Method and system for cleaning residual soldering flux at bottom of industrial-grade IC SMT (Integrated Circuit Surface Mount Technology) device

Abstract

The invention discloses a cleaning method and system for residual soldering flux at the bottom of an industrial-grade IC SMT device, the cleaning method for the residual soldering flux at the bottom of the industrial-grade IC SMT device comprises a first cleaning and a second cleaning, the first cleaning adopts a top-down spraying mode to clean an IC; and the second cleaning is to clean the IC by adopting an opposite flushing and spraying mode from the left side and the right side of the IC conveying direction. The invention aims to thoroughly remove residual soldering flux around and on the side surface of a bottom welding spot of an industrial-grade IC SMT device (especially a large-size inductor), avoid the layering phenomenon of an IC product in a reliability test caused by the residual soldering flux, prevent the layering from influencing the electrical performance of the IC product and causing use faults, reduce the cleaning frequency and improve the reliability of the product. The production period is shortened and the production cost is reduced.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of industrial IC packaging, and particularly relates to a cleaning method and system for residual flux at the bottom of an industrial IC SMT device. BACKGROUND

[0002] In the industrial IC packaging process, the packaging of large-size inductor devices is a key link. Figure 1 and Figure 2 As shown in the figures, this type of IC packaging is usually completed by combining surface mount technology (SMT) and flip chip (FC) technology. In this process, the large-size inductor device is first placed on the tin paste pre-printed on the substrate surface, then the inductor device is attached to the designated position by SMT patch technology, and then reflow soldering is performed to achieve reliable electrical connection and mechanical fixation between the inductor device and the substrate. However, after reflow soldering, there is often a lot of residual flux at the bottom of the large-size inductor device. If these residual fluxes are not removed in time, they will have an adverse effect on the IC product.

[0003] Currently, the industry generally uses saponifier solvent to clean this type of residual flux. However, the existing cleaning method mainly relies on single-direction spray cleaning from above (as shown in Figure 4a and Figure 4b ), that is, water is sprayed from top to bottom to wash away the residual flux. The flow washing effect of water on the substrate surface is limited, and it is difficult to completely remove the residual flux around and on the side of the solder joint. In particular, due to insufficient cleaning pressure, there is often a small amount of residual flux on the side of the solder joint, which often requires two to three cleaning processes to basically remove the residual flux at the bottom of the inductor, increasing the production cycle and cost. If the residual flux is not completely removed, after the MSL3 (moisture sensitivity level 3) reliability test, a small delamination may occur between the side of the solder joint and the plastic encapsulant (as shown in Figure 5 ), which will seriously affect the electrical performance of the IC product and even cause the product to malfunction during use. SUMMARY

[0004] To solve the above technical problems, the present application provides a cleaning method and system for residual flux at the bottom of an industrial IC SMT device, which aims to completely remove the residual flux around and on the side of the solder joint at the bottom of the industrial IC SMT device (especially large-size inductor devices), avoid the delamination phenomenon of the IC product during the reliability test caused by residual flux, prevent the delamination from affecting the electrical performance of the IC product and causing use failure, reduce the number of cleaning times, shorten the production cycle, and reduce the production cost.

[0005] To solve the above technical problems, the present application provides a cleaning method and system for residual flux at the bottom of an industrial IC SMT device, which aims to completely remove the residual flux around and on the side of the solder joint at the bottom of the industrial IC SMT device (especially large-size inductor devices), avoid the delamination phenomenon of the IC product during the reliability test caused by residual flux, prevent the delamination from affecting the electrical performance of the IC product and causing use failure, reduce the number of cleaning times, shorten the production cycle, and reduce the production cost. According to a first aspect of the present application, a cleaning method for industrial grade IC SMT device bottom soldering flux residue is provided, including a first cleaning and a second cleaning, the first cleaning is to clean the IC by using a top-down spraying method; the second cleaning is to clean the IC by using a head-on spraying method from the left and right sides of the IC conveying direction.

[0006] In a possible implementation manner of the first aspect, a spraying pressure of the first cleaning ranges from 0.4 MPA to 0.6 MPA.

