Tag: grinding process

When 1 Micron Determines Yield in the Field: Key Insights into the Chip Stacking Grinding Process

There is a joke often shared among semiconductor design engineers. “The more chips you stack, the better, but the problem is that stacking them is far too difficult.” In real packaging processes where dozens of chip layers are stacked, the first thing to fail is not the design drawing, but flatness. In a world where a 1 micron difference can disrupt overall yield, the meaning of “grinding well” carries far more weight than expected.

Why TTV Matters in Chip Stacking Structures

In structures where chips are stacked in multiple layers, thickness variation in each layer is not just a dimensional issue. As layers accumulate, microscopic errors build up and eventually lead to electrical bonding defects or concentrated structural stress. The metric used to express this numerically is total thickness variation, or TTV.

The TTV required in chip stacking structures is at the level of 1 micron or less, demanding precision far below one hundredth of the thickness of a human hair. If this standard is not met, bonding surfaces can lift during subsequent bonding processes or heat dissipation can become uneven, undermining the reliability of the device itself. For products such as AI semiconductors or high performance memory that vertically connect dozens of chips, the allowable variation range becomes even narrower.

One reason TTV control is difficult in the field is the structural variables of the grinding equipment itself. The wear pattern of the grinding wheel, microscopic vibration generated during spindle rotation, and changes in the flatness of the chuck that fixes the wafer act together to make the thickness profile uneven. Uniform flatness cannot be achieved simply by turning on the equipment. How precisely these variables are controlled is the key factor that determines the yield of the entire packaging process.

Ultra Precision Grinding Design of the PKG Grinder

There is a way to address this issue from the process equipment design stage. The PKG Grinder from Huvics combines a high precision stage with a diamond wheel to process various package types such as FCBGA, WLCSP, and QFN/DFN at micron level accuracy. The key is a control structure that keeps TTV variation within a defined range even during high speed processing. The TTV requirement for ultra thin wafer stacking processes is approximately 2.0 microns or less, and to meet this value reliably in a high speed grinding environment, spindle runout compensation and chuck flatness maintenance must be built into the equipment from the design stage.

Another practical challenge in production sites is line flexibility. In many cases, the same equipment must handle both low volume high mix processes and high volume continuous production. The option to choose Full Auto A·B types or a Manual type is a design choice made to respond to this requirement, and it directly contributes to reducing setup loss during process changeovers. Speed and uniformity are usually in conflict, but in grinding equipment, they are implemented in a way that satisfies both conditions at the same time.

The Role of Cleaning and Drying After Grinding

Flatness control does not end just because the grinding process is complete. Immediately after machining, grinding residue and fine particles remain on the wafer surface, and the way they are removed determines the final surface quality. This is where the choice of cleaning and drying methods becomes important.

Comparison of Air Knife and IPA Vapor Drying

The two drying methods mainly used in the industry are Air Knife and IPA vapor drying. Air Knife mechanically pushes liquid off the surface using a high speed gas jet, and according to research published on ResearchGate, drying within 2 seconds is possible under a speed condition of 150mm/s. In contrast, IPA vapor drying uses ultrapure isopropyl alcohol vapor to lower surface tension and guide moisture to flow away naturally without leaving marks.

Because the two methods control processing speed and the risk of surface residue in different ways, the selection criteria vary depending on the surface characteristics of the target device and the process requirements.

Multi Step Cleaning for Components Sensitive to Surface Contamination

For components sensitive to surface contamination, such as camera modules, sensors, and VCM motors, a multi step cleaning approach that combines micro bubbles and water jets is becoming established.

More than how many chips are stacked, how uniformly they are stacked determines the actual yield. From grinding precision to the selection of cleaning and drying methods, the quality of the packaging process is completed on a structure where each stage supports the next. The joke mentioned at the beginning, “stacking them is far too difficult,” turns out to describe the essence of process design quite accurately.

Huvics is an advanced technology company that develops and manufactures automation equipment and
production systems across the semiconductor, LED, Mobile, and Cosmetic industries.
With top tier talent and continuous technological innovation, we support improvements in customer productivity and
help secure quality competitiveness.

