From nanometre alignment to high-volume manufacturing

Advanced packaging has become a new frontline of semiconductor performance and manufacturing innovation. At the inaugural Advanced Packaging International Conference, held on 21–22 April at the Sheraton Brussels Airport Hotel, speakers revealed how chiplets, heterogeneous integration and co-packaged optics are intensifying demands for precision, thermal control, metrology and reliability as the industry moves towards high-volume production.

By Sarab Chopra, Editor, Advanced Packaging Magazine

Advanced packaging is becoming a critical determinant of system performance.

That was one of the central messages to emerge from the inaugural Advanced Packaging International Conference 2026, where semiconductor manufacturers, equipment suppliers, research organisations and technology developers examined how packaging is evolving beyond conventional assembly.

Across two days of presentations, speakers addressed chiplets, heterogeneous integration, hybrid bonding, photonic integration, co-packaged optics (CPO), advanced substrates, thermal management, metrology, reliability and manufacturing automation.

Although they approached these challenges from different positions in the supply chain, a common theme emerged. Advanced packaging is moving from an assembly function towards a highly controlled, multi-physics manufacturing discipline.

The transition is being driven by several pressures simultaneously. Moore’s Law scaling is becoming increasingly expensive, while AI and high-performance computing demand greater bandwidth and energy efficiency. At the same time, more functionality is being distributed across multiple dies and material platforms.

The result is a package containing logic, memory, analogue functions, photonics and potentially several material systems, all of which must operate together. Different materials expand at different rates. High-performance logic generates significant heat. Optical interfaces can be sensitive to displacement, while fine-pitch interconnects leave little room for placement error.

GlobalFoundries examined heterogeneous integration and CPO in the context of AI bandwidth. Physik Instrumente (PI) addressed precision and process control in photonic alignment, while PhotonBridge demonstrated a self-aligning alternative. Finetech explored advanced bonding and the convergence of front-end and back-end manufacturing. AIM Photonics focused on the relationship between photonic design and assembly. Fraunhofer IZM highlighted the role of collaborative pilot lines, IBM Research Zurich demonstrated a scalable approach to optical assembly, and Tyndall National Institute examined reliability in increasingly complex packages.

Together, these perspectives exposed the industry’s central challenge: turning increasingly complex package architectures into repeatable and economical manufacturing processes.

Heterogeneous integration becomes a scaling strategy
Heterogeneous integration allows designers to select the most appropriate process technology for each functional block instead of forcing every function onto one monolithic die.

A compute die can use an advanced logic process, memory can be optimised for density, and photonic functions can be produced using silicon photonics or other material platforms. These components can then be combined through 2.5D or 3D architectures.

This can improve performance, functionality and manufacturing flexibility, but it also transfers complexity into the package. Components produced using different processes, materials and thermal budgets must operate as one system. Their electrical connections, mechanical interfaces, thermal paths and optical interfaces all have to work together.

GlobalFoundries’ presentation, Heterogeneous Integration and Co-packaged Optics: Meeting AI Bandwidth Demand, placed this challenge in the context of rapidly rising AI requirements.

For Himani Kamineni, Director of the Advanced Packaging Lab within GlobalFoundries’ CTO organisation, the shift represents a change in where semiconductor scaling takes place.

“System-level innovation has really become the new scaling vector.”

Conventional transistor scaling alone cannot address the combination of data movement, bandwidth, energy consumption and compute requirements emerging from AI infrastructure. Kamineni identified reach, bandwidth density, energy efficiency and compute efficiency as key requirements driving architectural change.

As data movement becomes a greater constraint, the physical distance between processing, memory and optical interfaces becomes increasingly significant. Packaging architecture can therefore influence system performance rather than merely determine how a completed semiconductor connects to the outside world.

CPO is one consequence of this trend. Bringing photonic engines closer to switching or compute devices can reduce electrical losses and support greater bandwidth density. GlobalFoundries treats devices, integration, packaging and test as interconnected elements of its silicon photonics roadmap.

“We’re co-optimizing our devices, integration, packaging, and test to deliver solutions at scale with the real AI bandwidth and workloads,” said Kamineni.

TSMC is developing a similarly broad integration model. Its 3DFabric platform encompasses 2.5D and 3D integration, while its COUPE approach targets optical I/O integration through advanced semiconductor packaging.

A CPO assembly can include an ASIC, photonic integrated circuits, fibre arrays, bridges or interposers, through-silicon vias, redistribution structures and advanced substrates. Each element has its own thermal, mechanical and processing characteristics.

Electrical power produces heat; heat changes thermal distribution; thermal gradients cause mechanical deformation; and deformation can displace optical components and alter coupling. The package may remain mechanically intact while its optical performance changes.