[0007] In a possible implementation manner of the first aspect, a spraying pressure of the second cleaning ranges from 0.3 MPA to 0.5 MPA.

[0008] In a possible implementation manner of the first aspect, a temperature of the cleaning liquid used in the first cleaning and the second cleaning ranges from 50°C to 60°C.

[0009] In a possible implementation manner of the first aspect, a nozzle used in the top-down spraying in the first cleaning is a reverse conical structure.

[0010] In a possible implementation manner of the first aspect, a nozzle used in the head-on spraying in the second cleaning is a conical structure.

[0011] In a possible implementation manner of the first aspect, the conveying direction of the IC is perpendicular to the spraying directions of the left and right sides of the second cleaning.

[0012] According to a second aspect of the present application, a cleaning system for industrial grade IC SMT device bottom soldering flux residue is provided, including: a conveying device, configured to convey ICs along a conveying direction; a first spraying device, arranged above the conveying device, configured to perform the first cleaning; a second spraying device, arranged on the left and right sides of the conveying device respectively, configured to perform the second cleaning; wherein the first cleaning is to clean the IC by using a top-down spraying method; the second cleaning is to clean the IC by using a head-on spraying method from the left and right sides of the IC conveying direction.

[0013] In a possible implementation manner of the second aspect, a spraying pressure of the first cleaning ranges from 0.4 MPA to 0.6 MPA; a spraying pressure of the second cleaning ranges from 0.3 MPA to 0.5 MPA.

[0014] In a possible implementation manner of the second aspect, the nozzle of the first spraying device is in a reverse conical structure, and the nozzle of the second spraying device is in a conical structure.

[0015] Compared with the prior art, the present application has at least the following beneficial effects: The method for cleaning the industrial-grade IC SMT device bottom soldering flux residue provided by the present application can greatly improve the cleaning efficiency, and the soldering flux residue can be completely removed in a single cleaning cycle, thereby avoiding the need for repeated cleaning 2-3 times, shortening the process time, and improving the production efficiency; at the same time, through more complete removal of the soldering flux, the problem of delamination between the soldering point side and the plastic encapsulating material in the MSL3 reliability test is effectively avoided, so that the IC encapsulation is reliable, and the electrical performance of the product is stable; in addition, the method does not need to introduce complex equipment or expensive reagents, and only through optimization of the spraying layout and the cleaning process, the cleaning effect can be significantly improved.

[0016] In order to make the above-mentioned objects, features and advantages of the present application more apparent and easy to understand, the following preferred embodiments are specifically described below, and the accompanying drawings are described in detail as follows. BRIEF DESCRIPTION OF DRAWINGS

[0017] In order to more clearly illustrate the technical solutions in the specific embodiments of the present application, the following will briefly introduce the drawings needed to be used in the specific embodiments description. Obviously, the drawings in the following description are some embodiments of the present application, and other drawings can also be obtained by those skilled in the art without creative labor.

[0018] Figure 1 It is an IC product structure schematic diagram; Figure 2 It is an IC reflow soldering cleaning before schematic diagram; Figure 3 It is an IC reflow soldering cleaning schematic diagram; Figure 4a It is an IC reflow soldering after the prior art cleaning principle front view schematic diagram; Figure 4b It is an IC reflow soldering after the prior art cleaning principle side view schematic diagram; Figure 5 It is a small delamination diagram between the soldering point side and the plastic encapsulating material after MSL3 reliability; Figure 6 is a schematic diagram of the first cleaning principle of the embodiment of the present application after IC reflow soldering; Figure 7 is a schematic diagram of the second cleaning principle of the embodiment of the present application after IC reflow soldering. DETAILED DESCRIPTION

[0019] In order to make the purpose, technical scheme and advantages of the embodiments of the present application clearer, the technical scheme of the present application will be described below in detail with reference to the drawings. Obviously, the described embodiments are only some of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work fall within the scope of protection of the present application.

[0020] As shown in Figure 6 and Figure 7 , the embodiment of the present application provides a cleaning method for residual flux at the bottom of an industrial IC SMT device, mainly including two steps of first cleaning and second cleaning. The method is particularly suitable for removing residual flux around and on the side of the bottom of a large-size inductor device.

