阅读说明：本技术 一种低应力高导热功率器件的塑封工艺 (Plastic packaging process for low-stress high-thermal-conductivity device ) 是由 李科 蔡少峰 陈凤甫 邓波 李力 贺勇 蒲俊德 杨红伟 于 2020-01-02 设计创作，主要内容包括：本发明提供了一种低应力高导热功率器件的塑封工艺。所述工艺包括以下步骤：将塑封料在下进行预热；其中,塑封料包括按照质量百分比计的：17～19%环氧树脂、9～12%的硬化剂、1%以下的蜡,6～7%的应力释放剂,1～1.5%的阻燃剂,0.2～0.4%的着色剂,余量为填料；将预热后的塑封料注入到固定有功率器件的模具以对功率器件进行塑封；塑封结束后,使封装好的功率器件与模具分离。本发明的有益效果可包括：本发明能够降低功率器件对环氧塑封料的耗量,能够缩短生产工时,提高产品性价比。同时本发明能够降低产品应力、提高导热能力和产品可靠性。(The invention provides a plastic package process of a low-stress high-thermal-conductivity device. The process comprises the following steps: preheating the plastic packaging material; the plastic packaging material comprises the following components in percentage by mass: 17-19% of epoxy resin, 9-12% of a hardening agent, less than 1% of wax, 6-7% of a stress release agent, 1-1.5% of a flame retardant, 0.2-0.4% of a coloring agent and the balance of a filler; injecting the preheated plastic packaging material into a die fixed with a power device to carry out plastic packaging on the power device; and after the plastic package is finished, separating the packaged power device from the mold. The beneficial effects of the invention can include: the invention can reduce the consumption of the power device to the epoxy plastic package material, shorten the production working hour and improve the cost performance of the product. Meanwhile, the invention can reduce the stress of the product and improve the heat conducting capability and the reliability of the product.)

1. A plastic package process of a low-stress high-thermal-conductivity device is characterized by comprising the following steps:

preheating the plastic packaging material; the plastic packaging material comprises the following components in percentage by mass: 17-19% of epoxy resin, 9-12% of hardening agent, less than 1% of wax, 6-7% of stress release agent, 1-1.5% of flame retardant, 0.2-0.4% of colorant and the balance of filler;

injecting the preheated plastic packaging material into a die fixed with a power device to carry out plastic packaging on the power device;

and after the plastic package is finished, separating the packaged power device from the mold.

2. The plastic packaging process for the low-stress high-thermal-conductivity device according to claim 1, wherein in the plastic packaging process, the mold temperature is 160-180 ℃, and the injection pressure is 30-50 kg/cm ²The mold clamping pressure is 200-250T, the injection molding time is 35-55 s, and the curing time is 80-100 s.

3. A plastic package process for a low-stress high-thermal-conductivity device according to claim 2, wherein the mold comprises 240-320 molding cavities, and each molding cavity has a length of 9.5-10.2 mm, a width of 9-10 mm and a height of 4.5-5 mm.

4. A plastic package process for a low-stress high-thermal-conductivity device according to claim 3, wherein the mold comprises 1 main runner and 6-8 branch runners branching from an outlet end of the main runner, the branch runners can be communicated with the molding cavity, wherein,

the width of the main runner is 3.5-3.8 mm, the depth is 2-3 mm, and the length is 220-245 mm;

the width of the sub-runner is 1.8-2.1 mm, the depth is 2-3 mm, and the length is 65-75 mm.

5. The plastic packaging process for the low-stress high-thermal-conductivity device according to claim 2, wherein the single-mode dosage of the plastic packaging material is 210-300 g.

6. The plastic packaging process for the low-stress high-thermal-conductivity device according to claim 1 or 2, wherein the density of the plastic packaging material is 0.001-0.0015 g/mm ³The particle size is 20-50 mm.

