Burr cutting method for wettability side wing product and wettability side wing product

Abstract

The invention discloses a method for cutting burrs of a wettability side wing product and the wettability side wing product, a lead frame is placed in a low-temperature environment with a preset temperature to be cooled, so that the burrs are embrittled, favorable conditions are created for subsequent cutting, and meanwhile, the harsh requirement for the environment temperature in a dry ice deburring mode is avoided; the control difficulty of the operation environment is simplified; high-pressure water with preset pressure is adopted for cleaning, effective cutting of the burrs of the wettability side wing product is achieved, compared with dry ice deburring, the requirement for equipment is low, special equipment and a stable operation environment are not needed, and therefore the implementation difficulty and cost are reduced; the requirement of the method on environmental parameters is relatively low, and the influence on the functional integrity of the device in the burr cutting process is relatively small, so that the product yield can be ensured, and the reliability and the stability of the production process are improved. The method has remarkable effects in the aspects of simplifying the operation process, reducing the implementation difficulty, ensuring the product quality and the like.

Description

Technical Field

[0001] The invention belongs to the field of semiconductor integrated circuit packaging and testing, and in particular relates to a method for cutting burrs of a wettable flank product and a wettable flank product. Background Art

[0002] In order to ensure the safety and high reliability of the car, the standard automatic visual inspection (AVI) of the vehicle will be implemented for the vehicle components after the device is installed. When the standard QFN package is used, the connection terminal is located at the bottom of the package device, and the terminal copper material exposed at the edge of the package is prone to oxidation, which makes it difficult to solder the side wall. Therefore, it is impossible to determine whether the package is effectively soldered through AVI or X-ray. In order to better meet the needs of SMT automated assembly and inspection, wettability flank technology came into being.

[0003] Wettability flank technology improves the wettability of the package flank, improves welding quality, reduces production costs, and simplifies the inspection process. At present, in the industry, the separation method for wettable flank QFN devices is mainly cutting separation. During the cutting and separation process, the friction between the copper material and the saw knife will produce curling, which will attach to the pins to form burrs; if the burrs after the first cutting are not removed in time, it is easy to cause tin whiskers during subsequent electroplating, resulting in the risk of short circuit during the use of the device product; usually, dry ice deburring is used to deal with the burrs after the first cutting, but the dry ice deburring method has more stringent environmental requirements; mainly because the extremely low temperature and sublimation characteristics of dry ice require that the operating environment must be kept within a specific low temperature range and have good ventilation conditions; at the same time, the deburring process also has high requirements for equipment, requiring special equipment and a stable operating environment; therefore, the dry ice deburring method is not easy to implement. Once the environmental parameters cannot meet the process requirements, the functional integrity of the device is easily affected during the cutting of the burrs, and the product quality cannot be guaranteed.

[0004] It can be seen that the method of using dry ice to cut burrs is difficult to implement and can easily affect the functional integrity of the device due to its stringent environmental requirements. Summary of the invention

[0005] The purpose of the present invention is to provide a method for cutting burrs of a wettable flank product and a wettable flank product, so as to solve the technical problem that the method of using dry ice to cut burrs has strict environmental requirements, resulting in great difficulty in implementation and easily affecting the functional integrity of the device.

[0006] In order to achieve the above object, the present invention adopts the following technical solution:

[0007] A method for cutting burrs of a wettable flank product comprises the following steps:

[0008] S1: placing the lead frame formed with wettable flank steps in a low temperature environment at a preset temperature for cooling;

[0009] S2: The cooled lead frame is cleaned with high-pressure water at a preset pressure to complete the cutting of the burrs of the wettable flank products.

[0010] Furthermore, the preset temperature is -40°C to -55°C.

[0011] Furthermore, the lead frame with the wing steps formed thereon is placed in a low temperature environment for cooling, wherein the cooling time is 2 to 4 hours.

[0012] Furthermore, the preset pressure is 150-180 bar.

[0013] Furthermore, the wettable wing step is formed by performing a first cutting on the lead frame; after the first cutting, the UV film on the lead frame is firstly peeled off, and then the lead frame is placed in a low temperature environment for cooling.

[0014] Furthermore, the specific process of using high-pressure water with a preset pressure to clean the cooled lead frame includes:

[0015] The cooled lead frame is placed on the conveying rail of the cleaning machine, and the high-pressure water spraying direction and the preset pressure are adjusted so that the high-pressure water is sprayed in a direction parallel to the surface of the lead frame at the preset pressure.