[0021] In the first cleaning, a preliminary cleaning is performed on the IC product after reflow soldering by using a top-down spraying method. The cleaning liquid used in the spraying is a saponifier solvent, and the temperature is controlled between 50°C and 60°C. The spraying pressure is preferably 0.4 MPA to 0.6 MPA. In the spraying step, the nozzle used is a reverse conical structure, which can form a uniformly diffused liquid flow, covering the upper surface and part of the side area of the IC device, and effectively removing most of the residual flux on the surface.

[0022] After the first cleaning is completed, the IC product is conveyed into the second cleaning area along a predetermined direction by a conveying device. In the second cleaning, a counter-spraying method is used from both sides of the conveying direction. The cleaning liquid used in the spraying is also a saponifier solvent, and the temperature is kept at 50°C to 60°C. The spraying pressure is controlled between 0.3 MPA and 0.5 MPA. The nozzle is a conical structure, which can form a bundled liquid flow to improve the local impact force. The liquid flows from both sides meet at the bottom of the IC product, forming a turbulent flow effect, thereby effectively removing stubborn residual flux accumulated around and on the side of the solder joint.

[0023] The conveying direction of the IC product is perpendicular to the spraying direction of both sides in the second cleaning, so as to ensure that the counter-spraying coverage area is symmetrical and the impact force is balanced, avoiding cleaning dead angles.

[0024] The embodiment of the present application also provides a cleaning system for implementing the above cleaning method, which includes a conveying device, a first spraying device and a second spraying device.

[0025] The conveying device is used for conveying IC products in a horizontal direction, and is usually a belt conveyor or a guide rail structure, and the speed is adjustable to adapt to different production tempos.

[0026] The first spraying device is arranged above the conveying device, and comprises a plurality of inverted conical nozzles, a liquid path system and a pressure control unit, and is used for implementing the first top-down spraying cleaning.

[0027] The second spraying device is symmetrically arranged on the left and right sides of the conveying device respectively, and each side comprises a plurality of conical nozzles, an independent liquid path and a pressure adjusting mechanism, and is used for implementing the second left-right opposing spraying cleaning.

[0028] The system can further comprise a cleaning liquid circulating and filtering device, a temperature control unit and a control system, which are used for maintaining the stability of the temperature and pressure of the cleaning liquid, and realizing the automatic operation of the cleaning process.

[0029] In summary, the application improves the cleaning effect on the residual flux at the bottom of large-size inductor devices by combining two different spraying modes under the cooperation of appropriate temperature, pressure and nozzle structure, avoids the delamination problem in reliability test caused by residual flux, effectively reduces the number of cleaning repetitions and improves the production efficiency.

[0030] Embodiment 1 The embodiment provides a cleaning method for residual flux at the bottom of an industrial-grade IC SMT device, which is used for cleaning an industrial-grade microcontroller unit (MCU) module comprising two large-size power inductors and a plurality of FC chips. After reflow soldering, there is a large amount of stubborn rosin-type flux residue at the bottom of the inductor and the side of the solder joint.

[0031] The cleaning method is completed in a modified online spraying cleaning machine, and specifically comprises the following steps: The module product after reflow soldering is placed on the conveying belt of the cleaning machine, and the conveying belt uniformly advances at a speed of 1.2 meters per minute. A 5% saponifier aqueous solution is configured as the cleaning liquid, and the temperature of the cleaning liquid is stably controlled at (55±2) DEG C through the built-in heating system. The temperature rise helps to soften and saponify the flux residue, and improves the cleaning efficiency.

[0032] The product first enters the first spraying area for the first cleaning. An inverted conical nozzle (small inside and large outside) is arranged above the first spraying area, and this structure helps to converge the water flow and form a water column with high impact force. The cleaning liquid is sprayed downward under the pressure of 0.5 MPA, and the upper surface of the product is subjected to full-coverage impact cleaning. The main purpose of this step is to use the large vertical impact force to directly flush and remove most of the flux residue at the top and main part of the inductor, chip and other devices, and to preliminarily impact and soften the residue at the bottom.

