Copper wire bonds also need to be studied to determine the thickness of t he efl tover d ie metallization after the wire bonding process. Moreover, wire diameters also differ depending on whether au or cu was used. Recently, taking the reliability of the ic components into consideration, pdcoated copper wire and ag alloy wire are the most popular wires using in wire bonding. However, copper wire bonding has been around a long time and while it has been used a great deal for larger diameter wires 30. Factsheet cucoral aluminum cladded copper wire for power. Tis journey to highvolume copper wire bonding production 3 october 2014 operations in chip assembly and test at. A number of studies have been conducted on cu wire bonding 36 and the expected benefits of cu wire over au wire have been published 79. In this paper, a fundamental study was performed on the bonding condition of the interface of an au wire pt bonding pad. Johnson abstract there are three areas to consider when designingimplementing wire bonding to advanced ulsi damascene copper. Using design of experiments to optimize wire bond processes. The bonding conductors are to be 6 awg solid bare copper unless the system power conductors are larger than 10 awg, in which case they are to be 4 awg solid bare copper. Effect of gas type and flow rate on cu free air ball. The combination of aluminum al and silver ag for wire bonding is long established.
Wire bonding to advanced copper, lowk integrated circuits. Conductor fusing and gapping for bond wires kenneth c. Use of copper bonding wire reduces material costs by 90% to resolve the issue of steeply rising gold prices impacting profits. Dig a trench twelve inches from the pool wall and six inches deep to lay bonding wire. Quikpak can support prototype and preproduction volumes. With just a small capital investment, material costs can be reduced by 80%. Growth of intermetallic compounds in thermosonic copper wire bonding on aluminum metallization. Feb 07, 2018 copper and gold wire bonding course description wire bonding is a welding process that is the dominant chip interconnection method. Recommended practices for designing and installing copper. The capillary design selection process for ultra fine pitch copper wire bonding application did not encounter much difficulty as it is also dictated by the following the bond pad pitch bpp, bond pad opening bpo, and wire diameter wd basically, the same. Unfortunately copper has a few mechanical property differences that make it more difficult to use as a wire bond material. Cu wire bond to al pad is stronger than au bond to al pad high bond strength results in different failure modes in high strength bonds cu wire pull and ball shear meets cpk.
Significance of wire cost wire is a major contribution to bom. There are two basic types of wire bonding processes. Harris julyaugust 2001, june 2002 setting bonding parameters 1. It was shown that during wire bonding, the sam has been removed and a metal to metal weld has been formed. All splices to the bonding conductors shall be made using a cadweld oneshot kit as shown in the details below. Wire bonding is the method of making interconnections between an integrated circuit ic or other semiconductor device and its packaging during semiconductor device fabrication. For other diameters, please contact heraeus bonding wires sales representative.
Copper wire bonding concerns and best practices article pdf available in journal of electronic materials 428 august 20 with 6,181 reads how we measure reads. Electrical performance rlc wire inductance and capacitance are almost the same when wire diameter is fixed. Copper wire can be bonded to both gold and aluminum substrate. Placement and wire bonding of the diodes encapsulation and protection of the diodes. However, with this new technology, changes in the bonding processes as well as bonding metallurgy can affect product reliability. Connected to establish electrical continuity and conductivity. Copper innovations improved surface roughness mid copper x1 process better surface appearance, smoother deposit improved smt and wire bond performance fast plating speed mid copper 100 xd process 50% reduction in plating time improved adhesion to emerging plastics mid copper 100 xd process. Optimization of the cu wire bonding process for ic. With billions of units shipped, ti offers packaging solutions that deliver the performance, reliability, quality and cost advantages of copper. Pt bonding pad to the au wire, and high stability at high temperatures. Using this approach, direct wire bonding onto copper bond pad with both gold and copper wires have been achieved. Softer fab and higher bond reliability after aging 2000 hours. Copper ball bonding, an evolving process technology.
In a materials stack of a thin inorganic film over a metal pad, one should choose the film to have both a low ultimate strength. Bonding wires for semiconductor technology pdf heraeus. With a history of building its own chip assembly equipment, ti was able to experiment with copper wire bonding independently to evaluate the results and benefits. Enhancing fine pitch, high io devices with copper ball bonding. However, with this new technology, changes in the bonding processes as well as bonding metallurgy can affect. In contrast to thermosonic bonding and the attempt of. Wire bonding is a solid phase welding process, where the two metallic materials wire and pad surface are brought into intimate contact. Silver bonding wire exhibits excellent durability, conductivity and speed of production. To determine the benefit of copper plating thickness on wire bond reliability.
Thus, it is assumed that it is important to evaluate the joining interface in the pairs of au wire pt bonding pads. International traffic in arms regulations or the u. Release of copper bond wire, new mold compounds and 8. It also has higher thermal and electrical conductivity. This technique provides more control over loop height and bond placement. Copper wire bond failure mechanisms randy schueller, ph.
