CN106024651A - Intelligent power module and manufacturing method thereof - Google Patents

Abstract

An intelligent power module and its manufacturing method. The intelligent power module includes: a circuit wiring layer as a carrier, the circuit wiring layer has an upper surface and a lower surface opposite to the upper surface; it is reversed and welded to the circuit wiring layer A circuit element at a predetermined position on the upper surface of the circuit element; a radiator mounted on a power element in the circuit element; and a circuit element covering the upper surface of the circuit wiring layer and the circuit element, and exposing part of the surface of the radiator Sealing layer. The metal substrate is no longer needed, and the circuit wiring layer is fixed by a reusable bottom plate for processing, and the final fixation is done by resin, and the metal bonding wire is no longer required, which saves costs, and the back of the circuit wiring and the heat sink are completely exposed to the outside of the resin. The heat dissipation effect is maximized, the gap between the circuit wiring is completely exposed, and it is difficult for moisture to adhere. Moreover, even if external moisture invades in, it is difficult to cause corrosion because there are no metal wires.

Description

An intelligent power module and its manufacturing method

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 (IPM) is a power drive product that combines power electronics and integrated circuit technology. IPM integrates power switching devices and high-voltage drive circuits, and has built-in fault detection circuits such as overvoltage, overcurrent and overheating. On the one hand, the IPM receives the control signal from the MCU to drive the subsequent circuits to work, and on the other hand, sends the system status detection signal back to the MCU. Compared with the traditional discrete solution, IPM 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. An ideal power electronic device for electric traction, servo drive, and frequency conversion home appliances.

Smart power modules generally work in harsh working conditions, such as the outdoor unit of an inverter air conditioner, under high temperature and high humidity conditions, high temperature will increase the internal temperature of the smart power module, and the current smart power module is completely sealed by the sealing resin The structure of the intelligent power module is very easy to generate heat accumulation inside the intelligent power module. High humidity will cause water vapor to enter the internal circuit of the intelligent power module through the gap between the sealing resin and the pins. The high temperature inside the intelligent power module makes Ions, especially chloride ions and bromide ions, migrate under the action of water vapor and corrode metal wires. This corrosion often occurs at the joints between metal wires and circuit components or metal wires and the circuit wiring, resulting in open circuits. It will cause fatal damage to the intelligent power module, and in severe cases, it will cause an out-of-control explosion accident of the intelligent power module, causing damage to its application environment and causing major economic losses.

In addition, smart power modules have devices with different powers. For devices with different powers, the material and thickness of metal wires are different, which increases the processing difficulty of smart power modules. Purchasing different state wire equipment also increases processing costs. The combination of various wire-bang processes makes the manufacturing pass rate of the intelligent power module lower, and it is difficult to improve the production yield. Ultimately, the cost of the intelligent power module remains high, which affects the popularization and application of the intelligent power module.

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 process flow adapted to this 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 in this way, an intelligent power module, comprising:

A circuit wiring layer as a carrier, the circuit wiring layer having an upper surface and a lower surface opposite to the upper surface;

Undercut and soldered to the circuit element at a predetermined position on the upper surface of the circuit wiring layer;

heat sinks for power components mounted in said circuit components; and

A sealing layer that covers the upper surface of the circuit wiring layer and the circuit elements and exposes the surface of the heat sink part.

Further, pins are also included, and the circuit wiring layer includes pin pads close to the edge, and the pins are connected to the pin pads and extend outside the circuit wiring.

Further, the surface of the pin is covered with plating.

Further, the power element is a planar power device.

Further, the heat sink is a heat sink.

Further, the sealing layer is a resin layer.

The beneficial effects of the above-mentioned intelligent power module are: no metal base plate is needed, the circuit wiring layer is fixed by the reusable base plate for processing, and the final fixation is performed by resin, the metal bonding wire is no longer required, and the cost is saved, and the circuit wiring layer is fixed on the back The heat sink and the heat sink are completely exposed outside the resin to maximize the heat dissipation effect. The gap between the circuit wiring is completely exposed, and it is difficult for moisture to adhere. Moreover, even if the external moisture invades in, it is difficult to cause corrosion because there are no metal wires.

