Integrated circuit packaging method capable of wetting side wings

Abstract

The invention discloses an integrated circuit packaging method capable of wetting side wings, which belongs to the field of integrated circuit packaging, and comprises the following steps of: 1, coating a photoresist layer on the surface of a pin arranged on a material strip product, arranging a pin to-be-exposed area on the surface of the pin, irradiating the to-be-exposed area of the pin through a laser assembly to perform exposure operation so as to form a laser irradiation area; and 2, removing the photoresist layer from the laser irradiation region through a developing solution to form a region to be etched, and forming photoresist removing regions on two sides of the region to be etched, wherein the photoresist layer is not removed through the developing solution. The low-cost laser direct exposure equipment is adopted to complete scanning exposure of the photoresist material, the low-cost integrated online coating and exposure equipment is matched to improve the productivity, and finally the wettable side wings are formed on the side edges of the cut single finished product pins, so that the effective control of the process cost and the optimization of the production efficiency are realized, and the production efficiency is improved. And meanwhile, the requirement of a wettable structure of the packaging pin is met.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of integrated circuit packaging, and particularly relates to an integrated circuit packaging method with wettable flanks. BACKGROUND

[0002] In the field of integrated circuit packaging, QFN (Quad Flat No-lead Package) is widely used in consumer electronics, communication equipment and other products due to its lightness, thinness and excellent electrical performance. However, the traditional QFN packaging process has significant technical shortcomings. After the finished product is cut into a single piece, the cut side of the pin is in a bare copper state without plating layer protection, and is prone to oxidation. This directly leads to the fact that the pin cannot form a "wettable flank", and in the subsequent SMT (Surface Mount Technology) soldering process, the additional tin connection cannot be formed through the side edge, which not only reduces the mechanical strength and electrical connection reliability of soldering, but also affects the accurate judgment of the soldering quality by AOI (Automatic Optical Inspection) due to the lack of solder tin coverage on the side edge. SUMMARY

[0003] In view of the above problems, the present application provides an integrated circuit packaging method with wettable flanks to effectively solve the problem that the side edge of the pin of the traditional QFN packaging product on the market is prone to oxidation without plating layer protection after the finished product is cut into a single piece, and thus the side edge cannot form a wettable flank, which provides better additional side edge tin connection and corresponding AOI detection for subsequent surface mount technology.

[0004] The technical scheme adopted by the present application is as follows: the present application provides an integrated circuit packaging method with wettable flanks, which comprises the following steps: step one: applying a photoresist layer on the pin surface of a strip product, the pin surface is provided with a pin exposure area, and a laser assembly is used to irradiate the pin exposure area to form a laser irradiation area; Step two: the laser irradiation area is removed from the photoresist layer by developing solution to form an etching area, and the area on both sides of the etching area which is not removed from the photoresist layer by developing solution forms a stripping area; Step three: the copper metal of the etching area is etched by etching liquid to form an etching area; Step four: the photoresist layer of the stripping area is removed by stripping liquid; Step five: performing electroplating on the pin surface to form a plating layer.

[0005] Preferably, the laser assembly is a point laser source, which directly irradiates the pin exposure area along the Z direction or at an angle of 45-75 degrees away from the center.

[0006] Preferably, the laser assembly comprises a control unit and a laser head, the control unit converts the data file into a control program file of the exposure device, so as to control the start and stop of the work of the laser head, the irradiation time and the working power.

[0007] Preferably, a beam splitter is arranged on the laser head, the beam splitter divides the single incident light into 2-3 beams, and the incident light irradiates on the corresponding pin area to be exposed.

[0008] Preferably, in step three, the etching depth is 1 / 3-2 / 3 of the thickness of the pin.

[0009] Preferably, in step three, the etching liquid adopts an online track type spraying operation mode to spray the etching area.

[0010] Preferably, in step four, the degumming liquid adopts an online track type spraying operation mode to spray the degumming area.

[0011] Preferably, the plating layer is a tin plating layer.

