mounted on the power component in the circuit component; and a sealing layer is coated on a surface of the insulating layer, A sealing layer that covers the circuit component and exposes the surface of the heat sink portion.

The manufacturing method of the above intelligent power module has the beneficial effects that the metal is exposed at the top and the bottom of the module, which reduces the difficulty of positioning due to the thickness control of the upper and lower surfaces when the full-encapsulation technology is injected; The line bonding and cleaning process saves equipment investment, improves production efficiency, reduces process control requirements, greatly reduces the manufacturing difficulty of intelligent power modules, improves manufacturing yield, and further reduces the cost of intelligent power modules.

DRAWINGS

1(A) is a top plan view of an intelligent power module according to an embodiment of the present invention;

Figure 1 (B) is a cross-sectional view taken along line X-X' in Figure 1 (A);

1(C) is a plan view of the smart power module of the present invention with the sealing layer removed;

1(D) is a top plan view of the lower surface of the smart power module of the present invention;

2 is a flowchart of a manufacturing process of an intelligent power module according to an embodiment of the present invention;

3(A) and 3(B) are respectively a plan view and a side view process for fabricating a circuit wiring in the manufacturing method of the smart power module of the present invention;

Figure 4 (A) is a dimension drawing of the pin;

Figure 4 (B) is a schematic view of the process of making a lead;

Figure 5 is a schematic view of the process of mounting the heat sink on the bottom of the power component.

6(A) and 6(B) are schematic side and top plan views of the assembled circuit components and leads, respectively;

7 is a schematic view showing a sealing process of a method of manufacturing an intelligent power module;

8 is a schematic diagram of a detecting process of a method for manufacturing an intelligent power module;

9 is a process flow diagram of a method of manufacturing an intelligent power module.

detailed description

The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It is understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

As shown in FIG. 1(A), FIG. 1(B), FIG. 1(C), and FIG. 1(D), the smart power module includes a substrate 16, an insulating layer 17, a circuit wiring (circuit wiring) 18, and a circuit component 14. The heat sink 15 constitutes a circuit, and a pin 11 disposed at an edge of the circuit wiring 18, and a sealing layer 12 that seals the circuit and completely covers the circuit element 14 and the upper surface of the insulating layer 17. 1(A) is a top plan view of the upper surface of the smart power module 10 of the present invention, the heat sink 15 is exposed from the upper surface, and FIG. 1(B) is a cross section taken along line XX' of FIG. 1(A). 1(C) is a plan view showing the sealing layer 12 covering the circuit component 14 removed, and FIG. 1(D) is a top plan view of the smart power module 10 of the present invention.

The substrate 16 acts as a carrier for the smart power module 10 and has a first surface and a second surface opposite the first surface. The insulating layer 17 is disposed on the first surface of the substrate. a circuit wiring layer 18 is formed on the surface of the insulating layer; the circuit component 14 is inverted and soldered to a predetermined position on the upper surface of the circuit wiring layer 18; a power component mounted on the circuit component 14 by the heat sink 15; a sealing layer 12 is coated on the surface of the insulating layer 17, covering the circuit wiring layer 18 and the circuit component 14, and the surface of the heat sink 15 is exposed.

Specifically, the power component is a planar power device, such as an IGBT transistor, and an LIGBT must be used. The heat sink is a heat sink, and the surface of the heat sink can be treated with silver plating to increase the wettability. Sealing layer is dense Seal the resin layer.

Further, on at least one edge of the circuit wiring 18, there is a special circuit wiring for configuring the pin 11, which is referred to as a pin pad 18A. The pin 11 pin pad 18A is connected and extends from the outside of the circuit wiring 18. The surface of the lead is covered with a plating layer.

Each of these constituent elements will be described below.

The circuit board 16 is a rectangular plate material made of aluminum such as 1050 or 5052. Here, in order to reduce the cost, an aluminum material of 1050 may be used, and in order to increase the hardness, an aluminum material of 5052 may be selected; in order to increase the withstand voltage, the aluminum material may be anodized, and in order to improve heat dissipation, anodization may not be performed. The thickness of the circuit substrate 16 can be designed to be 1.5 mm to 2.0 mm.

The insulating layer 17 located on one surface of the substrate 16 can be designed to have a thickness of 100 μm to 200 μm and a thermal conductivity of 2 W/(m*K) to 3 W/(m*K). Here, in order to save cost and improve thermal conductivity, The thickness is selected to be 100 μm. In order to increase the withstand voltage, the thickness may be selected to be 200 μm, and the thickness should generally not exceed 200 μm. Here, the thicker the thickness of the insulating layer is selected, the higher the thermal conductivity should be selected accordingly.

