Method for forming a protective layer on an electronic module

Abstract

Method (100) for forming a protective layer (25) on an electronic module (10), comprising: Arranging the electronic module (10) and a protective material (20, 22) arranged on the electronic module (10) in a chamber (30), wherein the protective material (20, 22) and the electronic module (10) are in contact with each other; Performing a first heating process on the protective material (20, 22) in the chamber (30) to soften the protective material (20, 22) arranged on the electronic module (10), and performing a first pressure increasing process on the chamber (30), wherein a pressure in the first pressure increasing process is greater than 101 325 Pa; after softening the protective material (20, 22), maintaining the first heating process and performing an oscillating decompression process on the chamber (30), wherein the oscillating decompression process comprises alternately changing the pressures in the chamber (30) between a plurality of negative pressures of less than 101 325 Pa; Maintaining the first heating process and performing a second pressure increasing process on the chamber (30), wherein a pressure in the second pressure increasing process is less than the pressure in the first pressure increasing process and greater than 101 325 Pa; and Carrying out a second heating process of the protective material (20, 22) in the chamber (30) to cure the protective material (20, 22) covering the electronic module (10) to form the protective layer (25) covering the electronic module (10), wherein the method (100) further comprises, after performing the first pressure increasing process and the oscillating decompression process and before performing the second pressure increasing process: repeatedly performing the first pressure increasing process and the oscillating decompression process on the chamber (30), wherein after repeatedly performing the first pressure increasing process and the oscillating decompression process on the chamber (30) and before performing the second pressure increasing process, the method (100) further comprises: performing the first pressure increasing process and a decompression process on the chamber (30), wherein a pressure in the decompression process is lower than a pressure in the oscillating decompression process.

Description

BACKGROUNDTechnical field

[0001] The invention or disclosure relates to a method for forming a protective layer and in particular to a method for forming a protective layer on an electronic module. Description of the state of the art

[0002] Generally, a motherboard for an electronic device contains electronic components of various sizes. A conventional method is to mechanically or manually bond a protective adhesive to the motherboard to protect the motherboard and the electronic components on the motherboard. However, this method often leaves air bubbles between the protective adhesive and the motherboard, or between the protective adhesive and the electronic components, because the protective adhesive is difficult to adhere firmly. Therefore, water vapor deposition often occurs, which shortens the lifespan of the electronic components or causes reliability issues.

[0003] EP 0904923 A1 discloses the molding of plastics, and in particular the application of vibration waves in the molding of plastics or other materials. A molding system is provided for preventing the formation of internal cavities in a solidified molding compound.

[0004] US 6 933 179 B1 relates to a manufacturing method of a semiconductor device in a resin-molded packaging method and discloses that when a wafer which has completed a wafer process and has a main surface on which a plurality of bumps each connected to a plurality of electrode pads are formed is placed in a resin-molded type package to thereby manufacture a semiconductor device, a method for manufacturing such a semiconductor device comprises disposing a sheet encapsulant containing thermosetting resin over the wafer to cover the main surface of the wafer, and heating and curing the sheet encapsulant by a heater to thereby form an encapsulant resin layer.

[0005] JP 2001-332654 A discloses a module containing an electrical element such as a semiconductor chip or a surface acoustic wave element. In particular, the present invention relates to an electrical element-integrated module that can be extremely thin and suitable for high-density mounting. SUMMARY

[0006] The disclosure provides a method for forming a protective layer on an electronic module that can effectively reduce the likelihood of residual air bubbles between a protective adhesive and an electronic element.

[0007] A method for forming a protective layer on an electronic module in the disclosure includes the following. The electronic module and a protective material to be disposed on the electronic module are arranged in a chamber. The protective material and the electronic module are in contact with each other. A first heating process is performed on the protective material in the chamber to soften the protective material disposed on the electronic module, and a first pressurizing process is performed on the chamber. The pressure in the first pressurizing process is greater than 101,325 Pa. After the protective material is softened, the first heating process is maintained, and an oscillating decompression process is performed on the chamber. The oscillating decompression process includes alternately changing the pressures in the chamber between multiple negative pressures of less than 101,325 Pa.The first heating process is maintained, and a second pressurization process is performed on the chamber. The pressure in the second pressurization process is lower than the pressure in the first pressurization process and greater than 101,325 Pa. A second heating process is performed on the protective material in the chamber to cure the protective material covering the electronic module and form the protective layer covering the electronic module.