[0012] The beneficial effects of the application with the above structure are as follows: the present application provides an integrated circuit packaging method with wettable side wings, which uses a low-cost laser direct exposure device to perform laser scanning exposure on photoresist material, and uses a low-cost integrated online coating exposure device, thereby maximizing the production capacity, and finally forming a pin side edge with wettable side wings after cutting into single finished products. Compared with the traditional scheme, no mask plate is needed, and no expensive exposure machine is needed, thereby reducing the production cost. BRIEF DESCRIPTION OF DRAWINGS

[0013] Figure 1 FIG. 1 is a step one schematic diagram of the integrated circuit packaging method with wettable side wings provided by the present application; Figure 2 FIG. 2 is a step two schematic diagram of the integrated circuit packaging method with wettable side wings provided by the present application; Figure 3 FIG. 3 is a step three schematic diagram of the integrated circuit packaging method with wettable side wings provided by the present application; Figure 4 FIG. 4 is a step four schematic diagram of the integrated circuit packaging method with wettable side wings provided by the present application; Figure 5 FIG. 5 is a step five schematic diagram of the integrated circuit packaging method with wettable side wings provided by the present application; Figure 6 FIG. 6 is a schematic diagram of the laser assembly of the integrated circuit packaging method with wettable side wings provided by the present application; Figure 7An etching solution schematic diagram of a wettable side wing integrated circuit packaging method according to the present application; Figure 8 An LF downward schematic diagram of a wettable side wing integrated circuit packaging method according to the present application; Figure 9 An online track spray operation schematic diagram of a wettable side wing integrated circuit packaging method according to the present application.

[0014] 1, product; 2, photoresist layer; 3, pin; 31, pin to be exposed area; 32, to be etched area; 33, etched area; 34, adhesive removal area; 4, plating layer; 5, laser assembly; 51, control unit; 52, laser head; 53, beam splitter.

[0015] The accompanying drawings are used to provide a further understanding of the present application, and constitute a part of the specification, and are used to explain the present application together with embodiments of the present application, and do not constitute a limitation on the present application. DETAILED DESCRIPTION

[0016] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0017] In the description of the present application, it should be understood that the terms "upper", "lower", "front", "back", "left", "right", "top", "bottom", "inner", "outer" and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation on the present application.

[0018] As shown in Figures 1-9 As shown in Figure 1 The present application provides a wettable side wing integrated circuit packaging method, which comprises the following steps: Step 1: uniformly applying a photoresist agent on the surface of the pins 3 of the product 1 after plastic packaging to form a photoresist layer 2, and then directly exposing the pin to be exposed area 31 by a laser assembly 5 to form a laser irradiation area. The present application does not need consumables such as a mask and film in the traditional process, and also eliminates the cumbersome steps of film production and alignment, thereby reducing the production preparation time from 1-2 hours to 5 minutes, and avoiding the error accumulation of film alignment, so that the exposure accuracy is improved to the micron level.

[0019] As shown in Figure 6As shown, it should be noted that the laser assembly 5 adopts a Z-direction point laser source, and the irradiation range is accurately set by program to ensure matching with the position of the pin to be exposed area 31. The laser assembly 5 includes a control unit 51 and a laser head 52, wherein the control unit 51 converts the L / F design drawing (including the parameters related to the pin to be exposed area 31) of the product 1 into a control program file, and then realizes accurate control of the start and stop, irradiation time and power of the laser head 52.

[0020] It should be noted that the laser head 52 is equipped with a beam splitter 53, which can divide a single incident light into 2-3 beams, enabling single-point irradiation of multiple pin to be exposed areas 31 at the same time, greatly improving the efficiency of exposure operation.

[0021] As shown in Figure 2 Step two: developing the exposed pin 3, the surface photoresist layer 2 of the laser irradiation area is dissolved and removed by the developing solution to form the etching area 32. The etching area 32 on both sides is not exposed to laser irradiation in step one, so the photoresist layer 2 above it is not removed by the developing solution, and the corresponding area forms a stripping area 34. In summary, the photoresist layer 2 not irradiated by laser is retained on the surface of the pin 3. The developing process only removes the photoresist layer 2 in the exposed area, and the photoresist layer 2 in the non-exposed area can completely cover the non-processing area of the pin 3, effectively avoiding the corrosion of the subsequent etching liquid to the non-target area, and improving the accuracy of the pattern definition.

