阅读说明：本技术 一种qfp封装的元器件返修方法 (Component repairing method for QFP (quad Flat Package) packaging ) 是由 支强 韩亚国 丁磊 罗凯 郭帅 何永乐 于 2021-08-18 设计创作，主要内容包括：本发明公开了一种QFP封装的元器件返修方法,通过故障定位确定要拆卸的器件,除掉三防漆、按现有设备工艺参数完成特殊过程确认的参数和与拆卸器件封装相同的加热头拆除QFP封装元器件；拆除完成后对QFP封装元器件和印制板组件上的焊盘进行清洗；用局部钢网对准印制板焊盘,并用与局部钢网尺寸相适应的刮刀刷锡膏,刷完锡膏去掉局部钢网,重新贴装QFP封装元器件；用QUICK EA-A20E BGA返修系统重新焊接QFP封装元器件,焊接后对焊点进行检查和修复,修复完后进行清洗,清洗完成后进行上电测试；本发明方法能确保PCB板组件的返修质量,保证了产品使用的可靠性,返修的成功率能够达到85％以上,PCB板组件的返修成本降低90％,技术、经济效果显著。(The invention discloses a method for repairing a component packaged by QFP, which comprises the steps of determining a component to be disassembled through fault positioning, removing three-proofing paint, finishing parameters confirmed in a special process according to the process parameters of the existing equipment, and disassembling the QFP packaged component by a heating head which is the same as the component packaged by disassembling; after the removal is finished, cleaning the QFP package component and the bonding pad on the printed board assembly; aligning the local steel mesh to a bonding pad of the printed board, brushing solder paste by using a scraper which is adaptive to the size of the local steel mesh, removing the local steel mesh after brushing the solder paste, and re-mounting the QFP packaging component; the QFP packaging component is welded again by a QUICK EA-A20E BGA repair system, a welding point is checked and repaired after welding, cleaning is carried out after repairing, and a power-on test is carried out after cleaning is finished; the method can ensure the repair quality of the PCB assembly, ensure the use reliability of the product, ensure the repair success rate to be more than 85 percent, reduce the repair cost of the PCB assembly by 90 percent, and have obvious technical and economic effects.)

1. A method for repairing a component packaged by a QFP is characterized by comprising the following steps:

step 1: determining a component to be disassembled;

the component to be disassembled must be the component which completes fault positioning or the component with a defect is welded, otherwise, the component is not allowed to be disassembled;

step 2: removing three-proofing paint;

before the components of the printed board assembly are disassembled, removing the three-proofing paint of the components needing to be disassembled by adopting a solvent method or a thermal stripping method;

and step 3: removing the QFP package component;

after the paint of the component to be disassembled is removed, protecting other components around the component to be disassembled by using a high-temperature adhesive tape or a copper foil; a repair system is adopted to disassemble a fault component, and the size of a heating head of the repair system must be consistent with the size of a component package to be disassembled during disassembly;

heating the component to be disassembled according to the D1-D6 temperature flow section confirmed by the repair system in the completion of a special process, and sucking up the component by using an automatic suction nozzle after the D6 flow is finished to complete the disassembly of the component;

and 4, step 4: cleaning;

placing an electric soldering iron at the bonding pad where the QFP package component is dismounted to heat, sucking soldering tin of the bonding pad by using a tin sucking device, and cleaning the soldering tin on the bonding pad of the printed board;

cleaning the bonding pad of the removed QFP packaging component on the PCB by using industrial alcohol for at least a times until the bonding pad is cleaned;

and 5: coating solder paste;

placing the local steel mesh corresponding to the QFP package component package to the mounting position of the QFP package component of the printed board by using anti-static tweezers, and aligning the local steel mesh with a bonding pad of the QFP package component;

placing a certain amount of soldering paste on the local steel mesh, injecting the soldering paste into the leakage hole of the local steel mesh by using a scraper, wherein in the process of injecting the soldering paste, the angle between the scraper and the local steel mesh is 45-60 degrees, and after the printing of the local steel mesh and the soldering paste is completed, the local steel mesh is separated from the printed board assembly;