The buffer is selected with a combination of the buffer switch i, ii, iii and the rightmost thumbwheel switch position. This copper clip based package integration solution provides key advantages of. Diameter 15um to 50um cu copper alloy wire p3233 high reliability copper alloy bonding wire provides wider second bond process window and lower resistivity than bare copper. In the past gold wire was the dominant material in use but in 2015 copper and palladium coated copper wire captured more than 51% of the total market. We are able to manufacture and deliver magnet wire, when and where you need it.
Value settings differ according to the type of assembly package. Connects bare copper wire to water pipe, ground rod or copper metal tubing for grounding material. Fine pitch copper wire bonding process and materials study. Silver ag alloy and copper, palladium coated copper pcc wires have emerged as alternatives to gold bond wires. Among the challenges to copper wire bonding is the damage to bond pads that had been engineered for wire bonding with the softer gold wire. Microstructural observation of the bonding interface between. Essex magnet wire global leader for innovative magnet. Physically robust interconnect design in cup bond pads. Pdf copper wire bonding concerns and best practices. Copper and gold wire bonding course description wire bonding is a welding process that is the dominant chip interconnection method. Wire notes a length of 1 cm of one mil wire will burn out with about 0. Copper wire offers a significant cost advantage over gold and is an excellent replacement due to similar electrical properties. During the past 5 years there has been a major transition in our industry from ball bonding with gold wire to the use of copper, palladiumcoated copper, or silver wire.
Nontinning general copper and copper alloys are widely used because they combine unique properties at an economical price. How to bond a pool above ground swimming pool bonding. Looking at the wire bond process set up, qfn is much more complicated than other packages and these are highly influenced by the following three factors, as shown in figure 1 below. Silver alloy offers properties like those of gold with a cost similar to pcc. Copper wire bonding ics market scope, size, share, trends. Enepig, enep, wire bonding, gold wire bonding, copper wire bonding. Ssb wire bond macdermid alpha electronics solutions. Release of copper bond wire, new mold compounds and 8 inch wafer diameter in sot223 details of this planned change scheduled changes affect product types in sot223 package only. For condition g or h, the bond strength shall be determined by dividing the breaking force by the total. The high hardness of cu wire increases the occurrence of chip damage during bonding 1,3,4.
Essex magnet wire has been the leading global supplier of magnet wire since 1930. Cu wire bonding in general, to judge the wire bonding ability, we control the bonding ball shear and the bonding wire pull fig. Wire bonding in microelectronics, third edition, has been thoroughly revised to help you meet the challenges of todays smallscale and finepitch microelectronics. The composition of the premix inert gas used is 95%n2 with 5%h2. Wire bonding more than 90% of the 15 trillion interconnects for integrated circuits, hybrids, multi chip module and rf and microwave modules are manufactured by wire bonding. The enepig surface finish origin1990s as a modification of the conventional enig finish. Lu, the challenges of copper wire bonding, in microsystems packaging assembly and circuits technology conference impact, 2010 5th international, 2010, pp. Direct gold and copper wires bonding on copper sciencedirect. Quikpak offers copper ball bonding using wires with diameters ranging from 20m 0. For ribbon wire, use the equivalent round wire diameter width which gives the same crosssectional area as the ribbon wire being tested. Tis journey to highvolume copper wire bonding production. This authoritative guide covers every aspect of designing, manufacturing, and evaluating wire bonds engineered with cuttingedge techniques. Optimization of the cu wire bonding process for ic assembly. Wire bonding using copper wire has many advantages over wire bonding using gold wire, which are summarised in table i.
Wire bonding and soldering on enepig and enep surface. Cratering on thermosonic copper wire ball bonding pdf. An inert atmosphere, typically forming gas, is required to prevent cu oxidation. Ball bonding the first type is ball bonding or sometimes called ball and wedge bonding see figure 1. It has higher mechanical strength for better wire bond looping performance which is the key for high io count devices. Copper wire has two main drawbacks that have retarded its replacement of au wire. Self inductance and self capacitance are nearly the same for au and cu wire and cu wire has lower resistivity. If copper were an easy dropin replacement for gold the industry would have made the change long ago. With the recent increase in gold au wire cost, cu wire is an attractive way to manage overall package cost.
Bond integrity in aluminumcopper clad metals materion. Exclusive technology feature failure analysis on power. The advantages of wire bonding using copper wire wire bonding using copper wire has many advantages over wire bonding using gold wire, which are summarised in table i. The increasing need to reduce integrated circuit ic. The material mix of aluminum and copper provides excellent electrical and mechanical properties. Although less common, wire bonding can be used to connect an ic to other electronics or to connect from one printed circuit board pcb to another.
