A low-line arc packaging structure and its fabrication method

Abstract

This invention discloses a low-line-arc packaging structure and its processing method, including a molding compound and a substrate, chip, pads, bonding wires, and carrier encapsulated within the molding compound. The chip is disposed on top of the substrate, the pads are disposed on top of the chip, and the carrier is disposed on top of the substrate. One end of each bonding wire is connected to a pad via a first bonding point, and the other end of each bonding wire is connected to the carrier via a second bonding point. This invention has the beneficial effects of reducing parasitic resistance and capacitance of the circuit itself, improving high-frequency signal transmission, increasing packaging density, and reducing packaging volume.

Description

Technical Field

[0001] This invention relates to the field of semiconductor packaging technology, and more specifically to a low-line-arc packaging structure and its processing method. Background Technology

[0002] In semiconductor chip interconnect packaging, wire bonding is typically used to connect wires between the chip's pads and the substrate.

[0003] With the continuous development of mobile Internet products, there are more and more interconnection and packaging methods, chip interconnection and packaging technologies are becoming more and more advanced, the spacing between pads on the chip is getting smaller and smaller, and the packaging density is getting higher and higher. The radiation intensity of a signal is directly proportional to the length of the signal line. The longer the high-frequency signal bonding wire is, the easier it is to couple to the components close to it. Therefore, the requirement for high-frequency signal bonding wires is to be as short as possible, in order to meet the increasingly higher requirements of interconnection and packaging for high-frequency signal products.

[0004] There are two techniques for wire bonding: wedge bonding and ball bonding. In existing ball bonding technology, the first bonding point is formed when the lead wire passes through the clamp and the end of the bonding head (usually a capillary wedge). The bonding machine lowers the bonding head to make it contact the first bonding position for bonding. After bonding, the clamp opens and moves the wire backward a certain distance. The bonding head rises to the arc height position. The bonding machine moves the bonding head horizontally to above the second bonding point position and lowers the head height to make the surfaces of the bonding head and the second bonding point contact for welding. At this time, the clamp closes. After the second bonding point is welded, the bonding head moves backward and upward a certain distance to break the wire at the bonding point position. A section of wire is then fed out from the end of the bonding head to prepare for the next bonding.

[0005] Figure 3 The diagram illustrates a spherical soldering method using existing technology, in which a metal wire connects the chip's pads and the substrate wire arc. According to this method, a ball is formed at one end of the wire using an electrical discharge machine to perform the first point soldering on the chip's pads. Therefore, it is necessary to design pads of corresponding sizes for soldering, which cannot meet the requirements for increasing packaging density.

[0006] Figure 2 The diagram illustrates a ball-bonded ball formed using ball bonding according to existing technology. Through thermal and ultrasonic energy pressure bonding, the diameter of the ball widens, causing a sudden change in equivalent resistance, which fails to meet the requirements for high-frequency signal chip interconnection. The existing ball bonding technology results in line arc height and ball pad size, as shown... Figure 2 This limits the improvement of packaging density and affects the package size of semiconductor chips. Summary of the Invention

[0007] To address the aforementioned problems, the present invention aims to provide a low-line-arc packaging structure and its processing method that reduces the parasitic resistance and capacitance of the circuit itself, improves high-frequency signal transmission, increases packaging density, and reduces packaging volume.

[0008] According to one aspect of the present invention, a method for fabricating a low-line-arc packaging structure is provided, comprising the following steps:

[0009] Step (1), Preparation: Prepare the substrate and chip required for processing;

[0010] Step (2), Pad Setup: Set the pads on top of the chip;

[0011] Step (3), wire feeding: feed the welding wire through the through hole on the surface of the wedge-shaped welding head at an angle α;

[0012] Step (4), First solder joint bonding: The lead wire of the welding wire extends out of the end of the wedge-shaped welding head, and the bonding machine lowers the wedge-shaped welding head so that the wedge-shaped welding head contacts the first bonding position for bonding;

[0013] Step (5), Movement: Open the wire clamp and move the wire a certain distance backward;

[0014] Step (6), Lifting: The bonding head rises to the predetermined height H;

[0015] Step (7), Movement: The bonding machine moves the wedge welding head horizontally to above the second bonding point position;

[0016] Step (8), Second solder joint bonding: The bonding machine lowers the height of the wedge welding head so that the wedge welding head and the surface of the second solder joint come into contact for welding;

[0017] Step (9), Movement: Close the wire clamp and move the wedge welding head a certain distance L away from the second welding point;

[0018] Step (10), Cutting: Cut the welding wire at the second welding point position, and send out a section of welding wire from the wedge welding head to prepare for the next bonding.