step 6: mounting a QFP packaging component;

clamping or sucking a new QFP package component by using anti-static tweezers or an anti-static pen, aligning 1 pin or front end mark of the QFP package component with the front end mark of the characters of the printed board, aligning two sides or four sides of the pads, pasting the QFP package component in the middle, pressing the top surface of the component body by using anti-static tweezers to ensure that the pins of the component are not less than 1/2 thickness and are immersed in the soldering paste, and the pins of the component are all positioned on the pads;

mounting a narrow-spacing device with the pin spacing smaller than 0.65mm under a b-time desk magnifier;

and 7: welding the QFP package component;

heating the components by using the temperature process sections D1-D6 of the repair system, and finishing the welding process after 6 temperature process sections D1-D6 are finished;

and 8: inspecting and repairing the welded QFP packaged component;

removing high-temperature adhesive tape or copper foil for protecting other devices around the welded QFP packaged device, and checking the pin of the welded QFP packaged device under a 10-time desk magnifier or an electron microscope with the magnification of more than b times, wherein the installation direction of the QFP packaged device is required to be consistent with that of a drawing; if the QFP packaging component pin welding spot has a tin bead and pin connection defect, the welding defect is eliminated by adopting a manual repair welding mode;

and step 9: cleaning;

after the welding spots are checked to be qualified, cleaning the welded QFP packaging component, the pins and the welding spots by industrial alcohol at least three times until the QFP packaging component, the pins and the welding spots are cleaned; after cleaning, finally observing the welded device by using a b-time desk magnifier or an electron microscope with the magnification of more than b times;

step 10: electrifying, testing and repairing three-proofing paint;

after the cleaning is finished for c minutes, carrying out an electrifying test, and after the test is qualified, coating the three-proofing paint on the surface and the pin of the newly welded QFP packaging component; and (5) allowing subsequent work to be carried out d hours after the three-proofing paint is coated.

2. A component repairing method of QFP package as claimed in claim 1, wherein said repairing system is QUICK EA-a20E BGA repairing system.

3. A component repairing method of QFP package as claimed in claim 1, wherein a is 3, b is 10, c is 15 and d is 24.

Technical Field

The invention belongs to the technical field of electronic information, and particularly relates to a component repairing method.

Background

With the development of electronic technology, QFP packaged devices represented by DSP have the characteristics of powerful function, small size, light weight, high reliability, and the like, and are widely used. However, when the QFP package component fails and needs to be repaired, the QFP package component has the characteristics of dense pins, thin pins, high precision and the like, so that higher technical requirements are provided for the repair.

Meanwhile, with the improvement of requirements of the avionic device on salt spray resistance, mildew resistance and moisture resistance, polyurethane resin with high strength, high corrosion resistance and high moisture resistance is selected as a three-proofing coating for a large number of aviation printed board components, so that the reliability of the product is greatly improved. As shown in fig. 2, when the product is repaired with hot air, the resin coating is extremely difficult to remove, and the coking phenomenon is easy to occur, resulting in the reduction of the three-proofing performance. The solder joint without resin paint removed at the periphery of the repaired device can generate secondary reflux at high temperature, and the solder joint covered by the paint layer can have the defects of 'solder ball explosion', little tin, poor appearance, short circuit of the solder joint, missing of the solder and the like. When the device nozzle is moved away from the component, the solder joint tends to cool below the melting temperature of the solder, which can cause the solder pad to pull off. The reliability of the repaired device is influenced, the devices around the repaired area are greatly influenced, even one device is repaired, a plurality of devices around the repaired area need to be repaired for two or three times, and the reliability of the printed board assembly is reduced.

The invention creation of application No. 201210346047.4 discloses a LGA and BGA rework process, which uses hot air convection or a heating table to heat a device package, detaches the LGA/BGA from the PCB, and detaches the device package from the PCB with a vacuum suction nozzle or tweezers; and adding soldering tin on a land of the LGA/BGA, mounting the LGA/BGA on a PCB, welding by reflow soldering, and finishing repair to shorten the production period of a product, reduce waste and reduce cost. However, the invention has high requirements on the technical level of operators, and simultaneously causes the whole PCB to be heated, thereby reducing the reliability of the PCB.