[0022] As shown in Figure 3 Step three: etching the etching area 33 with etching liquid, the etching depth is 1 / 3-2 / 3 of the thickness of the product pin 3, and the preferred is 1 / 2 of the thickness of the product pin 3, so as to form a groove structure in the etching area 33. After the product 1 is cut into a single one along the dashed line above the groove as shown in Figure 5 The groove structure is exposed on the side of the product, providing a good interface for subsequent soldering and tin climbing, and better realizing the product side tin climbing connection and the corresponding AOI detection in the subsequent surface mounting process.

[0023] As shown in Figure 7 and Figure 8As shown, the etching process can adopt an online track spraying operation. This etching method can well control the etching depth of the product pin 3. When the strip product is above, the strip product above is provided with the pin 3, the etching liquid spraying outlet is below, and the etching liquid spraying outlet sprays upward to the pin 3 of the strip product, the etching pattern of the etching area 33 after etching can be better controlled. This design will not cause the etching liquid to accumulate at the bottom of the product pin 3 due to gravity, causing excessive etching of the bottom pin 3. By uniformly spraying the etching area 33, combined with parameterized control, the shape and depth consistency of the etched side wing structure is significantly improved, avoiding the problems of over-etching and under-etching that are prone to occur in traditional etching processes. At the same time, the online track spraying can ensure that the etching liquid is fully and uniformly contacted with the etching area 33, providing a good interface for subsequent soldering and tin climbing.

[0024] The etching area 33 is uniformly sprayed by using a spraying etching process, as shown in Figure 9 The precision consistency of the spraying etching is good, and the etching depth tolerance can be accurately controlled within ±30 microns.

[0025] It should be noted that by adjusting the concentration, pressure and other key parameters of the etching liquid, the shape and depth of the etching area 33 can be accurately controlled, and finally the etching area 33 forms a required wettable side wing groove structure on the pin 3. The specific adjustment and control should be combined with the characteristics of the etching liquid system. The adjustment and control logic of conventional high-precision packaging acidic copper chloride etching liquid and low-end alkaline ammonia copper etching liquid is significantly different.

[0026] Conventional etching liquid, for example, can include acidic copper chloride etching liquid. When using this etching liquid, the concentration, pressure, oxidant content, hydrochloric acid concentration and special additives (inhibitors, wetting agents, etc.) ratio need to be adjusted and controlled. The concentration of copper chloride and hydrochloric acid is accurately controlled to maintain etching activity and avoid precipitation, and the spraying pressure is matched to ensure uniform etching. Combined with automatic control of redox potential and specific gravity, the inhibitor is used to inhibit side etching, ensure the vertical shape of the side wing (etching factor > 3), and meet the high-precision requirements.

[0027] It can also include alkaline ammonia copper etching liquid. When using this etching liquid, the concentration of ammonia and ammonium chloride and pH value need to be adjusted and controlled. However, due to its low etching factor (<2) and serious side etching, it is difficult to form a high-precision side wing, and it has strong attack on photoresist, so it is only suitable for low-end low-precision products.

[0028] In actual high-precision preparation, the industry prefers to use acidic copper chloride etching liquid system. By matching the additive package and online regeneration system, the parameters are adjusted and controlled to ensure that the side wing has vertical side wall, uniform depth and good weldability, which meets the requirements of subsequent processes.

[0029] It needs to be explained that the application adopts low-cost integrated online coating, exposing and developing equipment, including coating photoresist agent, adopting track type baking unit to bake the product coated with photoresist agent, adopting laser to expose the product, adopting track type developing unit to develop, and adopting track type etching unit to etch the product, so that the integrated online coating, exposing and developing equipment can maximize the production capacity.