[0016] Furthermore, after the cooled lead frame is sprayed with high-pressure water, the sprayed lead frame is dried.

[0017] Furthermore, after the burr cutting is completed, the lead frame after the burr cutting is electroplated and cut for the second time.

[0018] Furthermore, after the electroplating and the second cutting process are completed, the lead frame after the second cutting is inspected for burrs, and the lead frame that meets the preset standard is transferred to the subsequent processing flow.

[0019] A wettable flank product is prepared by the above-mentioned method for cutting burrs of a wettable flank product. Compared with the prior art, the present invention has the following beneficial effects:

[0020] The present invention provides a method for cutting burrs of wettable flank products. The method cools the lead frame in a low-temperature environment of a preset temperature to make the burrs brittle, thereby creating favorable conditions for subsequent cutting. At the same time, the stringent requirements on the ambient temperature in the dry ice deburring method are avoided, and the difficulty of controlling the operating environment is simplified; secondly, high-pressure water of a preset pressure is used for cleaning, thereby effectively cutting the burrs of wettable flank products. Compared with dry ice deburring, the requirements for equipment are lower, and no special equipment and a stable operating environment are required, thereby reducing the difficulty and cost of implementation; since the requirements for environmental parameters of the method are relatively loose, and the impact on the functional integrity of the device during the burr cutting process is small, the product yield can be guaranteed, and the reliability and stability of the production process are improved. The method shows significant beneficial effects in simplifying the operating process, reducing the difficulty of implementation, and ensuring product quality.

[0021] Preferably, in the present invention, the lead frame is placed in a low temperature environment of -40°C to -55°C for cooling, which ensures the cooling effect while avoiding deformation or damage of the lead frame due to too low temperature, thereby improving the stability and reliability of the product.

[0022] Preferably, in the present invention, the cooling time in the low temperature environment is 2 to 4 hours, thereby ensuring the stability of the lead frame during the cooling process and the effect of subsequent processing.

[0023] Preferably, in the present invention, high-pressure water of 150-180 bar is used to clean the cooled lead frame, which ensures the cleaning effect while avoiding damage to the lead frame caused by excessive pressure, thereby improving the yield of the product.

[0024] Preferably, in the present invention, after the first cutting, the UV film on the lead frame is firstly peeled off, and then the lead frame is placed in a low temperature environment for cooling. Such a processing sequence is helpful to better remove burrs and improve the overall quality of the product.

[0025] Preferably, in the present invention, the cooled lead frame is placed on the transmission rail of the cleaning machine, and the high-pressure water spray direction and the preset pressure are adjusted so that the high-pressure water is sprayed in a direction parallel to the surface of the lead frame at the preset pressure, thereby ensuring the uniformity and effectiveness of cleaning and further improving the burr removal effect.

[0026] Preferably, in the present invention, electroplating and a second cutting process are required after the burr cutting is completed. Such subsequent processing steps help to further improve the performance and appearance quality of the product.

[0027] Preferably, in the present invention, a burr inspection step is added, and the lead frame that meets the standards is subsequently processed to ensure the quality and reliability of the final product.

[0028] The present invention also provides a wettable flank product, which is prepared by the above-mentioned burr cutting method. Due to the use of the burr cutting method, the burr removal effect is guaranteed, and the wettable flank product has higher functional integrity and reliability. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 A conventional process flow chart for step-by-step cutting of a wettable flank product provided by an embodiment of the present invention;

[0030] Figure 2 A schematic diagram of burrs generated on a lead after the first cutting provided by an embodiment of the present invention;

[0031] Figure 3 A schematic diagram of high-pressure water jet cutting burrs provided in an embodiment of the present invention;

[0032] Figure 4 A flow chart of a method for cutting burrs of a wettable flank product provided in an embodiment of the present invention.

[0033] Reference numerals:

[0034] First SAW knife - 1; pin - 2; frame connecting rib - 3; plastic package - 4; coating - 5; second SAW knife - 6; burr - 7. DETAILED DESCRIPTION

[0035] In order to enable those skilled in the art to better understand the technical solutions in the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0036] It should be noted that when an element is referred to as being "disposed on" another element, it may be directly on the other element or there may be a central element. When an element is considered to be "connected to" another element, it may be directly connected to the other element or there may be a central element at the same time. The terms "vertical", "horizontal", "left", "right" and similar expressions used herein are for illustrative purposes only and are not intended to be the only embodiment.

