July 19, 2024


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Technology Advances, Shortages Seen For Wire Bonders

A surge in desire for IC packages is resulting in long lead periods for wire bonders, which are applied to assemble three-fourths of the world’s deals. The wire bonder sector doubled final yr, alongside highly developed packaging’s increase.

Wirebonding is an older technological know-how that generally flies less than the radar. Even now, packaging homes have multitudes of these important instruments that assistance assemble a lot of — but not all — package varieties. Above the yrs, buyers have demanded quicker and extra able wire bonders. In reaction, wire bonder suppliers have created speedier systems, which include all those with AI-enabled defect detection and manufacturing facility automation abilities. Wirebonding is wholly different than copper hybrid bonding, which is a significantly a lot more state-of-the-art and high priced engineering employed for die stacking, packaging, and other purposes.

Even so, in wirebonding, packaging clients facial area significant new issues. For some time, a lot of packaging homes have been sold out of wirebonding capability amid huge demand from customers in the arena. So quite a few packaging houses want a lot more wire bonders to fulfill need. There is just one dilemma. Very last August, shipping and delivery lead occasions for many wire bonder types spiked and had been hovering all over 10 months. So considerably in 2022, the situation is enhancing, but it is nonetheless an situation. All of this impacts the delivery schedules of several offer sorts.

“There was panic getting of wire bonders in 2021. OSATs and others were being inserting orders even for 2022, as they feared getting also late in the buying queue,” explained Charles Shi, an analyst at Needham. “Lead situations are likely shorter than 6 months now. The need is nevertheless strong, but buying is shifting in direction of more reasonable stages.”

Wirebonding usually has been a dynamic but unsung section of the semiconductor ecosystem. Invented back in the 1950s, these bonders are made use of to build low-cost wired interconnects inside of a package. Interconnects are utilised to link one die to a further, or to a substrate in a package deal. Over time, wire bonders evolved and grew to become the workhorse assembly resource for quite a few deal styles. TechSearch reviews that 75% to 80% of today’s offers are centered on wirebonding. Wire bonders are employed for lower-cost legacy packages, midrange offers, and memory die stacks.

Wirebonding is a essential element of the assembly method. In one illustration of an assembly movement, a die is placed on a tiny rectangular body with metallic leads making use of a die-attach process. Then, a wire bonder will take these pieces and quickly attaches very small wires from the die to the metallic potential customers at superior speeds, forming electrical connections. Finally, working with a unique method, the construction is encapsulated, forming a offer.

Fig. 1: Wirebond wires in packages. Source: K&S

Fig. 1: Wirebond wires in deals. Supply: K&S

Wirebonding is not the only way to deliver interconnects in packages, and it does have complex restrictions. Over and above wirebonding, there are other techniques in which two or a lot more dies are assembled working with far more advanced interconnects techniques in an highly developed offer this sort of as admirer-outs, 2.5D or 3D-ICs.

Sophisticated packaging tends to get most of the headlines and is making sizeable sector gains. In comparison, wirebonded-primarily based packaging is a experienced know-how with single-digit-development costs. Even so, wire bonders are looking at meteoric progress. Around the globe profits attained $1.6 billion in 2021, up from $800 billion in 2020, according to VLSI Study. In 2022, the market place is envisioned to continue being flat with $1.6 billion in gross sales, in accordance to the company.

Besides the progress rates, other noteworthy trends involve:

  • The most up-to-date higher-end wire bonders have equipment studying and manufacturing facility automation abilities. Learning on these devices allows stop defect excursions, even though functioning with out human intervention.
  • Wire bonders are remaining utilised for far more complex offers.
  • These systems are pushing the restrictions of engineering in memory stacking.

What is wirebonding?
Bell Laboratories, once the world’s leading R&D corporation, invented the initial wire bonder in 1957. (Bell Labs also shown the to start with transistor in 1947. In 2016, Nokia assumed regulate of Bell Labs.)

With the assistance of Bell Labs, Kulicke & Soffa (K&S) in 1959 made the 1st business wire bonder, a method that paved the way towards chips with new and economical offers.

