Ultra-fine gold wire welding method, welding structure and application thereof

Abstract

The present invention discloses an ultra-fine gold wire welding method, welding structure, and application thereof. The welding method comprises: providing a substrate with a substrate pad and a chip with a chip pad; using gold wire to plant a chip solder ball on the chip pad as a first solder joint, and then drawing the wire from the first solder joint to a second solder joint on the substrate pad; wherein the diameter of the gold wire is less than 16 μm. The ultra-fine gold wire welding method of the present invention can achieve miniaturization of packaging and reduce packaging costs.

Description

Technical Field

[0001] The present invention belongs to the technical field of electronic packaging, and in particular relates to an ultra-fine gold wire welding method, a welding structure and applications thereof. Background Art

[0002] Currently, ultrasonic gold wire bonding is commonly used in chip and discrete device packaging, with wire diameters of 25µm, 20µm, and 18µm being the most common. Generally speaking, a larger wire diameter can carry more current and improve reliability, but also comes with higher costs and larger bump and package sizes.

[0003] With the trend toward miniaturization in electronic product packaging, chip pads are becoming smaller and smaller, and the spacing between pads is shrinking. Especially when the chip pad size is 40μm and the pad spacing is 50μm, 18μm gold wire is difficult to meet packaging requirements, and even smaller diameter gold wire is needed for bonding. As international gold prices continue to rise, the cost of gold wire accounts for an increasing proportion of the overall packaging cost. Reducing the cost of gold wire packaging has become a pressing issue. Summary of the Invention

[0004] The main purpose of the present invention is to provide an ultra-fine gold wire welding method, a welding structure and applications thereof, so as to overcome the deficiencies of the prior art.

[0005] To achieve the aforementioned object of the invention, the technical solutions adopted by the present invention include:

[0006] An embodiment of the present invention provides an ultra-fine gold wire welding method, which includes:

[0007] providing a substrate with a substrate pad and a chip with a chip pad;

[0008] A gold wire is used to plant a chip solder ball on the chip pad as a first soldering point, and a wire arc is drawn from the first soldering point to the substrate pad to solder a second soldering point;

[0009] Wherein, the diameter of the gold wire is less than 16 μm.

[0010] And according to the materials of substrate pads and chip pads, a set of process windows for ultra-fine gold wire welding and ball placement has been developed.

[0011] Another aspect of an embodiment of the present invention further provides an ultra-fine gold wire bonding structure formed by the above method.

[0012] Another aspect of an embodiment of the present invention further provides a packaging structure, which includes a substrate with a substrate pad and a chip with a chip pad, wherein the substrate pad and the chip pad are electrically connected via the above-mentioned ultra-fine gold wire welding structure.

[0013] Compared with the prior art, the present invention has the following beneficial effects:

[0014] (1) Different ball implantation process windows were developed based on pads of different materials, enabling gold wire bonding with a smaller diameter, effectively reducing packaging costs.

[0015] (2) The provided welding process method can meet the requirements of small-pitch welding and realize the miniaturization of packaging. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments recorded in the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0017] Figure 1 is a structural diagram of a packaging structure in an embodiment of the present invention;

[0018] Figure 2 It is a top view of a chip structure in an embodiment of the present invention.

[0019] Explanation of the accompanying figures: 1-substrate; 2-chip; 3-substrate pad; 4-chip pad; 5-substrate solder ball; 6-chip solder ball; 7-gold wire; 8-pad width; 9-pad spacing. DETAILED DESCRIPTION

[0020] In view of the defects of the existing technology, the inventor of this case was able to propose the technical solution of the present invention after long-term research and extensive practice. Different ball planting process windows were developed according to different pad materials, realizing the welding process of extremely fine gold wires, effectively reducing packaging costs.

[0021] The technical solution of the present invention will be described clearly and completely below. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. All other embodiments derived by persons of ordinary skill in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0022] One aspect of an embodiment of the present invention provides an ultra-fine gold wire bonding method, comprising:

[0023] providing a substrate with a substrate pad and a chip with a chip pad;

[0024] A gold wire is used to plant a chip solder ball on the chip pad as a first solder joint, and a wire arc is drawn from the first solder joint to the substrate pad to solder a second solder joint;

[0025] Wherein, the diameter of the gold wire is less than 16 μm.

[0026] Furthermore, a substrate solder ball is planted on the substrate solder pad in advance using a gold wire, and the wire arc is pulled onto the substrate solder ball to form a second solder joint.

[0027] Furthermore, the chip pads have a pad width of less than 40 μm and a pad spacing of less than 50 μm.

[0028] Furthermore, ultrasonic welding is used to plant substrate solder balls and chip solder balls on the substrate solder pads and chip solder pads.

[0029] Preferably, the welding blade used in the ultrasonic welding method includes a B0608-28-13-06 blade produced by PECO.