7. The plastic packaging process for low-stress high-thermal-conductivity device according to claim 6, wherein the plastic packaging process is characterized in thatThe bending strength of the sealing material is more than or equal to 10kgf/mm ²A flexural modulus of elasticity of 1150 to 1750 kgf/mm ²Thermal conductivity of not less than 15X 10 ^-4cal/cm sec DEG C, coefficient of thermal expansion less than or equal to 2.5 x 10 ^-5。

8. A process for plastic packaging of low stress high thermal conductivity devices according to claim 1, wherein the process further comprises:

before preheating the plastic packaging material, the plastic packaging material is subjected to material standing at the temperature of 20-30 ℃ and the RH of 40-60%.

9. The plastic package process for the low-stress high-thermal-conductivity device according to claim 1, wherein the preheating temperature is 80-100 ℃ and the preheating time is 16-24 s.

10. A process for plastic encapsulation of a low stress high thermal conductivity device according to claim 1, wherein the process further comprises the steps of:

and carrying out layered detection and thermal resistance detection on the packaged power device, wherein the layered detection comprises the following steps: and detecting whether the chip and the plastic package body are layered or not, and detecting whether the frame and the plastic package body are layered or not.

Technical Field

The invention relates to the technical field of semiconductor packaging, in particular to a plastic packaging process of a low-stress high-thermal-conductivity device.

Background

The plastic package is to protect the carrier, the chip and the bonded product by epoxy resin, so that the carrier, the chip and the bonded product are prevented from being polluted and corroded by moisture, paper, impurities, various chemical liquid medicines and the like in the atmosphere, and are also prevented from being influenced by external mechanical stress, internal heat generated by power consumption of the power device during working is effectively removed, and the power device or an integrated circuit can stably exert normal electrical functions.

With the development of ultra-thin electronic products, the requirement for smaller and smaller packages and higher power density of corresponding integrated circuits and power devices is increasing, so that the trend of replacing the plug-in with the patch in the large and small chip packages is inevitable. The large chip, the small chip and the chip products have higher requirements on stress and heat conduction of devices, and the stress and the heat conduction are mainly concentrated in the plastic packaging process.

Disclosure of Invention

In view of the deficiencies in the prior art, it is an object of the present invention to address one or more of the problems in the prior art as set forth above. For example, one of the objectives of the present invention is to provide a method for implementing a low-stress high-thermal-conductivity plastic package process.

In order to achieve the purpose, the invention provides a method for realizing a low-stress high-heat-conductivity plastic package process. The implementation method can comprise the following steps: preheating the plastic packaging material; the plastic package material comprises the following components in percentage by mass: 17-19% of epoxy resin, 9-12% of hardening agent, less than 1% of wax, 6-7% of stress release agent, 1-1.5% of flame retardant, 0.2-0.4% of colorant and the balance of filler; injecting the preheated plastic packaging material into a die fixed with a power device to carry out plastic packaging on the power device; and after the plastic package is finished, separating the packaged power device from the mold.

According to an exemplary embodiment of the present invention, in the plastic-sealing process, the mold temperature may be 160 to 180 ℃, and the injection pressure may be 30 to 50kg/cm ²The mold clamping pressure can be 200-250T, the injection molding time can be 35-55 s, and the curing time can be 80-100 s.

According to an exemplary embodiment of the present invention, the mold may include 240 to 320 molding cavities, each of which may have a length of 9.5 to 10.2mm, a width of 9 to 10mm, and a height of 4.5 to 5 mm.

According to an exemplary embodiment of the present invention, the mold may include 1 main runner, and 6 to 8 branch runners branched from an outlet end of the main runner, the branch runners being capable of communicating with the molding cavity, wherein the main runner may have a width of 3.5 to 3.8mm, a depth of 2 to 3mm, and a length of 220 to 245 mm; the width of the sub-runners can be 1.8-2.1 mm, the depth can be 2-3 mm, and the length can be 65-75 mm.

