Cleaning method of chip packaging structure

Abstract

The invention relates to a cleaning method of a chip packaging structure, which comprises the following steps: providing a chip packaging structure which comprises a welding pad, and the surface of the welding pad has oxide and / or saponifying agent residue; soldering flux is formed on the surface of the welding pad through printing; and heating the chip packaging structure to enable the soldering flux to chemically react with the oxide and / or the saponifying agent residue. According to the cleaning method of the chip packaging structure, the oxide layer and / or saponifying agent residues on the surface of the welding pad can be efficiently removed, corrosion to a welding pad base material is reduced, the surface of the welding pad is protected, welding defects are reduced, and the product yield is improved.

Description

Technical Field

[0001] The present application relates to the field of semiconductor technology, and particularly to a cleaning method for a chip packaging structure. Background Art

[0002] During the packaging and manufacturing process of a chip, after the surface of the solder pad comes into contact with oxygen in the air, an oxide layer is easily formed. The oxide layer on the solder pad will affect the bonding between the solder and the solder pad, resulting in welding defects and reducing the strength and tightness of the weld. In addition, the saponifier used in the previous process will also remain on the surface of the solder pad. If these residues are not treated, they may affect the normal operation of electronic components.

[0003] In the prior art, the methods for treating saponifier residues and oxide layers on solder pads mainly involve polishing the surface of the solder pad with tools such as sandpaper or wire brushes to remove the oxide layer and contaminants. However, this method is cumbersome, time-consuming and laborious, and is likely to cause scratches on the surface of the solder pad, affecting the welding quality. Or the cavitation effect of ultrasonic waves is used to remove the oxide layer and saponifier residues on the surface of the solder pad. Although the ultrasonic cleaning effect is good, the equipment cost is high, and its applicability to certain materials is limited. Or the active ions in the plasma react chemically or physically with the oxide layer or saponifier residues on the surface of the solder pad to convert them into volatile substances and discharge them. The reducibility of plasma cleaning to certain metal oxide layers is weak, and the oxide layer cannot be completely removed. Summary of the Invention

[0004] Based on this, it is necessary to provide a cleaning method for a chip packaging structure to solve the problems in the prior art that it is laborious, costly and inefficient to remove saponifier residues and oxide layers on solder pads.

[0005] To achieve the above object, on the one hand, the present invention provides a cleaning method for a chip packaging structure, including the following steps:

[0006] Provide a chip packaging structure, the chip packaging structure includes a solder pad, and an oxide and / or saponifier residue is present on the surface of the solder pad;

[0007] Form a soldering flux on the surface of the solder pad by printing;

[0008] Heat the chip packaging structure so that the soldering flux reacts chemically with the oxide and / or the saponifier residue.

[0009] In one embodiment, the flux is formed by mixing a solvent, a reactant, and an adjuvant. The solvent includes organic alcohols, organic ketones, and organic esters. The reactant includes organic acids and organic amines. The adjuvant includes polyethylene glycol. The concentration of the solvent is 50-60%, the concentration of the organic amine in the reactant is 15-25%, the concentration of the adjuvant is 10-20%, and the concentration of the organic acid in the reactant is 5-15%.

[0010] In one embodiment, before heating the chip package structure to cause a chemical reaction between the flux and the oxide and / or the saponifier residue, the method further includes:

[0011] Transferring the chip package structure into a heating device;

[0012] Raising the temperature in the heating device to a first preset temperature within a first preset time at a first heating rate to preheat the surface of the solder pad.

[0013] In one embodiment, heating the chip package structure to cause a chemical reaction between the flux and the oxide and / or the saponifier residue includes:

[0014] Raising the temperature in the heating device from the first preset temperature to a second preset temperature within a second preset time at a second heating rate, so that the flux on the surface of the solder pad reacts chemically with the oxide and / or the saponifier, and the second heating rate is less than the first heating rate.

[0015] In one embodiment, after heating the chip package structure to cause a chemical reaction between the flux and the oxide and / or the saponifier residue, the method further includes:

[0016] Cooling down the heating device.