[0008] In one embodiment of the disclosure, the negative pressures in the oscillating decompression process include a base negative pressure and a plurality of variable negative pressures. A pressure of the base negative pressure is greater than the pressures of the variable negative pressures. The variable negative pressures gradually decrease over time. The variable negative pressures alternate with the base negative pressure, such that two of the variable negative pressures return to the base negative pressure first in two adjacent time sequences.

[0009] In one embodiment of the disclosure, a time the chamber remains at each of the variable negative pressures is longer than the time the chamber remains at the base negative pressure.

[0010] In one embodiment of the disclosure, the method further includes the following after performing the first pressurization process and the oscillating decompression process and before performing the second pressurization process. The first pressurization process and the oscillating decompression process are repeatedly performed on the chamber.

[0011] In one embodiment of the disclosure, the pressure difference between the negative pressures in the oscillating decompression process for the second time is greater than the pressure difference between the negative pressures in the oscillating decompression process for the first time.

[0012] In one embodiment of the disclosure, the method further includes the following after repeatedly performing the first pressure-increasing process and the oscillating decompression process on the chamber and before performing the second pressure-increasing process. The first pressure-increasing process and a decompression process are performed on the chamber. A pressure in the decompression process is lower than a pressure in the oscillating decompression process.

[0013] In one embodiment of the disclosure, a time that the chamber remains at the pressure in the decompression process is longer than the time that the chamber remains at the pressure in the oscillating decompression process.

[0014] In one embodiment of the disclosure, the pressure in the first pressure increasing operation for the first time is the same as or different from the pressure in the first pressure increasing operation for the second time.

[0015] In one embodiment of the disclosure, when the second heating process is performed, a third pressurizing process is simultaneously performed in the chamber.

[0016] In one embodiment of the disclosure, the electronic module includes a plurality of electronic elements, and an outline of a surface of the protective layer covering the electronic module conforms to the outlines of the electronic elements.

[0017] In one embodiment of the disclosure, the electronic module includes a plurality of electronic elements, and a surface of the protective layer covering the electronic module is flat and non-conforming to the outlines of the electronic elements.

[0018] Based on the above, in the method for forming the protective layer on the electronic module, the first heating process is performed on the protective materials in the chamber to soften the protective materials arranged on the electronic module, and the first pressurizing process is performed on the chamber so that the air bubbles between the electronic module and the protective materials move upward to the positions near the surfaces of the protective materials. Then, the first heating process is maintained, and the oscillating decompression process is performed on the chamber. The oscillating decompression process includes alternately changing the pressures in the chamber between negative pressures of less than 101325 Pa. During the oscillating decompression process, the air bubbles in the protective materials and near the surfaces burst because the size moves back and forth with the change in pressure in the chamber.The first heating process is then continued, and the second pressurization process is performed in the chamber. The pressure in the second pressurization process is lower than the pressure in the first pressurization process and greater than 101,325 Pa. During the second pressurization process, the softened protective materials can be compressed and flattened. Finally, the second heating process is performed on the protective materials in the chamber to harden the protective materials covering the electronic module and form the protective layer covering the electronic module. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a schematic representation of the steps of a method for forming a protective layer on an electronic module according to an embodiment of the disclosure. Fig. 2A to 2C are schematic views of one of the flow charts for forming the protective layer on the electronic module in Fig. 1. Fig. 3A to 3C are schematic views of another flow chart for forming the protective layer on the electronic module in Fig. 1. Fig. Figure 4A is a schematic representation of the relationship between time and temperatures in the process in Fig. 1. Fig. Figure 4B is a schematic representation of the relationship between time and pressure in the process in Fig. 1. DETAILED DESCRIPTION OF THE DISCLOSED EMBODIMENTS

