Integrated circuit chip packaging structure and manufacturing process thereof

Abstract

The invention relates to the technical field of chip packaging, in particular to an integrated circuit chip packaging structure which comprises a base and epoxy resin, a chip is arranged above the base, multiple sets of pins used for providing working voltage for the chip are arranged on the two sides of the chip, and a bonding layer used for fixing the chip is arranged between the base and the pins. A plurality of sets of fins used for heat dissipation are arranged above the chip, a heat dissipation plate used for conducting heat is arranged below the fins, a heat conduction box used for assisting the fins in heat dissipation is arranged between the heat dissipation plate and the chip, a plurality of sets of installation grooves are formed in the surface of the heat conduction box, and a heat transfer plate is installed in each set of installation groove in a sliding mode. Fixing blocks for driving the fins to lift are arranged at the top ends of the heat transfer plates; the air bag automatically expands or contracts along with the temperature change to drive the heat transfer plate to ascend and descend, then the fins are driven to move synchronously, the contact area of the fins and air is dynamically adjusted, heat dissipation is enhanced when the temperature rises, energy consumption is reduced when the temperature drops, the heat dissipation efficiency of the chip is effectively improved, and stable operation of the chip is guaranteed.

Description

Technical Field

[0001] This invention relates to the field of chip packaging technology, and more specifically to an integrated circuit chip packaging structure and its manufacturing process. Background Technology

[0002] Integrated circuit chip packaging structure is a three-dimensional structure that fixes the chip on a substrate or carrier, achieves electrical connection through technologies such as wire bonding, flip-chip bonding or through-silicon vias, and seals and protects it with materials such as plastic and ceramics. Finally, it provides standardized pin interfaces to achieve physical support, signal transmission, heat dissipation and reliable installation with external circuits.

[0003] A search revealed a Chinese invention patent with publication number CN110265362B, which discloses a leadless integrated circuit chip packaging structure. By inflating a protective airbag, the airbag expands and completely encloses the pins on both sides. When operating in a humid environment, the thin rubber layer on the outer layer of the airbag provides excellent moisture resistance, thus protecting the pins and preventing short circuits due to moisture during operation. Simultaneously, the rubber's insulating properties prevent short circuits caused by static electricity between the pins, and the airbag's enclosure also provides excellent dust protection.

[0004] However, in actual use, the airbag occupies a certain space after inflating, reducing the contact area between the chip package and the external environment. The reduction in heat dissipation area will slow down the heat dissipation rate. Especially when the chip is working under high load, a lot of heat is generated, and it is difficult to dissipate the heat in a timely and effective manner, which can easily lead to a decline in chip performance. Summary of the Invention

[0005] In view of the above-mentioned shortcomings of the prior art, the present invention provides an integrated circuit chip packaging structure that can effectively solve the problems in the prior art where chips generate a lot of heat when working under high load, and the air bladder occupies a certain space after expansion, reducing the contact area between the chip package and the external environment, reducing the overall heat dissipation effect of the package, and easily leading to a decline in chip performance.

[0006] To achieve the above objectives, the present invention provides the following technical solution: This invention provides an integrated circuit chip packaging structure, including a base and epoxy resin. A chip is disposed on the base, and multiple sets of pins for providing operating voltage to the chip are disposed on both sides of the chip. An adhesive layer for fixing the chip is disposed between the base and the pins. Multiple sets of fins for heat dissipation are disposed on the top of the chip, and a heat dissipation plate for conducting heat is disposed below the fins. A heat conduction box for assisting fin heat dissipation is disposed between the heat dissipation plate and the chip. Multiple sets of mounting slots are formed on the surface of the heat conduction box. A heat transfer plate is slidably mounted inside each set of mounting slots. A fixing block for driving the fins to rise and fall is disposed at the top of the heat transfer plate. An airbag for driving the heat transfer plate to rise and fall is disposed inside each set of mounting slots, and the airbag is fixedly mounted on the inner wall of the mounting slot.

[0007] Furthermore, the outer wall of the heat-conducting box is provided with an inflation hole for connecting the airbag, and a one-way valve is provided inside the inflation hole.