[0017] In one embodiment, cooling down the heating device includes:

[0018] Lowering the temperature in the heating device from the second preset temperature to the first preset temperature within a third preset time at a first cooling rate;

[0019] Lowering the temperature in the heating device from the first preset temperature to a third preset temperature within a fourth preset time at a second cooling rate, and the second cooling rate is greater than the first cooling rate.

[0020] In one embodiment, the heating device includes a hot air reflow oven.

[0021] In one embodiment, the oxygen content in the heating device is less than 100 ppm.

[0022] In one embodiment, after cooling the heating device, the following steps are further included:

[0023] Clean the surface of the solder pad.

[0024] In one embodiment, the cleaning agent used for cleaning the surface of the solder pad includes pure water, the temperature of the cleaning agent is 45 - 55 °C, and the pressure of the cleaning agent is 3 - 6 kg / cm 2 .

[0025] The cleaning method of the above chip packaging structure forms a soldering flux on the surface of the solder pad and heats the chip packaging structure, so that the soldering flux reacts chemically with the oxide layer and / or saponifier residue on the surface of the solder pad. In some embodiments, by precisely controlling the composition and component concentration of the soldering flux, the temperature and temperature change rate during the process of heating the chip packaging structure, the oxide layer and / or saponifier residue on the surface of the solder pad can be efficiently removed, reducing the damage to the solder pad substrate, protecting the surface of the solder pad, reducing welding defects, and improving the yield of the product. And in some embodiments, by cleaning the surface of the solder pad after the chemical reaction of the soldering flux and precisely controlling the cleaning temperature and pressure, the thorough removal of the oxide and / or saponifier residue is further ensured. In addition, in some embodiments, the cleaning method of the chip packaging structure of the present application is carried out by using a loader, a printer, a hot air reflow oven, a cleaning machine and an unloader, and is automatically transferred between the loader, the printer, the hot air reflow oven, the cleaning machine and the unloader, realizing an automated cleaning process, improving the cleaning efficiency, and this method is applicable to a variety of cleaning processes, having good versatility and flexibility. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the following drawings are only some embodiments of the present application. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0027] Figure 1 It is a flowchart of the cleaning method of the chip packaging structure provided in one embodiment;

[0028] Figure 2 It is a schematic cross-sectional structure diagram of a printer in the cleaning method of the chip packaging structure provided in one embodiment;

[0029] Figure 3Schematic cross-sectional structure diagram of a hot air reflow oven in a cleaning method for a chip packaging structure provided in an embodiment;

[0030] Figure 4 Schematic cross-sectional structure diagram of a cleaning machine in a cleaning method for a chip packaging structure provided in an embodiment.

[0031] Explanation of reference numerals:

[0032] 1 - Chip packaging structure, 2 - Flux, 3 - Printer, 31 - Carrying base, 32 - Printing stencil, 33 - Blade, 34 - Printing frame, 4 - Hot air reflow oven, 41 - First heating zone, 42 - Second heating zone, 43 - Gas circulation device, 44 - Exhaust gas discharge port, 45 - Transfer plate, 46 - First cooling zone, 47 - Second cooling zone, 5 - Cleaning machine, 51 - Cleaning base, 52 - Spraying system. Detailed implementation manners

[0033] To facilitate the understanding of the present application, the present application will be described more comprehensively below with reference to the relevant drawings. Embodiments of the present application are shown in the drawings. However, the present application can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, these embodiments are provided so that the disclosure of the present application is more thorough and comprehensive.

[0034] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the technical field to which the present application belongs. The terms used in the description of the present application herein are only for the purpose of describing specific embodiments and are not intended to limit the present application.

[0035] It should be understood that when an element or layer is referred to as "on", "adjacent to", "connected to" or "coupled to" another element or layer, it can be directly on, adjacent to, connected or coupled to the other element or layer, or there may be intervening elements or layers. In contrast, when an element is referred to as "directly on", "directly adjacent to", "directly connected to" or "directly coupled to" another element or layer, there are no intervening elements or layers. It should be understood that although the terms first, second, third, etc. may be used to describe various elements, components, regions, layers, doping types and / or parts, these elements, components, regions, layers, doping types and / or parts should not be limited by these terms. These terms are only used to distinguish one element, component, region, layer, doping type or part from another element, component, region, layer, doping type or part. Therefore, without departing from the teachings of the present invention, the first element, component, region, layer, doping type or part discussed below may be denoted as the second element, component, region, layer or part.