[0019] Fig. 1 is a schematic view of steps of a method for forming a protective layer on an electronic module according to an embodiment of the disclosure. Fig. 2A to 2C are schematic views of one of the flow charts for forming the protective layer on the electronic module in Fig. 1. Fig.3A to 3C are schematic views of another of the flow charts for forming the protective layer on the electronic module in Fig. 1. Fig. Figure 4A is a schematic view of a relationship between time and temperatures in the process in Fig. 1. Fig. Figure 4B is a schematic representation of the relationship between time and pressure in the process in Fig. 1.

[0020] With reference to Fig. 1, Fig. 2A and Fig. 3A, a method 100 for forming a protective layer on an electronic module in this embodiment includes the following steps. First, in step 110, an electronic module 10 and the protective materials 20 ( Fig. 2A) and Fig. 22 ( Fig. 3A), which are arranged on the electronic module 10, are introduced into a chamber 30. The protective materials 20 and 22 and the electronic module 10 are in contact with each other.

[0021] In Fig. 2A, the electronic module 10 includes a circuit board 12 and a plurality of electronic elements 13 to 17 arranged on the circuit board 12. The electronic elements 13 to 17 have different heights. The protective material 20 is arranged over the electronic elements 13 to 17, and a portion of the protective material 20 does not extend beyond a portion of the circuit board 12.

[0022] The difference between the design of Fig. 3A and the embodiment of Fig. 2A is that in Fig. 3A the protective material 22 can be multi-layered, so that the protective materials 22 have a greater thickness.

[0023] Next, in step 120, a first heating process is performed on the protective materials 20 and 22 in the chamber 30 to soften the protective materials 20 and 22 arranged on the electronic module 10, and a first pressure increasing process is performed on the chamber 30. A pressure in the first pressure increasing process is greater than 101 325 Pa. The first heating process in this stage softens the protective materials 20 and 22, and the multilayer protective materials 22 in Fig. 3B will be integrated. As in Fig. 2B and Fig. 3B, the softened protective materials 20 and 22 collapse to be in contact with the circuit board 12, and a plurality of air bubbles 40 are formed between the protective materials 20 and 22 and the electronic elements 13 to 17. The first pressure increasing process is configured so that the air bubbles 40 between the electronic module 10 and the protective materials 20 and 22 gradually expand from the Fig.2B and Fig. 3B upwards into positions near the surfaces of the protective materials 20 and 22.

[0024] In this embodiment, the temperature of the first heating process is, for example, 130 degrees Celsius and the pressure is, for example, 1,114,575 Pa, i.e., the pressure difference to an external load is 1,013,250 Pa. The first pressure increase process can be carried out for 10 to 25 minutes. Of course, the values ​​for the first pressure increase and the first heating are not limited to this.

[0025] Then, in step 130, after the protective materials 20 and 22 have softened, the first heating process is maintained and an oscillating decompression process is performed in the chamber 30. The oscillating decompression process involves alternating the pressure in the chamber 30 between several negative pressures of less than 101,325 Pa.

[0026] As in Fig.As shown in Fig. 4B, the pressure first drops to less than 101,325 Pa, then, under the condition of less than 101,325 Pa, oscillation is performed to change the pressure magnitude. Then, the pressure is increased to a high pressure and then decreased to less than 101,325 Pa to perform oscillation to change the pressure magnitude, which is repeated several times. That is, in this embodiment, the first pressure-increasing process and the oscillating decompression process are repeatedly performed on the chamber 30. Of course, the repetition and the number of repetitions are not limited by the drawing.

[0027] In particular, in this embodiment, according to Fig.4B, the oscillating decompression procedure is performed three times, and during the oscillating decompression procedure, an oscillation occurs each time between a base negative pressure and several variable negative pressures. A pressure of the base negative pressure is greater than the variable negative pressures, and the variable negative pressures gradually decrease over time. The variable negative pressures alternate with the base negative pressure, so that two of the variable negative pressures return to the base negative pressure first in two adjacent time sequences.