[0033] After the first cleaning, the product continues to the second spray zone. The second spray zone is provided with a set of spray rods on both sides of the conveying belt, and the spray rods are provided with conical nozzles (large inside and small outside). This structure can make the cleaning liquid spray in a cluster, improving the local impact force. The installation positions of the nozzles on both sides are calibrated to ensure that the spray trajectories accurately collide in the bottom area of the product. The cleaning liquid is sprayed from both sides (perpendicular to the conveying direction) to the bottom of the product under a pressure of 0.4 MPA. The high-speed water flow on both sides forms a turbulent flow and a collision directly below the product, which can effectively penetrate narrow gaps and thoroughly flush the blind areas such as the bottom of the inductor, the side of the welding point, and the root of the pin, which are difficult to reach in the first cleaning. The softened residues are completely stripped and washed away.

[0034] It should be noted that after the first cleaning and the second cleaning, the subsequent process is a conventional operation. Specifically, after the above-mentioned two core cleanings, the product is subjected to a deionized water rinse to remove any trace of cleaning liquid residue, and finally undergoes a drying process in the drying area.

[0035] After the product is cleaned by the method of the embodiment, no solder joint interface delamination is found through ultrasonic scanning microscope detection after MSL3 level humidity sensitivity test and TCT temperature cycle test. Compared with the original process which requires 2-3 cleanings, the present method only needs one process to achieve better cleaning effect, the production efficiency is improved by about 50%, and the consumption of cleaning liquid and water and electricity is saved.

[0036] Example 2 This embodiment mainly illustrates a cleaning system for implementing the above method.

[0037] An industrial-grade IC SMT device bottom flux residue cleaning system, comprising: A conveying device adopts a stainless steel mesh belt conveying system with a speed of 0.5-2.0 meters / minute and is steplessly adjustable.

[0038] A first spray device is installed at the top of the first cleaning chamber and includes a horizontally arranged spray pipe, which is uniformly provided with 8 inverted conical nozzles made of PP plastic. The first spray device is connected to a high-pressure pump, which can stabilize the spray pressure in the range of 0.4 MPA to 0.6 MPA, and in this embodiment, the pressure is set to 0.55 MPA.

[0039] The second spraying device is installed in the second cleaning cabin, and a vertical spraying pipe is arranged on each side of the conveying belt, and five conical nozzles are installed on each pipe, and the conical nozzles are made of PP plastic. The two sides of the spraying pipe are connected to an independent pressure pump, and the spraying pressure can be independently adjusted in the range of 0.3 MPA to 0.5 MPA, and the embodiment is set to 0.4 MPA. The angle of the two sides of the nozzle can be finely adjusted to ensure that the collision point is located directly below the product.

[0040] The control system integrates a PLC controller, and key process parameters such as conveying speed, spraying pressure, cleaning liquid temperature and the like can be set and monitored to ensure that the cleaning process meets the requirements.

[0041] The cleaning system for the industrial-grade IC SMT device bottom soldering flux residue in the embodiment is designed as a two-stage cleaning process, and the two stages of spraying are complementary and cooperative in function, that is, one is above and the other is below, so that the complex structure of the industrial-grade IC product bottom is efficiently and completely cleaned.

[0042] In the description of the present application, it should be understood that the terms "upper", "lower", "bottom", "inner", "outer" and the like indicate the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation on the present application.

[0043] In addition, the terms "first", "second" are only for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the technical features indicated. Therefore, the features defined as "first", "second" can explicitly or implicitly include at least one of the features. In the description of the present application, the meaning of "a plurality of" is at least two, such as two, three, etc., unless otherwise specifically limited.