[0008] Furthermore, the outer wall of the heat-conducting box has multiple sets of exchange holes for connecting to the corresponding mounting slots. The exchange holes are inclined and located above the one-way valve.

[0009] Furthermore, a sliding groove is provided inside the mounting groove, and protrusions are provided on the three sides of the heat transfer plate away from the exchange hole, and the protrusions are slidably installed inside the sliding groove.

[0010] Furthermore, the heat transfer plate has a filling cavity for filling molecular sieve desiccant inside, and multiple sets of water absorption holes are opened at the bottom of the heat transfer plate.

[0011] Furthermore, the total volume of the airbag is smaller than the volume of a single set of mounting slots, and the outer surface of the airbag is provided with a rubber layer.

[0012] Furthermore, the fins are corrugated, and multiple sets of the fins are distributed in a linear array.

[0013] A manufacturing process for an integrated circuit chip packaging structure includes the following steps: S1: Base and pin pretreatment: Clean the surface and check the flatness. Pre-set the pin installation position on the base. Fix the pins by welding to ensure that the pin spacing meets the design requirements. Apply an adhesive layer to the contact surface between the base and the pins. The adhesive layer material is epoxy resin or silicone with high thermal conductivity and high temperature resistance. After curing, a stable connection is formed. S2: Chip mounting and heat dissipation component assembly: The chip is fixed to the base by flip-chip bonding to ensure reliable electrical connection between the chip and the pins. The flatness of the chip is checked to avoid uneven heat dissipation due to installation tilt. The heat conduction box and heat transfer plate are prepared. Molecular sieve desiccant is filled inside the heat transfer plate. A fixing block is installed on the top of the heat transfer plate. The fixing block contacts the bottom of the heat dissipation plate to form a mechanical linkage structure. Multiple sets of corrugated fins are installed on the top of the heat dissipation plate. S3: Airbag and inflation system integration: Inflation holes and exchange holes are opened on the outer wall of the heat conduction box. A one-way valve is installed in the inflation hole to prevent airbag leakage. Connect the external inflation device to the inflation hole, test the airbag inflation and deflation function, and verify the smoothness of the heat transfer plate lifting action. S4: Epoxy Resin Encapsulation and Curing: Place the assembled structure into the mold, inject epoxy resin for encapsulation, control the filling height of the epoxy resin to ensure coverage of the chip, pins and heat-conducting box area, while avoiding obstructing the heat dissipation surface of the fins, place the encapsulation in a high-temperature chamber for curing, the curing temperature is set according to the epoxy resin type (usually 150-180℃), and the curing time is in hours. S5: Performance Testing: Electrical Performance Testing: Use a probe station to check whether the electrical connection between the chip and the pins is good; Heat Dissipation Performance Testing: Use an infrared thermal imager to detect the temperature distribution on the fin surface to verify the uniformity of heat dissipation; Moisture Resistance Testing: Place the package in a high humidity environment to detect the change in humidity inside the chip and verify the moisture absorption effect of the molecular sieve desiccant. S6: Finished Product Packaging and Storage: Clean the qualified packaged products to remove residual epoxy resin from the surface. Seal them individually with anti-static packaging materials to avoid static damage during transportation. Store in a dry, low-temperature environment (temperature <25℃, humidity <30%) to ensure the long-term effectiveness of the molecular sieve desiccant.

[0014] Beneficial effects The technical solution provided by this invention has the following advantages compared with the known prior art: 1. By automatically expanding or contracting the airbag according to temperature changes, the heat transfer plate is driven to rise and fall, which in turn drives the fins to move synchronously. This dynamically adjusts the contact area between the fins and the air, thereby enhancing heat dissipation when the temperature rises and reducing energy consumption when the temperature drops, effectively improving the chip's heat dissipation efficiency and ensuring stable chip operation. Second, the corrugated fins create turbulence when air flows through them, disrupting the thermal boundary layer and making it easier for heat to be transferred into the air. Multiple sets of fins are arranged in a linear array to increase the total heat dissipation area, meet the heat dissipation requirements of the chip, and further improve the overall heat dissipation effect. Attached Figure Description

[0015] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the accompanying drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are merely some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without any creative effort.