[0037] Example 1

[0038] As mentioned in the background technology, currently, dry ice deburring is usually used to deal with the burrs after the first cutting, but this method has strict requirements on the environment; mainly because the extremely low temperature and sublimation characteristics of dry ice require that the operating environment must be maintained within a specific low temperature range and need to have good ventilation conditions; at the same time, the deburring process also has high requirements on equipment, requiring special equipment and a stable operating environment; therefore, the dry ice deburring method is not easy to implement. Once the environmental parameters cannot meet the process requirements, the functional integrity of the device is easily affected during the burr cutting process, and the product quality cannot be guaranteed.

[0039] Combination Figure 1 and Figure 2 As shown, the existing cutting and separation process is as follows: (1) Use a film laminating machine to apply UV film to the front of the lead frame after plastic sealing, and stick the edge of the UV film on the Ring; (2) Use a TAPE SAW cutting machine to place the wafer ring on the stage, and use a pre-designed wider first SAW knife 1 along the cutting path on the back of the frame, that is, the first cutting at the frame connecting rib 3 to form a step of wettable flanks; (3) Use a UV irradiator to remove the UV film on the frame; (4) Electroplating tin is performed on the pins 2 of the lead frame after the first cutting to obtain a coating 5; (5) Repeat the above steps (1) to (3) for the second cutting of the electroplated lead frame, wherein a narrow knife is used for cutting and the device is separated. Figure 2 As shown, burrs 7 are formed at the edges of the pins 2 on the plastic package 4; finally, the burrs 7 generated after the first cutting can be removed by using a dry ice deburring method.

[0040] In order to solve the above problems, the present embodiment provides a method for cutting burrs of wettable flank products. The method freezes the product after the first cutting for several hours to make the burrs brittle, and removes the brittle burrs by flushing with a high-pressure water gun. The method can effectively improve the burrs formed by the first cutting, significantly reduce the generation of tin whiskers during electroplating, effectively avoid short circuits in devices, improve product yield, and is simple to operate and low-cost.

[0041] In this embodiment, the specific inventive concept is as follows:

[0042] First, the method of embrittlement of burrs produced after the first cutting is provided:

[0043] During the first cutting process, the Saw knife is used to partially cut the pins according to the set cutting width. During the friction between the copper material and the Saw knife, curling will be formed upwards, and burrs will be attached to the pins; the frame is placed in a low-temperature refrigerator. Considering that the lowest tolerance temperature of conventional chips is -40℃~-55℃, and qualified chips can pass the low-temperature storage reliability verification, in order to ensure that the chip is not damaged, the low-temperature refrigerator is set at -40℃~-55℃, preferably -45℃~-50℃, and frozen for 2~4h. In this embodiment, the burrs targeted are metal copper, which has cold brittleness, that is, in a low-temperature environment, the toughness deteriorates and it is easy to break.

[0044] Secondly, a method for removing brittle burrs is provided:

[0045] Due to the particularity of step-by-step cutting, after the first cutting, the lead frame still has a complete structure and a certain strength. Therefore, it can be impacted by a high-pressure water gun without deformation. The frozen frame is taken out and placed in a cleaning machine. Conventional QFN frames can withstand a high-pressure water gun nozzle pressure of 200 bar. Since the strength of the frame is reduced after the first cutting, the nozzle pressure is reduced to 150-180 bar for the protection of the frame. The brittle burrs are broken under the instantaneous impact of the water flow and are washed away.

[0046] like Figure 4 As shown, this embodiment provides a method for cutting burrs of a wettable flank product, comprising:

[0047] S1: placing the lead frame formed with wettable flank steps in a low temperature environment at a preset temperature for cooling;

[0048] S2: The cooled lead frame is cleaned with high-pressure water at a preset pressure to complete the cutting of the burrs of the wettable flank products.

[0049] More specific steps include:

[0050] Step 1: Cooling treatment:

[0051] First, the lead frame with wettable flank steps formed thereon is placed in a preset low temperature environment for cooling, wherein the temperature range of the low temperature environment is set to -40°C to -55°C, and the cooling time is controlled between 2 and 4 hours.

[0052] Step 2: High-pressure water cleaning:

[0053] After cooling, the lead frame is cleaned with high-pressure water at a preset pressure; the preset pressure is set to 150 to 180 bar; during the cleaning process, the high-pressure water is sprayed in a direction parallel to the surface of the lead frame to effectively cut off the burrs on the flank product 7.