[0019] In some implementations, angle α is 30°-60°.

[0020] In some implementations, the height H ≤ 50 μm.

[0021] In some implementations, the distance L is 10um-20um.

[0022] In some embodiments, the wedge-shaped welding head includes a front chamfer and a rear chamfer, the length of the front chamfer being FR and the length of the rear chamfer being BR. Both the front and rear chamfers are pressed onto the welding wire in a chamfered shape. The length between the front and rear chamfers is F, the horizontal bonding distance is BF, BF = F + 25%FR + 25%BR, and the total planar bonding length is BL, BL = BF + 75%FR + 75%BR.

[0023] According to one aspect of the present invention, a low-line-arc package structure is provided, including a molding compound and a substrate, a chip, pads, bonding wires and a carrier encapsulated within the molding compound. The chip is disposed on the top of the substrate, the pads are disposed on the top of the chip, and the carrier is disposed on the top of the substrate. One end of the bonding wire is connected to the pads through a first bonding point, and the other end of the bonding wire is connected to the carrier through a second bonding point.

[0024] In some implementations, the bonding wire has a wire arc in the middle, and the height of the wire arc is less than or equal to 50 μm.

[0025] In some implementations, the welding wire material includes, but is not limited to, aluminum, copper, and gold.

[0026] Compared with existing technologies, this invention has the beneficial effects of reducing the parasitic resistance and capacitance of the circuit itself, improving high-frequency signal transmission, increasing packaging density, and reducing packaging size. The wedge bonding tool and processing method can be used to reduce the arc height, decrease parasitic resistance, and improve high-frequency signal transmission; simultaneously, it can be used to achieve finer pad spacing, increase pad density, and improve packaging density. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of the existing technology of bonding pads using wire bonding wrenches;

[0028] Figure 2 This is a schematic diagram of the existing technology of forming solder joints using wire bonding;

[0029] Figure 3 This is a schematic diagram of the existing technology of forming a wire arc using wire bonding;

[0030] Figure 4 This is a schematic diagram of the wedge-shaped solder head bonding on the solder pad in a low-line arc packaging structure and its processing method according to the present invention;

[0031] Figure 5 This is a schematic diagram of wire bonding forming a solder joint in a low-line arc packaging structure and its processing method according to the present invention.

[0032] Figure 6 This is a schematic diagram of wire bonding forming a low-line-arc packaging structure and its processing method according to the present invention.

[0033] Figure 7 This is a schematic diagram of wire bonding on a pad in a low-line arc packaging structure and its processing method according to the present invention.

[0034] Figure 8 This is a schematic diagram of step 1 of forming a low-line arc packaging structure and its processing method according to the present invention, which uses wire bonding to form a line arc structure;

[0035] Figure 9 This is a schematic diagram of step 2 of forming a low-line arc packaging structure and its processing method according to the present invention, which uses wire bonding to form a line arc structure;

[0036] Figure 10 This is a schematic diagram of step 3 of forming a low-line arc packaging structure and its processing method according to the present invention, which uses wire bonding to form a line arc structure;

[0037] Figure 11 This is a schematic diagram of step 4 of forming a low-line arc packaging structure and its processing method according to the present invention, which uses wire bonding to form a line arc structure.

[0038] Figure 12 This is a schematic diagram of step 5 of the low-line arc packaging structure and its processing method of the present invention, which uses wire bonding to form a line arc structure;

[0039] Figure 13 This is a schematic diagram of one embodiment of the low-line arc packaging structure and its processing method of the present invention using wire bonding;

[0040] Figure 14 This is a schematic diagram of another embodiment of the low-line arc packaging structure and its processing method of the present invention, which uses wire bonding.

[0041] Figure 15 This is a schematic diagram of the side lead structure of wire bonding in the low-line arc packaging structure and its processing method of the present invention.

[0042] Figure 16 This is a schematic diagram of a low-line arc packaging structure according to the present invention. Detailed Implementation

[0043] The present invention will now be described in detail with reference to the embodiments shown in the accompanying drawings. However, it should be noted that these embodiments are not intended to limit the present invention. Equivalent transformations or substitutions in function, method, or structure made by those skilled in the art based on these embodiments are all within the scope of protection of the present invention.

[0044] In the description of this invention, it should be noted that, unless otherwise specified and limited, the terms "installation", "connection" and "linking" should be interpreted broadly. For example, they can refer to mechanical or electrical connections, or internal connections between two components. They can be direct connections or indirect connections through an intermediate medium. Those skilled in the art can understand the specific meaning of the terms according to the specific circumstances.

