Novel vacuum Reflow welding packaging method

Abstract

The invention, which belongs to the technical field of vacuum reflow soldering, discloses a novel vacuum Reflow soldering packaging method comprising the following steps: preparing a wafer; cutting the wafer into single wafers; the wafer is bonded on the surface of a copper frame through solder paste containing no soldering flux; welding the wafer on the surface of the copper frame through a formic acid reflow process; connecting the metal connection points on the wafer with the metal connection points on the copper frame through a wire welding process; carrying out AOI (Automatic Optic Inspection) appearance detection on the wafer; packaging the copper frame, the wafer and the bonding wire through a plastic packaging material; curing the plastic packaging material through heating; and performing laser stamping on the surface of the product. The formic acid reflow soldering technology is matched with the soldering-flux-free solder paste for welding, so that the influence of soldering flux in the traditional welding process can be greatly reduced, and the welding quality is improved; and the method is environment-friendly.

Description

Technical Field

[0001] The invention belongs to the technical field of vacuum reflow soldering, and in particular relates to a novel vacuum reflow soldering packaging method. Background Art

[0002] In traditional semiconductor packaging processes, the solder paste used in the TSP PSOP20 DB process is typically produced using lead-containing solder paste, such as PbSn5Ag2.5, as a soldering agent. This solder paste contains a large amount of flux, which is used to improve solder wettability and remove oxides from the metal surface. However, after curing using a conventional reflow soldering machine, flux marks are often left on the product, and these residues are difficult to completely clean. In the WB (Wire Bonding) production process, these residues can seriously affect wire bonding quality, resulting in product defects and reduced yield.

[0003] To address this issue, existing production processes need to be improved. Traditional reflow soldering technology uses flux during the soldering process. While this helps the solder wet the metal, it also brings a series of problems, such as the formation of voids and the impact of flux residue on subsequent processes. Voids are caused by the outgassing and evaporation of the liquid components in the flux at high temperatures. This can lead to localized hot spots on the chip surface after soldering, increasing the risk of stress and fatigue cracks. In addition, the reaction of flux residue with water vapor can form an acidic solution on the surface of the component, affecting the long-term reliability of the device. Summary of the Invention

[0004] In view of the above situation, in order to overcome the defects of the prior art, the present invention uses formic acid reflow soldering technology in combination with flux-free solder paste for soldering, which can greatly reduce the influence of flux in the traditional soldering process.

[0005] In order to achieve the above objectives, the following technical solutions are adopted: The present invention provides a novel vacuum reflow welding packaging method, comprising:

[0006] Prepare the wafer;

[0007] cutting the wafer into individual chips;

[0008] The wafer is bonded to the surface of the copper frame by solder paste without flux;

[0009] Soldering the wafer on the surface of the copper frame through a formic acid reflow process;

[0010] Connecting the metal contacts on the wafer to the metal connection points on the copper frame through a wire bonding process;

[0011] Performing AOI appearance inspection on the wafer;

[0012] Encapsulating the copper frame, chip and bonding wires with plastic packaging material;

[0013] solidifying the plastic packaging material by heating;

[0014] Laser stamping is performed on the surface of the product.

[0015] Furthermore, the model, specifications and other information of the product are indicated by the laser stamp.

[0016] Furthermore, before laser stamping the surface of the product, the packaged product is electroplated or baked.

[0017] Furthermore, after laser stamping is performed on the surface of the product, the product is cut into individual pieces.

[0018] Furthermore, after laser stamping is performed on the surface of the product, the product is subjected to a pin forming process.

[0019] The beneficial effects of the present invention are:

[0020] (1) The formic acid reflow soldering technology of the present invention can greatly reduce the influence of flux residue in the traditional soldering process by combining it with flux-free solder paste for soldering;

[0021] (2) The present invention can remove surface oxides through formic acid vacuum reflow soldering, protect the soldering area from oxidation, and improve soldering quality;

[0022] (3) The method of the present invention is environmentally friendly. The CO2 and water produced by the decomposition of formic acid at high temperature are harmless substances and will not cause pollution to the environment. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 Schematic diagram of the process of the novel vacuum reflow welding packaging method of the present invention;

[0024] Figure 2 This is a diagram showing the residual flux material of a product produced by the novel vacuum reflow soldering packaging method of the present invention;

[0025] Figure 3 This is a diagram of the flux material residue of products produced using the traditional solder paste soldering process;

[0026] Figure 4 This is the X-ray test result of the product produced by the novel vacuum reflow welding packaging method of the present invention;

[0027] Figure 5 This is the X-ray inspection result of the product using the traditional solder paste soldering process.

