Microhole Arrays: PECM and the Micro-Architectures Driving Modern Cooling and Fluid-Control Systems
- Kirk Abolafia
- Nov 20
- 12 min read
Demand for microhole arrays (IE, high-density patterns of sub-millimeter diameter holes numbering from the dozens to the thousands on a given part) has risen sharply as industries push towards higher temperature-flux environments. Semiconductors are increasingly reliant on thousands of precisely-machined micro-jets. Power electronic cooling has to accommodate sub-millimeter-scale hotspot issues and build precise infrastructure to dissipate considerable heat spikes. Hundreds of billions of dollars’ worth of data center infrastructure increasingly relies on direct-to-chip cooling plates with densely-packed microhole arrays to prevent overheating.
While a wide range of industries and applications exist, the usage for microhole arrays generally boils down to two primary uses:
Acutely controlling the delivery of gases or liquids, such as “showerheads” in semiconductor manufacturing or drug delivery devices
Efficiently dissipating heat in dense, high temperature-flux environments like data centers and power electronics
However, as design engineers deal with higher part volumes, denser arrays, and more superfinished internal walls, conventional manufacturing methods are lagging behind. Producing each hole with consistent diameter, smooth internal surfaces, and minimal variation becomes increasingly harder as arrays grow denser. Repeatability, surface quality, and accuracy begin to decrease in these critical features as legacy processes continue to fail.
In this article, we’ll explain why conventional processes struggle with these evolving demands, how PECM overcomes the thermal and mechanical limitations inherent to laser drilling and CNC, and how these capabilities unlock new possibilities across semiconductors, power electronics, and medical device applications where microhole arrays directly define performance.
Conventional Challenges
Be it from budgetary, logistical, technical, or timeline constraints, manufacturers seeking to produce microhole arrays are still largely reliant on conventional manufacturing processes. While laser drilling seems to be the dominant method for producing these features, certain complex microhole arrays are machined individually via CNC machining, which can cause costs to dramatically increase for especially complex arrays.
Laser Drilling
Laser drilling’s greatest strength, its ability to deliver extremely concentrated heat, is in actuality a double-edged sword. Temperatures produced by industrial laser drilling equipment can climb to thousands of degrees (akin to the temperature of the surface of the sun), enough to instantly transform certain metals into their vapor and plasma states, evaporating from the workpiece. This material removal methodology has proven success: able to produce arrays of hundreds or even thousands of microholes at excellent speeds, some able to produce sub-millimeter diameter holes in stainless or nickel alloys in tens of microseconds to a few milliseconds per pulse, per hole.
However: despite the incredible capabilities of modern laser drilling, the inherent usage of heat comes with some critical caveats manufacturers must reckon with:
Recast layers can form as molten metal re-solidifies on the inside of the hole walls, causing surface irregularities (that may result in critical part failures we shall explain later)
Tapers on the hole entrance from repeated “pulses” of the laser can occur, leading to non-uniform hole diameters
Heat-affected-zones (HAZ) may occur around the hole entrance, which can create a “blast zone” that inherently affects the surrounding material’s molecular structure, hardness, ductility, etc.
While these challenges can sometimes be ignored, or individually alleviated on a single hole using CNC (with many of its own caveats we will discuss in a moment), when being utilized on arrays of identical microholes numbering into the hundreds, thousands, or tens of thousands, these issues cannot be ignored and can lead to catastrophic consequences. And, as we’ll explain, these heat-related challenges can be largely, or completely, avoided by utilizing Voxel’s PECM technology.
CNC
Conventional CNC acts as a juxtaposition to the benefits and disadvantages of laser drilling: CNC, in general, is capable of producing excellent features on both micro and high-aspect ratio holes, even in brittle nickel alloys like Inconel, by using a small drill bit. However, the caveats attached to CNC can be enormous, especially when tasked with machining a larger quantity of parts in-parallel:
Tool wear can decrease the repeatability of certain features over part volumes, requiring expensive and time-consuming tool replacement costs and lengthy bottlenecks
Material removal rates can be considerably slow to navigate tool fragility (a single 50µm hole in a nickel alloy may take minutes, as opposed to the seconds’ worth of time a laser would take)
Positional accuracy (and runout) across a larger array can be logistically challenging
Tool breakage becomes increasingly common utilizing the micro-thin tools required for microhole drilling, exacerbated across large arrays of holes
Process | Heat Input | Contact | Internal Issues | Scalability (hundreds–thousands) | Internal Feature Control | Typical Pain Points |
CNC | Low (friction) | Yes | Burrs, tool marks, work hardening | Poor | Limited by tool reach | Tool wear/breakage, slow MRR, runout |
Laser drilling | Extremely high | No | Recast, taper, HAZ, debris | Moderate (sequential) | Poor at depth | Taper, particles, unpredictable internals |
PCE | Chemical/none | No | Taper from isotropic etch | Good (thin foils only) | Planar only | Depth limits, undercut |
PECM | Minimal | No | None. Smooth walls, no recast/HAZ | High (parallel, low-thousands) | Strong, full-envelope | Cathode design + setup complexity |
Footnote: Hybrid Manufacturing & PCE
Some manufacturers attempt a “hybrid” approach between these two methods, utilizing the benefits of both of these processes, but this workflow doesn’t usually result in efficient processing for a few key reasons, as the lasers often leave mechanically unfriendly geometries to the follow-up CNC tools (tapered roles with recast layers, etc.), and micron-precise alignment can be significantly challenging for manufacturers. Furthermore, the workflow is usually very asymmetrical in this hybrid approach, as spending less than a second on each laser-drilling operation is bottlenecked by the 20-60 seconds it may take for CNC cleanup on each hole, effectively eliminating any benefit from laser speed. Before we discuss PECM’s role and advantages in this industry, it is worth briefly mentioning photochemical etching (PCE). See our other article on this subject.
