CN104112730A - Intelligent power module and manufacturing method thereof - Google Patents

Abstract

The present invention is applicable to electronic device technology, and provides an intelligent power module and a manufacturing method thereof. The intelligent power module includes a substrate covered with an insulating layer on the upper surface, circuit wiring arranged on the surface of the insulating layer, and corresponding to the circuit wiring. The intelligent power module further includes: pins connected to the circuit wiring and extending from the substrate, and completely covering the pins with a plating layer; a sealing layer laid on the substrate with The circuit wiring and the upper surface of the circuit element. The pins of the intelligent power module are completely sealed by plating, which greatly improves the corrosion resistance of the intelligent power module, and ensures that the pins of the intelligent power module will not be blown due to local overheating during long-term use.

Description

Intelligent power module and manufacturing method thereof

technical field

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

Background technique

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

Referring to FIG. 1 , the structure of a conventional smart power module 100 will be described. Fig. 1(A) is a top structural view of the smart power module 100, and Fig. 1(B) is a sectional view along line X-X' of Fig. 1(A).

The intelligent power module 100 has the following structure, which includes: a circuit substrate 106, an insulating layer 107 is provided on the surface of the circuit substrate 106, and a circuit wiring 108 formed on the insulating layer 107; is fixed on the circuit wiring 108 The circuit element 104 on the top; the metal wire 105 connecting the circuit element 104 and the circuit wiring 108; the pin 101 connected with the circuit wiring 108, there is an unplated gap 103 on the edge of the pin 101, and the pin The remaining part of 101 except the gap 103 is covered by electroplating layer; the whole of the intelligent power module 100 is sealed by sealing resin 102 . In addition, sealing may be performed in a state in which the back surface of the aluminum substrate 106 is exposed to the outside.

The intelligent power module 100 generally works in harsh working conditions, such as the outdoor unit of an inverter air conditioner, under high temperature and high humidity, the gap 103 is easy to be invaded by water vapor, which will corrode aluminum or copper when it is used for a long time. It will cause the pin 101 to become thinner. For some pins 101 that need to withstand high current and high voltage, heat accumulation is easy to occur in the thinned part, which accelerates the corrosion process of the pin 101 and eventually causes the pin 101 to fuse. Smart power Module 100 fails.

In addition, referring to FIG. 1(C), because the pins 101 of the traditional smart power module 100 are connected by ribs 109 during the manufacturing process, when manipulators and workers in the manufacturing process carry the smart power module 100 by clamping the pins 101 , is generally achieved by clamping two pins 101 on opposite sides. In this way, the connection between the pins 101 and the circuit wiring 108 will generate a large tensile force, which will cause loose welding. In the injection molding and forming process, it is possible Part of the pin 101 is separated from the circuit wiring, causing an open circuit, which seriously affects the process qualification rate; if the pin 101 and the circuit wiring 108 are partially separated but not completely separated, such a product is difficult to detect during the finished product test. After entering the market, after a period of use, it will cause open circuit failure, make the equipment stop working, and in severe cases, the equipment will be out of control and burn down.

Contents of the invention

The present invention aims to solve the deficiencies of the prior art, and provides a high-reliability intelligent power module and a manufacturing method of the intelligent power module with a simplified process flow, which can ensure that the intelligent power module is not damaged by static electricity during processing , so that the pins of the manufactured intelligent power module are completely sealed by the coating.

The present invention is achieved in this way. An intelligent power module includes a substrate covered with an insulating layer on the upper surface, circuit wiring arranged on the surface of the insulating layer, and circuit elements arranged at corresponding positions of the circuit wiring. The power module also includes:

pins, connected to circuit wiring and extending from the substrate, and completely covering the pins with a plating layer;

The sealing layer is laid on the upper surface of the substrate with the circuit wiring and circuit elements.

The beneficial effect of the intelligent power module of the present invention is: the pins are completely covered with plating, which greatly improves the corrosion resistance of the intelligent power module, and ensures that the pins of the intelligent power module will not burn due to local overheating during long-term use. This improves the long-term reliability of the intelligent power module and avoids safety hazards such as explosions.