The early wire bonders ended up handbook systems, which had been employed to assemble straightforward twin-in-line deals (DIPs) and other commodity products and solutions. In DIPs, a die sits on a metal body with qualified prospects. A bonder connects the die to the potential customers with little wires.

Wirebonding originally was a labor-intensive undertaking. Beginning in the 1960s, quite a few North American chipmakers began moving their assembly plants from the U.S. to low-expense web-sites in Asia. Human operators ended up necessary to transfer unbonded parts to the bonders, the place they were being loaded into the device.

Early on, wire bonders morphed into two styles, ball bonders and wedge bonders. Ball bonders, the most significant sector, are used for a myriad of package deal styles, and benefit from copper, gold or silver wires. Wedge bonders are made use of for energy units.

Generally, a ball bonder consists of a observe, keyboard, handlers, conveyor programs, and a capillary unit. In a ball bonder application, let us say you want to kind a wired link among a bond pad on a die with a individual lead publish positioned off the chip. In procedure, a spool of wire is loaded into the system. From the spool, a solitary wire is fed through a capillary device with a tiny hollow tube. In the procedure, a spark is created, which melts the wire conclusion and kinds a spherical ball at the idea.

Up coming, the bonder scans though depositing a wire strip from post to bond pad. Then, in the ball bonder, the ball on the pad is mechanically pressed to electrically secure the link. The capillary tube retracts, completing the wire loop concerning die pad and lead.

Next, the superior-speed system is recurring until finally each individual link necessary in the bundle is linked.

Simply put, wirebonding is a minimal-price way to make interconnects in packages. But a long time in the past, wire bonders ended up supposed to disappear due to raising technical calls for.

“People were being conversing about state-of-the-art packaging erasing wirebonding way again in the late-1970s and early-1980s,” reported Dan Hutcheson, CEO of VLSI Research.

That in no way occurred. In the 1980s, the advent of automatic wire bonders helped simplify the method. “If you imagine about wirebonding, you have this leadframe, and the sales opportunities prolong out. There is a house in between these qualified prospects in the pad wherever the die goes,” Hutcheson explained. “If the die dimensions improvements, it doesn’t make a difference. All you have to do is reprogram the wire bonder.”

All told, wirebonding took off early on. “The greatest motive is due to the fact it’s less costly and a lot more flexible,” Hutcheson mentioned. “There are two matters that drove the advancement. One is the full number of packages. It’s not just offers that wanted to be bonded. It’s also the range of sales opportunities that will need to be bonded for any specified yr.”

Wire bonders are used to make numerous deal types. Each bundle has a unique amount of bond wires with numerous wire lengths, loops, and pitches. The pitch is bigger than the place between the wire heart to the centre or bond pod center to the centre on a wafer.

“The primary two initiatives we were being driving with each individual new machines growth were being to boost the throughput of the bonder and cut down its bond pad pitch capability,” said John Foley, director of product or service advancement at K&S. “In the late 2000s, consumers ended up driving down to 40μm, and extra recently going toward 35μm pad pitches. Today, our equipment is able of 30μm in-line bond pad pitches, despite the fact that most purposes really do not still call for this capacity.”

Right now, in wirebonded offers, the mainstream bond pad pitch ranges from 40μm to 45μm. “According to that requirement, the wire diameter stabilized about .7- to .8-mil diameter, relying on the bond-pad pitch. As we shift towards 35μm pad pitches, .6-mil diameter wire will be necessary,” Foley mentioned.

Nevertheless, there are numerous difficulties with wirebonding. For a person detail, the deals have grow to be extra complicated. “In the earlier, we bonded older, more unwieldy packages these kinds of as plastic leaded chip carriers (PLCCs) and DIPs,” claimed Rosie Medina, vice president of product sales and marketing and advertising at Promex, the father or mother enterprise of QP Systems. “What’s altered is the need to have for scaled-down bond pad openings, better pin rely/finer pitch, and staggered bond pads – all of which lend them selves to custom substrates and deals.”

Whilst the offers have come to be extra elaborate, the wire bonders by themselves ought to stay forward of the curve. “For a high-yield approach, you involve minimal loops. You demand smaller and spherical balls that need to be uniformly fashioned at large speeds (accelerations of >25g),” said Choon Lee, chief know-how officer of JCET.