[0030] Furthermore, the material of the substrate pad and the chip pad includes any one of aluminum, gold, and nickel gold, but is not limited thereto.

[0031] Furthermore, the ball implantation process of the welding wrecking knife includes a first stage, a second stage and a third stage.

[0032] Furthermore, if the substrate pads and chip pads are made of aluminum, the ball placement process conditions for the substrate solder balls and chip solder balls include:

[0033] The pressure mode is used in the first to third stages;

[0034] The ultrasonic energy, ball planting time and ball planting pressure in the first stage are set to 5-20mA, 3-5mS and 25-45g respectively;

[0035] The ultrasonic energy, ball planting time and ball planting pressure in the second stage are set to 10-30mA, 1-3mS and 10-30g respectively;

[0036] The ultrasonic energy, ball planting time and ball planting pressure in the third stage are set to 65-110 mA, 11-13 mS and 7-10 g respectively.

[0037] Furthermore, if the substrate pads and chip pads are made of gold, the ball placement process conditions for the substrate solder balls and chip solder balls include:

[0038] The pressure mode is used in the first to third stages;

[0039] The ultrasonic energy, ball planting time and ball planting pressure in the first stage are set to 0-15mA, 3-5mS and 20-45g respectively;

[0040] The ultrasonic energy, ball implantation time, and ball implantation pressure in the second stage are set to 25-55 mA, 5-7 mS, and 5-7 g, respectively;

[0041] The ultrasonic energy, ball planting time and ball planting pressure in the third stage are set to 40-85 mA, 7-10 mS and 7-10 g respectively.

[0042] Furthermore, if the substrate pads and chip pads are made of nickel-gold, the ball implantation process conditions for the substrate solder balls and chip solder balls include:

[0043] The pressure mode is used in the first to third stages;

[0044] The ultrasonic energy, ball planting time and ball planting pressure in the first stage are set to 0-15mA, 1-3mS and 25-50g respectively;

[0045] The ultrasonic energy, ball planting time, and ball planting pressure in the second stage are set to 100-130 mA, 8-12 mS, and 5-8 g, respectively;

[0046] The ultrasonic energy, ball planting time and ball planting pressure in the third stage are set to 120-150 mA, 13-17 mS and 10-15 g respectively.

[0047] Another aspect of an embodiment of the present invention further provides a packaging structure, which includes a substrate with a substrate pad and a chip with a chip pad, wherein the substrate pad and the chip pad are electrically connected via the above-mentioned ultra-fine gold wire welding structure.

[0048] The technical solution in the embodiment of the present invention will be further described in detail below in conjunction with the accompanying drawings. This embodiment is implemented on the premise of the technical solution of the invention, and a detailed implementation method and specific operation process are given, but the protection scope of the present invention is not limited to the following embodiments.

[0049] Example 1

[0050] See also Figure 1 , which is a packaging structure realized by the ultra-fine gold wire welding method in an embodiment of the present invention, includes a substrate 1 with a substrate pad 3 and a chip 2 with a chip pad 4. The chip 2 is fixed on the substrate 1 through a die bonding process.

[0051] For further information, see Figure 2 The width 8 of the chip pad 4 is 40 μm, and the pad spacing 9 between two adjacent chip pads 4 is 50 μm.

[0052] Specifically, in this embodiment, a gold wire 7 with a diameter of 16 μm is used for welding. The splitter is first moved to the position of the substrate pad 3 to plant the substrate solder ball 5, and then the splitter is moved to the position of the chip pad 4 to plant the chip solder ball 6 as the first welding point, and a wire arc is pulled to the substrate solder ball 5 to weld and fix it to form a second welding point, thereby realizing the electrical connection between the chip 2 and the substrate 1.

[0053] The cleaver used is the B0608-28-13-06 cleaver produced by PECO.

[0054] Specifically, the substrate pad 3 and the chip pad 4 in this embodiment are made of aluminum. The ball implantation process is divided into three stages, and each stage is completed under specific process conditions.

[0055] Specifically, the working mode of each stage is set to pressure mode, in which the ultrasonic energy, ball planting time, and ball planting pressure of the first stage are set to 10mA, 3mS, and 35g respectively; the ultrasonic energy, ball planting time, and ball planting pressure of the second stage are set to 20mA, 1mS, and 15g respectively; the working mode of the third stage is set to F, and the ultrasonic energy, ball planting time, and ball planting pressure are set to 80mA, 12mS, and 8g respectively.

[0056] The ball implantation completed through the above three stages can meet the requirements of welding fine gold wire with a diameter of 16μm. On the basis of meeting the requirements of miniaturized packaging, the packaging cost of the gold wire is reduced. Compared with the use of 18μm gold wire, the mass of gold used can be reduced by about 21%.