[0028] For the first oscillation, a pressure-time relationship is given in Table 1. The time the chamber 30 remains at each of the variable negative pressures is longer than the time the chamber 30 remains at the base negative pressure. In this embodiment, the base negative pressure is 50,662.36 Pa (380 Torr) and lasts 0 seconds, and the variable negative pressure gradually decreases from 35,996.94 Pa (270 Torr) to 27,997.62 Pa (210 Torr), each lasting 30 seconds. During this process, the air bubbles 40 in the protective materials 20 and 22 and near the surfaces burst back and forth due to the size change accompanying the change in pressure in the chamber 30. Table 1 Pressure in Pa (Torr) Time (sec) 35 996, 94 (270) 30 50 662,36 (380) 0 33 330,5 (250) 30 50 662,36 (380) 0 30 664,06 (230) 30 50 662,36 (380) 0 27 997,62 (210) 30 50 662,36 (380) 0 27 997,62 (210) 30 99 991,5 (750) 0

[0029] Subsequently, the first pressure increase in chamber 30 is performed for the second time. For example, the pressure during the first pressure increase for the second time is 1 013 250 Pa and lasts six minutes. In this embodiment, the pressure during the first pressure increase for the second time is the same as during the first pressure increase for the first time. However, in other embodiments, the pressure during the first pressure increase for the second time may also differ from the pressure during the first pressure increase for the first time.

[0030] Then, the oscillating decompression process is performed for the second time. One purpose of the second oscillating decompression process is to burst the air bubbles 40 that did not burst in the first oscillating decompression process. The pressure difference of the negative pressures in the second oscillating decompression process is greater than that of the negative pressures in the first oscillating decompression process. Due to the material properties of the protective materials 20 and 22, the viscosity of a protective adhesive increases with the curing reaction at the same temperature over time, making it more difficult for the air bubbles 40 to burst. Therefore, by increasing the pressure difference, the range of volume change of the air bubbles 40 is expanded, which makes it easier for the air bubbles 40 to burst.

[0031] The pressures and times of the second oscillating decompression cycle are listed in Table 2 below. In this embodiment, the base negative pressure is 50,662.36 Pa (380 Torr) and lasts 0 seconds, and the variable negative pressure gradually decreases from 27,997.62 Pa (210 Torr) to 17,331.86 Pa (130 Torr) and lasts 30 seconds each. Table 2 Pressure in Pa (Torr) Time (sec) 27 997,62 (210) 30 50 662,36 (380) 0 25 331,18 (190) 30 50 662,36 (380) 0 22 664,74 (170) 30 50 662,36 (380) 0 19 998,3 (150) 30 50 662,36 (380) 0 17 331,86 (130) 30 99 991,5 (750) 0

[0032] Subsequently, the first pressure increase is performed on chamber 30 for the third time. The pressure during the third pressure increase is, for example, 1,013,250 Pa and lasts six minutes. Then, the oscillating decompression process is performed for the third time. The pressures and duration of the third oscillating decompression process are listed in Table 3 below. In this embodiment, the base negative pressure is 50,662.36 Pa (380 Torr) and lasts 0 seconds, and the variable negative pressure gradually decreases from 17,331.86 Pa (130 Torr) to 3,999.66 Pa (30 Torr), lasting 40 seconds each time. Table 3 Pressure in Pa (Torr) Time (sec) 17 331,86 (130) 40 50 662,36 (380) 0 13 332,2 (100) 40 50 662,36 (380) 0 9 332,54 (70) 40 50 662,36 (380) 0 3 999,66 (30) 40 99 991,5 (750) 0

[0033] Then, the first pressurizing process is performed for the fourth time on the chamber 30. The pressure in the first pressurizing process for the fourth time is 1,013,250 Pa and lasts for six minutes. After that, a decompression process is performed. In this embodiment, the pressure in the decompression process is lower than the pressure in the oscillating decompression process, and the time that the chamber 30 remains pressurized in the decompression process is longer than the time that the chamber 30 remains pressurized in the oscillating decompression process. Specifically, the pressure in the decompression process is 3999.66 Pa (30 Torr), and the time is 300 seconds. In this step, the remaining air bubbles 40 can be directly burst by using the relatively low pressure (a large negative pressure value) near a vacuum for a relatively long time.