The circuit wiring 18 is formed by stamping or etching a copper material having a thickness of 5 ounces or more. To prevent oxidation, the upper surface of the circuit wiring 18 may be subjected to gold plating treatment, and the circuit wiring 18 is provided for cost. The surface can also be silver plated or shipped in a vacuum or nitrogen-filled package with no treatment on the upper surface.

The circuit component 14 is flip-chip mounted on the circuit wiring 18. The circuit element 14 uses an active element such as a transistor or a diode, or a passive element such as a capacitor or a resistor. Further, the heat sink 15 made of copper or the like is attached to the back surface of the element having a large amount of heat such as a power element.

Here, it is designed such that a plurality of pins 11 are provided on one side, and have functions of inputting and outputting, for example, from the outside. The lead 11 and the lead pad 18A are soldered by a conductive electrical adhesive such as solder.

The lead 11 is generally made of a metal such as copper. The surface of the copper is formed by electroless plating and electroplating to form a layer of nickel-tin alloy. The thickness of the alloy layer is generally 5 μm. The plating layer protects the copper from corrosion and oxidation and improves solderability.

The sealing layer 12 can be molded by using a thermosetting resin or a molding die by a transfer molding method. The mold is molded using a thermoplastic resin. Here, the sealing layer 12 completely seals all the elements on one side of the circuit wiring 18, the heat sink 15 is exposed from the sealing layer 12, and the lower surface of the substrate 16 is exposed from the sealing layer 12, so that the heat of the power component is quickly Lost.

The beneficial effect of the intelligent power module is that the circuit components are electrically connected by the flip-chip method, the metal bonding wire is no longer needed, and the cost is saved; the heat sink and the aluminum substrate are completely exposed outside the resin, thereby maximizing the heat dissipation effect; External moisture intrusion, because there is no metal wire, it has been difficult to form corrosion.

Referring to FIG. 2, a method for manufacturing the smart power module is provided, including the following steps:

Step S110, preparing a substrate as a carrier, covering the first surface of the substrate with an insulating layer; wherein the substrate further has a second surface opposite to the first surface; and step S120, laying the surface of the insulating layer a circuit wiring layer; step S130, assembling a circuit component on a surface of the circuit wiring layer, wherein the circuit component is assembled in an inverted manner; and step S140, mounting a heat sink on the power component in the circuit component; Step S150, a sealing layer is coated on the surface of the insulating layer to cover the circuit element and expose the surface of the heat sink portion.

Step S150 specifically includes: providing a thermosetting resin frame around the surface of the insulating layer; and injecting a thermoplastic resin into the range of the thermosetting resin frame to seal the circuit wiring layer and the circuit component.

Also included before step S130 is the step of making a separate coated pin. The step specifically includes: selecting a copper substrate, forming a row of pins by punching or etching the copper substrate, connecting the pins through the ribs; forming a nickel layer and a nickel tin on the surface of the lead The alloy layer gives a plated lead.

Before the step S150, the method further includes the steps of: soldering the circuit component to the circuit wiring layer by reflow soldering; and removing the flux remaining in the insulating layer.

The top and bottom of the module are exposed with metal, which reduces the difficulty of positioning due to the thickness control of the upper and lower surfaces when the full-encapsulation technology is injected; the metal wire bonding and cleaning process are eliminated, and the equipment investment is saved. The production efficiency is improved, the process control requirements are reduced, the manufacturing difficulty of the intelligent power module is greatly reduced, the manufacturing yield is improved, and the cost of the intelligent power module is further reduced.

In a more specific embodiment, in conjunction with FIGS. 3(A) through 9, the method of manufacturing the smart power module includes the following steps.

9 is a process flow diagram of a method of manufacturing an intelligent power module.

As shown in FIG. 9, the first process 902 refers to FIGS. 3(A) and 3(B):

The first step 902 of the present invention is a step of the present invention, and the step is a step of forming a circuit wiring on an aluminum plate of an appropriate size.

First, referring to FIG. 3(A), a circuit board 16 of a suitable size is designed according to a required circuit layout. For a general smart power module, a size of 64 mm×30 mm can be selected. An insulating layer 17 is provided on the surface of the aluminum substrate 16. Further, a copper foil as the circuit wiring 18 is bonded to the surface of the insulating layer 17. Then, the copper foil produced in this step is etched to partially remove the copper foil to form the circuit wiring 18 and the lead pad 18A.