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

Utilize the metal plate to make the circuit wiring layer as the carrier;

Installing circuit elements on the surface of the circuit wiring layer, wherein the circuit elements are assembled in an inverted manner;

Mounting a radiator on the power element in the circuit element;

A sealing layer is coated on the surface of the circuit wiring layer to cover the circuit elements and expose at least part of the surface of the radiator.

The beneficial effect of the manufacturing method of the above-mentioned intelligent power module is that the process of making the substrate and the insulating layer on it is eliminated, and the positioning is performed through the base, which reduces the difficulty of positioning during plastic sealing, and the bottom is completely exposed, reducing the difference in thickness between the upper and lower surfaces when injecting glue. For the difficulty of parameter control, metal wire bonding and cleaning processes are eliminated, equipment investment is saved, production efficiency is improved, process control requirements are reduced, the difficulty of manufacturing intelligent power modules is greatly reduced, and the manufacturing yield is improved. Reduced cost of intelligent power modules.

Description of drawings

FIG. 1(A) is a top view of an intelligent power module provided by an embodiment of the present invention;

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

Fig. 1 (C) is a top view of the intelligent power module of the present invention after removing the sealing layer;

FIG. 1(D) is a top view of the lower surface of the intelligent power module of the present invention;

FIG. 2 is a flow chart of the manufacturing process of the intelligent power module provided by the embodiment of the present invention;

3(A) and 3(B) are schematic diagrams of top and side view processes for making circuit wiring in the manufacturing method of the smart power module of the present invention, respectively;

Fig. 4 (A) is the size marking diagram of the pin;

Fig. 4 (B) is the schematic diagram of the procedure of making pin;

Figure 5 is a schematic diagram of the process of mounting on the heat sink at the bottom of the power element

Figure 6(A) is a schematic diagram of the process of configuring circuit wiring on the base;

6(B) and 6(C) are schematic diagrams of the side view and top view process of assembling circuit components and pins, respectively;

7 is a schematic diagram of the sealing process of the manufacturing method of the intelligent power module;

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

FIG. 9 is a process flowchart of a manufacturing method of an intelligent power module.

detailed description

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.

As shown in Figure 1(A), Figure 1(B), Figure 1(C), and Figure 1(D), the intelligent power module includes a circuit composed of a circuit wiring layer (circuit wiring) 18, a circuit element 14, and a heat sink 15 , and the pins 11 disposed on the edge of the circuit wiring layer 18, and the sealing layer 12 that seals the circuit and completely covers the upper surface of the circuit elements 14 and the circuit wiring 18. Wherein, Fig. 1(A) is a top view of the upper surface of the intelligent power module 10 of the present invention, and the heat sink 15 is exposed from the upper surface, and Fig. 1(B) is a cross section along the XX' line of Fig. 1(A) Figure 1 (C) is a top view after removing the sealing layer 12 covering the circuit element 14, and Fig. 1 (D) is a top view of the lower surface of the intelligent power module 10 of the present invention, and the circuit wiring 18 is viewed from below The surface is exposed.

Specifically, the circuit wiring layer 18 is used as the carrier of the intelligent power module 10, and the circuit wiring layer 18 has an upper surface and a lower surface opposite to the upper surface; the circuit element 14 is reversed and welded on the circuit wiring layer 18 Predetermined position on the surface; the heat sink 15 is attached to the power element in the circuit element 14; the sealing layer 12 covers the upper surface of the circuit wiring layer 18 and the circuit element 18, and exposes part of the surface of the heat sink 15 .

Specifically, the power element is a planar power device, such as an IGBT tube, and LIGBT must be used. The heat sink 15 is a heat sink, and the surface of the heat sink can be considered to be electroplated with silver to increase the wetness. The sealing layer 12 is a sealing 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 called the pin pad 18A. The pin 11 is connected to and extends from the circuit wiring 18 to the pin pad 18A. The surface of the pin 11 is covered with plating.

Each of these constituent elements will be described below.