[0028] The accompanying drawings are used to provide further understanding of the present invention and constitute a part of the specification. They are used to explain the present invention together with the embodiments of the present invention and do not constitute a limitation of the present invention. DETAILED DESCRIPTION

[0029] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0030] Unless otherwise defined, all technical and scientific terms used herein have the same meanings as those familiar to those skilled in the art. Furthermore, any methods and materials similar or equivalent to those described herein can be applied to the present invention. The preferred embodiments and materials described herein are for illustrative purposes only and are not intended to limit the scope of this application.

[0031] The experimental methods in the following examples, unless otherwise specified, are all conventional methods, and the experimental materials used in the following examples, unless otherwise specified, are all purchased from commercial channels.

[0032] Example

[0033] New vacuum reflow welding packaging method

[0034] like Figure 1 As shown, the packaging method includes:

[0035] Prepare the wafer;

[0036] cutting the wafer into individual chips;

[0037] The wafer is bonded to the surface of the copper frame by solder paste without flux;

[0038] Soldering the wafer on the surface of the copper frame through a formic acid reflow process;

[0039] Connecting the metal contacts on the wafer to the metal connection points on the copper frame through a wire bonding process;

[0040] Performing AOI appearance inspection on the wafer;

[0041] Encapsulating the copper frame, chip and bonding wires with plastic packaging material;

[0042] solidifying the plastic packaging material by heating;

[0043] Electroplating or baking the packaged products;

[0044] Performing laser stamping on the surface of the product, and indicating the model, specifications and other information of the product through the laser stamping;

[0045] Cutting the product into individual pieces;

[0046] The product is subjected to a lead forming process.

[0047] Comparative Example

[0048] This comparative example provides a traditional solder paste soldering packaging method, which includes:

[0049] Prepare the wafer;

[0050] cutting the wafer into individual chips;

[0051] Adhere the wafer to the surface of the copper frame via solder paste containing flux;

[0052] Soldering the wafer on the surface of the copper frame through a reflow process;

[0053] Connecting the metal contacts on the wafer to the metal connection points on the copper frame through a wire bonding process;

[0054] Performing AOI appearance inspection on the wafer;

[0055] Encapsulating the copper frame, chip and bonding wires with plastic packaging material;

[0056] heating the plastic packaging material to solidify it;

[0057] Electroplating or baking the packaged products;

[0058] Laser stamping is performed on the surface of the product to indicate the product model, specifications and other information;

[0059] Performing singulation and lead forming processes on the product;

[0060] Reflow soldering is performed on individual packaged product units.

[0061] Result Analysis

[0062] Figure 2 and Figure 3 These are the flux material status diagrams for products using the new vacuum reflow soldering packaging method and products using the traditional solder paste soldering process. As can be seen from the diagrams, the product obtained using the method of the present invention has no flux residue, thereby improving the soldering yield of the subsequent wire bonding process.

[0063] Figure 4 and Figure 5The figures show the X-ray inspection results of products using the new vacuum reflow soldering packaging method and the traditional solder paste soldering process. As can be seen from the figure, the present invention reduces the void problem under the chip during the soldering process, thereby improving product performance.

[0064] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

[0065] The present invention and its embodiments are described above. Such description is not restrictive. The drawings show only one embodiment of the present invention, and actual applications are not limited thereto. In short, if a person skilled in the art is inspired by the above, and does not deviate from the purpose of the present invention, any method and embodiment similar to the technical solution without creative design shall fall within the scope of protection of the present invention.

Claims

1. A new vacuum Reflow welding packaging method, characterized by: include: Prepare the wafer; Cutting the wafer into individual chips; Bonding the wafer to the surface of the copper frame by solder paste without flux; Soldering the wafer on the surface of the copper frame through a formic acid reflow process; Connecting the metal contacts on the wafer to the metal connection points on the copper frame by wire bonding; Performing AOI appearance inspection on the wafer; Encapsulating the copper frame, the chip and the bonding wires with a plastic encapsulation material; Curing the plastic packaging material by heating; Laser stamping is performed on the surface of the product.

2. The novel vacuum reflow welding packaging method according to claim 1 is characterized in that: The model, specifications and other information of the product are indicated by the laser stamp.

3. The novel vacuum reflow welding packaging method according to claim 1 is characterized in that: Before laser stamping the surface of the product, the packaged product is electroplated or baked.

4. The novel vacuum reflow welding packaging method according to claim 1 is characterized in that: After laser stamping is performed on the surface of the product, the product is cut into individual pieces.

5. The novel vacuum reflow welding packaging method according to claim 1 is characterized in that: After laser stamping is performed on the surface of the product, the product is subjected to a lead forming process.

Images