Here, the aluminum substrate of a suitable size is formed by directly processing a 1 m×1 m aluminum material, and the file is made of high-speed steel, and the motor is rotated at 5000 rpm, and the boring tool and the aluminum material are used. The plane is cut at a right angle to make the edge of the 1100 aluminum material at right angles, and the burr is less than 10μm. It can also be etched into a specific shape by chemical reaction through an etching tool. Referring to the X-X' line cross-sectional view 3(B) of the extension 3(A) and the Y-Y' line cross-sectional view 3(C) of the extension 3(A).

In the case where the anti-oxidation requirement is high, a gold layer may be formed on the surface of the circuit wiring 18 by means of electroplating gold or chemical immersion gold.

Here, the thickness of the copper plate used to manufacture the circuit wiring 18 should be not less than 2 ounces, ensuring sufficient flow capacity.

The second process 904, referring to FIG. 4(A) and FIG. 4(B):

The second step 904 of the present invention is a step of the present invention, and the step is a step of forming an independent lead 11 with a plating layer.

Each of the leads 11 is made of a copper substrate, and is formed into a strip shape having a length C of 25 mm, a width K of 1.5 mm, and a thickness H of 1 mm, as shown in Fig. 4(A); here, for ease of assembly, At one end, a certain curvature is pressed, as shown in Fig. 4(B); then a nickel layer is formed by electroless plating: through nickel a mixed solution of salt and sodium hypophosphite, and a suitable complexing agent is added to form a nickel layer on the surface of the copper material having a specific shape, which has a strong passivation ability in the metallic nickel, and can rapidly form a very thin layer. Passivation film, resistant to atmospheric, alkali and certain acid corrosion. The nickel-plated crystal is extremely fine, and the thickness of the nickel layer is generally 0.1 μm; then the copper material having the shape and the nickel layer is immersed in a plating solution with positive tin ions at room temperature by an acidic sulfate process, in the nickel layer. A nickel-tin alloy layer is formed on the surface, and the thickness of the nickel layer is generally controlled to 5 μm. The formation of the nickel layer greatly improves the protection and solderability; thus, the pin 11 is completed.

Here, the pin 11 of the present invention is a single pin, which is different from the entire row of pins of the prior art, because the circuit wiring 18 to which the pin 11 is fixed is only wrapped by a resin portion. The impact strength is limited, and the separate pins avoid the process of cutting the ribs, and the systemic impact on the smart power module 10 of the present invention can be reduced.

The third process 906, refer to FIG. 5:

The third step of the present invention is a step of the present invention. This step is a step of manufacturing the heat sink 15 and attaching the bottom of the L-type power element 14 to the heat sink 15.

The heat sink 15 can be designed as a copper sheet having a thickness of about 1.5 mm, which is formed by stamping or etching. The copper sheet is silver plated by electroplating, and the thickness of the silver layer can be designed to be 22 to 30 μm.

Then, by using a high-temperature solder paste having a melting point of 300 ° C or higher by a eutectic process, it is conceivable to mount the back surface of the L-type power element 14 on the heat sink 15 by using the Tamura brand. Here, the L-type power device 14 is a planar power device, and all the electrodes of the power device are located on the front side of the power device, and the front electrode is connected to the circuit wiring 18 in the following process.

Here, the eutectic flatness of the power device 14 is controlled to be <0.1 mm.

Fourth process 908, with reference to Figures 6(A) and 6(B):

The fourth step 908 of the present invention is a step of the present invention. This step is a step of flip-chip bonding the circuit element 14 on the surface of the circuit wiring 18 and arranging the lead pins 11.

First, referring to the side view of FIG. 6(A) and the top view of FIG. 6(B), the fabricated circuit wiring 18 is placed at a corresponding recess of the carrier 20, and the stencil is used by a solder paste printing machine. The solder paste is applied to a specific position of the wiring 18, and the steel mesh can be used with a thickness of 0.13 mm. Via SMT machine or DA Equipment, etc., performs circuit component 14, including circuit component 14 on which heat sink 15 has been disposed, and mounting of pin 11, which can be flipped directly at a specific location of said circuit wiring 18 The foot 11 is to be placed on the pad 18A at one end, and the carrier 20 is required to be fixed at the other end. The carrier 20 is made of a material such as synthetic stone.

Then, the circuit substrate 16 placed on the carrier 20 is reflowed, the solder paste is cured, and the circuit component 14 and the lead 11 are fixed.

In the fifth process 910, refer to FIG. 7:

The fifth step 910 of the present invention is a step of the present invention, and this step is a step of explaining that the circuit wiring 18 is sealed by the sealing resin 12. FIG. 7 is a cross-sectional view showing a step of sealing the circuit wiring 18 carried by the base 16 with a sealing resin using a mold 50.

First, the circuit wiring 18 is baked in an oxygen-free environment, the baking time should not be less than 2 hours, the baking temperature and the selection of 125 °C.

