Multi-chip superfine palladium-plated copper wire bonding process for enhancing interface bonding strength

Abstract

The invention discloses a multi-chip superfine palladium-plated copper wire bonding process for enhancing interface bonding strength, which is applied to the technical field of semiconductor packaging, and comprises the following steps of: heating a palladium-plated copper wire by ultrasonic waves in advance when the operation of a second welding spot is carried out, and then carrying out extension operation of an end body; the extending end body pushes the molten palladium-plated copper wire to descend to be combined with the second bonding position, and the end body is obliquely and downwards pushed by the electric telescopic rod, so that after the palladium-plated copper wire is cut off by the wire cutter, the end body pushes the molten palladium-plated copper wire to slide and draw close together, and the size of a formed second welding spot is increased; compared with a traditional bonding mode, the interface bonding strength of the second welding spot is effectively enhanced.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of semiconductor packaging, in particular to a multi-chip ultra-fine palladium-plated copper wire bonding process for strengthening the interface bonding strength. BACKGROUND

[0002] The development of semiconductor chip flip-chip technology has led to the widespread application of chip bonding equipment in the chip packaging field. Currently, gold wire bonding is still the main method in the packaging industry. However, the cost of gold wire bonding is high, and the use of copper wire as a substitute for gold wire bonding has gained a stable trend. For example, Chinese patent CN115938959A discloses a chip lead bonding process. The advantages of copper wire include higher electrical conductivity and thermal conductivity than gold, and the cost of copper material is lower than that of gold.

[0003] During lead bonding, the lead includes two bonding steps, namely the so-called first solder joint bonding and second solder joint bonding. The second solder joint bonding is achieved by pressing the wire tail on the bonding position after the blade is arranged with the lead, and then breaking the lead by melting, forming a second solder joint only in the area where the lead is pressed. For example, Chinese patent CN107256834A discloses a semiconductor bonding process based on palladium-copper wire. Therefore, the second solder joint is relatively small as a whole, and the interface bonding strength between the second solder joint and the chip is low. SUMMARY

[0004] The core of the present application is to solve the problem of the small overall size of the second solder joint formed by the existing bonding method in the prior art, and the low interface bonding strength between the second solder joint and the chip by forming a second solder joint by folding.

[0005] To solve the above problems, the present application adopts the following technical solutions.

[0006] A multi-chip ultra-fine palladium-plated copper wire bonding process for strengthening the interface bonding strength, comprising the following steps: Step one: install the bonding tip assembly at the head end of the blade by inserting, and pass the palladium-plated copper wire through the blade to the bonding tip assembly; Step two: move the blade to the top of the chip, press the head of the palladium-plated copper wire on the first bonding position of the chip, and weld the head of the palladium-plated copper wire on the first bonding position by ultrasonic heating to complete the setting of the first solder joint; Step three: lift the blade up, pull the palladium-plated copper wire to a set height, and then move the blade from the highest point to the second bonding position of the chip to complete the wire routing process of the palladium-plated copper wire; Step four: the cleaver drives the palladium-plated copper wire, when it is about to contact with the second bonding position, the ultrasonic wave is started to heat the tail of the palladium-plated copper wire, and the bonding tip assembly is started to stretch out the head end of the cleaver, the bonding tip assembly first pulls off the heated palladium-plated copper wire, and then the palladium-plated copper wire is pressed to the second bonding position by the bonding tip assembly, so that the second welding point is set.

[0007] Further, the bonding tip assembly comprises a tip body and an electric telescopic rod fixedly installed outside the cleaver, the output end of the electric telescopic rod is fixedly connected with the tip body, and the electric telescopic rod is arranged in an inclined state.

[0008] Further, the tip body is provided with a tail groove at one end away from the electric telescopic rod, and the palladium-plated copper wire is clamped with the tail groove.

[0009] Further, the head end of the cleaver is provided with a plug-in hole for plugging the tip body, and the inner wall of the plug-in hole is fixedly connected with a filling guide block, and the filling guide block is slidingly connected with the tail groove.

[0010] Further, the top end of the tip body is fixedly connected with a wire cutting knife, and the wire cutting knife is in contact with the top end inner wall of the plug-in hole.

[0011] Optionally, the end of the cleaver away from the electric telescopic rod is fixedly connected with a protective gas nozzle, and the outlet end of the protective gas nozzle is inclined downward to the bottom end of the cleaver.

[0012] Further, the outlet end of the protective gas nozzle is fixedly connected with a deflection nozzle, the deflection nozzle is conical, and the deflection nozzle is made of rubber material.

[0013] Further, the top of the deflection nozzle is fixedly connected with a guide needle, and the end of the guide needle away from the deflection nozzle is fixedly connected with the output end of the electric telescopic rod.