The circuit wiring 18 is made of a copper material with a thickness of more than 5 ounces by stamping or etching. In order to prevent oxidation, the upper surface of the circuit wiring 18 can be gold-plated. For cost, the upper surface of the circuit wiring 18 The surface can also be silver-plated, or shipped in vacuum or nitrogen-filled packaging with the upper surface untreated.

The circuit element 14 is flip-chip fixed on the circuit wiring 18 . The circuit element 14 is an active element such as a transistor or a diode, or a passive element such as a capacitor or a resistor. In addition, the heat sink 15 made of copper or the like is mounted on the back surface of components that generate a large amount of heat, such as power components.

Here, it is designed that a plurality of pins 11 are provided on one side, for example, for input and output with the outside. The pin 11 and the pin pad 18A are soldered with a conductive 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.

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 side of the circuit wiring 18, and wraps most of the depth of the circuit wiring 18, only exposing a small part of the lower surface 18B of the circuit wiring, and the depth of the lower surface 18B of the circuit wiring is Generally, it can be considered to be designed to be about 0.5 ounces. If the depth of the lower surface 18B of the circuit wiring is too small, it may cause the intelligent power module 10 of the present invention to be difficult to be wrapped by solder such as solder paste during the subsequent welding and fixing process. If the depth of the lower surface 18B of the circuit wiring is too deep If it is too large, it may cause the solder paste height to not completely cover the circuit wiring lower surface 18B during the subsequent welding and fixing process of the intelligent power module 10 of the present invention; here, the heat sink 15 is exposed from the sealing layer 12, so that The heat of the power components is quickly dissipated.

The beneficial effects of the intelligent power module are: no metal base plate is needed, the circuit wiring layer is fixed by the reusable base plate for processing, the final fixation is done by resin, the metal bonding wire is no longer needed, the cost is saved, and the circuit wiring backside and The heat sink is completely exposed to the outside of the resin to maximize the heat dissipation effect. The gap between the circuit wiring is completely exposed, and it is difficult for moisture to adhere. Moreover, even if the external moisture invades in, it is difficult to cause corrosion because there are no metal wires.

Referring to Fig. 2, the manufacturing method of the intelligent power module is illustrated, including the following steps:

Step S110, using a metal plate to make a circuit wiring layer as a carrier;

Step S120, assembling circuit elements on the surface of the circuit wiring layer, wherein the circuit elements are assembled in an upside-down manner;

Step S120, mounting a radiator on the power element in the circuit element;

Step S140 , covering the surface of the circuit wiring layer with a sealing layer, covering the circuit elements and exposing at least part of the surface of the radiator.

Step S140 specifically includes: setting a thermosetting resin frame around the surface of the circuit wiring layer; injecting thermoplastic resin into the range of the thermosetting resin frame to seal the circuit wiring layer and circuit elements.

Before the step S120, it also includes: a step of making independent pins with plating. This step specifically includes: selecting a copper base material, forming a row of pins on the copper base material by punching or etching, and connecting the pins through reinforcing ribs; forming a nickel layer and nickel-tin layer on the surface of the pins in sequence Alloy layer to get plated pins.

Before the step S140, the following step is also included: removing the soldering flux remaining on the insulating layer.

Positioning through the base reduces the difficulty of positioning during plastic sealing, and the bottom is completely exposed, which reduces the difficulty of parameter control due to the difference in thickness between the upper and lower surfaces during glue injection. Production efficiency reduces the requirements for process control, greatly reduces the difficulty of manufacturing smart power modules, improves the manufacturing yield, and further reduces the cost of smart power modules.

In a more specific embodiment, referring to FIG. 3(A) to FIG. 9 , the manufacturing method of the smart power module includes the following steps.

The first process, with reference to Figure 3 (A) and 3 (B):

The first step of the present invention is a characteristic step of the present invention, and this step is a step of forming circuit wiring on a copper substrate having an appropriate size.