Huvics Contact

Phone: 031-374-8285
Email: cdpark@huvics.com

2026-10-22
How to Manage Grinding, Lamination, and UV Curing Stages to Improve Chip Stacking Yield

If you are an engineer designing semiconductor packages, you have probably encountered this situation at least once. Even after carefully setting the process conditions, step differences appear between chips after stacking, and yield data begins to fall below expectations. When tracing the root cause, the issue often comes down to thickness variation and flatness control. Even though this pain point is well known, the same trial and error is often repeated on production sites.

Why the shift to stacked structures made thickness control a prerequisite for the process

As semiconductor package structures have shifted from single layer designs to stacked architectures, the thickness and flatness of each individual chip now require a level of precision that cannot be compared with the past. In single layer structures, a certain degree of thickness variation in individual chips could be tolerated, but in 3D stacked structures where multiple chips are stacked vertically, errors in each layer accumulate, meaning even one uneven chip can compromise the reliability of the entire package.

In fact, research published on NCBI/PMC confirms that in advanced 3D stacking processes, chip thickness is reduced from around 780μm to 10μm or less, while total thickness variation TTV must be controlled to 1μm or below. As chips become thinner, the signal travel distance decreases, improving power efficiency, while lower thermal resistance also enhances heat dissipation performance.

In this way, thinning is directly linked to performance improvement, but it also raises the difficulty of maintaining thickness uniformity. Micron level variation can change mechanical stress at the bonding interface after stacking and may ultimately lead to failures in long term reliability testing. As packaging technology advances, thickness control is becoming not an option, but a prerequisite for the process.

How the precision of grinding equipment determines thickness uniformity

To secure thickness uniformity in an actual process, the precision of the grinding equipment becomes a key variable. A grinding method that combines a high precision stage with a diamond wheel can uniformly process wafer or package surfaces down to the micron level, enabling stable achievement of target thickness across various package types such as FCBGA·WLCSP·QFN/DFN.

What matters is whether the equipment not only grinds thinner, but also has the control capability to minimize variation throughout the grinding process. The Huvics PKG Grinder is high precision grinding equipment designed based on this principle, supporting both Full Auto and Manual Type configurations so it can be flexibly applied according to the production line scale and automation level of customers.

The ability to maintain quality stability even under high speed process conditions and achieve high yield is an especially important criterion in mass production environments. Consistent processing capability that stays within allowable tolerances regardless of package type is the first standard to examine when selecting grinding equipment for a stacked package process.

How lamination and UV curing connect grinding precision to yield

If the grinding process plays the role of precisely removing thickness, then how safely chips are fixed and separated in the preceding and following stages also determines the yield of the overall process. In the tape mounting process using dicing tape, if adhesion is too strong, surface damage can occur when separating chips. Conversely, if adhesion is insufficient, chips can shift during processing and increase thickness variation.

The key method for achieving this balance is UV curing. UV curable dicing tape weakens under controlled adhesion conditions after UV irradiation, allowing chips to be separated without damage. Furthermore, when UV curing is applied as a pretreatment before lamination, it can permanently reduce the adhesion of the dicing tape and improve the stability of subsequent processes. In this way, the timing and condition settings of UV curing are not simply an additional process, but a turning point that connects grinding precision to actual yield.

The Huvics laminator system supports a one stop configuration that handles everything from Expander to UV Curing within a single line, and both Lamp and LED methods can be selected, enabling adhesion strength control tailored to product characteristics and process requirements. By integrating process steps, tact time is reduced, and the risk of contamination or damage that may occur during transfer between stages is also lowered. When grinding and lamination are designed as one continuous flow rather than separate processes, the meaning of securing thickness uniformity is finally completed.

In the era of stacked semiconductors, thickness uniformity and flatness are ultimately not issues of just one process step. Only when grinding precision, tape adhesion control, and UV curing timing work together organically can they lead to yield stability. When tracing the causes of repeated step defects and yield loss on production sites, the answer ultimately returns to how precisely these processes are connected.