According to an exemplary embodiment of the invention, the single-mode dosage of the molding compound may be 210-300 g.

According to an exemplary embodiment of the present invention, the density of the molding compound may be 0.001 to 0.0015g/mm ³The particle size may be 20 to 50 mm.

According to one example of the present inventionIn the exemplary embodiment, the flexural strength of the molding compound can be more than or equal to 10kgf/mm ²The flexural modulus of elasticity may be 1150 to 1750 kgf/mm ²The thermal conductivity can be more than or equal to 15 multiplied by 10 ^-4cal/cm sec DEG C, the coefficient of thermal expansion can be less than or equal to 2.5 multiplied by 10 ^-5。

According to an exemplary embodiment of the present invention, the process may further include: before preheating the plastic packaging material, the plastic packaging material is subjected to material standing at the temperature of 20-30 ℃ and the RH of 40-60%.

According to an exemplary embodiment of the present invention, the preheating temperature may be 80-100 ℃ and the time may be 16-24 seconds.

According to an exemplary embodiment of the present invention, the method may further comprise the steps of: and carrying out layered detection and thermal resistance detection on the packaged power device, wherein the layered detection comprises the following steps: and detecting whether the chip and the plastic package body are layered or not, and detecting whether the frame and the plastic package body are layered or not.

Compared with the prior art, the beneficial effects of the invention can include: the invention can reduce the consumption of the power device to the epoxy plastic package material, shorten the production working hour and improve the cost performance of the product. Meanwhile, the invention can reduce the stress of the product and improve the heat conducting capability and the reliability of the product.

Detailed Description

Hereinafter, a mold-packaging process of the low-stress high-thermal-power device of the present invention will be described in detail with reference to exemplary embodiments.

In an exemplary embodiment of the present invention, the plastic packaging process of the low-stress high-thermal-conductivity device may include the following steps:

s01: preheating the plastic packaging material at 80-100 ℃.

S02: and injecting the preheated plastic packaging material into a mold fixed with the power device to carry out plastic packaging on the power device.

S03: and after the plastic package is finished, separating the packaged power device from the mold.

S04: and carrying out layered detection and thermal resistance test on the packaged power device. The thermal resistances include RJC and RJA. The layered detection comprises the following steps: and detecting whether the chip and the plastic package body are layered or not, and detecting whether the frame and the plastic package body are layered or not.

In this embodiment, the molding compound may include, by mass: 17-19% of epoxy resin, 9-12% of hardening agent, less than 1% of wax, 6-7% of stress release agent, 1-1.5% of flame retardant, 0.2-0.4% of colorant and the balance of filler. Further, in the plastic package material, the mass ratio of the epoxy resin can be 18 +/-0.5%, the mass ratio of the hardening agent can be 10.5 +/-0.5%, the mass ratio of the wax can be 0.6 +/-0.2%, the mass ratio of the stress releasing agent can be 6.5 +/-0.2%, the mass ratio of the flame retardant can be 1.25 +/-0.1%, the mass ratio of the coloring agent can be 0.3 +/-0.05%, and the balance is the filler. Further, the curing agent may include a phenolic resin, and the filler may include spherical SiO ₂At least one of powder, aluminum nitride and boron oxide.

In this example, the molding compound had the properties shown in table 1. The plastic package material meeting the properties shown in the following table and the plastic package process can jointly generate synergistic beneficial effects, the stress of a product can be reduced, and the heat conduction capability of a power device can be improved.