[0034] Subsequently, in step 140, the first heating is maintained, and a second pressurization process is performed on the chamber 30. A pressure in the second pressurization process is lower than the pressure in the first pressurization process and greater than 101,325 Pa. In this embodiment, for example, the second pressurization process consists of first increasing the pressure to 202,650 Pa for 20 minutes and then to 303,975 Pa for 5 minutes. In the previous step, the surfaces of the protective materials 20 and 22 are uneven due to the bursting of the air bubbles 40, so the lower high pressure (202,650 Pa to 303,975 Pa) can be used to smooth the surfaces of the protective materials 20 and 22 without being too high to impede the flow of the protective materials 20 and 22.

[0035] Since the viscosity of the protective materials 20 and 22 gradually increases over time at a certain temperature, the second pressurization process is divided into two pressurization steps, which is more helpful for flattening the surfaces of the protective materials 20 and 22. Of course, in other embodiments, only one pressurization step may be performed. Furthermore, it may be performed in multiple steps.

[0036] Next, in step 150, a second heating process is performed for the protective materials 20 and 22 in the chamber 30 to cure the protective materials 20 and 22 covering the electronic module 10 and to form a protective layer 25 covering the electronic module 10, as shown in the Fig. 2C and Fig.3C. For example, the protective materials 20 and 22 are thermosetting materials. In the second heating step, the temperature can be increased to 175 degrees Celsius to cure the protective materials 20 and 22. During the second heating step, a third pressurization step is performed on the chamber 30 simultaneously. The pressure during this step can be 1,114,575 Pa, and the duration can be 30 to 60 minutes, or the minimum curing time required for the protective materials 20 and 22.

[0037] Finally, as in the Fig. 4A and Fig. 4B, the temperature is lowered and the pressure is reduced. The temperature at this stage is 80 degrees, the pressure can be 607,950 Pa, and the time can be 25 minutes. However, the disclosure is not limited to this.

[0038] In Fig.Figure 2C is an outline of an area of ​​the protective layer 25 covering the electronic module 10, conforming to the outlines of the electronic elements 13 to 17. Since the protective layer 25 in Fig. 3C is relatively thick, the surface of the protective layer 25 covering the electronic module 10 may be flat and may not match the outlines of the electronic elements 13 to 17. In addition, the protective layer 25 covers Fig. 2C and Fig. 3C only an upper side of the circuit board 12, without extending to a side or back of the circuit board 12.

[0039] It is worth mentioning that if the area of ​​the protective layer 25 in Fig.3C is to be manufactured as a planar structure, since the protective material 22 used initially has more layers or is thicker, it is difficult for the protective material 22 to remove the air bubbles 40. The method 100 for forming the protective layer 25 on the electronic module 10 in this embodiment can effectively remove the air bubbles 40 by the oscillating decompression process, and the structure of Fig. 3C can be completed.

[0040] Based on the above, in the method for forming the protective layer on the electronic module, the first heating process is performed on the protective materials in the chamber to soften the protective materials arranged on the electronic module, and the first pressurizing process is performed on the chamber so that the air bubbles between the electronic module and the protective materials move upward to the positions near the surfaces of the protective materials. Then, the first heating process is maintained, and the oscillating decompression process is performed on the chamber. The oscillating decompression process includes alternately changing the pressures in the chamber between negative pressures of less than 101325 Pa. During the oscillating decompression process, the air bubbles in the protective materials and near the surfaces burst because the size moves back and forth with the change in pressure in the chamber.The first heating process is then continued, and the second pressurization process is performed in the chamber. The pressure in the second pressurization process is lower than the pressure in the first pressurization process and greater than 101,325 Pa. During the second pressurization process, the softened protective materials can be compressed and flattened. Finally, the second heating process is performed on the protective materials in the chamber to harden the protective materials covering the electronic module and form the protective layer covering the electronic module.