[0014] Compared with the prior art, the advantages of the present application are: (1) The present scheme preheats the palladium-plated copper wire by ultrasonic wave when the second welding point is operated, and then the tip body is stretched out, the tip body pushes the molten palladium-plated copper wire to drop and combine with the second bonding position, because the tip body is pushed obliquely downward by the electric telescopic rod, so that the tip body pushes the molten palladium-plated copper wire to slide and concentrate after being cut off by the wire cutting knife, so that the volume of the second welding point is increased, and the interface bonding strength of the second welding point is effectively enhanced compared with the traditional bonding method.

[0015] (2) The protective gas of the protective gas nozzle provides isolation oxygen for the bonding of the first bonding point and the second bonding point, effectively reduces the oxidation degree of the first bonding point and the second bonding point, and according to the particularity of the second bonding point bonding mode of the application, the steering nozzle is still directed to the bonding operation position when the splitting knife is stalled by guiding the needle to drive the steering nozzle, effectively improving the anti-oxidation ability of the second bonding point bonding of the application. BRIEF DESCRIPTION OF DRAWINGS

[0016] Figure 1 Flow chart of the application; Figure 2 Stereoscopic structure diagram of the application; Figure 3 Flow demonstration diagram of step one and step two of the application; Figure 4 Flow demonstration diagram of step three of the application; Figure 5 Flow demonstration diagram of step four of the application; Figure 6 Comparison diagram of the second bonding point obtained by the application and the second bonding point obtained by the prior art; Figure 7 Stereoscopic enlarged view of the head body of the application and the head-end integral combination state of the splitting knife; Figure 8 Stereoscopic structure diagram of the head body of the application and the head-end split state of the splitting knife; Figure 9 Stereoscopic structure diagram of the head body of the application; Figure 10 Enlarged stereoscopic structure diagram of the steering nozzle of the application; Figure 11 Stereoscopic structure diagram of the steering nozzle of the application affected by the guiding needle pushing force; Figure 12 Demonstration diagram of the outlet end pipe diameter of the steering nozzle of the application being pinched by the guiding needle.

[0017] Explanation of figure numbers: 1 splitting knife, 101 palladium copper wire, 102 first bonding position, 103 second bonding position, 2 head body, 201 electric telescopic rod, 202 wire tail groove, 203 plug-in hole, 204 filling guide block, 205 wire cutting knife, 3 protective gas nozzle, 301 steering nozzle, 302 guiding needle. DETAILED DESCRIPTION

[0018] The technical solutions will be described clearly and completely below by combining the drawings in the embodiments of the application.

[0019] First embodiment: Please refer toFigures 1 to 6 A multi-chip ultra-fine palladium-plated copper wire bonding process for strengthening the interface bonding strength, comprising the following steps: Step one: install the bonding tip assembly at the head end of the cleaver 1 by inserting, and the palladium-plated copper wire 101 passes through the cleaver 1 to the bonding tip assembly; Step two: move the cleaver 1 to the top of the chip, press the head of the palladium-plated copper wire 101 at the first bonding position 102 of the chip, and heat by ultrasonic wave to weld the head of the palladium-plated copper wire 101 at the first bonding position 102, to complete the setting of the first welding point; Step three: lift the cleaver 1 up, and the palladium-plated copper wire 101 is pulled up to the set height, then move the cleaver 1 from the highest point to the second bonding position 103 of the chip, to complete the wiring process of the palladium-plated copper wire 101; Step four: the cleaver 1 drives the palladium-plated copper wire 101, and when it is about to contact the second bonding position 103, start to heat the tail of the palladium-plated copper wire 101 by ultrasonic wave, and start the bonding tip assembly to make it extend out of the head end of the cleaver 1, the heated palladium-plated copper wire 101 is first pulled off by the bonding tip assembly, then the palladium-plated copper wire 101 is pushed to the second bonding position 103 by the bonding tip assembly, to complete the setting of the second welding point.