[0036] Spatial relationship terms such as "under", "below", "beneath", "underneath", "above", "over", etc. can be used herein to describe the relationship of one element or feature shown in the figures with other elements or features. It should be understood that, in addition to the orientations shown in the figures, spatial relationship terms also include different orientations of the device during use and operation. For example, if the device in the figures is flipped, an element or feature described as "under other elements" or "beneath them" or "underneath them" will be oriented "over" other elements or features. Thus, the exemplary terms "under" and "underneath" can include both upper and lower orientations. In addition, the device may also have other orientations (such as rotated 90 degrees or other orientations), and the spatial descriptors used herein are to be interpreted accordingly.

[0037] As used herein, the singular forms "a", "an" and "the" may also include the plural forms unless the context clearly dictates otherwise. It should also be understood that the terms "comprises / include" or "has" etc. specify the presence of the stated features, integers, steps, operations, components, parts or combinations thereof, but do not preclude the presence or addition of one or more other features, integers, steps, operations, components, parts or combinations thereof. Also, in this specification, the term "and / or" includes any and all combinations of the related listed items.

[0038] Please refer to Figure 1 , the present invention provides a cleaning method for a chip packaging structure, comprising the following steps:

[0039] S1: Provide a chip packaging structure 1, the chip packaging structure 1 includes solder pads (not shown), and the surface of the solder pads has oxides and / or saponifier residues;

[0040] S2: Form a soldering flux 2 on the surface of the solder pads by printing;

[0041] S3: Heat the chip packaging structure 1 so that the soldering flux 2 reacts chemically with the oxides and / or saponifier residues.

[0042] The above cleaning method for the chip packaging structure 1 forms a soldering flux on the surface of the solder pads and heats the chip packaging structure 1, so that the soldering flux reacts chemically with the oxide layer and / or saponifier residues on the surface of the solder pads, can efficiently remove the oxide layer and / or saponifier residues on the surface of the solder pads, reduces the corrosion of the solder pad substrate, protects the surface of the solder pads, reduces welding defects, and improves the yield of the product.

[0043] Specifically, perform step S1 to provide a chip packaging structure 1, the chip packaging structure 1 includes solder pads, and the surface of the solder pads has oxides and / or saponifier residues.

[0044] Exemplarily, the chip packaging structure 1 further includes a substrate, an integrated circuit chip, and chip packaging materials. Among them, the substrate includes a BGA substrate (Ball Grid Array Substrate), and its main function is to carry the integrated circuit chip. The integrated circuit chip is the core part of the chip packaging structure 1, usually made of silicon or other semiconductor materials, and integrates various electronic components and circuits. The packaging materials are used to protect the chip, prevent physical damage, chemical corrosion, and moisture intrusion, and the materials of the packaging materials include plastics, ceramics, and metals.

[0045] Exemplarily, the solder pad is a metal contact point on the integrated circuit chip or the substrate, used to achieve electrical connection. The solder pad is usually made of conductive materials such as copper, gold, nickel, and tin. Among them, the oxide on the surface of the solder pad is a metal oxide layer formed after the solder pad contacts with oxygen in the air, and the saponifier is left over from the previous process. If it is not removed sufficiently, it will affect the performance of the chip packaging structure 1.

[0046] Please refer to Figure 2 , perform step S2, and form the flux 2 on the surface of the solder pad by printing.

[0047] In some embodiments, forming the flux 2 on the surface of the solder pad by printing includes:

[0048] Place the chip packaging structure 1 on a loader (not shown).

[0049] Use the loader to automatically transfer the chip packaging structure 1 to the printer 3.

[0050] Use the printer 3 to print and form the flux 2 on the surface of the solder pad.

