Semi-water cleaning method for micro-gap system-in-package device

Abstract

The invention discloses a semi-water cleaning method for a micro-gap system-in-package device, and the method comprises the steps: placing a to-be-cleaned device in a cleaning chamber, and spraying a semi-water cleaning agent to the surface of the device for pre-cleaning and infiltration; the cleaning cavity is pumped to a first vacuum degree, so that air in the micro gaps is pumped out, and a semi-water cleaning agent is injected; the normal pressure of the cleaning cavity is recovered, and cleaning and dissolving are conducted through multi-angle spraying of the cleaning agent; the cleaning chamber is pumped to a second vacuum degree, so that the cleaning liquid dissolved with the residues reacts in the micro-gaps; ultrapure deionized water is introduced for rinsing, and residual ionic pollutants on the surface of the device are removed; performing vacuum drying, and vacuumizing the cleaning chamber to a third vacuum degree to vaporize the residual deionized water in the micro-gap; and heating inert gas is introduced into the cleaning cavity for pulse type purging, vaporized water molecules are brought out of the micro gaps, and drying is completed. According to the invention, 100-300 micron micro gaps can be effectively cleaned, and thoroughness in cleaning and completeness in drying are ensured.

Description

Technical Field

[0001] This invention belongs to the field of semiconductor manufacturing technology, and specifically relates to a semi-aqueous cleaning method for micro-gap system-in-package devices. Background Technology

[0002] System-in-Package (SiP) technology integrates multiple functional chips (such as processors, memory, passive components, etc.) into a single package, achieving high performance, miniaturization, and low power consumption. During SiP assembly, a large amount of flux remains on the substrate, chip sides, and bottom after reflow soldering.

[0003] As packaging density continues to increase, pin pitch and the gap between the chip and the substrate are shrinking to the micro-gap level of 100-300 micrometers. Traditional cleaning technologies (such as pure water cleaning and ultrasonic cleaning) face the following serious challenges: 1. Capillary action and "water wall" effect: The surface tension of the liquid in the micro gap is significant, making it difficult for the cleaning fluid to effectively penetrate and replace the residue. It is easy to form a "water wall" at the opening, which hinders the entry of liquid and the discharge of waste liquid. 2. Incomplete cleaning: Even if liquid enters, its poor flowability results in insufficient cleaning power, and high-resistance ionic contaminants are easily left in dead corners; 3. Difficulty in drying: After cleaning, the moisture in the micro gaps is difficult to completely remove by conventional hot air drying. The residual moisture may cause electrochemical migration in subsequent processes or use, leading to device failure. 4. Risk of physical damage: Although ultrasonic cleaning has strong cleaning power, its cavitation effect may cause physical damage to tiny solder joints or low-strength chips.

[0004] Semi-aqueous cleaning technology uses a cleaning agent that mixes organic solvents and water, combining the good solubility of organic contaminants by organic solvents with the safety and environmental friendliness of water. However, existing semi-aqueous cleaning processes are still not ideal in terms of cleaning effect and drying efficiency for micro-gap structures. Therefore, there is an urgent need for a highly efficient, non-destructive, and thorough semi-aqueous cleaning solution for micro-gap SiP devices. Summary of the Invention

[0005] The purpose of this invention is to address the problems existing in the prior art by providing a semi-aqueous cleaning method for micro-gap system-in-package devices, which can effectively clean micro-gap of 100-300 micrometers and ensure thorough cleaning and complete drying.