However, it also comes with certain technological challenges that need to be overcome. Rising gold prices day by day, increasing adoption of copper wire bonding in automotive, and consumer electronics industry also drives market demand. Advantages of cu wire bonding the main advantage of cu wire bonding is the lower cost. Today heraeus is a leading provider of technological solutions for gold, aluminum and copper bonding wires, serving our customers. However, there are significant tradeoffs with copper wire bonding copper has twice. Copper wire is harder than au wire and oxidizes in air. Tis extensive relationships with at tool and materials. This work describes the current status of copper wire bonding, including the need for special processes to address the metallurgical challenges created by the new systems. These bonding conditions increase the possibility of silicon cratering during the wire bonding process.
Bond conductor size shall be determined by the ampere rating of the service entrance equipment as shown on the grounding and bonding table. Copper wire bonding book lays out the challenges involved in replacing gold with copper as a wire bond material, and includes the bonding process changes. Challenges and developments of copper wire bonding technology article pdf available in microelectronics reliability 526. The reliability of wire bonding using ag and al sciencedirect. However, in recent years the price of au has greatly increased, fueling the demand for highvolume wire bonding. Aluminum cladded copper wire for power application the cucoral bonding wire is a composite wire type with a copper core and aluminum coating. Copper wire bonding book lays out the challenges involved in replacing gold with copper as a wire bond material, and includes the bonding process changesbond force, electric flame off, current and ultrasonic energy optimization, and bonding tools and equipment changes for first and second bond formation. The wire bond process wire bonding is an electrical interconnection technique using thin wire and a combination of heat, pressure andor ultrasonic energy. Effect of laser assistance in ultrasonic copper wire bonding. This paper presents an extensive evaluation of electroless nipd and nipdau bond pads that offer a much more robust alternative to the standard al pad.
In summary, copper wire bonding offer many advantages over gold and aluminum wire bonding. These have been carried out without the use of plasma cleaning to remove the copper surface oxidation prior to wire bonding. We have increased output of copper and aluminum, ensuring. In applications where resistance due to bond wire can negatively impact circuit performance, using cu wire can offer improvement. Corrosion study and intermetallics formation in gold and. Wire bonding process the critical steps in the wire bonding process include achieving reliable bonds first bond, second bond, and tail bonds, maintaining desired loops, and positioning the bonds accurately. Throughput also is an important factor, since it affects the cost of the device. Wire bonding to advanced copper, lowk integrated circuits, the metaldielectric stacks, and materials considerations george g.
This bonding is occasionally em ployed for the purpose of preventing poletop fires. Copper wire bonding is fast becoming the preferred material for wire. Cu wire bonding has been widely accepted as a less expensive alternative to au. Effective groundingbonding for fire prevention ground all containers for extra safety in the handling of containers of flammable liquids having high electrical resistance and low flash points, possible loss of life, loss of property and interruption to business can be greatly minimized by effective grounding and bonding of the containers. Copper wire bonding of microelectronic parts has developed as a means to cut the costs of using the more mature technology of gold wire bonding. Gold wire provides the ability to use a ball and stitch process. D material properties that effect wire bonding to copper through thin inorganic films. Pdf challenges and developments of copper wire bonding. Wire bonding is currently the most widely used ic to leadframe. Gold wire has been the most widely used wire in wire bonding. Copper wire bonding ics market has witnessed significant growth since last few years and is anticipated to grow at a decent rate during the forecast period. These include high thermal and electrical conductivity, ease of manufacture, high recyclability and good corrosion resistance.
Barriers need to be overcome in cu wire bonding due to the high oxidation rate and hardness of cu wires. Research focusing on methods of softening the cu wire and its free air ball fab during bonding were reported in. The minimum thickness of the aluminum layer remaining under the copper wire bonds is a critical factor for the long term reliability of copper wire bonded products. Bonding jumpers shall be installed around any section of nonmetallic duct, pipe, device or fitting that will break the continuity of the ground. However, such a bonding process modification introduces new complexities into the assembly operation, such as parameter optimization for the nitrogen or forming gas used. Qfn wire bonding has its own special characteristics as compared with other leaded packages. Effect of laser assistance in ultrasonic copper wire bonding f. Wire bonding is a solid state welding process, where two metallic materials are in intimate contact, and the rate of metallic interdiffusion is a function of temperature, force, ultrasonic power, and time. Copper wire bonding book lays out the challenges involved in replacing gold with copper as a wire bond material, and includes the bonding process changes bond force, electric flame off, current and ultrasonic energy optimization, and bonding tools and equipment changes for first and second bond formation. The next section will examine the technological advantages and disadvantages of both copper and gold bonding wire. For highpower devices a loop height of about 14 of bond length is a good. The copper bonding kit consisted of a nitrogen nozzle fixture at the fab free air ball formation area and a flow meter for inert gas.
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