[0016] Figure 1 This is a schematic diagram of the overall appearance and structure of the present invention; Figure 2 This is a schematic diagram of the chip structure of the present invention; Figure 3 For the present invention Figure 2 Enlarged view of point A in the middle; Figure 4 This is a schematic diagram of the fin structure of the present invention; Figure 5 For the present invention Figure 4 Enlarged view of point B in the middle; Figure 6 This is a partial cross-sectional view of the heat-conducting box of the present invention; Figure 7 This is a partial cross-sectional view of the heat transfer plate of the present invention.

[0017] Reference numerals: 1. Base; 101. Pin; 102. Adhesive layer; 103. Chip; 104. Heat-conducting box; 105. Heat sink; 106. Fin; 107. Heat transfer plate; 108. Fixing block; 109. Airbag; 110. Mounting groove; 111. Slide groove; 112. Exchange hole; 113. Inflation hole; 114. One-way valve; 115. Filling cavity; 2. Epoxy resin; 201. Vent hole. Detailed Implementation

[0018] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0019] The present invention will be further described below with reference to embodiments.

[0020] An integrated circuit chip packaging structure, as shown in the attached figure. Figure 1-7The system includes a base 1 and epoxy resin 2. A chip 103 is mounted on top of the base 1. Multiple sets of pins 101 for providing operating voltage to the chip 103 are provided on both sides of the chip 103. An adhesive layer 102 for fixing the chip 103 is provided between the base 1 and the pins 101. Multiple sets of fins 106 for heat dissipation are provided above the chip 103. A heat sink 105 for heat conduction is provided below the fins 106. A heat conduction box 104 for assisting heat dissipation of the fins 106 is provided between the heat sink 105 and the chip 103. Multiple sets of mounting slots 110 are formed on the surface of the heat conduction box 104. A heat transfer plate 107 is slidably mounted inside each mounting slot 110. A fixing block 108 for driving the fins 106 to rise and fall is provided at the top of the heat transfer plate 107. Each mounting slot 110 has an airbag 109 inside for driving the heat transfer plate 107 to rise and fall. The airbag 109 is fixedly installed on the inner wall of the mounting slot 110. The base 1 carries the chip 103 and is fixed by the adhesive layer 102. The pin 101 supplies power to the chip. When the chip is working, the heat is transferred to the heat sink 105 through the heat conduction box 104 and then dissipated by the fins 106. The airbag 109 automatically expands or contracts with temperature changes, driving the heat transfer plate 107, which is slidably installed in the mounting slot 110, to rise and fall. The heat transfer plate 107 drives the fins 106 to move synchronously through the top fixing block 108, thereby dynamically adjusting the contact area between the fins 106 and the air, achieving efficient thermal management that enhances heat dissipation when the temperature rises and reduces energy consumption when the temperature falls.

[0021] Furthermore, the outer wall of the heat-conducting box 104 is provided with an inflation hole 113 for connecting the airbag 109. The inflation hole 113 is provided with a one-way valve 114. After the airbag 109 is inflated, the one-way valve 114 can effectively prevent gas leakage in the airbag. In addition, when the packaging structure is subjected to external mechanical impact, the airbag 109 acts as an elastic buffer layer, absorbing part of the impact energy through its own deformation, reducing the stress directly transmitted to the chip 103.

[0022] Furthermore, the outer wall of the heat conduction box 104 has multiple sets of exchange holes 112 for connecting to the corresponding mounting slots 110. The exchange holes 112 are inclined and located above the one-way valve 114. In environments with large temperature changes, condensation may occur in the heat conduction box 104 and the mounting slots 110. The inclined exchange holes 112 utilize gravity to make it easier for condensation to flow out, preventing condensation from accumulating in the heat conduction box 104 and causing short circuits or other damage to the chip 103, thus ensuring the safe operation of the chip 103.

[0023] Furthermore, a sliding groove 111 is provided inside the mounting groove 110, and protrusions are provided on three sides of the heat transfer plate 107 away from the exchange hole 112. The protrusions are slidably installed inside the sliding groove 111. Through the arrangement of the sliding groove 111 and the protrusions, the heat transfer plate 107 can only slide in the vertical direction defined by the sliding groove 111, which effectively prevents the heat transfer plate 107 from shaking and shifting in the horizontal direction, ensuring that the heat transfer plate 107 can rise and fall stably along the vertical trajectory, thereby ensuring that the fins 106 can accurately adjust the height and achieve efficient heat dissipation function.