[0051] In some embodiments, the printer 3 includes a carrier base 31, a printing stencil 32, a squeegee 33, and a printing frame 34. Using the printer 3 to print and form the flux 2 on the surface of the solder pad includes:

[0052] Use the loader to automatically transfer the chip packaging structure 1 onto the carrier base 31.

[0053] Use the squeegee 33 to scrape and coat the flux 2 on the printing stencil 32, and press the flux 2 through the printing stencil 32 onto the solder pad.

[0054] The loader can automatically grab and transfer the chip packaging structure 1, making the production process more efficient. The loader can also be conveniently integrated with other production equipment (such as the subsequent printer used) to form a complete automated production line, facilitating the optimization and adjustment of the production process and improving production efficiency.

[0055] Such as Figure 2As shown, the printing machine 3 includes a carrying base 31, a printing stencil 32, a squeegee 33, and a printing frame 34. The carrying base 31 is the basic structure of the printing machine 3 and is used to support and fix the printing stencil 32 and the squeegee 33. The printing stencil 32 is the core component of screen printing and is used to imprint the flux 2 onto the pads of the chip package structure 1 through the mesh holes. The function of the squeegee 33 is to evenly scrape the flux 2 onto the printing stencil 32 and imprint the flux 2 through the mesh holes onto the pads of the chip package structure 1 by applying a certain pressure. In addition, printing frames 34 are provided at both ends of the printing stencil 32 to prevent the loss of the group solder flux. By means of screen printing the flux 2, the flux can be accurately formed, while ensuring the effect of removing oxide and / or saponifier residues, it will not cause excessive material loss, reduce the waste generated due to material waste, and has certain environmental benefits.

[0056] Please refer to Figure 3 , perform step S3 to heat the chip package structure 1 so that the flux 2 reacts chemically with the oxide and / or saponifier residues.

[0057] In some embodiments, before heating the chip package structure 1 so that the flux 2 reacts chemically with the oxide and / or saponifier residues, it further includes:

[0058] Transfer the chip package structure 1 into the heating device;

[0059] At the first heating rate, raise the temperature in the heating device to the first preset temperature within the first preset time to preheat the surface of the pads. Among them, preheating the surface of the pads can ensure that the flux fully reaches the reaction temperature. The first preset time is 180 - 240 s, the temperature in the heating device before preheating is 25 - 30 °C, and the first preset temperature is 150 °C.

[0060] Exemplarily, the heating device includes a hot air reflow oven 4, and the oxygen concentration in the heating device is less than 100 ppm.

[0061] Exemplarily, the hot air reflow oven 4 includes a first heating zone 41, a second heating zone 42, a gas circulation device 43, an exhaust gas outlet 44, and a conveyor plate 45. Among them, the first heating zone 41 and the second heating zone 42 are arranged opposite to each other, the conveyor plate 45 is located between the first heating zone 41 and the second heating zone 42. The first heating zone 41 and the second heating zone 42 are responsible for preheating the chip package structure and the flux, and ensuring that the chip package structure 1 and the flux 2 fully reach the reaction temperature, so as to ensure that the flux 2 can fully react on the surface of the solder pad. The gas circulation device 43 is responsible for circulating hot air in the furnace to ensure uniform temperature distribution, improve the welding efficiency and quality. The exhaust gas outlet 44 is responsible for discharging the exhaust gas generated during the reaction process to reduce environmental pollution. The conveyor plate 45 is responsible for transporting the chip package structure 1 from the inlet of the hot air reflow oven 4 to the outlet at a certain speed, ensuring the full progress of the reaction process and the automation of the process flow, so as to improve the process efficiency.

[0062] Therefore, using the hot air reflow oven 4 as the heating device to preheat the surface of the solder pad includes:

[0063] Automatically transfer the chip package structure 1 to between the first heating zone 41 and the second heating zone 42 through the conveyor plate 45, and raise the temperature in the hot air reflow oven 4 to the first preset temperature within the first preset time to preheat the surface of the solder pad.

