Palladium mesh alloy wire without plating thereon and method for manufacturing the same

Abstract

The invention relates to a palladium mesh alloy wire without plating thereon and a method for manufacturing the same. The manufacturing method comprises the steps of: plating a palladium layer with the thickness of 5-120nm on a surface of a silver baseline, heating it up to 600-800 DEG C and maintaining the temperature for not more than 4 hours so that palladium on the surface is completely thermally diffused to a grain boundary grid surface of the silver baseline, thereby forming a grain-boundary band containing palladium. The palladium mesh alloy wire without plating thereon is prepared by the abovementioned method, and consists of the silver base and the grain-boundary band containing palladium. Compared with a known silver series bonding wire, the palladium mesh alloy wire in the invention has better hardness of a ball part, neck strength and fusing current density, and more particularly, has excellent weather resistance. The palladium mesh alloy wire without plating thereon in the invention can be applied to LED technology directly without protective gas, has low impedance and can avoid the application problems of crooked ball, low neck strength and short preservation time caused by the solidification and segregation when the known bonding wire is used.

Description

technical field [0001] The invention relates to a non-coated palladium mesh alloy wire and a manufacturing method thereof, in particular to a non-coated silver or silver alloy packaged wire, which belongs to the technical field of packaged wires in the electronics industry. Background technique [0002] Low resistivity is the basic requirement for packaging wires of general electronic products. For high-speed and high-frequency integrated circuit components (such as: high-speed amplifiers, oscillators, power management integrated circuits, and high-speed communication components, etc.), in order to avoid signal Delay (signal delaying) and crosstalk interference (cross talk interference), the resistivity requirements of the wire are more stringent; in addition, in order to ensure that the product can maintain normal life and function (weather resistance) under long-term and harsh conditions, reliable The consideration of the degree of precision is also extremely important; th...

AI Technical Summary

Problems solved by technology

[0003] At present, common packaging wires include gold wires, copper wires, silver wires, alloy wires, etc. Taking silver wires as an example, silver is the element with the lowest resistivity among all materials. Brittle intermetallic compounds (Ag 2 Al or Ag 4 Al); in addition, pure silver wires are prone to electrolytic ion migration (ion migration) inside the packaging material containing moisture, that is, pure silver will be hydrolyzed and dissolved by the action of an electric current to dissolve silver ions, and then react with oxygen to form Unstable silver oxide (AgO), the silver oxide will deoxidize to form silver atoms, and grow leaf-like silver whiskers to the positive electrode, and finally cause a short circuit between the positive and negative electrodes; therefore At present, pure silver wires cannot provide the ball forming and stability required by the industry; therefore, some operators use silver-based alloy wires (such as copper, platinum, manganese, chromium, gold and other elements) as packaging wires, but all The formed wire still cannot have the properties of low impedance and high reliability

[0004] In addition, in order to solve the problem that pure silver bonding wires are also oxidized, some operators have proposed to coat the surface with other metal coatings to improve oxidation and corrosion. Please also refer to Nippon Steel Advanced Materials Co., Ltd. and Nippon Steel Micrometals Co., Ltd. applied for a series of Taiwan invention patents related to junction wires for semiconductor devices, including "junction wires for semiconductor devices" disclosed in announcement No. I342809, "junction wires for semiconductor devices" disclosed in announcement No. I364806, and announcement No. "Bonding wires for semiconductors" disclosed in I364806, "Copper alloy bonding wires for semiconductors" disclosed in Publication No. 201107499, "Copper bonding wires for semiconductors and its bonding structure" disclosed in Publication No. The bonding structure of the previous case is generally provided with a skin layer (which can be palladium, ruthenium, rhodium, platinum, and silver) on the surface of a core material (which can be made of metals such as copper, gold, and silver). constituted), the above-mentioned bonding wire often has the following disadvantages in actual implementation and use: (a) Because the surface of the metal-plated wire has a skin layer, the hardness is relatively high, and the process current is not easy to control, often resulting in uneven thickness of the coating , resulting in poor overall yield and low yield in the packaging process; (b) when silver or silver alloy is plated with a palladium layer and used for electric frame off (EFO), the palladium layer on the surface makes balls (free air Ball, FAB) has too hard a ball center, resulting in insufficient strength of the neck above the solder ball. After wire bonding (WB), the neck often breaks, which in turn leads to the problem of peeling off the joint interface; and the palladium element There is also a problem of segregation in the solder ball, and the difference in the structure of the ball part greatly affects the bonding conditions

[0005] In addition, generally, when the end of the wire bonding wire is melted to form a solder ball, a gas delivery device is used to continuously supply a protective gas (such as nitrogen, argon, or nitrogen-hydrogen mixture) to protect the solder ball from forming. Argon can cover and protect the solder balls to avoid oxidation, and the hydrogen in the nitrogen-hydrogen mixture can reduce the oxidized parts on the solder balls, which helps to protect the solder balls from forming. Finally, the solder connected with the solder wire The ball is bonded to the die or the pad of the carrier; however, the use of shielding gas not only increases the manufacturing cost, but also when the shielding gas is not properly controlled, the flow rate is unstable or turbulent, which will lead to abnormal burning of the solder balls, making the wire bonding process The quality of the final product is abnormal, causing problems such as insufficient electrical and interface strength; and pure silver or silver alloy bonding wires are not ball-forming in an environment without protective gas, and cannot meet the quality requirements of the LED packaging industry process reliability

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