Uncoated palladium mesh alloy wire and manufacturing method thereof

Abstract

The present invention relates to an uncoated palladium mesh alloy wire and a manufacturing method thereof. In the manufacturing method, a palladium layer of 5nm-120nm is plated on the surface of a silver baseline, and then heated to a temperature of 600-800°C, and the temperature is continued for no more than 4 hours, so that the surface layer palladium is completely thermally diffused to the surface of the silver baseline grain boundary grid , thereby forming palladium-containing grain boundary zones. The uncoated palladium mesh alloy wire is prepared by the above method, that is, it is composed of a silver base and a palladium-containing mesh grain boundary zone. Compared with the known silver-based bonding wire, the uncoated palladium mesh alloy wire of the present invention has better ball hardness, neck strength and fusing current density, and also has excellent weather resistance. The uncoated palladium mesh alloy wire of the present invention can be directly used in the LED process without protective gas, which not only takes into account the low impedance but also avoids the skewed ball caused by the solidification segregation of the known bonding wire during the implementation and use, and the neck strength is low. Application problems such as short time.

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...

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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 (ionmigration) inside the packaging material containing moisture, that is, pure silver will be hydrolyzed and dissolved by the action of electric current to dissolve silver ions, and then react with oxygen to become indestructible Stable silver oxide (AgO), this silver oxide will deoxidize to form silver atoms, and grow leaf vein-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 the formed The wire still cannot have both low impedance and high reliability properties

[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 wirebonding (WB), the neck fracture often occurs, which in turn leads to the problem of peeling off the joint interface; and the palladium element is in the 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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