[0064] In some embodiments, heating the chip package structure 1 to cause the flux 2 to chemically react with the oxide and / or saponifier residue includes:

[0065] At the second heating rate, raise the temperature in the heating device from the first preset temperature to the second preset temperature within the second preset time, so that the flux 2 on the surface of the solder pad chemically reacts with the oxide and saponifier. The first heating rate is greater than the second heating rate. That is, the flux reacts with the oxide and saponifier residues on the surface of the solder pad between the first preset temperature and the second preset temperature. The first preset temperature and the second preset temperature are the lowest and highest temperatures of the reaction respectively, and the second preset time is the reaction time. Among them, the second preset time is 30 - 80 s, and the second preset temperature is 180 - 200 °C. Setting the first heating rate greater than the second heating rate can ensure quickly reaching the reaction temperature and the stability of the temperature change during the reaction process.

[0066] Then, using the hot air reflow oven 4 as the heating device to cause the flux 2 on the surface of the solder pad to chemically react with the oxide and / or saponifier residue includes:

[0067] By further regulating the hot air reflow oven 4, the temperature between the first heating zone 41 and the second heating zone 42 is increased from the first preset temperature to the second preset temperature within the second preset time, so that the soldering flux on the surface of the solder pad reacts chemically with the oxide and / or saponifier residue.

[0068] In some embodiments, the soldering flux is a mixture of a solvent, a reactant, and an auxiliary agent. The main function of the solvent is to dissolve the other components in the soldering flux together to form a uniform mixture, which is convenient for the application and use of the soldering flux; the reactant is used to chemically react with the oxide and saponifier residue on the surface of the solder pad, thereby removing the oxide and / or saponifier residue on the surface of the solder pad, ensuring the cleanliness of the soldering surface, thereby improving the soldering quality; the auxiliary agent is used to improve the solubility and dispersibility of each component in the soldering flux, ensuring the uniformity and stability of the soldering flux, so as to ensure that the reactant fully reacts with the oxide and saponifier residue on the surface of the solder pad.

[0069] Exemplarily, the oxide on the surface of the pad includes at least one of nickel oxide, tin oxide, and copper oxide, and the saponifier includes an organic component and a substance that can be partially dissolved in an organic solvent, such as a mixture of ethanolamine, glycolic acid, propylene glycol, and lactic acid, wherein the concentration of ethanolamine is 20%, the concentration of glycolic acid is 12%, the concentration of propylene glycol is 18%, the concentration of lactic acid is 12%, and the concentration of deionized water is 38%.

[0070] Exemplarily, the solvent includes alcohol organic matter, ketone organic matter and lipid organic matter, such as ethanol, isopropanol, butanol, diethylene glycol monobutyl ether. The above organic solvents have good dissolving power, have a direct dissolving effect on the saponifier residue, can destroy the intermolecular force of the saponifier residue, decompose it into small molecules or ions, and make it soluble, so as to facilitate cleaning and removal. The solvent can also dissolve other effective ingredients in the flux, such as reactants, and bring them to the metal surface, so that these ingredients can fully contact and react with the oxide layer, thereby indirectly removing the oxide. In addition, the solvent has a certain physical scouring and dissolving effect on some loose oxides, which can help remove some loose oxides.

[0071] The reactants include organic acids and organic amines. Among them, organic amines are alkaline, and some components in the saponifier residue may have acidic properties or the characteristics of reacting with alkaline substances (such as glycolic acid, lactic acid). Organic amines can react with these acidic or reactive components in the saponifier residue to undergo neutralization reactions or other chemical reactions, generating substances that are more soluble in water or organic solvents, which helps to remove the saponifier residue. At the same time, some organic amines have surface-active effects, which can reduce the surface tension, making it easier for the solvent to penetrate into the interior of the saponifier residue, enhancing the dissolution and cleaning effects. Organic amines can also react with the oxides on the metal surface through acid-base neutralization reactions or complexation reactions, converting the oxides with poor welding performance into soluble or volatile substances, achieving the purpose of removing oxides. And some organic amines with reducibility can, under conditions such as heating, also reduce metal oxides to metal elements and be oxidized themselves, thereby removing the oxide layer.