TABLE 1

Serial number	Item	Unit of	Specification value
				1	Spiral flow	cm	68±15
2	Gel time（175℃）	sec	27±8
				3	Coefficient of thermal expansion (α 1)	1/℃	≤2.5×10 -5
4	Strength of tortuosity	kgf/mm 2	≥10.0
				5	Flexural modulus of elasticity	kgf/mm 2	1450±300
6	Thermal conductivity	cal/cm·sec·℃	≥15×10 -4
				7	Flame resistance (0.8 mm)	/	94V～0

For example, the Spiral flow (flow length) may be 70cm, the Gel time (i.e., Gel time) (175 ℃) may be 26sec, and the coefficient of thermal expansion (α 1) may be 2X 10 ^-5The flexural strength may be 12kgf/mm ²The flexural modulus of elasticity canIs 1350kgf/mm ²The thermal conductivity may be 20X 10 ^-4cal/cm sec. degree.C.the flame resistance (0.8 mm) may be 80V.

In the embodiment, the mold can be a mold with 240-320 cavities, and each molding cavity can be used for placing a power device. Wherein, the length of each molding cavity can be 9.5-10.2 mm, the width can be 9-10 mm, and the height can be 4.5-5 mm.

The mold can include a sprue to and 6 ~ 8 subchannel that divide from the sprue exit. The injection molding compound can flow through the main runner, the sub-runners and finally into the individual molding cavities.

The width of the main runner can be 3.5-3.8 mm, the depth can be 2-3 mm, and the length can be 220-245 mm, such as 3.7 + -0.05 mm wide, 2.5 + -0.3 mm deep, 235 + -5 mm long, further such as 3.72mm wide, 2.6mm deep, and 238mm long.

The width of the sub-runners can be 1.8-2.1 mm, the depth can be 2-3 mm, and the length can be 65-75 mm, for example, the width is 2.0 + -0.05 mm, the depth is 2.5 + -0.3 mm, the length is 70 + -3 mm, and further, the width is 2.08mm, the depth is 2.05mm, and the length is 72 mm.

In this embodiment, preferably, the cross sections of the main runner and the sub-runners may be arc-shaped, wherein the width of the main runner and the sub-runner refers to the length between two end points of the arc-shaped cross section, i.e. the length of the chord length, and the depth refers to the deepest depth in the runner.

In this embodiment, the die may include corresponding upper and lower central plates, and the upper central plate may overlie the lower central plate. Wherein the content of the first and second substances,

the upper surface of the lower central plate can be provided with a lower glue feeding main channel strip (also called as a main channel), a lower glue dividing channel strip (also called as a sub channel) and a forming cavity which are connected in sequence. The number of the molding cavities can be 240-320.

The lower surface of the upper central plate may be provided with: the upper center strip corresponding to the lower glue feeding main channel strip and the lower glue dividing channel strip corresponds to the upper molding strip of the molding cavity.

The mould can also comprise an injection charging barrel, and the plastic package material can enter the lower glue feeding main channel strip through the injection charging barrel.

The die also comprises a lower ejector rod, and the lower ejector rod can eject the product out of the die cavity (namely a die cavity) after the product is formed and opened.

The mold can be matched with a plastic package material and a plastic package process, can meet the quality requirement of plastic package, and can reduce the width and the length of a flow passage, reduce resin waste and reduce material cost.

In this embodiment, the size of the power device may be 24-28 mm ²The thickness may be 100 to 280 μm.

In the present embodiment, since the pre-molding resin mass (i.e., the molding compound) is generally stored in an environment of 5-10 ℃, moisture absorption occurs to various degrees. Before use, the material needs to be proofed in a dry place for not less than 16 hours, such as 16-20 hours. Furthermore, the material can be stirred at the temperature of 20-30 ℃ and the RH of 40-60 percent.

In this embodiment, the density of the molding compound may be 0.001-0.0015 g/mm ³The particle size may be 20 to 50 mm. Further, the density can be 0.0011-0.0013 g/mm ³The particle size may be 30 to 40 mm. The density and the granularity are mutually adaptive, so that the plastic packaging material does not contain excessive air and moisture, does not cause poor filling and difficult stripping of the mold, and is favorable for the plastic packaging process.

In this embodiment, the plastic packaging process can be controlled according to the parameters in table 2.