[0030] As shown in Figure 4 Step four: the remaining photoresist layer 2 on the pin 3 is removed by using a stripping solution, the surface of the pin 3 after stripping is free of the photoresist layer 2, avoiding the pollution of the residual substances to the subsequent electroplating process, and ensuring the bonding force of the plating layer 4.

[0031] As shown in Figure 5 Step five: the surface of the pin 3 after stripping is subjected to electroplating operation to form a protective plating layer 4, and the plating layer 4 is preferably a tin plating layer. The tin plating layer has excellent solderability, and during subsequent soldering, the solder can quickly wet and completely cover the wettable side wing surface, compared with the traditional flat pin, the soldering area is greatly improved, and the soldering reliability of the pin 3 and the external substrate is significantly enhanced, and the risk of solder failure in thermal cycle test (TC) is reduced.

[0032] It needs to be explained that in this paper, the relationship terms such as first and second are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between the entities or operations. Moreover, the terms "include", "contain" or any other variants thereof are intended to cover non-exclusive inclusion, so that the process, method, article or equipment including a series of elements not only includes those elements, but also includes other elements not explicitly listed or inherent to such process, method, article or equipment.

[0033] Although the embodiments of the application have been shown and described, it can be understood by those of ordinary skill in the art that various changes, modifications, replacements and variations can be made to the embodiments without departing from the principles and spirits of the application, and the scope of the application is defined by the appended claims and their equivalents.

[0034] The application and its embodiments have been described above, and such description is not restrictive, and the embodiments shown in the drawings are only one of the embodiments of the application, and the actual structure is not limited thereto. In general, if those skilled in the art are inspired by it, without departing from the purpose of the application, without creative design, similar structure and embodiments of the technical solution can be designed, which should belong to the protection scope of the application.

Claims

1. A method for packaging an integrated circuit with wettable side wings, characterized in that: The integrated circuit packaging method includes the following steps: Step 1: A photoresist layer (2) is coated on the surface of the pin (3) set on the strip product (1). The pin (3) has an exposure area (31). The laser assembly (5) is used to irradiate the exposure area (31) to form a laser irradiation area. Step 2: The laser irradiation area is formed by removing the photoresist layer (2) with the developing solution to form the etching area (32), and the areas on both sides of the etching area (32) where the photoresist layer (2) is not removed by the developing solution are formed into the adhesive removal area (34). Step 3: Etch the copper metal in the area to be etched (32) with an etching solution to form an etched area (33). Step 4: Remove the photoresist layer (2) in the adhesive removal area (34) using adhesive remover; Step 5: Electroplating is performed on the surface of the pin (3) to form a plating layer (4).

2. The integrated circuit packaging method with wettable side wings according to claim 1, characterized in that: The laser component (5) is a point laser source that directly irradiates the area (31) to be exposed on the pin along the Z direction or along the center at a deviation of 45°-75°.

3. The integrated circuit packaging method with wettable side wings according to claim 1, characterized in that: The laser assembly (5) includes a control unit (51) and a laser head (52). The control unit (51) converts the data file into a control program file for the exposure device to control the start and stop of the laser head (52), the irradiation time and the working power.

4. The integrated circuit packaging method with wettable side wings according to claim 3, characterized in that: The laser head (52) is provided with a beam splitter (53), which splits a single incident light beam into 2 to 3 beams, and the incident light beams illuminate the corresponding pin exposure area (31) at a single point.

5. The integrated circuit packaging method with wettable side wings according to claim 1, characterized in that: In step three, the etching depth is 1 / 3 to 2 / 3 of the thickness of the pin (3).

6. The integrated circuit packaging method with wettable side wings according to claim 1, characterized in that: In step three, the etching solution is sprayed onto the etching area (33) using an online track-type spraying method.

7. The integrated circuit packaging method with wettable side wings according to claim 1, characterized in that: In step four, the adhesive remover is applied to the adhesive remover area (34) using an online track-type spraying method.

8. The integrated circuit packaging method with wettable side wings according to claim 1, characterized in that: The plating layer (4) is a tin plating layer.

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