[0072] Organic acids have strong redox capabilities and can effectively remove oxides. At the same time, they have relatively little corrosiveness to the surface of the welded parts. Organic acids can undergo neutralization reactions with the alkaline components (such as ethanolamine) in the saponifier or can also undergo saponification reactions with the alkaline components (such as ethanolamine) in the saponifier. The organic acids in the flux can also react with the oxides on the surface of the solder pad through redox reactions. The hydrogen ions in the organic acids react with the oxides. For example, the carboxyl group of the organic acid and metal ions remove the oxides in the form of metal soaps.

[0073] In addition, during the reaction process, organic amines themselves contain amino - NH and are reactive. Adding organic amines can promote the subsequent welding effect. To reduce the corrosive effect of the flux on the solder pad, a certain amount of corrosion inhibitor can be added to the prepared flux, and organic amines can also be used as corrosion inhibitors. When organic acids and organic amines are mixed, a neutralization reaction occurs, generating a neutralization product. However, this neutralization product is unstable and will quickly decompose at the reaction temperature, regenerating organic acids and organic amines, which can ensure the original activity of the organic acids. After the reaction, the remaining organic acids will be neutralized by the organic amines, reducing the acidity of the residue and reducing corrosion. Therefore, organic amines can not only act as reactants in the flux, reacting with oxides and saponifier residues, but also act as corrosion inhibitors, reducing the corrosion of the solder pad surface without reducing the activity of the flux.

[0074] The auxiliary agent includes polyethylene glycol. Polyethylene glycol has good solubility and dispersibility. When removing the residue of the saponifying agent, it can act as a dispersant to help the solvent better disperse on the surface of the saponifying agent residue, increasing the contact area between the solvent and the saponifying agent residue, thereby improving the dissolution efficiency of the solvent for the saponifying agent residue. At the same time, polyethylene glycol itself can also play a certain role in dissolving and dispersing some saponifying agent residue substances, making the saponifying agent residue easier to be carried away by the cleaning solution; when removing oxides, polyethylene glycol can help the active components in the flux better disperse and contact the oxides on the surface of the solder pad, enabling the active components to react more fully with the oxides. In addition, when heated, polyethylene glycol will melt, and the liquid film formed on the surface of the solder pad helps to reduce the surface tension of the flux, enabling the flux to spread better on the surface of the solder pad and allowing the oxides to come into full contact with the reactants. At the same time, this liquid film can also play a certain role in isolating air, reducing the re-oxidation of the surface of the solder pad during the welding process and effectively improving the stability of the flux.

[0075] Among them, in some embodiments, the concentration of the solvent is 50 - 60%, the concentration of the organic amine in the reactant is 15 - 25%, the concentration of the organic acid in the reactant is 5 - 15%, and the concentration of the auxiliary agent is 10 - 20%. By regulating the components and the concentration ratios of the components in the flux, the composition and concentration of the flux are optimized, so that the active components in the flux can fully chemically react with the oxides and saponifying agent residues on the metal surface, achieving effective cleaning of the surface of the solder pad, providing better welding conditions, and ensuring the stability of the welding process and the reliability of the welding quality.

[0076] In some embodiments, after heating the chip package structure 1 to cause the flux 2 to chemically react with the oxides and / or saponifying agent residues, it further includes:

[0077] Cooling down the heating device.

[0078] In some embodiments, cooling down the heating device includes:

[0079] At a first cooling rate, the temperature inside the heating device is lowered from a second preset temperature to a first preset temperature within a third preset time; wherein, the third preset time is 120 - 160 s, and the first preset temperature is 150 °C; that is, at this time, the temperature inside the heating device is still within the reaction temperature range, so further setting the temperature inside the heating device to the first preset temperature within a certain period of time can further ensure that the chemical reactions of the flux on the surface of the solder pad with the oxides and saponifying agent proceed fully;

[0080] At a second cooling rate, the temperature inside the heating device is decreased from a first preset temperature to a third preset temperature within a fourth preset time, and the second cooling rate is greater than the first cooling rate. Among them, the fourth preset time is 240 - 320 s, and the third preset temperature is 40 - 60 °C. By gradually cooling, the thermal stress concentration caused by rapid cooling can be reduced, thereby ensuring the stability of the solder pads.