[0045] In the existing technology, Figure 1 The solder joint shown is a BPD (Browser Diameter Particle Size). To form a ball at the bonding point, a wrench is used to press the ball together to form a solder joint, as shown in the image. Figure 2 As shown, due to the large solder joint size BPD and as... Figure 3 The arc height shown is relatively large, resulting in a large spacing between adjacent pads 3 in the prior art. Through thermal and ultrasonic energy pressure bonding, the diameter of the sphere widens, causing a sudden change in equivalent resistance, which cannot meet the interconnection requirements of the high-frequency signal chip 2. The arc height and pad size obtained by the spherical bonding used in the prior art limit the improvement in packaging density, thus affecting the package volume of the semiconductor chip 2.

[0046] The low-line arc packaging structure and its processing method include the following steps:

[0047] Step (1), Preparation: Prepare the substrate 1 and chip 2 required for processing;

[0048] Step (2), Pad 3 setting: Set the pad 3 on the top of the chip 2;

[0049] Step (3), wire feeding: feed the welding wire through the through hole on the surface of the wedge-shaped welding head 9 at an angle α;

[0050] Step (4), First solder joint bonding: The lead wire of the welding wire extends out of the end of the wedge-shaped welding head 9. The wedge-shaped welding head 9 is lowered by the bonding machine so that the wedge-shaped welding head 9 contacts the first bonding position for bonding.

[0051] Step (5), Movement: Open the wire clamp and move the wire a certain distance backward;

[0052] Step (6), Lifting: The bonding head rises to the predetermined height H;

[0053] Step (7), Movement: The bonding machine moves the wedge welding head 9 horizontally to above the position of the second bonding point 8;

[0054] Step (8), Second solder joint bonding: The bonding machine lowers the height of the wedge welding head so that the wedge welding head and the surface of the second solder joint come into contact for welding;

[0055] Step (9), Movement: Close the welding wire clamp and move the wedge welding head 9 a certain distance L away from the second welding point;

[0056] Step (10), Cut off: Cut the welding wire at the second welding point position, and the wedge welding head 9 sends out a section of welding wire 4 to prepare for the next bonding.

[0057] like Figure 4 As shown, in step (3), the welding wire is fed through the through hole on the surface of the wedge welding head 9 at an angle a. The angle a is 30°-60°. In specific operation, the length of the welding point is reduced by using the wedge welding head 9. At the same time, due to the spherical bonding, the arc height is generally 150μm and the arc length is less than 100 times the wire diameter. The bonding head size should not exceed 3 / 4 of the size of the pad 3. The ball size is generally 2 to 3 times the wire diameter and the fine pitch is about 1.5 times.

[0058] like Figure 5 and Figure 6 As shown, the bonding joint size formed by the present invention is smaller. Therefore, the wedge-shaped welding head 9 is used to reduce the arc height and the size of the bonding joint. As a result, the arc height will be lower than that of the wire bonding arc in the prior art. The radiation intensity of the signal is proportional to the trace length of the signal line. The longer the high-frequency signal bonding lead is, the easier it is to couple to the components close to it.

[0059] like Figure 7 As shown, due to the above technical solution, the size of the pad 3 required in this invention is relatively small, which facilitates increasing the density of the chip 2.

[0060] like Figure 8 As shown, in step (4), when bonding the first solder joint: the lead wire of the welding wire extends out of the end of the wedge-shaped welding head 9, and the bonding machine lowers the wedge-shaped welding head 9 so that the wedge-shaped welding head 9 contacts the first bonding position for bonding.

[0061] like Figure 9 As shown, in step (5), the movement is: the wire clamp opens and moves backward a distance of wire.

[0062] like Figure 10 As shown, in step (6), the rising part is raised to a predetermined height H, where H ≤ 50 μm, and the arc height of the present invention is reduced by using the predetermined rising height. After reaching the predetermined height, step (7) is performed: the wedge welding head 9 is moved to a position above the second bonding point 8.

[0063] like Figure 11 As shown, in step (8), the second solder joint is bonded: the bonding machine lowers the height of the wedge welding head so that the wedge welding head and the surface of the second solder joint come into contact for welding.

[0064] like Figure 12As shown, after moving a certain distance, step (10) is executed: the welding wire is cut off from the second welding point position, and the wedge welding head 9 sends out a section of welding wire 4 to prepare for the next bonding.