The invention creation of application number 201910135751.7 discloses a repair removal process of epoxy resin coated components, which comprises the following steps: cleaning a reworked area, covering and protecting a non-reworked area, unsoldering a welding spot, softening by hot air, removing a coating layer, and cleaning a stripping area. However, the invention has higher requirements on the technical level of operators and the performance of the hot air gun, easily causes the damage of devices or the falling of the printed board bonding pad, causes the damage of a mother board, increases and reduces the repair difficulty of the PCB assembly and reduces the repair qualification rate of the PCB assembly.

Disclosure of Invention

In order to overcome the defects of the prior art, the invention provides a method for repairing a component of QFP package, which comprises the steps of determining a component to be disassembled through fault positioning, removing three-proofing paint, finishing parameters confirmed in a special process according to the process parameters of the prior equipment, and disassembling the component of the QFP package by a heating head which is the same as the component package to be disassembled; after the removal is finished, cleaning the QFP package component and the bonding pad on the printed board assembly; aligning the local steel mesh to a bonding pad of the printed board, brushing solder paste by using a scraper which is adaptive to the size of the local steel mesh, removing the local steel mesh after brushing the solder paste, and re-mounting the QFP packaging component; the QFP packaging component is welded again by a QUICK EA-A20E BGA repair system, a welding point is checked and repaired after welding, cleaning is carried out after repairing, and a power-on test is carried out after cleaning is finished; the method can ensure the repair quality of the PCB assembly, ensure the use reliability of the product, ensure the repair success rate to be more than 85 percent, reduce the repair cost of the PCB assembly by 90 percent, and have obvious technical and economic effects.

The technical scheme adopted by the invention for solving the technical problem comprises the following steps:

step 1: determining a component to be disassembled;

the component to be disassembled must be the component which completes fault positioning or the component with a defect is welded, otherwise, the component is not allowed to be disassembled;

step 2: removing three-proofing paint;

before the components of the printed board assembly are disassembled, removing the three-proofing paint of the components needing to be disassembled by adopting a solvent method or a thermal stripping method;

and step 3: removing the QFP package component;

after the paint of the component to be disassembled is removed, protecting other components around the component to be disassembled by using a high-temperature adhesive tape or a copper foil; a repair system is adopted to disassemble a fault component, and the size of a heating head of the repair system must be consistent with the size of a component package to be disassembled during disassembly;

heating the component to be disassembled according to the D1-D6 temperature flow section confirmed by the repair system in the completion of a special process, and sucking up the component by using an automatic suction nozzle after the D6 flow is finished to complete the disassembly of the component;

and 4, step 4: cleaning;

placing an electric soldering iron at the bonding pad where the QFP package component is dismounted to heat, sucking soldering tin of the bonding pad by using a tin sucking device, and cleaning the soldering tin on the bonding pad of the printed board;

cleaning the bonding pad of the removed QFP packaging component on the PCB by using industrial alcohol for at least a times until the bonding pad is cleaned;

and 5: coating solder paste;

placing the local steel mesh corresponding to the QFP package component package to the mounting position of the QFP package component of the printed board by using anti-static tweezers, and aligning the local steel mesh with a bonding pad of the QFP package component;

placing a certain amount of soldering paste on the local steel mesh, injecting the soldering paste into the leakage hole of the local steel mesh by using a scraper, wherein in the process of injecting the soldering paste, the angle between the scraper and the local steel mesh is 45-60 degrees, and after the printing of the local steel mesh and the soldering paste is completed, the local steel mesh is separated from the printed board assembly;

step 6: mounting a QFP packaging component;