[0006] To achieve the above objectives, one aspect of the present invention provides a semi-aqueous cleaning method for micro-gap system-in-package devices, comprising: Step S1: Place the device to be cleaned in the cleaning chamber and spray semi-aqueous cleaning agent onto the surface of the device to pre-clean and wet the surface of the device. Step S2, perform stepped vacuum pressure cleaning, including: The pressure in the cleaning chamber is reduced from atmospheric pressure to the first vacuum level, which removes the air from the micro gaps. Then, a semi-aqueous cleaning agent is injected, and the pressure difference is used to allow the cleaning agent to penetrate deep into the micro gaps. The cleaning chamber is restored to normal pressure. By spraying cleaning agent from multiple angles from the top and bottom, turbulence is formed in the cleaning chamber to flush the device and peel off the residue from the device surface. The pressure in the cleaning chamber is reduced from atmospheric pressure to a second vacuum level, which is lower than the first vacuum level. This causes the cleaning solution containing the residue to react within the micro-gap, generating microbubbles that carry the residue from the bottom of the micro-gap into the cleaning solution. Step S3: Rinse with ultrapure deionized water to remove residual ionic contaminants from the device surface; Step S4, perform vacuum-assisted gradient drying, including: The cleaning chamber is evacuated to a third vacuum level, which is lower than the second vacuum level, causing the residual deionized water in the micro-gap to vaporize. Heated inert gas is introduced into the cleaning chamber for pulsed purging, which carries the vaporized water molecules out of the micro-gap, thus completing the drying process.

[0007] The semi-aqueous cleaning method for micro-gap system-in-package devices according to the above aspects of the present invention can effectively clean micro-gap of 100-300 micrometers, ensuring thorough cleaning and complete drying. Attached Figure Description

[0008] To more clearly illustrate the technical solutions of the present invention, the accompanying drawings used in the description of the embodiments of the present invention will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort: Figure 1 This is a schematic diagram of the structure of a semi-aqueous cleaning device according to an embodiment of the present invention; Figure 2 This is a partial schematic diagram of the interior of the cleaning chamber according to an embodiment of the present invention; Figure 3 This is a partial schematic diagram of a top cleaning device according to an embodiment of the present invention; Figure 4 This is a partial schematic diagram of a rotating tray and spray nozzle according to an embodiment of the present invention. Detailed Implementation

[0009] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0010] One embodiment of the present invention provides a semi-aqueous cleaning method for micro-gap system-in-package (SiP) devices, which is particularly suitable for cleaning flux residues from SiP devices, especially for high-density SiP devices with pin pitch or chip gap between 100 micrometers and 300 micrometers.

[0011] The semi-aqueous cleaning method of this invention adopts the following approach: Figure 1 The semi-aqueous cleaning device shown includes a cleaning chamber door 1, a top cleaning device 2, a sealed cleaning chamber 3, a control device 4, a cleaning agent valve 5, a liquid tank 6, a fixing frame 7, a rotating tray motor 8, and a rotating tray 9 that can be raised and lowered by the drive of the motor 8. The interior of the cleaning chamber 3 is formed as shown in the figure. Figure 2 The cleaning chamber shown has the cleaning device 2 installed at the top of the cleaning chamber 3, for example... Figure 3 The atomizing spray head is shown. A rotating tray 9 is positioned within the cleaning chamber to hold the SiP devices to be cleaned. Multi-angle nozzles are arranged around the rotating tray 9, such as... Figure 4 As shown.

[0012] The semi-aqueous cleaning agent used is a commercially available, environmentally friendly semi-aqueous cleaning agent. This cleaning agent has good solubility for rosin residues and low surface tension. The rinsing solvent is ultrapure deionized water, and the drying gas is high-purity nitrogen (99.999% purity).

[0013] Set the process parameters as follows: Pre-cleaning and wetting: time 30-60 seconds, pressure 0.5-1.5 bar; Immersion (first vacuum): vacuum degree (-80 kPa ~ -90 kPa), time 10-20 seconds; Atmospheric pressure turbulent cleaning: time 60-120 seconds; Deposition (second vacuum): vacuum degree (-90 kPa ~ -95 kPa), time 15-25 seconds. Rinsing: deionized water, 10 min; Vacuum flash evaporation: vacuum degree (-95 kPa ~ -100 kPa); Heated inert gas purging: inert gas (such as nitrogen) at 60-80℃, 2 min. After setting the process parameters, execute the following cleaning process.

[0014] Step S1: Pre-cleaning and soaking Open the cleaning chamber door 1 and secure the SiP device onto the rotating tray 9 inside the cleaning chamber, ensuring the device is placed stably. Using the cleaning device 2 at the top, spray a semi-aqueous cleaning agent onto the device surface at a pressure of 0.8 bar for 45 seconds. During this process, the rotating tray 9 rotates slowly at a speed of 72° / s to ensure even spraying.