[0054] Step 3: Post-cleaning treatment:

[0055] After high-pressure water cleaning, the lead frame needs to be dried to remove residual moisture.

[0056] Step 4: Subsequent processing:

[0057] After the burr cutting is completed, the lead frame will be electroplated and cut for the second time; then the lead frame after the second cutting will be inspected for burrs to ensure that the product quality meets the preset standards. Only lead frames that meet the standards will be transferred to the subsequent processing flow. If the burrs on the edge of the pins are controlled within 50μm, it is considered to meet the preset standard requirements.

[0058] In addition, in this embodiment, the wettable flank step is formed by cutting the lead frame for the first time. After the first cutting, the UV film on the lead frame needs to be removed first, and then low-temperature cooling treatment is performed; such a processing sequence helps to better remove burrs and improve the overall quality of the product.

[0059] Based on the above-mentioned method for cutting burrs of a wettable flank product, this embodiment also provides a wettable flank product. Since the burr cutting method is adopted, the burr removal effect is guaranteed, and the wettable flank product has higher functional integrity and reliability.

[0060] It can be seen that the present method for cutting burrs of wettable flank products can effectively remove burrs and ensure the subsequent processing quality of the lead frame through a combination of low-temperature cooling and high-pressure water cleaning.

[0061] Example 2

[0062] Combination Figure 3 As shown, this embodiment provides a method for cutting burrs of wettable flank products, and performs wettable flank product processing for QFN-3×3×0.75 package type, with a chip size of 1.0mm×1.0mm, a flank pin thickness of 0.203mm, and a cutting lane width of 0.32mm.

[0063] The specific implementation steps are as follows:

[0064] Step 1: Use a film laminating machine to stick a UV film on the front of the lead frame, with the edge of the UV film attached to the Ring;

[0065] Step 2: Use a TAPE SAW cutting machine to place the wafer ring on the stage, use a first SAW blade 1 with a width of 0.46 mm, make the first cut along the cutting path on the back of the lead frame, and the cutting depth is 0.12 mm to form a step of the wettable flank; after observation, the length of the burr on the edge of the lead after the first cut is 100 to 120 μm;

[0066] Step 3: Use a UV light machine to remove the UV film on the lead frame by ultraviolet light.

[0067] Step 4: Place the lead frame in a low-temperature refrigerator, adjust the temperature to -40°C, and take it out after freezing for 2 hours;

[0068] Step 5: Use a cleaning machine to place the lead frame on the transfer rail, adjust the high-pressure water to spray parallel to the frame surface, and remove the lead frame after cleaning and drying at a water pressure of 150 bar;

[0069] Step 6: Use tinning wire to electroplate tin on the lead frame pin 3;

[0070] Step 7: Repeat steps 1 to 3, wherein the second SAW knife 6 with the same width of 0.32 mm as the cutting path is used for secondary cutting to cut and separate the products;

[0071] Step 8: Inspect and observe the separated products, and the burrs on the edges of the pins are controlled within 50μm.

[0072] Example 3

[0073] Combination Figure 3 As shown, this embodiment provides a method for cutting burrs of wettable flank products, and processes wettable flank products for QFN-5×5×0.75 package type, with a chip size of 1.8mm×1.8mm, a flank pin thickness of 0.203mm, and a cutting lane width of 0.32mm. The specific implementation steps are as follows:

[0074] Step 1: Use a film laminating machine to stick a UV film on the front of the lead frame, with the edge of the UV film attached to the Ring;

[0075] Step 2: Use a TAPE SAW cutting machine to place the wafer ring on the stage, and use a 0.42mm wide first SAW blade 1 to make the first cut along the cutting path on the back of the lead frame, with a cutting depth of 0.15mm to form a step of the wettable flank; after observation, the length of the burr on the edge of the lead after the first cut is about 150μm;

[0076] Step 3: Use a UV light machine to remove the UV film on the lead frame by ultraviolet light.