The base 16 on which the circuit board 18 is placed is transported to the models 44 and 45. The positioning of the circuit substrate 16 is performed by bringing a specific portion of the pin 11 into contact with the fixture 46.

At the time of mold clamping, the circuit substrate 16 is placed in a cavity formed inside the mold 50, and then the sealing resin is injected from the gate 53 to form the sealing layer 12. The method of performing the sealing can be carried out by transfer molding using a thermosetting resin or injection molding using a thermosetting resin. Further, the gas inside the cavity of the sealing resin 12 injected corresponding to the gate 103 is discharged to the outside through the exhaust port 54.

Here, the upper mold 44 should be in contact with the heat sink 15, and the lower mold 45 should be in contact with the base 16.

In the sixth process 912, refer to FIG. 8:

The sixth step 912 of the present invention is a step of performing the pin 11 molding and the module function test, and the smart power module is completed as a product through this process.

In the pre-process, that is, the transfer mold mounting process, the portion other than the lead 11 is sealed by the resin 12. This step is required according to the length and shape used, for example, the outer lead 11 is bent into a shape at the position of the broken line 51 to facilitate subsequent assembly.

Then put the module into the test equipment and perform the normal electrical parameter test. Because the pins 11 are independent of each other, some pins may not be on the same level after molding, which affects the contact, so it is generally necessary to first test the machine gold finger. Contact test with the pin. If the contact test does not pass, the pin 11 needs to be trimmed until the contact test passes, and then the electrical characteristic test is performed, including insulation withstand voltage, static power consumption, delay time, etc. For the project, the qualified person is the finished product.

The smart power module 10 shown in Fig. 2 is completed by the above steps.

The above are only the preferred embodiments of the present invention, and are not intended to limit the present invention. Any modifications, equivalents, and improvements made within the spirit and scope of the present invention should be included in the scope of the present invention. Inside.

Claims (10)

An intelligent power module, comprising: a substrate having a first surface and a second surface opposite the first surface as a carrier; An insulating layer disposed on the first surface of the substrate; a circuit wiring layer formed on a surface of the insulating layer; a circuit component that is reversed and soldered to a predetermined position on an upper surface of the circuit wiring layer; a heat sink mounted to the power component of the circuit component; and A sealing layer covering the surface of the insulating layer, covering the circuit wiring layer and the circuit component, and exposing the surface of the heat sink portion. The intelligent power module of claim 1 further comprising a lead, said circuit routing layer comprising a pin pad proximate the edge, said pin being coupled to said pin pad and said The circuit wiring extends outside. The intelligent power module of claim 2 wherein said pin surface is covered with a plating. The intelligent power module according to any one of claims 1 to 3, wherein the power component is a planar power device. The intelligent power module according to any one of claims 1 to 3, wherein the heat sink is a heat sink. The intelligent power module according to any one of claims 1 to 3, wherein the sealing layer is a resin layer. A method for manufacturing an intelligent power module, comprising the steps of: Forming a substrate as a carrier, covering the first surface of the substrate with an insulating layer; wherein the substrate further has a second surface opposite to the first surface; Laying a circuit wiring layer on a surface of the insulating layer; Assembling a circuit component on a surface of the circuit wiring layer, wherein the circuit component is assembled in an inverted manner; Mounting a heat sink on the power component in the circuit component; A sealing layer is coated on the surface of the insulating layer to cover the circuit element and expose the surface of the heat sink portion. The method of manufacturing an intelligent power module according to claim 7, wherein the surface of the insulating layer is coated with a sealing layer, and the step of sealing the circuit element and exposing the surface of the heat sink portion is specifically performed. for: Providing a thermosetting resin frame around the surface of the circuit insulating layer; A thermoplastic resin is injected in the range of the thermosetting resin frame to seal the circuit wiring layer and the circuit component. The method of manufacturing the smart power module according to claim 7 or 8, wherein before the step of assembling the circuit component on the surface of the circuit wiring layer, the method further comprises: Made of independent coated pins; specifically: Selecting a copper substrate, forming a row of pins by punching or etching the copper substrate, and connecting the pins through the reinforcing ribs; Forming a nickel layer and a nickel-tin alloy layer on the surface of the lead to obtain a plated lead; The pins are soldered to the pin pads on the edge of the circuit wiring layer by reflow soldering. The method of manufacturing an intelligent power module according to claim 7 or 8, wherein a sealing layer is coated on a surface of the insulating layer, and the circuit element is covered and the surface of the heat sink portion is exposed. The layer steps also include the following steps: The flux remaining in the insulating layer is removed.

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