[0081] Exemplarily, the hot air reflow oven 4 further includes a first cooling zone 46 and a second cooling zone 47, which are responsible for reducing the temperature of the chip packaging structure to ensure the stability of the solder pads and the welding quality. Therefore, using the hot air reflow oven 4 as the heating device and cooling the heating device includes:

[0082] The chip packaging structure 1 is conveyed to between the first cooling zone 46 and the second cooling zone 47 through a conveyor plate, and at a first cooling rate, the temperature inside the hot air reflow oven 4 is decreased from a second preset temperature to a first preset temperature within a third preset time;

[0083] At a second cooling rate, the temperature inside the hot air reflow oven 4 is decreased from the first preset temperature to the second preset temperature within the fourth preset time.

[0084] Among them, the conveying speed of the conveyor plate 45 inside the hot air reflow oven 4 is 50 - 70 cm / min, and the gas atmosphere inside the hot air reflow oven 4 is a nitrogen atmosphere.

[0085] Exemplarily, by heating the chip packaging structure 1, during the chemical reaction process of the flux 2 with the oxide and / or saponifier residue, preheating, reaction, and cooling stages are set, and parameters such as the temperature and the temperature change rate during each stage are precisely controlled, ensuring the full progress of the reaction, ensuring the full cleaning of the solder pad surface, and also avoiding damage to the chip packaging structure during the reaction process.

[0086] In addition, since the substrate is a BGA substrate, and common substrate materials such as BGA substrates have good high-temperature resistance. For example, polyimide (PI) has a high glass transition temperature, excellent thermal stability and mechanical properties, and can maintain structural integrity and performance stability at high temperatures; glass fiber-reinforced epoxy substrates can also withstand a certain high temperature without significant deformation or performance degradation; chip packaging materials such as ceramics and plastics consider the influence of the high temperature of reflow soldering during design and have a certain high-temperature resistance. Ceramic packaging has a high melting point and good thermal stability, and can protect the chip at high temperatures; plastic packaging materials are also designed with special formulas and can withstand the reflow soldering temperature; semiconductor materials such as silicon inside the integrated circuit chip have a relatively high melting point and thermal stability and will not melt or suffer structural damage at the reflow soldering temperature. At the same time, the processes and materials used in the manufacturing process of integrated circuit chips also enable them to work normally in a certain high-temperature environment. Therefore, the chip packaging structure can be unaffected by temperature in the hot air reflow furnace and its performance will not be affected.

[0087] In some embodiments, after cooling the heating device, it further includes:

[0088] Cleaning the surface of the solder pad.

[0089] Exemplarily, the cleaning device used for cleaning the surface of the solder pad includes a cleaning machine 5, and the cleaning machine 5 includes a cleaning base 51 and a spraying system 52. The cleaning base 51 is used to carry the chip packaging structure 1, and the spraying system 52 is used to spray a cleaning agent onto the chip packaging structure 1. Among them, cleaning the surface of the solder pad includes:

[0090] Automatically transferring the chip packaging structure 1 to the cleaning base 51;

[0091] Adjust the temperature and pressure of the cleaning agent sprayed by the spraying system 52, and use the spraying system 52 to spray the cleaning agent onto the chip packaging structure 1 located on the cleaning base to clean the solder pad. Among them, the cleaning agent used for cleaning the surface of the solder pad includes pure water, the temperature of the cleaning agent is 45 - 55 °C, and the pressure of the cleaning agent is 3 - 6 kg / cm 2 . By adjusting the temperature and pressure of the cleaning agent, the cleaning effect of the chip packaging structure 1 can be significantly improved, ensuring the sufficient removal of oxides and saponifier residues on the surface of the solder pad, protecting the chip packaging structure 1, improving process stability, reducing costs and environmental impacts, and at the same time extending the service life of the equipment.

[0092] In some embodiments, after cleaning the solder pad, it further includes:

[0093] Transferring the chip packaging structure 1 from the cleaning machine 5 to a blanking machine (not shown) for blanking.