[0024] Furthermore, the heat transfer plate 107 has a filling cavity 115 for filling with molecular sieve desiccant, and the bottom of the heat transfer plate 107 has multiple sets of water absorption holes. The molecular sieve desiccant has good chemical and thermal stability. When water vapor in the surrounding environment enters the area where the heat transfer plate 107 is located, the molecular sieve desiccant can quickly adsorb and fix this water vapor in its micropores, effectively reducing the ambient humidity and preventing moisture from damaging the chip 103 and related electronic components. The molecular sieve desiccant can continuously play a drying role, providing a long-term stable drying environment for the chip 103 and reducing failures and performance degradation caused by humidity changes.

[0025] Furthermore, the total volume of the airbag 109 is smaller than the volume of a single mounting slot 110, and a rubber layer is provided on the outer surface of the airbag 109. The bottom of the airbag 109 is supported by a heat-conducting box 104. When the chip 103 is in normal working condition, the heat transfer plate 107 is used to block the connection between the outside world and the chamber where the chip 103 is located. When the chip 103 is under load, the heat transfer plate 107 moves upward to connect 112 with the chamber where the chip 103 is located. The total volume of the airbag 109 is smaller than the volume of a single mounting slot 110 to prevent damage to the airbag 109. During the expansion process, if there is insufficient expansion space, the airbag 109 will be subjected to excessive pressure, which may cause the rubber layer to rupture or the internal structure of the airbag 109 to be damaged, affecting its normal operation. The space in the mounting slot 110 that is not occupied by the airbag 109 can serve as a channel for gas exchange. On the one hand, this helps to regulate the temperature in the mounting slot 110 and prevent heat accumulation in the mounting slot 110 due to the expansion of the airbag 109. On the other hand, the flow of gas can also carry away some of the heat conducted from the chip 103, assisting in heat dissipation and improving the efficiency of the entire heat dissipation system.

[0026] Furthermore, the fins 106 are corrugated, and multiple sets of fins 106 are arranged in a linear array. When air flows over the corrugated fins 106, the undulations of the corrugations will cause the air to turbulent. The air flow in the turbulent state is more intense, which can destroy the thermal boundary layer formed on the surface of the fins, making it easier for heat to be transferred from the surface of the fins 106 to the air, thereby further improving the heat dissipation effect. The multiple sets of fins 106 are arranged in a linear array to increase the total heat dissipation area, meet the heat dissipation requirements of the chip 103, and ensure that the chip 103 operates stably within the normal operating temperature range.