[0015] Objective: To initially remove most of the loose flux residue on the surface of the device, and at the same time, to use the low surface tension of the cleaning agent to initially wet the micro-gap inlet, in preparation for subsequent deep penetration.

[0016] Step S2: Stepped vacuum pressure cleaning, including steps S21 to S23.

[0017] S21: First vacuum impregnation Control device 4 starts the vacuum pump, reducing the pressure in the cleaning chamber from atmospheric pressure to -85 kPa within 15 seconds and maintaining this pressure for 15 seconds. This process removes most of the air from the micro-gap. While the vacuum pump is running, quickly open the cleaning agent valve 5 to inject semi-aqueous cleaning agent into the chamber until the device is completely submerged.

[0018] Technical effect: By utilizing the pressure difference of up to 85 kPa between the inside and outside of the chamber, the cleaning agent is "forced" into the depths of the near-vacuum micro-gap, achieving a forced filling effect that cannot be achieved by traditional atmospheric pressure immersion.

[0019] S22: Normal pressure turbulent cleaning Control device 4 opens the exhaust valve, allowing the chamber to quickly return to normal pressure. Simultaneously, control device 4 activates the top spray device 2 and the multi-angle nozzles located on the bottom rotating tray 9, spraying cleaning agent onto the device from different directions at a pressure of 2.0 bar for 90 seconds. During this time, the rotating tray 9 continues to rotate slowly at a speed of 72° / s to ensure uniform spraying.

[0020] Technical effect: It creates strong turbulence in the chamber, physically flushing the device from all directions, peeling off the dissolved and loosened residues from the surface and carrying them into the mainstream liquid.

[0021] S23: Second Vacuum Analysis Control device 4 starts the vacuum pump, rapidly reducing the chamber pressure to -93 kPa (absolute pressure approximately 8 kPa) and maintaining it for 20 seconds.

[0022] Technical effect: Under this high vacuum, the cleaning solution containing dissolved flux undergoes violent "boiling" (flash evaporation) within the micro-gap, generating a large number of microbubbles. These bubbles escape upwards from the bottom of the gap, creating a strong stirring and pumping effect that completely "prys up" the stubborn residues adhering to the bottom and carries them into the liquid.

[0023] Step S3: Rinse with deionized water Controller 4 opens the deionized water valve, allowing ultrapure deionized water to flow in for rinsing. The rinsing time is 5 minutes. This process is repeated twice, and the wastewater is completely drained after each rinse.

[0024] Objective: To thoroughly remove any possible residual ionic contaminants from the surface of the device, achieving an extremely high level of surface cleanliness.

[0025] Step S4: Vacuum-assisted gradient drying, including steps S41 and S42.

[0026] S41: Vacuum flash evaporation Controller 4 starts the vacuum pump, reducing the chamber pressure to -98 kPa (absolute pressure approximately 3 kPa) and maintaining it for 60 seconds.

[0027] Technical effect: Under extremely low pressure, the deionized water remaining in the micro gap will quickly vaporize (flash evaporate), directly changing from liquid to gas, avoiding "adhesion" in the gap due to surface tension.

[0028] S42: Inert gas purging Controller 4 opens the inert gas valve and introduces high-purity nitrogen gas.

[0029] The pulse purging mode is adopted: purging for 2 seconds, pausing for 1 second, and the entire purging process lasts for 3 minutes.

[0030] Technical benefits: Pulse purging creates a dynamic airflow within the chamber, avoiding blind spots caused by laminar flow. Nitrogen, acting as a carrier, rapidly and thoroughly removes vaporized water molecules from the micro-gap and chamber.

[0031] The following example verifies the cleaning effect of the semi-aqueous cleaning method of this invention. In this example, the substrate of the SiP device to be cleaned is a multilayer mixed-phase dielectric substrate, on which one logic chip and two memory chips are integrated. The critical gap between the chip and the substrate is 150 micrometers. After reflow soldering, a large amount of flux residue is visible on the substrate surface and around the chip. Using the semi-aqueous cleaning method of this invention to clean the SiP device, the results show that for this extremely narrow gap of 150 micrometers, this invention can achieve effective cleaning and drying through high-vacuum immersion and desorption. For a gap of 300 micrometers, the cleaning effect of this invention is even better, and the drying time can be slightly shortened. This proves that the method of this invention has good universality in the range of 100-300 micrometers.