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

S11: Set up a substrate, cover the upper surface of the substrate with an insulating layer, and lay out circuit wiring on the surface of the insulating layer, wherein a fuse that can be fused by a corresponding current is formed between the pads of the circuit wiring to be soldered. Pad connection;

S13: setting the pin, and forming a plating layer on the surface of the pin;

S15: Arranging circuit elements at corresponding positions of the circuit wiring, and soldering the pins to corresponding pin pads to extend from the substrate;

S17: sealing the upper surface of the substrate with the circuit wiring and circuit elements;

S19: Connecting corresponding currents between adjacent pins to fuse the bonding pads.

The beneficial effect of the manufacturing method of the present invention is: without increasing the production process and ensuring that the processing is not damaged by static electricity, the pins are independent of each other, and when the intelligent power module is picked and placed by clamping the pins, it will not be strengthened by the tradition. The existence of the ribs produces a leverage effect, which results in a huge tension between the pins and the circuit wiring, which ensures the reliable connection between the pins and the circuit wiring, further improves the reliability of the intelligent power module, and improves the yield of the intelligent power module.

Description of drawings

Fig. 1 (A) is a top view structural schematic diagram of an existing intelligent power module;

Fig. 1 (B) is the X-X' line sectional view of Fig. 1 (A);

Figure 1 (C) is a schematic diagram of the pin structure of an existing intelligent power module;

Fig. 2 (A) is a top view structural diagram of the intelligent power module provided by the embodiment of the present invention;

Fig. 2 (B) is the X-X' line sectional view of Fig. 1 (A);

Fig. 2(C) is a top view of the smart power module in Fig. 1(A) after removing the sealing layer;

Fig. 3 is a process flow chart of the manufacturing method of the intelligent power module provided by the embodiment of the present invention;

Figures 4(A) and 4(B) are the process of setting the substrate, insulating layer and circuit wiring provided by the embodiment of the present invention;

Figure 5(A) and 5(B) are the process of setting pins and their plating provided by the embodiment of the present invention;

Figure 6(A) and 6(B) are the process of arranging circuit elements and soldering pins provided by the embodiment of the present invention;

Fig. 7 is the sealing process of the intelligent power module provided by the embodiment of the present invention;

Fig. 8 is the process of fusing pad connection and module function test provided by the embodiment of the present invention;

9(A) and 9(B) are the bonding and cleaning processes of the manufacturing method of the smart power module provided by the embodiment of the present invention.

Detailed ways

In order to make the technical problems, technical solutions and beneficial effects to be solved by the present invention clearer, the present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described here are only used to explain the present invention, not to limit the present invention.

2(A), 2(B) and 2(C), the intelligent power module includes pins 11 , sealing layer 12 , circuit elements 14 , bonding wires 15 , substrate 16 , insulating layer 17 , and circuit wiring 18 .

The insulating layer 17 covers the upper surface of the substrate 16 , the circuit wiring 18 is disposed on the surface of the insulating layer 17 , and the circuit element 14 is arranged at a corresponding position of the circuit wiring 18 . The circuit wiring 18 includes element pads for arranging the circuit elements 14, lead pads 18A for soldering the pins 11, and pad connections for temporarily fixing the pitch of the pins 11 connected between the pin pads 18A. Line 18B.

The pins 11 are connected to the circuit wiring 18 and extend from the substrate 16, and are completely covered by a plating layer (not shown in the figure). The sealing layer 12 is laid on the upper surface of the substrate 16 having the circuit wiring 18 and the circuit element 14 .

Further, referring to FIG. 2(B), the circuit wiring 18 is provided with pin pads 18A for soldering the pins 11 . The pin 11 includes a bent portion 112 and an extension portion 114 connected to each other. The bent portion 112 is accommodated in the sealing layer 12, and one end of the bent portion 112 is welded to the lead pad 18A of the corresponding circuit wiring 18. The other end of the folded portion 112 is connected to the extension portion 114 . Furthermore, the extending portion 114 is L-shaped, and its long side is in contact with the bending portion 112 .

Actually, the pins 11 are fixed on the pin pads 18A provided on one edge of the substrate 16 , which have the functions of inputting and outputting with the outside. Here, a plurality of pins 11 are provided on one side, and the pins 11 and the lead pads 18A are soldered with an electrical adhesive such as solder. Pin 11 is generally made of copper and other metals. The copper surface forms a layer of nickel-tin alloy layer through electroless plating and electroplating. The thickness of the alloy layer is generally 5 μm. The plating layer can protect copper from corrosion and oxidation and improve solderability.