[0044] In the present application, unless otherwise specifically defined and limited, the terms "connected", "connected" and the like should be understood broadly, for example, it can be fixedly connected, or it can be detachably connected, or it can be integrated; it can be mechanically connected, or it can be electrically connected or in communication with each other; it can be directly connected, or it can be indirectly connected through an intermediate medium; it can be the internal communication or interaction relationship of two elements, unless otherwise specifically limited. For ordinary skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0045] In the present application, unless otherwise explicitly specified and limited, a first feature is "on" or "under" a second feature can mean that the first and second features are in direct contact, or the first and second features are in indirect contact through an intermediate medium. Moreover, the first feature "over", "above" and "on top of" the second feature can mean that the first feature is directly above or obliquely above the second feature, or simply means that the first feature is horizontally higher than the second feature. The first feature "under", "below" and "underneath" the second feature can mean that the first feature is directly below or obliquely below the second feature, or simply means that the first feature is horizontally lower than the second feature.

[0046] In the present application, the terms "one embodiment", "some embodiments", "an example", "a specific example", or "some examples" and the like mean that the particular feature, structure, material, or characteristic being described is included in at least one embodiment or example of the present application. The illustrative appearances of the above-mentioned terms in various places in the specification are not necessarily referring to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics can be combined in any suitable manner in one or more embodiments or examples. Moreover, the terminology used in the specification is for the purpose of describing the particular embodiments or examples only and is not intended to be limiting. It is also possible in the present application that the different embodiments or examples described herein and the characteristics from different embodiments or examples can be combined and combined with each other, if not mutually exclusive.

[0047] Finally, it should be noted that the above-described embodiments are merely specific implementations of the present application, for the purpose of illustrating the technical solutions of the present application, but not for limiting the same. The protection scope of the present application is not limited thereto, even though the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that any person skilled in the art can make modifications or easily think of changes to the technical solutions recorded in the foregoing embodiments, or make equivalent replacements to some of the technical features; and such modifications, changes or replacements do not cause the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present application, and should be covered within the protection scope of the present application.

Claims

1. A method for cleaning flux residue on the bottom of industrial-grade IC SMT devices, characterized in that, The process includes a first cleaning stage and a second cleaning stage. The first cleaning stage involves spraying the IC from top to bottom. The second cleaning stage involves spraying the IC from both sides of the IC's conveying direction.

2. The method for cleaning flux residue on the bottom of industrial-grade IC SMT devices according to claim 1, characterized in that, The spray pressure range for the first cleaning stage is 0.4 MPa to 0.6 MPa.

3. The method for cleaning flux residue on the bottom of industrial-grade IC SMT devices according to claim 1, characterized in that, The spray pressure range for the second cleaning stage is 0.3 MPa to 0.5 MPa.

4. The method for cleaning flux residue on the bottom of industrial-grade IC SMT devices according to claim 1, characterized in that, The temperature of the cleaning solution used in the first and second cleaning processes is 50°C to 60°C.

5. The method for cleaning flux residue on the bottom of industrial-grade IC SMT devices according to claim 1, characterized in that, The nozzles used for the top-down spraying in the first cleaning stage have an inverted conical structure.

6. The method for cleaning flux residue on the bottom of industrial-grade IC SMT devices according to claim 1, characterized in that, The nozzles used in the counter-current spraying during the second cleaning process are conical in shape.

7. A method for cleaning flux residue on the bottom of industrial-grade IC SMT devices according to any one of claims 1 to 6, characterized in that, The conveying direction of the IC is perpendicular to the spraying directions on the left and right sides of the second cleaning stage.

8. A cleaning system for flux residue on the bottom of industrial-grade IC SMT devices, characterized in that, include: A conveying device for transporting ICs along the conveying direction; A first spraying device is disposed above the conveying device and is used to perform the first cleaning step; The second spraying device is respectively installed on the left and right sides of the conveying device to perform the second cleaning. The first cleaning process involves spraying the IC from top to bottom; the second cleaning process involves spraying the IC from both sides of the IC's transport direction.

9. A cleaning system for bottom flux residue of industrial-grade IC SMT devices according to claim 8, characterized in that, The spray pressure range for the first cleaning stage is 0.4 MPa to 0.6 MPa; the spray pressure range for the second cleaning stage is 0.3 MPa to 0.5 MPa.

10. A cleaning system for bottom flux residue of industrial-grade IC SMT devices according to claim 8, characterized in that, The nozzle of the first spray device is an inverted conical structure, and the nozzle of the second spray device is a conical structure.

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