CPO is therefore a multi-physics manufacturing problem in which electrical, optical, thermal and mechanical behaviour must be considered together.

Two routes to photonic alignment
Photonic integration provides one of the clearest examples of conventional assembly tolerances being replaced by functional alignment requirements.

Fibre-array assembly can be particularly demanding because several optical channels must be aligned simultaneously. Movement may need to be controlled across multiple axes while the system measures the resulting optical response.

David Forer, Director Semiconductor Strategy, Global, at PI, examined sub-micron active alignment and the role of precision motion and feedback in photonic assembly.

Rather than relying exclusively on mechanical reference features, active alignment measures the functional response while positioning takes place. The component is moved, optical power or coupling efficiency is measured, and the position is adjusted.

“Submicron alignment is the decisive technology for yield and throughput and cost control,” said Forer.

Precision cannot be defined simply by the resolution of a positioning stage. It also depends on repeatability, stability, measurement accuracy and response speed. The manufacturing system must establish not only whether a component reached its intended coordinates, but whether its actual position delivers the required performance.

PhotonBridge presented an alternative based on designing alignment into the package.

Paul Marshall, CEO of PhotonBridge, described a self-aligned cantilever architecture for combining III-V lasers with silicon photonics. MEMS-like silicon photonic waveguides extend from the silicon platform, while corresponding slots in the III-V component allow the laser to locate itself on the silicon photonics structure.

Marshall compared this to placing the III-V element onto the silicon photonics “like a Lego” structure that self-aligns.

“We can actually achieve coupling losses less than 0.4 dB across our process window.”

The approach is intended to replace lengthy active-alignment operations with passive mechanical alignment. This could be especially valuable when many lasers must be integrated and could potentially enable high-throughput assembly using conventional outsourced semiconductor assembly and test methods.

The company’s silicon photonics platform uses six mask steps, according to Marshall, with the laser components manufactured separately and subsequently integrated.

PI and PhotonBridge therefore attack the same problem from different directions. One uses precision motion and functional feedback; the other changes the package architecture to reduce the precision demanded from the equipment.

Neither accuracy nor speed is sufficient in isolation. The manufacturing objective is to achieve the required functional performance through the simplest, fastest and most repeatable process.

Bonding moves precision into the interface
The same pressure is reshaping die bonding. Hybrid bonding combines dielectric-to-dielectric bonding with direct metal-to-metal connections, enabling finer interconnect pitches than conventional solder-bump approaches.

The electrical benefits can include shorter interconnects, reduced parasitics and greater connection density. However, as dimensions shrink, the bonding interface becomes a critical manufacturing surface. Particles, contamination, roughness and local topography can prevent uniform bonding, making planarisation, cleaning and surface preparation important contributors to yield.

Travis Scott, Senior Product Manager, Advanced Packaging Systems, at Finetech, placed hybrid bonding within a wider transformation in assembly.

“The scaling of Moore’s Law is slowing down, the price per node is going up, and this is driving the next generation of scaling into advanced packaging.”

Finetech’s presentation illustrated how bonding processes are diversifying. Alongside hybrid bonding and thermal compression bonding, manufacturers are investigating laser-assisted, ultrasonic and ultraviolet-curable processes. Each offers a different balance of speed, temperature, accuracy and complexity.

The relevant process window depends on bonding architecture, pitch, overlay tolerance, die size and process sequence. Temperature adds another variable. During bonding and subsequent processing, materials expand and contract at different rates, so alignment established at one stage may change during later thermal cycles.

David Volk , Product Manager Coating Systems, SUSS MicroTec Solutions.

This helps explain why the traditional boundary between front-end semiconductor manufacturing and back-end packaging is becoming increasingly blurred. Advanced packaging now demands equipment, cleanliness, alignment and metrology that resemble aspects of wafer fabrication.

“It’s definitely a very clear impulse from the industry that this is coming,” said Scott.

Testing is also moving earlier in the manufacturing process. As packages incorporate more valuable dies and additional process steps, manufacturers cannot afford to complete an entire module before discovering that one constituent component has failed.

Finetech expects this convergence to extend towards wafer-scale and panel-level processing as substrates become larger and architectures more complex.

Warpage becomes a system-level constraint
Warpage has long been a concern in semiconductor packaging, but its importance increases as packages grow larger and interconnects become finer.

A heterogeneous package may combine silicon, glass, organic substrates, metals, adhesives and underfills. These materials have different coefficients of thermal expansion, stiffnesses and thermal properties. During bonding, curing and cooling, they do not expand or contract uniformly. Internal stresses develop and the package can deform.

Larger interconnects can absorb some deformation within the process window. Fine-pitch interfaces have lesstolerance, while optical connections can be disrupted by very small relative movements. A package may therefore remain structurally intact but move far enough to reduce optical coupling or compromise an electrical interface.