Huvics is an advanced technology company that develops and manufactures automation equipment and
production systems across the semiconductor, LED, Mobile, and Cosmetic industries.
With top talent and continuous technological innovation, we support customers in improving productivity and
securing quality competitiveness.

Huvics Contact

Phone: 031-374-8285
Email: cdpark@huvics.com

2026-10-18
AI Semiconductor Stacked Packages: Why the Grinding Process Became the Starting Point for Yield
In semiconductor packaging, controlling thickness was long regarded as simply grinding materials thin enough. However, with the arrival of high-performance artificial intelligence semiconductors that stack multiple chip layers, that standard has changed completely. Simply making the material thinner is no longer enough to ensure bonding reliability in stacked structures, and minute thickness variations in each layer can accumulate and affect the performance of the entire package. Today, a completely different level of grinding technology is required, one that can secure micron-level uniformity and flatness at the same time.

Why Thickness Uniformity Becomes a Prerequisite in Stacked Packages

In stacked package structures where dozens of chips are piled vertically, thickness variation in each layer is not merely a dimensional issue. The more precisely designed the package substrate structure is, as in FCBGA(Flip Chip Ball Grid Array) or WLCSP(Wafer Level Chip Scale Package), the more the uniformity of remaining thickness after grinding becomes a prerequisite for all subsequent processes.

In particular, WLCSP eliminates the substrate and mounts the chip directly onto the main board, so the impact of grinding precision appears immediately in electrical characteristics as the signal path becomes shorter. According to data from the United States Patent and Trademark Office(USPTO), the current target thickness for wafer backside grinding is about 300μm(microns), and it is expected to become even thinner in the 200 to 250μm range going forward. As the thickness target becomes lower, the allowable margin of error also becomes narrower, while the level of precision required in the process increases inversely. In this trend, the role of the grinding process is increasingly becoming a key variable in packaging quality.

The Two-Step Structure and Tolerance Standards of Precision Grinding

To understand the tolerance level required by precision grinding, a sense of proportion is more important than the numbers themselves. The allowable tolerance required in grinding for semiconductor manufacturing equipment is about ±2.54μm(microns), which is only a few dozenths of the thickness of a human hair, considering that human hair is about 70 to 100μm thick.

To reliably achieve this level of precision, commercial grinding systems operate two process stages in sequence.
- Coarse grinding stage: Rapidly removes material at a speed of about 5μm per second.
- Fine grinding stage: Reduces the speed to 1μm per second or less to secure surface roughness and thickness uniformity.
Reducing speed is the core principle for increasing precision, and how precisely the transition point and conditions between the two stages are controlled is the key factor that determines final yield. Equipment configuration that combines a diamond wheel with a high-precision stage is the core hardware that reliably supports this transition process, and the completeness of equipment design is directly revealed under conditions that must satisfy both fine tolerance control and repeatable reproducibility.

How PKG Grinder Responds to On-Site Conditions

When introducing grinding equipment at an AI semiconductor packaging site, the first practical question is “which package types can it support”. In many cases, a single production line must handle multiple packages at the same time, including FCBGA, WLCSP, and QFN/DFN(Quad Flat No Lead), while the target thickness required by customers differs by product.

Huvics PKG Grinder is designed for these on-site conditions with Full Auto A/B types and Manual type options, allowing flexible selection according to the automation level of the production line and the characteristics of the product. Processing uniformly and precisely to the thickness customers require is not simply a matter of equipment specifications. It means the equipment must allow settings that reflect actual process conditions and package structures.

The requirement to maintain stable yield even during high-speed processes in manufacturing sites that handle ultra-precision components, such as camera modules or autonomous driving sensors, directly shows how important repeatable reproducibility and in-process consistency are for equipment. As stacked structures become more complex and target thickness becomes thinner, the range of precision that grinding equipment must handle also expands. This is where the significance of PKG Grinder in this process becomes clear.

The complexity of stacked structures required by AI semiconductors has transformed the grinding process from a simple post-processing step into the starting point of quality. The ability to repeatedly achieve micron-level tolerances ultimately shows where the reliability and yield of the entire package are determined. As thickness targets become thinner and the number of stacked layers increases, the demand for grinding precision will continue to rise.