Dependability is essential. Copper, the mainstream wire type in bonding, is low-cost and has higher conductivity. But copper can corrode, creating failure in wirebonded deals. This is due to halogens like chlorine, which are existing in mildew compounds.

Wire bonder distributors have satisfied all of those people troubles. The previously mentioned failure manner can be prevented by using fairly priced, halogen-cost-free compounds.

Nonetheless, buyers want more able and a lot quicker machines. In new years, wirebonding throughput has enhanced roughly 2% for every calendar year.

The throughput is dependent on quite a few variables, these kinds of as deal sort and wire depend. At the small-stop, LEDs may have 2 to 3 wires. A quad-flat deal (QFP), a common bundle style, ranges from 50 to 80 wires per device.

“We see offers with far more than 2,000 wires at the high conclude. That would be for chips that are currently being made use of in utility smartphones, tablets and IoT products,” K&S’ Foley said.

Wire bonder landscape, traits
Meanwhile, wirebonding has grow to be a sizable organization. Among the 14 providers competing in the wire bonder current market, K&S has >60% share, followed by ASM Pacific with >20%, according to VLSI Analysis.

It’s by no indicates a static sector. For decades, wirebonded deals largely utilized gold wires, since the materials is hugely conductive and trustworthy.

That started to modify close to 2009, when gold selling prices jumped by 300% in the worldwide marketplace. Most likely, the soaring price tag of gold spelled difficulties for the value of wirebonded packages.

The good news is, the sector predicted the difficulty. Even before the disaster, providers developed wire bonders that employed significantly less high priced copper wire.

With the migration from gold to copper wirebonding, sellers have been able to lower assembly costs by up to 30%. Gold wires still are made use of in some programs currently, but copper became the mainstream technological know-how virtually right away.

The future major inflection stage occurred in the very last yr or two, when ASM Pacific, K&S, and a few other suppliers started to create their respective Industry 4. (fourth industrial revolution) initiatives, also regarded as wise production. The aim is to improve production performance by applying new technologies and much better interaction.

This is not new in the semiconductor sector. In excess of the many years, chipmakers moved towards far more automated fabs. Then, fab gear makers included more sensors into their techniques. This, in switch, generates wide amounts of details that enables chipmakers to pinpoint challenges earlier in the production move.

Some fab products also incorporates machine understanding. A subset of artificial intelligence (AI), device learning makes use of superior algorithms in methods to understand patterns in inline info, study, and make predictions from the facts.

Device mastering is used in some but not all components of a semiconductor fab. It’s made use of seriously in inspection machines to assist track down most likely fatal defects in chips.

Some of these systems are transferring into the packaging entire world. In truth, various memory makers commenced transferring toward so-referred to as “lights-out” assembly services, in which the intention is to remove operator intervention, thereby reducing fees.

Not long ago, quite a few OSATs and chipmakers with packaging models moved in a equivalent course. Generally, many packaging properties deploy many kinds of manufacturing facility automation techniques, like automated guided autos (AGVs), rail guided autos (RGVs), and overhead transport programs.

Wire bonder suppliers have formulated the interfaces to converse with individuals systems. “AVGs contain a robotic that travels in the front of the wire bonder tools, delivering publications of unbonded components and later on picks up journals of completely bonded parts,” K&S’ Foley explained. “We also see rail-guided automobiles, exactly where rows of wire bonders are back again-to-back with ample space for a robot on a rail that routinely masses product from the rear of the equipment.”

In overhead transfer mechanisms, meanwhile, a robotic carrier moves about the plant in an overhead conveyer belt. The provider can decide up and drop off unbonded or bonded pieces.

In addition to the automation element, higher-finish wire bonders incorporate pc vision devices with equipment finding out for defect regulate. Using these algorithms, the bonder can detect whether or not a ball bond is also significant or modest. That is 1 of several applications.

“The present-day emphasis is on enabling actual-time course of action monitoring and fault detection. There is a prosperity of details accessible from key subsystems on the bonder and we are introducing further sensors to empower extra advanced detection. We are monitoring details in genuine time and using state-of-the-art equipment learning algorithms,” Foley stated.