Peter O’Brien, Head of Research Group, Director of Photonics Packaging Pilot Line, Head of European Photonics Academy.

The solution is not necessarily to make every package as rigid as possible. Increasing stiffness can improve dimensional stability but transfer greater stress into brittle components and interfaces. More compliant materials may absorb displacement, but can introduce creep or long-term dimensional change.

The objective is predictable behaviour. If deformation can be modelled, measured and kept within the functional process window, it becomes a manufacturing variable that can be controlled. This places greater importance on package simulation, material characterisation and in-process metrology before final assembly.

Packaging moves upstream into design
Increasing manufacturing complexity is also forcing packaging considerations into the earliest stages of product development.

AIM Photonics’ presentation on assembly design kits addressed the relationship between photonic integrated circuit design and packaging. The organisation spans PICs, interposers, electronic-photonic design automation, assembly and packaging, allowing it to approach the problem across several stages of development.

The principle behind an assembly design kit is straightforward: packaging constraints should be understood while the photonic device is being designed, not after fabrication.

David Harame, Chief Operating Officer at AIM Photonics, explained:

“So you modify the PIC because you’re doing the PDK and the ADK simultaneously.”

The approach incorporates design rules, package-ready PIC layouts, optical characterisation and mechanical information into the development flow. Fibre interfaces, optical coupling structures and attachment points can affect the PIC layout, while thermal requirements can influence the placement of optical and electronic functions.

Development consequently becomes an iterative process connecting design, simulation, fabrication, assembly, measurement and optimisation.

Test structures can characterise fibre attachment and coupling behaviour, with the resulting information incorporated into subsequent design rules. Packaging knowledge is captured before production instead of remaining dependent on the expertise of individual assembly engineers.

Materials must be considered in the same way. Silicon, glass, organic laminates, metals, III-V compounds, silicon nitride and lithium niobate
can have very different thermal, mechanical and processing characteristics. A process suitable for one component may damage another, while adhesive curing, moisture absorption and differences in thermal expansion can change dimensions over time.

Assembly sequence therefore becomes an engineering parameter. The package must be designed around the complete material stack and the order in which those materials can safely be processed.

Thermal management becomes spatial
Higher power density is making thermal management more complicated than keeping the overall package below a specified temperature. The distribution of temperature can be as important as the average.

A high-power compute die can create localised hotspots while neighbouring photonic components may have different temperature sensitivities. Thermal gradients can produce differential expansion, mechanical stress and optical displacement. Three-dimensional integration compounds the problem because stacked dies can place active layers farther from the primary cooling surface, while bonding layers and interposers add thermal resistance.

Joana Mendes, Researcher, Instituto de Telecomunicações.

Cooling must therefore be considered as part of the complete package architecture. Heat spreaders, liquid cooling, thermal vias and advanced thermal interface materials can improve heat extraction, but they can also affect mechanical stiffness, stress and manufacturability.

The best thermal solution is not simply the one with the lowest thermal resistance. It must remove heat while preserving dimensional stability, reliability and compatibility with the rest of the package.

This is especially important for CPO, where a thermal gradient can change optical alignment and performance even when component temperatures remain within their individual operating limits.

Christian Keil, Director Business Development & Sales, Lidrotec GmbH.

Building a packaging ecosystem
The need to connect design, manufacturing and packaging was also central to the presentation by Ulrike Gnesch, Director at Fraunhofer IZM and head of the APEX pilot line.

Gnesch argued that increasingly complex packaging challenges cannot be solved effectively by organisations working in isolation.

“We cannot afford anymore to be in our silos as researchers.”

Fraunhofer IZM is developing the APEX pilot line as part of a European ecosystem intended to support advanced packaging development, technology transfer, manufacturing capacity and skills.

One example involves a consortium of 17 partners covering the value chain for fan-out wafer-level and panel-level packaging.

A common platform can establish capabilities that several companies can access, avoiding the need to repeat development work separately for each customer.

Fraunhofer IZM is also pursuing glass-core substrates and CPO through a consortium approach.

This includes multilayer glass substrates with through-glass vias, embedded waveguides and the co-assembly of electronic and photonic ICs.

Gnesch argued that European capabilities could focus on areas including high-power, high-frequency, photonic and biomedical applications rather than attempting to replicate the hyperscale semiconductor manufacturing models of Asia and the US. In this model, the packaging ecosystem itself becomes part of the competitive strategy.

Optical assembly seeks electronic scale
IBM Research Zurich offered another perspective on manufacturability.

Bert Offrein, Manager Co-packaged Optics and Principal Research Scientist at IBM Research Zurich, examined how optical connections could be incorporated into package assembly without repeating the highly manual processes that have historically made photonics expensive.