[0032] The semi-aqueous cleaning method for micro-gap system-in-package devices according to embodiments of the present invention has the following beneficial effects: 1. High-efficiency penetration and cleaning: Through the “stepped vacuum pressure” design, air is first extracted using vacuum, then the pressure difference is used to make the cleaning agent penetrate powerfully, and finally the “micro-boiling” effect is triggered by high vacuum to “pump” out the deep residue, which completely solves the cleaning problem of micro gaps. 2. Non-destructive cleaning: It avoids the use of high-energy ultrasound and adopts a combination of physical pressure difference and turbulence to eliminate potential damage to microstructures; 3. Thorough drying: The gradient drying method, which combines "vacuum flash evaporation" with "heated inert gas purging", can quickly and thoroughly remove moisture from the micro-gap, preventing failure caused by residual moisture. 4. High reliability: Rinsing with deionized water ensures the ionic cleanliness of the device surface, greatly improving the long-term reliability of SiP packaged products.

[0033] The foregoing has only described certain exemplary embodiments of the present invention by way of illustration. Undoubtedly, those skilled in the art can modify the described embodiments in various ways without departing from the spirit and scope of the present invention. Therefore, the foregoing drawings and descriptions are illustrative in nature and should not be construed as limiting the scope of protection of the claims of the present invention.

Claims

1. A semi-aqueous cleaning method for micro-gap system-in-package devices, characterized in that, include: Step S1: Place the device to be cleaned in the cleaning chamber and spray semi-aqueous cleaning agent onto the surface of the device to pre-clean and wet the surface of the device. Step S2, perform stepped vacuum pressure cleaning, including: The pressure in the cleaning chamber is reduced from atmospheric pressure to the first vacuum level, which removes the air from the micro gaps. Then, a semi-aqueous cleaning agent is injected, and the pressure difference is used to allow the cleaning agent to penetrate deep into the micro gaps. The cleaning chamber is restored to normal pressure. By spraying cleaning agent from multiple angles from the top and bottom, turbulence is formed in the cleaning chamber to flush the device and peel off the residue from the device surface. The pressure in the cleaning chamber is reduced from atmospheric pressure to a second vacuum level, which is lower than the first vacuum level. This causes the cleaning solution containing the residue to react within the micro-gap, generating microbubbles that carry the residue from the bottom of the micro-gap into the cleaning solution. Step S3: Rinse with ultrapure deionized water to remove residual ionic contaminants from the device surface; Step S4, perform vacuum-assisted gradient drying, including: The cleaning chamber is evacuated to a third vacuum level, which is lower than the second vacuum level, causing the residual deionized water in the micro-gap to vaporize. Heated inert gas is introduced into the cleaning chamber for pulsed purging, which carries the vaporized water molecules out of the micro-gap, thus completing the drying process.

2. The method as described in claim 1, characterized in that, In step S1, the SIP device is fixed on a rotating tray in the cleaning chamber. The rotating tray rotates slowly, and a semi-aqueous cleaning agent is sprayed onto the surface of the device using a low-pressure atomization spray method.

3. The method as described in claim 1 or 2, characterized in that, In step S1, the pre-cleaning and soaking time is 30-60 seconds, and the pressure is 0.5-1.5 bar.

4. The method as described in claim 1 or 2, characterized in that, In step S2, the first vacuum degree is -80 kPa to -90 kPa and is maintained for 10-20 seconds, and the second vacuum degree is -90 kPa to -95 kPa and is maintained for 15-25 seconds.

5. The method as described in claim 1 or 2, characterized in that, In step S2, cleaning agent is sprayed onto the device from different directions through a spray device located at the top of the cleaning chamber and a multi-angle nozzle located at the bottom of the cleaning chamber.

6. The method as described in claim 1 or 2, characterized in that, In step S4, the third vacuum degree is -95 kPa to -100 kPa, and the inert gas is high-purity nitrogen heated to 60-80℃.

7. The method as described in claim 1 or 2, characterized in that, In step S4, the pulse purging mode is: purging for 2 seconds, pausing for 1 second, and the entire purging process lasts for 3 minutes.

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