[0077] Step 4: Place the lead frame in a low-temperature refrigerator, adjust the temperature to -40°C, and take it out after freezing for 4 hours;

[0078] Step 5: Use a cleaning machine to place the lead frame on the transfer rail, adjust the high-pressure water to spray parallel to the frame surface, the water pressure is 180 bar, and remove the frame after cleaning and drying;

[0079] Step 6: Use tinning wire to electroplate tin on part 2 of the lead frame pin;

[0080] Step 7: Repeat steps 1 to 3, wherein the second SAW knife 6 with the same width of 0.32 mm as the cutting path is used for secondary cutting to cut and separate the products;

[0081] Step 8: Inspect and observe the separated products, and the burrs on the edges of the pins are controlled within 80μm.

[0082] It can be seen that the present invention provides a method for cutting burrs of wettable flank products, which has the following advantages over the existing burr cutting methods:

[0083] First, efficient burr removal: Through the combination of low-temperature ambient cooling at a preset temperature and high-pressure water cleaning at a preset pressure, the burrs on the wettable flank products can be effectively removed, improving the processing accuracy and quality of the products.

[0084] Second, precise control of parameters: This method provides the temperature range of the low-temperature environment (-40℃~-55℃) and the preset pressure of high-pressure water (150~180bar), as well as the cooling time (2~4 hours). These precise parameter controls help to achieve consistency and stability in burr cutting.

[0085] Third, protect the lead frame: After the first cutting, remove the UV film and then perform low-temperature cooling. This step helps protect the lead frame from damage in subsequent processing and also helps to better remove burrs.

[0086] Fourth, optimize the processing flow: After completing the burr cutting, the method also includes electroplating and a second cutting process, as well as a burr inspection step for the lead frame after the second cutting; the optimization of these steps helps to improve the overall processing efficiency and ensure that the quality of the final product meets the preset standards.

[0087] Fifth, improve product competitiveness: Through precise and efficient burr cutting methods, it helps to improve the processing quality and consistency of wettable flank products, thereby enhancing the competitiveness of products in the market.

[0088] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which the present invention belongs. The terms used herein in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention. The term "and / or" used herein includes any and all combinations of one or more of the related listed items.

[0089] The above are only preferred specific implementation modes of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and the disclosed concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

[0090] The further detailed description made in the disclosure cannot be used to determine that the specific implementation modes of the present invention are limited to these. For ordinary technicians in the technical field to which the present invention belongs, several simple deductions or substitutions can be made without departing from the concept of the present invention, which should be regarded as belonging to the protection scope of the present invention determined by the submitted claims.

Claims

1. A method for cutting burrs of wettable flank products, characterized in that: The steps include: S1: placing the lead frame formed with wettable flank steps in a low temperature environment at a preset temperature for cooling; S2: The cooled lead frame is cleaned with high-pressure water at a preset pressure to complete the cutting of the burrs of the wettable flank products.

2. The method for cutting burrs of wettable flank products according to claim 1, characterized in that: The preset temperature is -40°C to -55°C.

3. The method for cutting burrs of wettable flank products according to claim 2, characterized in that: The lead frame with the wing steps formed thereon is placed in a low temperature environment for cooling, wherein the cooling time is 2 to 4 hours.

4. The method for cutting burrs of wettable flank products according to claim 1, characterized in that: The preset pressure is 150-180 bar.

5. The method for cutting burrs of wettable flank products according to claim 1, characterized in that: The wettable wing step is formed by cutting the lead frame for the first time; after the first cutting, the UV film on the lead frame is peeled off, and then the lead frame is placed in a low temperature environment for cooling.

6. The method for cutting burrs of wettable flank products according to claim 1, characterized in that: The specific process of using high-pressure water with a preset pressure to clean the cooled lead frame includes: The cooled lead frame is placed on the conveying rail of the cleaning machine, and the high-pressure water spraying direction and the preset pressure are adjusted so that the high-pressure water is sprayed in a direction parallel to the surface of the lead frame at the preset pressure.

7. The method for cutting burrs of a wettable flank product according to claim 6, characterized in that: After the cooled lead frame is sprayed with high-pressure water, the sprayed lead frame is dried.

8. The method for cutting burrs of wettable flank products according to claim 1, characterized in that: After the burr cutting is completed, the lead frame after the burr cutting is electroplated and cut for the second time.

9. The method for cutting burrs of a wettable flank product according to claim 1, characterized in that: After the electroplating and the second cutting process are completed, the lead frame after the second cutting is inspected for burrs, and the lead frame that meets the preset standards is transferred to the subsequent processing flow.

10. A wettable wing product, characterized in that: The product is prepared by the method for cutting burrs of a wettable flank product as described in any one of claims 1 to 9.

Images