Further, the sealing layer 12 is laid on the upper surface and the lower surface of the substrate 16 . In other embodiments, the sealing layer 12 is provided on the upper, lower and side surfaces of the substrate 16 .

The sealing layer 12 may be molded using a thermosetting resin by transfer molding or may be molded using a thermoplastic resin by injection molding. Here, the sealing layer 12 completely seals all elements on one surface of the substrate 16 with the circuit wiring 18 ; and for smart power modules that require high compactness, the other surface of the substrate 16 without the circuit wiring 18 is generally also sealed.

The state wire 15 can be an aluminum wire, a gold wire or a copper wire, and through the bonding of the state wire 15, an electrical connection relationship is established between each circuit element 14, between each circuit wiring 18, and between the circuit element 14 and the circuit wiring 18, sometimes It is also used to establish an electrical connection relationship between the substrate 16 or the pin 11 and the circuit wiring 18 or the circuit element 14 .

The intelligent module provided by the present invention greatly improves the anti-corrosion ability of the intelligent power module by completely sealing the pin 11 with a coating, and ensures that the pin 11 of the intelligent power module will not be burned due to local overheating during long-term use. This improves the long-term reliability of the intelligent power module and avoids safety hazards such as explosions.

In addition, a manufacturing method for manufacturing the above-mentioned smart module is also provided. In a more preferred embodiment, referring to FIGS. 2(A), 2(B), 2(C) and 3, the manufacturing method includes the following steps:

Step S11: Set up the substrate 16, cover the upper surface of the substrate 16 with the insulating layer 17, and lay out the circuit wiring 18 on the surface of the insulating layer 7, wherein the circuit wiring 18 is formed between the pin pads 18A to which the pins 11 are to be soldered. Current-fuse pad connection 18B.

The first step of the manufacturing method: This step is a step of forming an insulating layer 17 on a substrate 16 having an appropriate size and forming circuit wiring 18 on the surface of the insulating layer 17 .

First, referring to FIG. 4(A) and the cross-sectional view 4(B) along the line X-X' in FIG. 4(A), design a circuit substrate 16 with a suitable size according to the required circuit layout. For general intelligent power modules, the size of one piece can be selected as 64±10mm×30±10mm, and anti-corrosion treatment is carried out on both sides. An insulating layer 17 is provided on at least one surface of the aluminum substrate. In addition, copper foil as circuit wiring 18 is pasted on the surface of insulating layer 17 . Then, the copper foil produced in this process is etched, and the copper foil is partially removed to form circuit wiring 18. Circuit wiring 18 includes element pads for arranging circuit elements 14 and lead pads 18A for soldering pins 11. and the pad connection 18B connected between the pin pads 18A for temporarily fixing the pitch of the pins 11.

Here, the substrate 16 with a suitable size is formed by directly performing gong-plate treatment on aluminum or copper materials of 2±1m×2±1m. The gong knife is made of high-speed steel, and the motor uses a speed of 5000 rpm. , the gong knife is cut at right angles to the plane of the plate; it can also be formed by stamping.

S13: setting the pin, and forming a plating layer on the surface of the pin.

As the second process of the manufacturing method: refer to FIG. 5(A) and FIG. 5(B): this process is a process of making an independent pin 11 with plating.

Each pin 11 is made of copper or aluminum base material, and made into a long strip with a length C of 25±10mm, a width K of 1.5±0.5mm, and a thickness H of 1±0.5mm, as shown in Figure 5(A) Show.

Here, preferably, as shown in FIG. 5(B) for ease of assembly, the step 15 includes step S151: after the pin 11 is bent, one side end of the bent part (that is, the above-mentioned bent part 112 ) is Solder it on the pin pad 18A, and accommodate the bent part of the pin 11 in the sealing layer 12, that is, press a certain arc on one end of the pin 11.