TABLE 2

The single-mode dosage of the plastic package material in table 2 is as follows: 3-4 plastic packaging materials (also called plastic packaging material cakes) with the weight of 70-75 g are needed in the primary plastic packaging process.

In the packaging and forming process, the temperature of the mold, the injection molding time, the mold closing pressure, the injection pressure, the curing time and the like are relevant parameters.

The temperature of the mould is controlled within the temperature range, and the plastic package material can obtain ideal fluidity. If the temperature of the mold is too high, the plastic packaging material is cured too fast, the internal stress is increased, the bonding force between the packaging layer and the frame is reduced, and meanwhile, the mold is not full due to the too fast curing. If the temperature of the mold is too low, the flowability of the plastic packaging material is poor, the mold filling is poor, and the mechanical strength of the packaging layer is reduced. The temperature of each area of the die is kept uniform, and if the temperature of the die is not uniform, the curing degree of the plastic packaging material is not uniform, so that the mechanical strength of a device is inconsistent.

If the preheating time of the plastic packaging material is not enough, the plastic packaging material can not be melted and can not be fully wrapped; if the preheating time of the molding compound is too long and the reaction speed of the preheated EMC (namely epoxy resin) is accelerated at high temperature, the gelling time of the molding compound is relatively shortened, the fluidity is deteriorated, the viscosity of the molding compound is rapidly increased when the cavity is not completely filled, the flow resistance is increased, so that good filling can not be obtained, and thus a tendency unfilled state is formed.

The injection pressure (i.e., injection pressure) of the present invention is determined based on the flowability of the injection molding material and the mold temperature. Meanwhile, the injection pressure of the invention can be verified and determined according to the quality result of the injection encapsulated C-SCAN layered scanning and the appearance condition of the product.

If the injection pressure is too low, the density of the encapsulating layer of the power device is low, the bonding property with the frame is poor, moisture absorption corrosion is easy to occur, and poor appearance phenomena such as no full encapsulation can occur. If the injection pressure is too high, the product welding wire is broken and deflected or welding spots are impacted by stress, so that the product has poor open circuit and short circuit performance; meanwhile, the undesirable phenomena such as flash and the like may occur.

If the temperature of the mold is too high, the curing time and the flow length of the plastic package material can be shortened, the plastic package material can be cured in advance in a mold cavity, and air holes can appear at the top end, the inside or a pouring gate of a product, so that the reliability and the appearance of the product can be influenced. If the temperature of the mold is too low, the molding compound cannot be melted and also cannot be fully coated.

If the clamping pressure is not sufficient, the product is subjected to the common defect form, namely flash, and the subsequent weldability and appearance are affected.

In this embodiment, after the product is subjected to the C-SCAN layered scanning detection, the chip and the plastic package body are not layered, the layering of the frame and the plastic package body is less than 6%, and the layering of the pin and the plastic package body is less than 5%, which is better than the industry standard by within 10%.

Meanwhile, through the Phase12 test of the analytical Tech company in the United states, RJC and RJA are RJC (0.8-1.2 ℃/W) and RJA (55-65 ℃/W), respectively. Wherein RJC is the temperature of the junction to the housing (or heat sink); RJA is the temperature of the junction to ambient.

In summary, the advantages of the plastic package process of the low-stress high-thermal-conductivity device of the present invention may include:

(1) the epoxy molding compound, the mold and the injection molding process can be matched with each other, can generate a synergistic effect, and can produce a high-heat-conductivity low-stress power device product; (2) meanwhile, the invention can reduce the consumption of the power device to the epoxy plastic package material, can shorten the production man-hour by controlling the curing time, and improve the cost performance of the product; (3) the invention can reduce the stress of the product, improve the heat conduction capability of the power device, and improve the reliability and the application field of the product.

Although the present invention has been described above in connection with exemplary embodiments, it will be apparent to those skilled in the art that various modifications and changes may be made to the exemplary embodiments of the present invention without departing from the spirit and scope of the invention as defined in the appended claims.