[0057] Example 2

[0058] This embodiment is similar to embodiment 1, except that the material of the substrate pad 3 and the chip pad 4 is gold-plated using a sputtering process or an evaporation process, and the corresponding ball planting process conditions are: the ultrasonic energy, ball planting time, and ball planting pressure of the first stage are set to 10mA, 3mS, and 25g respectively; the ultrasonic energy, ball planting time, and ball planting pressure of the second stage are set to 35mA, 6mS, and 6g respectively; the ultrasonic energy, ball planting time, and ball planting pressure of the third stage are set to 55mA, 8mS, and 8g respectively.

[0059] Example 3

[0060] This embodiment is similar to Example 1, except that the materials of the substrate pad 3 and the chip pad 4 are nickel gold, and the corresponding ball planting process conditions are: the ultrasonic energy, ball planting time, and ball planting pressure of the first stage are set to 15mA, 1mS, and 35g respectively; the ultrasonic energy, ball planting time, and ball planting pressure of the second stage are set to 120mA, 10mS, and 6g respectively; the ultrasonic energy, ball planting time, and ball planting pressure of the third stage are set to 135mA, 15mS, and 12g respectively.

[0061] It should be understood that the technical solution of the present invention is not limited to the above-mentioned specific implementation cases. Any technical variations made according to the technical solution of the present invention without departing from the scope of protection of the purpose of the present invention and the claims shall fall within the scope of protection of the present invention.

Claims

1. A method for welding ultra-fine gold wires, characterized in that include: Providing a substrate (1) with a substrate pad (3) and a chip (2) with a chip pad (4); A chip solder ball (6) is planted on a chip solder pad (4) using a gold wire (7) as a first soldering point, a substrate solder ball (5) is planted on a substrate solder pad (3) using a gold wire (7) in advance, and a wire arc is drawn from the first soldering point to the substrate solder ball (5) to form a second soldering point; Ultrasonic welding is used to plant substrate solder balls (5) and chip solder balls (6) on the substrate solder pads (3) and chip solder pads (4); the ball planting process of the welding splitter used in the ultrasonic welding method includes a first stage, a second stage and a third stage; The diameter of the gold wire (7) is less than 16 μm, the pad width of the chip pad (4) is less than 40 μm, and the pad spacing is less than 50 μm. The material of the substrate pad (3) and the chip pad (4) is selected from any one of aluminum, gold, and nickel gold. If the substrate pad (3) and the chip pad (4) are made of aluminum, the ball planting process conditions of the substrate solder ball (5) and the chip solder ball (6) include: the pressure mode is adopted in the first stage to the third stage; wherein the ultrasonic energy, ball planting time, and ball planting pressure of the first stage are respectively set to 5~20mA, 3~5mS, and 25~45g; the ultrasonic energy, ball planting time, and ball planting pressure of the second stage are respectively set to 10~30mA, 1~3mS, and 10~30g; the ultrasonic energy, ball planting time, and ball planting pressure of the third stage are respectively set to 65~110mA, 11~13mS, and 7~10g; If the substrate pad (3) and the chip pad (4) are made of gold, the ball planting process conditions of the substrate solder ball (5) and the chip solder ball (6) include: the pressure mode is adopted in the first stage to the third stage; wherein the ultrasonic energy, ball planting time, and ball planting pressure of the first stage are respectively set to 0~15mA, 3~5mS, and 20~45g; the ultrasonic energy, ball planting time, and ball planting pressure of the second stage are respectively set to 25~55mA, 5~7mS, and 5~7g; the ultrasonic energy, ball planting time, and ball planting pressure of the third stage are respectively set to 40~85mA, 7~10mS, and 7~10g; If the material of the substrate pad (3) and the chip pad (4) is nickel-gold, the ball planting process conditions of the substrate solder ball (5) and the chip solder ball (6) include: the pressure mode is adopted in the first stage to the third stage; wherein the ultrasonic energy, ball planting time, and ball planting pressure of the first stage are respectively set to 0~15mA, 1~3mS, and 25~50g; the ultrasonic energy, ball planting time, and ball planting pressure of the second stage are respectively set to 100~130mA, 8~12mS, and 5~8g; and the ultrasonic energy, ball planting time, and ball planting pressure of the third stage are respectively set to 120~150mA, 13~17mS, and 10~15g.

2. The ultra-fine gold wire bonding method according to claim 1, wherein: The welding splitter is a B0608-28-13-06 splitter produced by PECO.

3. An ultra-fine gold wire bonding structure formed by the method according to claim 1 or 2.

4. A packaging structure comprising a substrate (1) with a substrate pad (3) and a chip (2) with a chip pad (4), characterized in that: The substrate pad (3) and the chip pad (4) are electrically connected via the ultra-fine gold wire welding structure according to claim 3.

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