Then, a plating layer is formed on the surface of the pin 11 by electroless plating. Through the mixed solution of nickel salt and sodium hypophosphite, and adding an appropriate complexing agent, a nickel layer is formed on the surface of the copper material that has formed a specific shape. The metal nickel has a strong passivation ability and can quickly form a layer of electrode. Thin passivation film, resistant to corrosion by atmosphere, alkali and some acids. The crystals of nickel plating are very small, and the thickness of nickel layer is generally 0.1±0.01μm;

Then, through the acid sulfate process, at room temperature, the copper material with the formed shape and nickel layer is immersed in the plating solution with positive tin ions and energized, and a nickel-tin alloy layer is formed on the surface of the nickel layer. The thickness of the nickel layer is generally controlled at 5 ±1μm, the formation of nickel layer greatly improves the protection and solderability. So far, pin 11 is manufactured.

S15 : arrange the circuit element 14 at the corresponding position of the circuit wiring 18 , and weld the pin 11 on the corresponding pin pad 18A to make it extend from the substrate 16 . Specifically, the circuit element 14 is arranged on the element pad of the circuit wiring 18 .

As the third step of the manufacturing method: referring to FIG. 6(A) and FIG. 6(B), this step is a step of mounting circuit elements 14 and pins 11 on the surface of circuit wiring 18 .

In one embodiment, firstly, a solder paste printing machine is used to coat a specific position of the circuit wiring 18 of the substrate 16 with a stencil, and the thickness of the stencil can be 0.13±0.03 mm.

Secondly, referring to the side view Figure 6(A) and the top view Figure 6(B), the installation of the circuit element 14 and the pin 11 is carried out. The circuit element 14 can be directly placed on a specific position of the circuit wiring 18, and one end of the pin 11 needs to be It is placed on the pin pad 18A, and the other end needs to be fixed by a carrier 20, and the carrier 20 is made of synthetic stone and other materials.

Then, the substrate 16 placed on the carrier 20 undergoes reflow soldering, the solder paste is solidified, and the circuit elements 14 and the pins 11 are fixed.

S17: The substrate 16 is provided with a sealing layer on the upper surface of the circuit wiring 18 and the circuit element 14 .

The fourth step of the manufacturing method: with reference to FIG. 7 , the step of laying the sealing layer 12 on the circuit board 16 will be described. FIG. 7 is a cross-sectional view showing a step of sealing the circuit board 16 with the sealing layer 12 using the mold 50 .

Further, step S18 : laying a sealing layer on the lower surface of the substrate 15 .

Firstly, the substrate 16 is baked in an oxygen-free environment, the baking time should not be less than 2 hours, and the baking temperature is selected to be around 125°C.

The circuit board 16 on which the pins 11 are arranged is transferred to the molds 44 and 45 . The positioning of the substrate 16 is performed by bringing the bent portion of the lead 11 into contact with the fixture 46 .

When closing the mold, the substrate 16 is placed in the cavity formed inside the mold 50 , and then the sealing resin is injected through the gate 53 . A method of sealing may employ transfer molding using a thermosetting resin or injection molding using a thermosetting resin. Also, the gas corresponding to the inside of the sealing resin cavity injected from the gate 53 is discharged to the outside through the exhaust port 54 .

Step S18 : Connect corresponding currents between adjacent pins 11 to fuse the pad connection 18B.

As the fifth process of the manufacturing method: referring to FIG. 8 , it is the process of forming the pins 11, fusing the pad connection 18B and testing the module function. The intelligent power module is completed as a product through this process.

In this process, the outer pin 11 is bent into a certain shape at the position of the dotted line 51 according to the length and shape of the pin 11 to facilitate subsequent assembly. And this process can also be completed in step S153 in step 15, step S153: fold the extension part of the lead into an L shape, and its long side is connected with the bent part.

Then put the intelligent power module into the test equipment, and pass a certain amount of current for adjacent pins 11. For example, according to the size of the pad connection 18B of this embodiment, the current value can be set to 0.35A, when the current from The sudden decrease of 0.35A proves that the pad connection 18B has been fused. After the pad connection 18B has been fused, conduct conventional electrical parameter tests, generally including insulation withstand voltage, static power consumption, delay time and other test items, and those who pass the test for the finished product.

It can be understood that the fourth process, that is, prior to step S17 , also includes the process of connecting the bonding wire 15 and cleaning the substrate 16 .

Referring to Fig. 9(A) and Fig. 9(B), electrical connections are established between the circuit elements 14, between the circuit wirings 18, between the circuit elements 14 and the circuit wiring 18, and sometimes It is used to establish an electrical connection relationship between the substrate 16 or the pin 11 and the circuit wiring 18 or the circuit element 14 . Bond wire 15 can be aluminum wire, gold wire or copper wire.