[0020] Please refer to Figures 7 to 9The bonding end head assembly comprises an end head body 2 and a motorized telescopic rod 201 fixedly installed outside the cleaver 1, an output end of the motorized telescopic rod 201 is fixedly connected with the end head body 2, the telescopic movement of the end head body 2 is driven by the motorized telescopic rod 201, so that the end head body 2 drives the palladium-plated copper wire 101 to be welded to the second bonding position 103, and the motorized telescopic rod 201 is arranged in an inclined state, the motorized telescopic rod 201 arranged in the inclined state drives the end head body 2 to move downward in an inclined state, so as to push the molten palladium-plated copper wire 101 to be close to each other, the volume of the second welding spot formed is increased, and then the interfacial bonding strength of the second welding spot is enhanced, the end head body 2 is provided with a wire tail groove 202 at an end away from the motorized telescopic rod 201, the palladium-plated copper wire 101 is clamped with the wire tail groove 202, so that the tail wire of the palladium-plated copper wire 101 can be stretched out of the wire tail groove 202, the head end of the cleaver 1 is provided with a plug-in hole 203 for plugging in the end head body 2, the end head body 2 is in the plug-in hole 203, so that the end head body 2 and the cleaver 1 are integrally combined, an inner wall of the plug-in hole 203 is fixedly connected with a filling guide block 204, the filling guide block 204 is used for filling the wire tail groove 202, so that the combination stability of the end head body 2 and the cleaver 1 is effectively improved, and the influence of the wire tail groove 202 on the bonding operation of the first welding spot is reduced, the filling guide block 204 is slidingly connected with the wire tail groove 202, a wire cutting knife 205 is fixedly connected with a top end of the end head body 2, the wire cutting knife 205 is in contact with the top end inner wall of the plug-in hole 203, when the end head body 2 moves downward in an inclined state, the wire cutting knife 205 cuts the palladium-plated copper wire 101, so that the palladium-plated copper wire 101 is convenient to cut after the second welding spot is completed; When the bonding operation of the first welding spot is performed, the bonding end head assembly is in a retracted state, that is, the end head body 2 is retracted in the wire tail groove 202 at the head end of the cleaver 1, and the end head body 2 is integrally combined with the cleaver 1, which is the same as the traditional first welding spot bonding mode, a pre-burning ball is prepared, the head end of the palladium-plated copper wire 101 is preheated, the head end of the palladium-plated copper wire 101 is melted to be spherical, this step is a pre-burning ball stage, then the cleaver 1 presses the burning ball formed to the first bonding position 102, and the first welding spot is obtained after cooling; In the operation of the second welding spot, after confirming the stability of the first welding spot, the cleaver 1 is lifted up, and the palladium-copper-plated wire 101 is pulled up and then lowered, so as to guide the palladium-copper-plated wire 101 to the second bonding position 103. When the palladium-copper-plated wire 101 is about to contact the second bonding position 103, the ultrasonic heating is started to make the palladium-copper-plated wire 101, and then the extension operation of the end body 2 is performed. The extended end body 2 pushes the molten palladium-copper-plated wire 101 to descend and combine with the second bonding position 103. Since the end body 2 is pushed obliquely downward by the electric telescopic rod 201, after the palladium-copper-plated wire 101 is cut by the cutting knife 205, the end body 2 pushes the molten palladium-copper-plated wire 101 to slide and concentrate, so that the volume of the formed second welding spot is increased, and the interface bonding strength of the second welding spot is effectively enhanced compared with the traditional bonding method.

[0021] Second embodiment: Compared with the first embodiment, the main addition is the protection gas nozzle 3, and the specific added structure is as follows, and the remaining structure is consistent with the first embodiment.

[0022] Please refer to Figures 10 to 12 The end of the cleaver 1 far away from the electric telescopic rod 201 is fixedly connected with the protection gas nozzle 3. The protection gas nozzle 3 sprays protection gas for isolating oxygen. The composition of the protection gas is: 95%-99% nitrogen and 1%-5% hydrogen. A small amount of hydrogen can reduce part of the copper oxide. The outlet end of the protection gas nozzle 3 is inclined downward toward the bottom end of the cleaver 1. The outlet end of the protection gas nozzle 3 is fixedly connected with the deflection nozzle 301. The deflection nozzle 301 is conical and is made of rubber material. The deflection nozzle 301 made of rubber material is convenient for bending and adjusting. The top of the deflection nozzle 301 is fixedly connected with the guide needle 302. The end of the guide needle 302 far away from the deflection nozzle 301 is fixedly connected with the output end of the electric telescopic rod 201. When the electric telescopic rod 201 drives the end body 2 to extend, the deflection nozzle 301 is driven by the guide needle 302 synchronously, so that when the cleaver 1 stops, the deflection nozzle 301 still faces the bonding operation position, so that the protection gas blown by the deflection nozzle 301 blows into the wire tail groove 202 of the end body 2. When the deflection nozzle 301 is pressed downward by the guide needle 302, the nozzle of the deflection nozzle 301 is pressed flat by the guide needle 302, so that the outlet diameter of the deflection nozzle 301 is reduced, so that the protection gas is blown out at high speed from the deflated deflection nozzle 301, which is convenient for blowing the protection gas into the end body 2, effectively improving the oxygen isolation effect of the protection gas on the second welding spot, and further effectively improving the conductivity of the second welding spot; Compared to the first embodiment, the bonding of the first and second solder joints is provided with an oxygen-isolated protective gas, which effectively reduces the oxidation level of the first and second solder joints and thus effectively improves the conductivity of the first and second solder joints. Furthermore, the protective gas nozzle 3 is steered by the steering nozzle 301. In addition, according to the special characteristics of the second solder joint bonding method of the present invention, the steering nozzle 301 is driven by the guide pin 302, so that when the cutting tool 1 stops, the steering nozzle 301 still faces the bonding operation position, which effectively improves the anti-oxidation capability of the second solder joint bonding of the present invention.