First, refer to Figure 3(A) and the cross-sectional view 3(B) along the XX' line of Figure 3(A), according to the required circuit layout design, for general intelligent power modules, the circuit layout should not be greater than 64mm× 30mm. Manufacture a suitable stamping die to punch out a specific shape. It is also possible to use high-speed steel as the material through the gong knife, and the motor uses a rotating speed of 5000 rpm. The gong knife and the aluminum plane are at right angles to the specific shape of the knife stroke. Specific shapes can also be etched through chemical reactions with etching tools.

Here, this specific shape is the circuit wiring 18 .

In occasions where the anti-oxidation requirement is very high, a gold layer can 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 not be less than 5 ounces to ensure a larger contact area with the subsequent resin 12, so that the finished product of the intelligent power module 10 has a stronger fixation. Effect.

The second process, referring to Figure 4(A) and Figure 4(B):

The second step of the present invention is a characteristic step of the present invention, and this step is a step of forming an independent plated pin 11 .

Each pin 11 is all to use copper base material, makes length C be 25mm, and width K is 1.5mm, and thickness H is the elongated shape of 1mm, as shown in Figure 4 (A); Here, for ease of assembly, A certain arc is pressed at one end, as shown in Figure 4(B);

Then the nickel layer is formed 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, and the metal nickel has a strong Passivation ability, can quickly form an extremely thin passivation film, which can resist the corrosion of atmosphere, alkali and some acids. The crystals of nickel plating are very small, and the thickness of nickel layer is generally 0.1μm;

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

So far, the manufacturing of the pin 11 is completed.

Here, the pins 11 of the present invention are individual pins, which are different from the entire row of pins in the prior art, because the circuit wiring 18 on which the pins 11 are fixed is only partially wrapped and fixed by resin , the impact strength is limited, and the single pin avoids the process of cutting the reinforcing rib, which can reduce the systemic impact on the intelligent power module 10 of the present invention.

The third process, refer to Figure 5:

The third step of the present invention is a characteristic step of the present invention. This step is to manufacture the heat sink 15 and mount the bottom of the L-shaped power element 14 on the heat sink 15 .

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

Then, through the eutectic process, the back of the L-shaped power element 14 is mounted on the heat sink 15 with a high-temperature solder paste with a melting point above 300° C., which may be considered to be Tamura brand. Here, the L-shaped power device 14 is a planar power device, and all electrodes of this power device are located on the front side of the power device, and the electrodes on the front side are connected to the circuit wiring 18 in the following process.

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

The fourth process, with reference to Figures 6(A), 6(B) and 6(C):

The third process of the present invention is a process that is characteristic of the present invention. In this process, the circuit wiring 18 is arranged on the base plate 16, and the circuit element 14 and the pins 11 are arranged on the surface of the circuit wiring 18. process.

First, make the base plate 16 as shown in FIG. 6(A), the base plate 16 can be made of high-strength stainless steel, and on the surface of the base plate 16, there are recesses 17 dug out according to the shape of the circuit wiring 18, The width of the recess 17 is slightly larger than that of the corresponding circuit wiring 18, and the depth of the recess 17 is about 0.5 ounces.

Next, referring to the side view FIG. 6(B) and the top view FIG. 6(C), the prepared circuit wiring 18 is placed in the corresponding depression of the bottom plate 16, and is passed through a solder paste printing machine, using a steel mesh, for The specific position of the circuit wiring 18 is coated with solder paste, and the thickness of the stencil can be 0.13 mm. Through equipment such as SMT machine or DA machine, carry out circuit element 14, comprise the circuit element 14 that has configured described radiator 15, and the installation of pin 11, described circuit element 14 can be directly flip-chip on described circuit wiring 18 A specific position, while one end of the pin 11 should be placed on the 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 base plate 16 placed on the carrier 20 is reflowed, the solder paste is solidified, and the circuit elements 14 and the pins 11 are fixed.

The fifth process, refer to Figure 7:

The fifth step of the present invention is a characteristic step of the present invention. Referring to FIG. 7 , this step is a step of sealing the circuit wiring 18 with the sealing resin 12 . 7 is a cross-sectional view showing a step of sealing the circuit wiring 18 carried by the base plate 16 with a sealing resin using a mold 50 .