[0027] A manufacturing process for an integrated circuit chip packaging structure includes the following steps: S1: Pre-treatment of base 1 and pin 101: Clean the surface and check the flatness. Pre-set the installation position of pin 101 on base 1. Fix pin 101 by welding. Ensure that the spacing of pin 101 meets the design requirements. Apply adhesive layer 102 to the contact surface between base 1 and pin 101. The adhesive layer 102 material is selected from epoxy resin or silicone with high thermal conductivity and high temperature resistance. After curing, a stable connection is formed. S2: Chip mounting and heat dissipation component assembly: The chip 103 is fixed to the base 1 by flip-chip bonding to ensure reliable electrical connection between the chip 103 and the pin 101. The flatness of the chip 103 is checked to avoid uneven heat dissipation due to installation tilt. The heat conduction box 104 and the heat transfer plate 107 are prepared. Molecular sieve desiccant is filled inside the heat transfer plate 107. A fixing block 108 is installed on the top of the heat transfer plate 107. The fixing block 108 contacts the bottom of the heat dissipation plate 105 to form a mechanical linkage structure. Multiple sets of corrugated fins 106 are installed above the heat dissipation plate 105. S3: Integration of airbag and inflation system: An inflation hole 113 and an exchange hole 112 are opened on the outer wall of the heat conduction box 104. A one-way valve 114 is installed in the inflation hole 113 to prevent airbag 109 from leaking. An external inflation device is connected to the inflation hole 113 to test the inflation and deflation function of the airbag 109 and verify the smoothness of the lifting and lowering action of the heat transfer plate 107. S4: Epoxy Resin Encapsulation and Curing: Place the assembled structure into the mold, inject epoxy resin 2 for encapsulation, control the filling height of epoxy resin 2 to ensure that it covers part of the chip 103, pin 101 and heat conduction box 104, while avoiding blocking the heat dissipation surface of fin 106. Place the encapsulation in a high-temperature chamber for curing. The curing temperature is set according to the epoxy resin 2 model (usually 150-180℃), and the curing time is 2-4 hours. S5: Performance Test: Electrical Performance Test: Use a probe station to check whether the electrical connection between chip 103 and pin 101 is good; Heat Dissipation Performance Test: Use an infrared thermal imager to detect the surface temperature distribution of fins 106 to verify the heat dissipation uniformity; Moisture Resistance Test: Place the package in a high humidity environment and detect the humidity change inside chip 103 to verify the moisture absorption effect of the molecular sieve desiccant. S6: Finished Product Packaging and Storage: Clean the qualified packaged products to remove residual epoxy resin 2 from the surface. Use anti-static packaging materials for individual packaging to avoid electrostatic damage during transportation. Store in a dry, low-temperature environment (temperature <25℃, humidity <30%) to ensure the long-term effectiveness of the molecular sieve desiccant.

[0028] Working principle: When chip 103 is working normally, it generates heat. This heat is conducted sequentially through the heat-conducting box 104 and the heat sink 105 to the fins 106, where it is dissipated. When chip 103 is under load, the internal temperature of epoxy resin 2 rises, the air bladder 109 expands, and pushes up the heat transfer plate 107, causing it to slide vertically upwards along the slide groove 111 until the bottom of the heat transfer plate 107 is higher than the exchange hole 112. At this point, the exchange hole 112 connects with the mounting groove 110, reducing heat conduction through the heat-conducting box 104 and facilitating timely heat removal from the epoxy resin 2. Simultaneously, heat transfer... The plate 107 drives the fixing block 108 to move vertically upward synchronously. Multiple sets of fixing blocks 108 jointly apply an upward thrust to the heat sink 105, causing the heat sink 105 to move vertically upward. The heat sink 105 drives the fins 106 to move vertically upward synchronously. The fins 106 extend from the top of the epoxy resin 2. At this time, part of the heat generated by the chip 103 is transferred to the heat sink 105 and fins 106 through the heat conduction box 104, and heat is exchanged with the air through the surface of the fins 106. Part of the heat is directly discharged through the mounting groove 110 and the exchange hole 112, realizing efficient thermal management that enhances heat dissipation when the temperature rises and reduces energy consumption when the temperature drops.

[0029] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions will not cause the essence of the corresponding technical solutions to deviate from the protection scope of the technical solutions of the embodiments of the present invention.

Claims

1. An integrated circuit chip packaging structure, comprising a substrate (1) and an epoxy resin (2), characterized in that, A chip (103) is disposed above the base (1). Multiple sets of pins (101) for providing operating voltage to the chip (103) are disposed on both sides of the chip (103). An adhesive layer (102) for fixing the chip (103) is disposed between the base (1) and the pins (101). Multiple sets of fins (106) for heat dissipation are disposed above the chip (103). A heat sink (105) for heat conduction is disposed below the fins (106). A heat sink (105) is disposed between the heat sink (105) and the chip (103). A heat-conducting box (104) for assisting the heat dissipation of the fins (106) has multiple sets of mounting slots (110) on its surface. A heat transfer plate (107) is slidably installed inside each set of mounting slots (110). A fixing block (108) for driving the fins (106) to rise and fall is provided at the top of the heat transfer plate (107). An airbag (109) for driving the heat transfer plate (107) to rise and fall is provided inside each set of mounting slots (110). The airbag (109) is fixedly installed on the inner wall of the mounting slot (110).

2. The integrated circuit chip packaging structure according to claim 1, characterized in that, The outer wall of the heat-conducting box (104) is provided with an inflation hole (113) for connecting the air bag (109), and a one-way valve (114) is provided inside the inflation hole (113).