Claims

[1] Method (100) for forming a protective layer (25) on an electronic module (10), comprising: Arranging the electronic module (10) and a protective material (20, 22) arranged on the electronic module (10) in a chamber (30), wherein the protective material (20, 22) and the electronic module (10) are in contact with each other; Performing a first heating process on the protective material (20, 22) in the chamber (30) to soften the protective material (20, 22) arranged on the electronic module (10), and performing a first pressure increasing process on the chamber (30), wherein a pressure in the first pressure increasing process is greater than 101 325 Pa; after softening the protective material (20, 22), maintaining the first heating process and performing an oscillating decompression process on the chamber (30), wherein the oscillating decompression process comprises alternately changing the pressures in the chamber (30) between a plurality of negative pressures of less than 101 325 Pa; Maintaining the first heating process and performing a second pressure increasing process on the chamber (30), wherein a pressure in the second pressure increasing process is less than the pressure in the first pressure increasing process and greater than 101 325 Pa; and Carrying out a second heating process of the protective material (20, 22) in the chamber (30) to cure the protective material (20, 22) covering the electronic module (10) to form the protective layer (25) covering the electronic module (10), wherein the method (100) further comprises, after performing the first pressure increasing process and the oscillating decompression process and before performing the second pressure increasing process: repeatedly performing the first pressure increasing process and the oscillating decompression process on the chamber (30), wherein after repeatedly performing the first pressure increasing process and the oscillating decompression process on the chamber (30) and before performing the second pressure increasing process, the method (100) further comprises: performing the first pressure increasing process and a decompression process on the chamber (30), wherein a pressure in the decompression process is lower than a pressure in the oscillating decompression process. [2] A method (100) for forming the protective layer (25) on the electronic module (10) according to claim 1, wherein in the oscillating decompression process, the negative pressures comprise a base negative pressure and a plurality of variable negative pressures, a pressure of the base negative pressure is greater than pressures of the variable negative pressures, the variable negative pressures gradually decrease over time, and the variable negative pressures alternate with the base negative pressure such that two of the variable negative pressures first return to the base negative pressure in two adjacent time sequences. [3] The method (100) for forming the protective layer (25) on the electronic module (10) according to claim 2, wherein a time for the chamber (30) to remain at each of the variable negative pressures is longer than a time for the chamber (30) to remain at the base negative pressure. [4] The method (100) for forming the protective layer (25) on the electronic module (10) according to claim 1, wherein a pressure difference of the negative pressures in the oscillating decompression process for the second time is larger than the pressure difference of the negative pressures in the oscillating decompression process for the first time. [5] The method (100) for forming the protective layer (25) on the electronic module (10) according to claim 1, wherein a time for which the chamber (30) remains at the pressure in the decompression process is longer than a time for which the chamber (30) remains at the pressure in the oscillating decompression process. [6] The method (100) for forming the protective layer (25) on the electronic module (10) according to claim 1, wherein the pressure in the first pressure increasing process for the first time is the same as or different from the pressure in the first pressure increasing process for the second time. [7] A method (100) for forming the protective layer (25) on the electronic module (10) according to claim 1, wherein, when the second heating process is performed, a third pressurizing process is simultaneously performed on the chamber (30). [8] A method (100) for forming the protective layer (25) on the electronic module (10) according to claim 1, wherein the electronic module (10) comprises a plurality of electronic elements (13-17) and an outline of a surface of the protective layer (25) covering the electronic module (10) conforms to the outlines of the electronic elements (13-17). [9] A method (100) for forming the protective layer (25) on the electronic module (10) according to claim 1, wherein the electronic module (10) comprises a plurality of electronic elements (13-17) and a surface of the protective layer (25) covering the electronic module (10) is flat and non-conformal to the outlines of the electronic elements (13-17).

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