To begin with, automotive shoppers drove these developments. Automobile makers want zero flaws in the procedure, including wirebonding. Now, all shoppers want these abilities.

Marketplace outlook
For some time, the business has knowledgeable unprecedented demand from customers for semiconductor chips and deals, which is driving the have to have for a lot of much more assembly tools.

“We have found wide-primarily based progress in all sectors, with momentum that carried around to at the very least 2022,” mentioned Tien Wu, chief functioning officer at ASE, in the course of a latest convention call. “In 2021, we have noticed state-of-the-art packaging earnings expand 23% 12 months-in excess of-calendar year. We do anticipate the expansion rate in 2022 to be superior than that selection. The 2021 wirebond profits grew 36%. We keep on to see wirebond to be absolutely loaded. And we do expect wirebond revenue in 2022 will realize double-digit growth.”

That’s the good news. The lousy news is that the direct instances for K&S’ wire bonders are six to seven months for most shoppers. In reaction, K&S is growing its producing capacity. Other wire bonder suppliers are observing equivalent demand.

Fig. 2: K&S wirebonding machine. Source: K&S

Fig. 2: K&S wirebonding equipment. Source: K&S

“Ongoing worldwide demand from customers for 5G, linked gadgets, automotive and memory is continuing from 2021,” K&S’ Foley said. “2022 packaged semiconductor growth is expected to sequentially lessen from 2021, despite the fact that this is still just about 2X the historic field common.”

In the early days, wirebonding was utilised to assemble very simple deals. Over time, the wirebonded deals have grow to be far more sophisticated. In the 2000s, for example, QFNs appeared.

QFNs fall into the leadframe loved ones of packages. A leadframe is an alloy frame with extended potential customers. In QFN, a die is attached to a frame. Then, using a wire bonder, small wires hook up the die to each individual direct. Lastly, the deal is encapsulated.

QFNs are greatly utilised now, but they are far more intricate. “We are seeing multi-tier QFNs with a few to 4 tiers to accommodate a lot more I/Os. We are seeing bigger QFNs (<12mm),” JCET’s Lee said.

Wire bonders are used for other complex package types. “Today, we are doing more ball-grid arrays (BGAs), chip-on-board (COB), and multi-chip modules (MCMs),” Promex’ Medina said. “Although they aren’t pushing the boundaries as much since they have lower pin counts, sensors are another important wirebonding application. Many sensors require access to the surface of the die in the end application, thus using wirebonding for the interconnects is ideal.”

Memory is another big driver for wirebonding. In 2016, Apple introduced the iPhone 7. The phone stacked 16 NAND flash dies, enabling 128GB of storage. Each die was stacked in a pyramid-like formation and connected using tiny wirebonded wires.

Today, memory vendors are stacking 8 or 16 NAND flash dies in a package. In R&D, the industry is developing 24 die stacked packages.

This trend presents some challenges. “The memory die will be quite large and incredibly thin. So handling these fragile dies require the use of specialized needle-less pickup tools to minimize stress and reduce the risk of cracking during these processes,” said Knowlton Olmstead, a senior engineer at Amkor, in a video. “These thin dies will also have an overhang in the die stack. That requires selection of proper die-attach film and mold compound materials to minimize warpage and stress in the package, preventing failure in the final assembled package.”

That’s not the only issue. “Increasing the number of stack die in the package, while maintaining a low package height introduces challenges in a number of areas. There’s continual improvements being made in reducing the substrate ‘Z’ height to allow for higher stacking,” Olmstead said. “The wirebonding that cascades down the die also needs to be done in a controlled manner, so it minimizes stress on that whole overhanging area. Also, we want to maintain a low wirebond loop height, which lets us have a very low die-to-mold-cap clearance height.”

Clearly, wire bonders are an important part of the semiconductor ecosystem. Despite the growth and attention paid to advanced packaging, wirebonding will continue to be used for many package types.

Procuring enough wire bonders is one of the big challenges right now. But at some point there will be a glut of wirebonding capacity, which is the cyclical nature of an older but critical technology.

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