3. The integrated circuit chip packaging structure according to claim 2, characterized in that, The outer wall of the heat-conducting box (104) has multiple sets of exchange holes (112) for connecting to the corresponding mounting slots (110). The exchange holes (112) are inclined and located above the one-way valve (114).

4. The integrated circuit chip packaging structure according to claim 3, characterized in that, The mounting groove (110) has a sliding groove (111) inside. The heat transfer plate (107) has protrusions on three sides away from the exchange hole (112). The protrusions are slidably installed inside the sliding groove (111).

5. An integrated circuit chip packaging structure according to claim 4, characterized in that, The heat transfer plate (107) has a filling cavity (115) for filling molecular sieve desiccant, and the bottom of the heat transfer plate (107) has multiple sets of water absorption holes.

6. The integrated circuit chip packaging structure according to claim 5, characterized in that, The total volume of the airbag (109) is smaller than the volume of a single set of mounting slots (110), and the outer surface of the airbag (109) is provided with a rubber layer.

7. An integrated circuit chip packaging structure according to claim 6, characterized in that, The fins (106) are corrugated, and multiple sets of the fins (106) are arranged in a linear array.

8. A manufacturing process for an integrated circuit chip packaging structure, applied to the integrated circuit chip packaging structure described in claim 7, characterized in that, Includes the following steps: S1: Pre-treatment of base (1) and pin (101): Clean the surface and check the flatness. Pre-set the pin (101) installation position on the base (1). Fix the pin (101) by welding. Ensure that the pin (101) spacing meets the design requirements. Apply adhesive layer (102) to the contact surface between base (1) and pin (101). The adhesive layer (102) material is selected as epoxy resin or silicone with high thermal conductivity and high temperature resistance. After curing, a stable connection is formed. S2: Chip mounting and heat dissipation component assembly: The chip (103) is fixed on the base (1) by flip-chip bonding to ensure reliable electrical connection between the chip (103) and the pin (101). The flatness of the chip (103) is checked to avoid uneven heat dissipation due to installation tilt. A heat conduction box (104) and a heat transfer plate (107) are prepared. Molecular sieve desiccant is filled inside the heat transfer plate (107). A fixing block (108) is installed on the top of the heat transfer plate (107). The fixing block (108) contacts the bottom of the heat dissipation plate (105) to form a mechanical linkage structure. Multiple sets of corrugated fins (106) are installed on the top of the heat dissipation plate (105). S3: Integration of airbag and inflation system: An inflation hole (113) and an exchange hole (112) are opened on the outer wall of the heat conduction box (104). A one-way valve (114) is installed in the inflation hole (113) to prevent the airbag (109) from leaking. An external inflation device is connected to the inflation hole (113) to test the inflation and deflation function of the airbag (109) and verify the smoothness of the lifting and lowering action of the heat transfer plate (107). S4: Epoxy resin encapsulation and curing: Place the assembled structure in the mold, inject epoxy resin (2) for encapsulation, control the filling height of epoxy resin (2) to ensure that it covers part of the chip (103), pins (101) and heat-conducting box (104), while avoiding blocking the heat dissipation surface of the fins (106), place the encapsulation in a high-temperature chamber for curing, the curing temperature is set according to the epoxy resin (2) model (usually 150-180℃), and the curing time is 2-4 hours; S5: Performance test: Electrical performance test: Use a probe station to check whether the electrical connection between the chip (103) and the pin (101) is good. Heat dissipation performance test: Use an infrared thermal imager to detect the surface temperature distribution of the fins (106) to verify the heat dissipation uniformity. Moisture resistance performance test: Place the package in a high humidity environment and detect the humidity change inside the chip (103) to verify the moisture absorption effect of the molecular sieve desiccant. S6: Finished product packaging and storage: Clean the qualified packaged body to remove residual epoxy resin (2) from the surface, and use anti-static packaging materials for independent packaging to avoid static damage during transportation. Store in a dry, low-temperature environment (temperature <25℃, humidity <30%) to ensure the long-term effectiveness of molecular sieve desiccant.

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