[0065] like Figure 13 The image shown is a cross-sectional view of the bonding point lead. Figure 14 The schematic diagram of the wire bonding bonding joint of the present invention is shown. Specifically, the chamfer is pressed onto the bonding wire 4. The chamfer has a front chamfer 91 (FR) and a rear chamfer 92 (BR). The two chamfers are pressed onto the gold wire in a chamfered shape. The horizontal distance is shown as F, the horizontal bonding distance is shown as BF, and the total planar bonding length is shown as BL. BF = F + 25%FR + 25%BR, and BL = BF + 75%FR + 75%BR. For a more intuitive understanding, see... Figure 15 The schematic diagram of the bonding solder joint of the present invention shown is shown, where d represents the width of the solder joint. Unlike the prior art, however... Figure 1 The solder joint size BPD shown is intended to form a ball at the bonding point. A wedge is used to press the ball together to form a solder joint, as shown in the diagram. Figure 2 As shown in the figure, the d shown in the sphere width dimension diagram of the present invention is greater than that of the prior art. Figure 1 The solder joint size BPD shown is smaller, which allows for a shorter spacing between adjacent pads and increases package density.

[0066] like Figure 16 As shown, a low-line arc package structure includes a molding compound 6 and a substrate 1, a chip 2, pads 3, bonding wires 4 and a carrier 5 encapsulated within the molding compound 6. The chip 2 is disposed on the top of the substrate 1, the pads 3 are disposed on the top of the chip 2, and the carrier 5 is disposed on the top of the substrate 1. One end of the bonding wire 4 is connected to the pads 3 through a first bonding point 7, and the other end of the bonding wire 4 is connected to the carrier 5 through a second bonding point 8.

[0067] The bonding wire 4 has a wire arc in the middle, with a height of less than or equal to 50µm. By reducing the height of the wire arc, parasitic resistance is reduced, and the transmission of high-frequency signals is improved.

[0068] The welding wire material includes, but is not limited to, aluminum, copper, and gold. The material of the wedge welding tool depends on the metal wire used for bonding. Tungsten carbide is used for aluminum wire bonding, and titanium carbide is used for gold wire bonding.

[0069] The above descriptions are merely some embodiments of the present invention. It should be noted that those skilled in the art can make other modifications and improvements without departing from the inventive concept of the present invention, and these all fall within the protection scope of the present invention.

Claims

1. A method for fabricating a low-line arc packaging structure, characterized in that, Includes the following steps: Step (1), Preparation: Prepare the substrate and chip required for processing; Step (2), Pad Setup: Set the pads on top of the chip; Step (3), wire feeding: feed the welding wire through the through hole on the surface of the wedge-shaped welding head at an angle α; Step (4), First solder joint bonding: The lead wire of the welding wire extends out of the end of the wedge-shaped welding head. The wedge-shaped welding head is lowered by the bonding machine so that the wedge-shaped welding head contacts the first bonding position for bonding. The wedge-shaped welding head includes a front chamfer and a back chamfer. The length of the front chamfer is FR and the length of the back chamfer is BR. The front chamfer and the back chamfer are pressed onto the welding wire in a chamfer shape. The length between the front chamfer and the back chamfer is F. The horizontal bonding distance is BF, BF=F+25%FR+25%BR. The total length of planar bonding is BL, BL=BF+75%FR+75%BR. Step (5), Movement: Open the wire clamp and move the wire a certain distance backward; Step (6), Lifting: The bonding head rises to the predetermined height H; Step (7), Movement: The bonding machine moves the wedge welding head horizontally to above the second bonding point position; Step (8), Second solder joint bonding: The bonding machine lowers the height of the wedge welding head so that the wedge welding head and the surface of the second solder joint come into contact for welding; Step (9), Movement: Close the wire clamp and move the wedge welding head a certain distance L away from the second welding point; Step (10), Cutting: Cut the welding wire at the second welding point position, and send out a section of welding wire from the wedge welding head to prepare for the next bonding.

2. The processing method of a low-line arc packaging structure according to claim 1, characterized in that, The angle α is 30°-60°.

3. The processing method of a low-line arc packaging structure according to claim 1, characterized in that, The height H is ≤ 50 μm.

4. The processing method of a low-line arc packaging structure according to claim 1, characterized in that, The distance L is 10um-20um.

5. The low-line arc packaging structure prepared by the processing method according to claim 1, characterized in that, The device includes a molding compound and a substrate, a chip, pads, bonding wires, and a carrier encapsulated within the molding compound. The chip is disposed on the top of the substrate, the pads are disposed on the top of the chip, and the carrier is disposed on the top of the substrate. One end of the bonding wire is connected to the pads through a first bonding point, and the other end of the bonding wire is connected to the carrier through a second bonding point.

6. The low-line arc packaging structure according to claim 5, characterized in that, The welding wire has an arc in the middle, and the height of the arc is less than or equal to 50 μm.

7. The low-line arc packaging structure according to claim 5, characterized in that, The welding wire material includes, but is not limited to, aluminum, copper, and gold.

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