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

The base plate 16 on which the circuit wiring 18 is arranged is conveyed to the molds 44 and 45 . The positioning of the circuit substrate 16 is performed by bringing specific portions of the pins 11 into contact with the fixing means 46 .

When closing the mold, the bottom plate 16 is placed in the mold cavity formed inside the mold 50 , and then the sealing resin is injected through the gate 53 to form the sealing layer 12 . A method of performing sealing may employ transfer molding using a thermosetting resin or injection molding using a thermosetting resin. Also, the gas inside the cavity corresponding to the sealing resin 12 injected from the gate 53 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 bottom plate 16 .

The sixth process, refer to Figure 8:

The sixth process of the present invention is the process of forming the pin 11 and testing the module function, and the intelligent power module is completed as a product through this process.

The parts other than the lead 11 are sealed with the resin 12 in the previous process, that is, the transfer molding process. In this process, according to the length and shape required, for example, the external pin 11 is bent into a certain shape at the position of the dotted line 51 to facilitate subsequent assembly.

Then put the module into the test equipment and conduct conventional electrical parameter tests. Because the pins 11 are independent of each other, some pins may not be on the same level after molding, which will affect the contact. Therefore, it is generally necessary to test the golden finger of the machine first The contact test with the pin, if the contact test fails, the pin 11 needs to be trimmed until the contact test is passed, and then the electrical characteristic test, including insulation withstand voltage, static power consumption, delay time, etc. Items that pass the test are finished products.

Through the above steps, the smart power module 10 shown in FIG. 2 is completed.

The above 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 scope of the present invention. Inside.

Claims (10)

1. a SPM, it is characterised in that including:

As the circuit-wiring layer of carrier, described circuit-wiring layer has upper surface and relative with this upper surface Lower surface；

Back-off is also welded in the component in upper surface precalculated position of described circuit-wiring layer；

The radiator of the power component being mounted in described component；And

Cover the upper surface of described circuit-wiring layer and described component, and make described heat sink part surface Exposed sealant.

2. SPM as claimed in claim 1, it is characterised in that also include pin, described electricity Road wiring layer includes that, by antermarginal pin pad, described pin is connected and from described electricity with described pin pad Road wiring is outer to be extended.

3. SPM as claimed in claim 2, it is characterised in that described pin surface is coated with Coating.

4. SPM as claimed in claim 1, it is characterised in that described power component is plane Power device.

5. SPM as claimed in claim 1, it is characterised in that described radiator is fin.

6. SPM as claimed in claim 1, it is characterised in that described sealant is resin bed.

7. the manufacture method of a SPM, it is characterised in that comprise the following steps:

Sheet metal is utilized to make the circuit-wiring layer as carrier；

In the surface-mounted component of described circuit-wiring layer, wherein, described component is with the side of back-off Formula is assembled；

Radiator is mounted on power component in described component；

In the Surface coating sealant of described circuit-wiring layer, described component is covered and makes described heat radiation At least part of surface exposure of device.

8. the manufacture method of SPM as claimed in claim 7, it is characterised in that be set forth in The Surface coating sealant of described circuit-wiring layer, covers described component and makes described heat sink part The sealant step of surface exposure particularly as follows:

It is arranged around thermosetting resin frame on the surface of described circuit-wiring layer；

Thermoplastic resin is injected to seal described circuit-wiring layer and electricity in the range of described thermosetting resin frame Circuit component.

9. the manufacture method of SPM as claimed in claim 7, it is characterised in that be set forth in Also include before the surface-mounted component step of described circuit-wiring layer:

Make the pin of independent band coating；Specifically include:

Choose Copper base material, to Copper base material by the way of punching press or etching, make pin in a row, between pin Connected by reinforcement；

Sequentially form nickel dam and nickeltin layer at described pin surface, obtain the pin of band coating；

Described pin is welded on the pin pad at described circuit-wiring layer edge by Reflow Soldering.

10. the manufacture method of SPM as claimed in claim 7, it is characterised in that described In the Surface coating sealant of described circuit-wiring layer, described component is covered and makes described radiator extremely Before the step of the sealant of small part surface exposure further comprising the steps of:

Remove the scaling powder remaining in described insulating barrier.