clamping or sucking a new QFP package component by using anti-static tweezers or an anti-static pen, aligning 1 pin or front end mark of the QFP package component with the front end mark of the characters of the printed board, aligning two sides or four sides of the pads, pasting the QFP package component in the middle, pressing the top surface of the component body by using anti-static tweezers to ensure that the pins of the component are not less than 1/2 thickness and are immersed in the soldering paste, and the pins of the component are all positioned on the pads;

mounting a narrow-spacing device with the pin spacing smaller than 0.65mm under a b-time desk magnifier;

and 7: welding the QFP package component;

heating the components by using the temperature process sections D1-D6 of the repair system, and finishing the welding process after 6 temperature process sections D1-D6 are finished;

and 8: inspecting and repairing the welded QFP packaged component;

removing high-temperature adhesive tape or copper foil for protecting other devices around the welded QFP packaged device, and checking the pin of the welded QFP packaged device under a 10-time desk magnifier or an electron microscope with the magnification of more than b times, wherein the installation direction of the QFP packaged device is required to be consistent with that of a drawing; if the QFP packaging component pin welding spot has a tin bead and pin connection defect, the welding defect is eliminated by adopting a manual repair welding mode;

and step 9: cleaning;

after the welding spots are checked to be qualified, cleaning the welded QFP packaging component, the pins and the welding spots by industrial alcohol at least three times until the QFP packaging component, the pins and the welding spots are cleaned; after cleaning, finally observing the welded device by using a b-time desk magnifier or an electron microscope with the magnification of more than b times;

step 10: electrifying, testing and repairing three-proofing paint;

after the cleaning is finished for c minutes, carrying out an electrifying test, and after the test is qualified, coating the three-proofing paint on the surface and the pin of the newly welded QFP packaging component; and (5) allowing subsequent work to be carried out d hours after the three-proofing paint is coated.

Preferably, the rework system is a QUICK EA-A20E BGA rework system.

Preferably, a is 3, b is 10, c is 15, and d is 24.

The invention has the following beneficial effects:

the invention realizes the repair of the components (also suitable for SOIC, CHIP, QFN, BGA and the like) of the QFP package, the repair process adopts local heating, the repair heating temperature of each component is confirmed by a special process, the heating process is stable and controllable and is not influenced by human factors, and the problem that the PCB assembly is damaged in the disassembling process or the disassembling and welding process due to the falling of a welding plate of the printed board assembly or the damage of other devices around the disassembling and welding device of the printed board assembly caused by the hot air gun and the human factors is solved. The problems that the welding disc falls off and the like in the dismounting process of the printed board assembly are avoided, the repair success rate of the QFP packaging component is improved, and the repair cost of the PCB assembly is reduced. Compared with the prior art, the method can ensure the repair quality of the PCB assembly, ensure the use reliability of the product, ensure that the repair success rate can reach more than 85 percent, reduce the repair cost of the PCB assembly by 90 percent, and have obvious technical and economic effects.

Drawings

FIG. 1 is a schematic block diagram of a rework method of the present invention.

Fig. 2 is a schematic block diagram of a prior art rework process.

FIG. 3 is a partial steel mesh profile according to the present invention.

Detailed Description

The invention is further illustrated with reference to the following figures and examples.

As shown in fig. 1, a method for repairing a component of a QFP package includes the following steps:

step one, determining a device to be disassembled;

the device to be disassembled must be one that has completed the fault location or one that has been soldered to a defect, otherwise, the disassembly of the electronic components is not allowed.

Removing three-proofing paint;

before the electronic components are disassembled, the three-proofing paint of the components needing to be disassembled is removed by adopting a solvent method or a thermal stripping method, and the printed board and the electronic components are prevented from being damaged due to improper use of tools in the paint removing process.

Removing the QFP package component;

after the device to be disassembled is subjected to paint removal, other devices around the device to be disassembled are subjected to protection treatment by using a high-temperature adhesive tape or a copper foil. The defective component is removed using the QUICK EA-A20E BGA rework system, which must in principle have the dimensions of the heater head of the rework system matched to the dimensions of the chip package to be removed.