First, put the substrate 16 into a cleaning machine for cleaning, and clean the residual flux such as rosin during reflow soldering and the foreign matter such as aluminum wire remaining during stamping. According to the arrangement density of the circuit components 14 on the circuit wiring 18, cleaning can Spray or ultrasonic or a combination of both. When cleaning, two or more pins 11 are clamped by the mechanical arm, and the substrate 16 is placed in the cleaning tank, because the pins 11 are independent of each other and there is no reinforcing rib connected to each other, even if the mechanical arm clamps each pin The strength is uneven, and the vibration during the cleaning process will not generate force transmission between the pins, causing some of the pins 11 to separate from the pad 18A.

Secondly, an electrical connection is formed by bonding a metal wire of a certain diameter at a specific position of the circuit element 14 and the circuit wiring 18. Comprehensive considerations such as processability, generally, the diameter of a single metal wire should not be greater than 400 μm, and should not be less than 15 μm. For the connection of power devices, multiple 400 μm aluminum wires can be used in parallel. For the connection of functional devices, Consider using a single 38μm aluminum wire for bonding.

It can be understood that, in the actual operation or other embodiments of the above-mentioned manufacturing method, the labels S11, S13, S15, S17, and S19 are only set for the convenience of describing the specific implementation, but in fact the order of the steps S11 to S19 can be according to Changes are required.

Therefore, through the above-mentioned manufacturing method, without increasing the production process and ensuring that the processing is not damaged by static electricity, the pins 11 are independent of each other, and the intelligent power module will not be strengthened by the traditional The presence of the ribs produces a leverage effect that causes a huge tension between the pin 11 and the circuit wiring 18, ensuring a reliable connection between the pin 11 and the circuit wiring 18, further improving the reliability of the intelligent power module, and improving the reliability of the intelligent power module. yield rate.

The above descriptions are only preferred embodiments of the present invention, and are not intended to limit the present invention. Any modifications, equivalent replacements and improvements made within the spirit and principles of the present invention should be included in the protection of the present invention. within range.

Claims (8)

1. An intelligent power module, comprising a substrate covered with an insulating layer on the upper surface, circuit wiring arranged on the surface of the insulating layer, and circuit elements arranged at corresponding positions of the circuit wiring, characterized in that the intelligent power Modules also include: pins, connected to circuit wiring and extending from the substrate, and completely covering the pins with a plating layer; The sealing layer is laid on the upper surface of the substrate with the circuit wiring and circuit elements. 2. The intelligent power module according to claim 1, wherein the pins include a bent portion and an extension portion connected to each other, the bent portion is accommodated in the sealing layer, and one end of the pin is welded The other end of the pin pad on the circuit wiring is in contact with the extension part. 3 . The intelligent power module according to claim 2 , wherein the extension part is L-shaped, and its long side is in contact with the bent part. 4 . 4. The intelligent power module according to claim 1 or 2, wherein the sealing layer is laid on both the upper surface and the lower surface of the substrate. 5. A method for manufacturing an intelligent power module, comprising the following steps: S11: Set up a substrate, cover the upper surface of the substrate with an insulating layer, and lay out circuit wiring on the surface of the insulating layer, wherein a fuse that can be fused by a corresponding current is formed between the pads of the circuit wiring to be soldered. Pad connection; S13: setting the pin, and forming a plating layer on the surface of the pin; S15: Arranging circuit elements at corresponding positions of the circuit wiring, and soldering the pins to corresponding pin pads to extend from the substrate; S17: sealing the upper surface of the substrate with the circuit wiring and circuit elements; S19: Connecting corresponding currents between adjacent pins to fuse the bonding pads. 6. The method for manufacturing an intelligent power module according to claim 5, wherein the step S15 comprises: Step S151 : after the lead is bent, one end of the bent portion is welded to the pad of the lead, and the bent portion of the lead is accommodated in the sealing layer. 7. The method for manufacturing an intelligent power module according to claim 6, wherein the step 14 further comprises: Step S153: Fold the extension part of the pin into an L shape, and its long side is connected with the bent part. 8. The method for manufacturing an intelligent power module according to claim 5, further comprising: after the step S17: Step S18: laying a sealing layer on the lower surface of the substrate.