Huvics is an advanced technology company that develops and manufactures automation equipment and
production systems across the semiconductor, LED, Mobile, and Cosmetic industries.
With top-level talent and continuous technological innovation, we support customers in improving productivity and
securing quality competitiveness.

Huvics Contact Information

Phone: 031-374-8285
Email: cdpark@huvics.com
2026-09-30
How Grinding Process Uniformity Determines AI Semiconductor Packaging Yield

There is one fact that only some people in the semiconductor industry know. The factor that determines the performance of cutting-edge AI chips is not the design or the material, but ‘is hidden in the uniformity of the grinding process’, which is difficult to see with the naked eye. Over time, a yield gap that is difficult to close emerges between sites that understand this fact and those that do not.

Why thickness uniformity and flatness determine yield

In the packaging of AI semiconductors and high-performance memory semiconductors, thickness uniformity and flatness are not simple dimensional requirements. In a 3D stacked structure where chips are stacked vertically, the surface condition of each layer directly determines the bonding quality of the upper and lower layers. According to a technical report by Applied Materials, the uniformity of the wafer surface directly affects stacking yield, reliability, and electrical performance, and even slight surface variations can degrade bonding quality.

As the number of stacked layers increases, these requirements become even stricter. According to industry discussions reported by TrendForce, the current thickness standard for HBM4, fourth-generation high-bandwidth memory, is 775 micrometers, and raising it to the 825~900 micrometer level is being considered for next-generation HBM4E and HBM5. As technology evolves toward stacking more chips higher, how precisely the flatness of each layer is controlled determines the reliability of the entire package.

A single thickness error can distort the path of an electrical signal, and that leads to yield loss. This is why ultra-precision processing becomes a prerequisite, not an option, and standards for equipment that meets these requirements are also rising.

Ultra-precision grinding technology of the PKG Grinder

Huvics PKG Grinder is high-precision grinding equipment designed to respond to these strict standards. By combining a high-precision stage with a diamond wheel, it enables thickness processing at the micron level and can be applied to various package types, including FCBGA, flip chip ball grid array, WLCSP, wafer level chip scale package, QFN·DFN, and solar cells.

What is highly valued on production sites is not only its high precision, but also the fact that it maintains stable quality even in high-speed processes and achieves high yield. Depending on the characteristics of the production line, users can choose from fully automated, Full Auto, A type·B type and Manual types, making it flexible for both high-mix low-volume lines and high-volume continuous production lines. For packages that require micron-level precision, the repeatability of equipment determines yield, and whether that repeatability can be maintained even under high-speed conditions is the key factor in equipment selection.

The relationship between process automation and cost control

On the production floor, the impact of equipment selection on the cost structure is greater than many expect. In the industry, unplanned downtime in semiconductor manufacturing lines is known to cause losses of more than 260,000 dollars per hour, and even the same repair is reported to cost 3~5 times more in an unplanned situation than when handled during scheduled maintenance. This is why equipment stability and maintenance predictability become financial decision criteria beyond simple operational convenience.

The same logic applies to the cleaning process. A method that combines micro bubbles, water jets, and air knives in stages for cleaning various components such as camera modules, sensors, VCM motors, and trays is an approach that removes contamination particles and lowers defect rates in a single process. The laminator system also integrates everything from lamination to UV curing into one flow, reducing process steps and shortening tact time.

The direction of integrating processes and raising the level of automation is ultimately the way to secure both predictable quality and cost control, and its significance is confirmed in the actual numbers from production sites.

The precision requirements for AI semiconductor packaging will continue to rise. In this trend, which equipment is used and how processes are configured determine not only current yield, but also the capability to handle next-generation products. The fact that a single grinding process holds the reliability of the entire package is why precision processing equipment deserves attention in this market.

Huvics is an advanced technology company that develops and manufactures automation equipment and
production systems across the semiconductor, LED, mobile, and cosmetics industries.
With top talent and continuous technological innovation, we support customers in improving productivity and
securing quality competitiveness.

Huvics Contact

Telephone: 031-374-8285
Email: cdpark@huvics.com

2026-09-18