Heating according to the temperature flow sections D1-D6 confirmed by the QUICK EA-A20E BGA repair system completing the special process, wherein the temperatures of 6 temperature flow sections D1-D6 are required to be subjected to test verification and special process confirmation, and the disassembly process is required to ensure that the device and the printed board are not damaged; and D6, sucking up the chip by using an automatic suction nozzle after the flow is finished, and completing the disassembly of the device.

Step four, cleaning;

and placing an electric soldering iron at the position of the bonding pad of the QFP package component after being dismounted for heating, and sucking soldering tin on the bonding pad by using a tin sucking device to clean the soldering tin on the bonding pad of the printed board.

And cleaning the bonding pad of the removed QFP packaging component on the PCB by using industrial alcohol for three times, and cleaning the bonding pad.

Step five, coating tin paste;

and placing the local steel mesh corresponding to the QFP component package on the mounting position of the QFP component of the printed board by using anti-static tweezers, aligning the local steel mesh with the bonding pad of the QFP component, and taking a positioning measure between the steel mesh and the printed board component when needed. The steel mesh is shown in fig. 3.

And placing a certain amount of soldering paste on a local steel mesh as required, wherein the local steel mesh is a special repair tool for the QFP package component, the shape of the local steel mesh is square, and the input amount of the soldering paste is added according to the length of the scraper. With the scraper with during the small opening of solder paste injection local steel mesh, inject into the in-process of solder paste, the angle of scraper and local steel mesh is 45 ~ 60, accomplish the printing back of local steel mesh and solder paste, with local steel mesh and printing board subassembly separation, the separating speed of local steel mesh should slow as far as possible, prevent the solder paste adhesion.

Step six, mounting the QFP package component;

clamping or sucking a newly taken QFP package component by using anti-static tweezers or an anti-static pen, aligning 1 pin or front end mark of the QFP package component with the front end mark of the characters of the printed board, aligning the front end mark with the pads on two sides or four sides, pasting the QFP package component in the middle, slightly shoveling the top surface of the device body by using the anti-static tweezers to ensure that the pins of the component are not less than 1/2 thickness and are immersed in the soldering paste, and requiring that the pins of the component are all positioned on the pads. Narrow-pitch devices with a pin pitch of less than 0.65mm should be mounted under a 10-fold desk magnifier.

Welding a QFP packaging component;

heating by using QUICK EA-A20E BGA repair system D1-D6 temperature flow sections, wherein the temperature of 6 temperature flow sections D1-D6 must be a special temperature curve of the QFP package component confirmed by a special process, and the welding process must ensure good welding between the QFP package component and the printed board assembly; meanwhile, the damage of QFP packaging components and parts is avoided, and the damage of layering or other states of the printed board is avoided. And finishing the welding process after finishing 6 temperature process sections D1-D6.

Step eight, checking and repairing the welded QFP packaged component;

removing other devices around the welded QFP package component by using a high-temperature adhesive tape or copper foil, and checking the pin of the welded QFP package component under a 10-time desk magnifier or an electron microscope with a larger magnification, wherein the installation direction of the QFP package component is required to be consistent with that of a drawing; the pin welding spots of the QFP packaging component are bright and smooth, and no cross-linking, burr, tin nodule, crack and the like exist. If the welding spot of the pin of the QFP packaging component has the defects of tin bead, pin connection and the like, the welding defect is eliminated by adopting a manual repair welding mode.

Step nine, cleaning;

after repair welding is finished and welding spots are checked to be qualified, cleaning the welded QFP packaging component, the pins and the welding spots by industrial alcohol for three times until the QFP packaging component, the pins and the welding spots are cleaned; and finally observing the welded device by using a 10-time desk type magnifier or an electron microscope with higher magnification after cleaning.

Step ten, electrifying, testing and repairing three-proofing paint;

after cleaning is finished for 15min, performing a dotting test, and after the test is qualified, coating a three-proofing paint on the surface and the pins of the newly welded QFP packaging component; and after the three-proofing paint is coated for 24h, the subsequent work is allowed to be carried out.