Earlier systems had demonstrated an important lesson: a technically viable optical package is not necessarily commercially viable.

“We must make sure that now optics comes in in a way that is scalable and manufacturable and cost-effective in the end,” said Offrein.

IBM is investigating polymer waveguides as one route to this goal. The approach uses a polymer waveguide interface between silicon photonics and optical fibre, with adiabatic coupling providing the transition between waveguide structures.

In one demonstration, a silicon chip was flip-chip attached to a glass substrate containing polymer waveguides, producing 100 simultaneous optical connections in a single attach operation.

That result is significant because conventional optical assembly can require individual alignment operations. The objective is to scale the number of optical connections in a manner more comparable with electrical assembly.

Offrein also identified a possible route towards offering the technology as a packaging service, reinforcing the need for chip designers, foundries and packaging providers to build their processes around one another.

Reliability must measure performance, not just survival
Greater integration density also changes the reliability challenge.

A package may contain fine-pitch electrical connections, optical structures, fibre assemblies, organic materials and multiple interfaces. Each responds differently to thermal cycling, humidity, vibration and mechanical shock.

Finbarr Waldron, Principal Engineer at Tyndall National Institute, linked manufacturing complexity directly to reliability.

“With every advance in manufacturing complexity, it poses many new challenges for reliability.”

The problem becomes particularly severe in aerospace and space applications. Waldron described low-Earth-orbit temperature cycling between approximately -65°C and 125°C, potentially reaching thousands of cycles per year depending on orbital conditions. Vacuum, radiation, mechanical shock and vibration add further stresses.

Such environments expose a fundamental issue: structural survival does not necessarily guarantee functional survival.

A fibre can remain mechanically attached while optical coupling degrades. An optical element can develop a defect without immediately producing an electrical failure, while vibration can alter alignment without physically separating components.

Reliability testing must therefore consider functional performance alongside structural integrity. The package has to survive, but it also has to continue operating within specification.

Waldron’s contribution also demonstrated why accelerated testing must reflect the interactions within the package rather than evaluate individual components in isolation.

Himani Suhag Kamineni , Head of Advanced Packaging at GlobalFoundries.

Temperature cycling, vibration, humidity, vacuum and radiation can act on several interfaces simultaneously. Failure analysis therefore needs to distinguish between a component defect, an attachment failure and a gradual shift in system performance.

As commercial components are considered for more demanding applications, qualification also has to establish whether their original test regimes represent the conditions they will face in service. Advanced packaging expands the number of possible failure mechanisms, making construction analysis and physical analysis increasingly important alongside conventional electrical testing.

Closing the manufacturing loop
As tolerances shrink, inspection can no longer remain an activity performed only at the end of production. Alignment, overlay, surface roughness, coplanarity, warpage and bond quality increasingly need to be measured while manufacturing is taking place.

Active optical assembly can use coupling data to adjust component position. Bonding systems can use surface and overlay measurements to identify variation, while thermal measurements can expose deformation before it becomes a final-assembly problem.

The emerging manufacturing philosophy can be expressed as a continuous sequence: measure, calculate, correct and verify. Instead of following fixed coordinates and checking the finished result, equipment can increasingly measure the state of an assembly and respond during the process.

Paul Marchal, Chief Executive Officer, Photon Bridge.

Process data can reveal drift and establish relationships between equipment conditions and final package performance. AIM Photonics’ methodology shows how measurement can also feed back into design, with assembly results refining subsequent design rules. Metrology is consequently moving from final inspection into the production loop and, ultimately, into the design process itself.

This is both a technical and an economic requirement. Discovering a defect after several valuable components have been integrated represents a much greater loss than identifying process drift earlier.

The approaches presented at the conference connect different parts of this manufacturing loop. PI uses functional feedback to control active alignment. PhotonBridge seeks to remove an alignment step through package design. Finetech combines placement, bonding and test. AIM Photonics feeds assembly measurements back into design rules.

David Harame, COO AIM Photonics and Associate Vice President for Process Development, EPDA, and Test Assembly and Packaging, AIM Photonics.

Fraunhofer IZM connects capabilities across an ecosystem, while IBM aims to complete many optical connections in one operation. Tyndall tests whether the resulting package continues to perform throughout its operating life.

Together, they show that advanced packaging precision extends far beyond the motion stage. It includes control of thermal gradients, material interactions, warpage, interfaces, throughput and long-term reliability.

The next phase of semiconductor scaling will not depend solely on smaller transistors. It will also depend on the industry’s ability to integrate different dies, materials and technologies with sufficient precision and stability to create repeatable products.

The central challenge is no longer simply how to connect more components. It is how to make the entire package behave as one system, and how to manufacture that system consistently, economically and at scale.

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• In 2027, AP International will be held on 13-14 April at the Sheraton Brussels Airport Hotel.