[0094] In some embodiments, by combining a loader, a printer 3, a hot air reflow oven 4, a cleaning machine 5, and an unloader, an automated cleaning process is achieved, improving the cleaning efficiency. Moreover, this method is applicable to various cleaning processes and has good versatility and flexibility.

[0095] In the description of this specification, the description referring to terms such as "some embodiments", "other embodiments", "ideal embodiments", etc. means that the specific features, structures, materials, or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic description of the above terms does not necessarily refer to the same embodiment or example.

[0096] The technical features of the above-described embodiments can be combined arbitrarily. For the sake of brevity of description, not all possible combinations of the technical features of the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, it should be considered as within the scope described in this specification.

[0097] The above-described embodiments merely represent several implementation manners of the present application. The description is relatively specific and detailed, but it should not be construed as a limitation on the scope of the patent application. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present application, several modifications and improvements can still be made, and these all belong to the protection scope of the present application. Therefore, the protection scope of the patent of the present application shall be subject to the appended claims.

Claims

1. A method for cleaning a chip packaging structure, characterized in that: The steps include: A chip packaging structure is provided, wherein the chip packaging structure comprises a solder pad, and oxide and / or saponifier residues are present on the surface of the solder pad; Forming soldering flux on the surface of the solder pad by printing; The chip packaging structure is heated to allow the soldering flux to chemically react with the oxide and / or the saponifier residue.

2. The cleaning method of the chip packaging structure according to claim 1, characterized in that: The soldering flux is formed by mixing a solvent, a reactant and an auxiliary agent, wherein the solvent includes alcohol organic matter, ketone organic matter and lipid organic matter, the reactant includes organic acid and organic amine, the auxiliary agent includes polyethylene glycol, and the concentration of the solvent is 50-60%, the concentration of the organic amine in the reactant is 15-25%, the concentration of the auxiliary agent is 10-20%, and the concentration of the organic acid in the reactant is 5-15%.

3. The cleaning method of the chip packaging structure according to claim 1, characterized in that: Before heating the chip packaging structure so that the soldering flux reacts chemically with the oxide and / or the saponifier residue, the method further comprises: transferring the chip packaging structure into a heating device; The temperature in the heating device is raised to a first preset temperature within a first preset time at a first heating rate to preheat the surface of the pad.

4. The method for cleaning a chip packaging structure according to claim 3, characterized in that: The step of heating the chip packaging structure so that the soldering flux reacts chemically with the oxide and / or the saponifier residue comprises: At a second heating rate, the temperature in the heating device is raised from the first preset temperature to a second preset temperature within a second preset time, so that the flux on the surface of the solder pad reacts chemically with the oxide and / or the saponifier, and the second heating rate is less than the first heating rate.

5. The method for cleaning a chip packaging structure according to claim 4, characterized in that: After heating the chip packaging structure so that the soldering flux reacts chemically with the oxide and / or the saponifier residue, the method further comprises: The heating device is cooled down.

6. The method for cleaning a chip packaging structure according to claim 5, characterized in that: The step of cooling the heating device comprises: At a first cooling rate, reducing the temperature in the heating device from the second preset temperature to the first preset temperature within a third preset time; The temperature in the heating device is reduced from the first preset temperature to a third preset temperature within a fourth preset time at a second cooling rate, wherein the second cooling rate is greater than the first cooling rate.

7. The method for cleaning a chip packaging structure according to claim 3, characterized in that: The heating device comprises a hot air reflow oven.

8. The method for cleaning a chip packaging structure according to claim 3, characterized in that: The oxygen content in the heating device is less than 100 ppm.

9. The method for cleaning a chip packaging structure according to claim 6, characterized in that: After cooling the heating device, the method further comprises: The surface of the welding pad is cleaned.

10. The method for cleaning a chip packaging structure according to claim 9, characterized in that: The cleaning agent used for cleaning the surface of the pad includes pure water, the temperature of the cleaning agent is 45-55°C, and the pressure of the cleaning agent is 3-6 kg / cm 2 .

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