[0023] The above description is merely a preferred embodiment of the present invention; it encompasses all the protection scope of the present invention. Any equivalent substitutions or modifications made by those skilled in the art within the technical scope disclosed in the present invention, based on the technical solutions and improved concepts of the present invention, should be covered within the protection scope of the present invention.

Claims

1. A multi-chip ultra-fine palladium plated copper wire bonding process for strengthening the interfacial bond strength, characterized by: The method comprises the following steps: Step one: install the bonding tip assembly at the head end of the cleaver (1) by inserting, and the palladium-plated copper wire (101) passes through the cleaver (1) to the bonding tip assembly; Step two: move the cleaver (1) to the top of the chip, press the head of the palladium-plated copper wire (101) at the first bonding position (102) of the chip, heat by ultrasonic wave to weld the head of the palladium-plated copper wire (101) at the first bonding position (102), and complete the setting of the first welding point; Step three: lift the cleaver (1) up, pull the palladium-plated copper wire (101) to the set height, and then move the cleaver (1) from the highest point to the second bonding position (103) of the chip, to complete the wiring process of the palladium-plated copper wire (101); Step four: drive the palladium-plated copper wire (101) by the cleaver (1), start to heat the tail of the palladium-plated copper wire (101) when it is about to contact the second bonding position (103), and start the bonding tip assembly to make it extend out of the head end of the cleaver (1), the bonding tip assembly first pulls off the heated palladium-plated copper wire (101), and then the palladium-plated copper wire (101) is pushed to the second bonding position (103) by the bonding tip assembly, to complete the setting of the second welding point.

2. The process for multi-chip ultra-fine palladium-coated copper wire bonding with enhanced interfacial bond strength as claimed in claim 1 wherein: The bonding tip assembly comprises a tip body (2) and an electric telescopic rod (201) fixedly installed outside the cleaver (1), the output end of the electric telescopic rod (201) is fixedly connected with the tip body (2), and the electric telescopic rod (201) is arranged in an inclined state.

3. The process for multi-chip ultra-fine palladium-coated copper wire bonding with enhanced interfacial bond strength according to claim 2, wherein: One end of the tip body (2) away from the electric telescopic rod (201) is provided with a tail groove (202), and the palladium-plated copper wire (101) is connected with the tail groove (202).

4. The process for multi-chip ultra-fine palladium-coated copper wire bonding with enhanced interfacial bond strength according to claim 3, wherein: The head end of the cleaver (1) is provided with an insertion hole (203) for inserting the tip body (2), the inner wall of the insertion hole (203) is fixedly connected with a filling guide block (204), and the filling guide block (204) is slidingly connected with the tail groove (202).

5. The process for multi-chip ultra-fine palladium-coated copper wire bonding with enhanced interfacial bond strength according to claim 4, wherein: The top end of the tip body (2) is fixedly connected with a wire cutting knife (205), and the wire cutting knife (205) is in contact with the top end inner wall of the insertion hole (203).

6. The process for multi-chip ultra-fine palladium-coated copper wire bonding with enhanced interfacial bond strength as claimed in claim 2 wherein: One end of the cleaver (1) away from the electric telescopic rod (201) is fixedly connected with a protective gas nozzle (3), and the outlet end of the protective gas nozzle (3) is inclined downward to the bottom end of the cleaver (1).

7. The process for multi-chip ultra-fine palladium-coated copper wire bonding with enhanced interfacial bond strength as claimed in claim 6 wherein: The outlet end of the protective gas nozzle (3) is fixedly connected with a deflection nozzle (301), the deflection nozzle (301) is conical, and the deflection nozzle (301) is made of rubber material.

8. The process for multi-chip ultra-fine palladium-coated copper wire bonding with enhanced interfacial bond strength as claimed in claim 7 wherein: The top of the deflection nozzle (301) is fixedly connected with a guide needle (302), and one end of the guide needle (302) away from the deflection nozzle (301) is fixedly connected with the output end of the electric telescopic rod (201).

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