In short, PCE fulfills a very specific niche in the microhole world as it excels at producing high-density arrays in extremely thin materials where hole depth can go down to a tenth of a millimeter. As PCE works by removing material isotropically through a patterned photoresist, it can produce excellent, dense features with low-cost, high-volume work. In these specific applications, PCE is more competitively efficient than laser drilling, CNC, and even PECM.
However, PCE works only in this niche. Its competitive angle plummets if tasked to produce holes with higher aspect ratios, unique internal features or varied diameters. And as those featured holes comprise the overwhelming majority of applications requiring dense microhole arrays, PCE is largely limited to work within its own niche.
PECM’s Role
When tasked with producing sub-millimeter holes in tough materials at scale, PECM excels by, largely, avoiding many of the aforementioned problems with contact-based processes like CNC and even the heat-based processes like laser drilling. In this section, we will discuss PECM’s specific advantages when it comes to heat, contact, parallelization and internal-feature machining for microhole array features.
For a more well-rounded explanation of PECM’s capabilities outside of this application set, consider reading these articles.
No Heat
Unlike the immense heat produced by laser drilling, or the friction-based heat produced by CNC, the use of an electrochemical reaction produced by PECM produces no significant temperature flux, allowing it to produce a variety of otherwise thermally sensitive features (such as thin walls in heat exchangers) with ease. The key aspect of PECM that avoids this heat is the flow of the electrolytic fluid, which acts as both a catalyst for the electrochemical reaction and a flushing agent for the removal of material waste as a result of the reaction. When tasked with producing internal features such as within dense microchannel arrays, this lack of heat helps PECM avoid key problems, including:
No recast layers, as the low temperature of the reaction and the flow of the electrolyte prevents material from re-solidifying to the internal walls of microholes
No heat-affected zones (HAZ), as the electrochemical reaction can only occur where electrolyte flows, ensuring there is no “run-off” machining in other unwanted areas
No Contact:
The key challenges of CNC are a result of its inherent reliance on contact between the tool and workpiece that inevitably leads to its Achilles Heel, tool wear. This single issue (a dull tool) cascades into a multitude of technical, logistic and financial challenges exacerbated by large arrays of holes, including but not limited to, reductions in tool accuracy, alignment challenges, increased cutting forces, and tool replacement costs. The electrochemical process can largely ignore these challenges, as the lack of contact required between the tool and workpiece (separated by a microscopic inter-electrode gap, or IEG) results in a significant reduction in tool wear for PECM, providing unique benefits for microhole drilling:
"Diameter drift” across the array is significantly reduced when using a PECM cathode, as the material loss on each operation is negligible compared to other processes, allowing repeatable features across hundreds or even thousands of holes (exemplified further by custom cathode parallelization, which we’ll discuss in a moment)
Tool replacement costs, while more expensive under PECM, are multiple magnitudes less common, allowing operators to create lights-out, automated production environments machining arrays of microholes without worry of frequent tool readjustments or replacements
Microhole features that may otherwise be sensitive to tool vibration, high cutting forces or runout can be machined easily via PECM, as the cathode never comes in direct contact with the workpiece
380μm-diameter microholes machined in stainless steel via PECM
High Parallelization and Scalability
While the case for a highly-scalable CNC operation to produce these microholes is a logistical and financial nightmare, the case for utilizing laser drilling’s high speeds and scalability is much more appealing for manufacturers. However, for many microhole array applications, PECM’s parallelization and scalability provides it a few key advantages over processes like laser drilling, boiling down to a single key advantage: Multi-featured cathodes. This allows:
Significant reductions in positional accuracy challenges, as a single cathode with dozens or hundreds of features machining all holes simultaneously reduces the individual positional changes required in laser drilling of arrays
Uniformity across the entire array; so long as each feature of the cathode is geometrically identical, so too will be each hole on each operation; PECM regularly achieves repeatability down to <10µm.
Cycle times primarily scaling with feature depth rather than hole count, allowing cathodes from tens to low-thousands of micro-features with minimal impact on processing time
Internal-feature precision
On critical microhole array applications (such as gas delivery systems for semiconductor fabs) the tolerances on the inside of microholes are among the most important features to machine, but both laser drilling and CNC operations may struggle to realize sub-µm surface qualities on individual holes, let alone arrays of thousands of holes or holes with non-line-of-sight features. Voxel’s internal research on non-line-of-sight geometries and in-situ machining provides it distinct advantages in this respect:
PECM’s surface finishing capabilities meet or exceed the capabilities of other conventional processes, down to .005-0.4µm Ra, including on internal features in microholes
PECM does not require line-of-sight access to machine and finish internal features, in juxtaposition with a straight laser or micro-drill, and is capable of uniformly removing material in unique geometries, even in-situ on serpentine geometries
PECM is capable of producing varied-diameter or tapered holes if needed [such as the photo in Nitinol] utilizing proprietary technology
Quick Case Study: Copper
To illustrate PECM’s rapid ability to create complex microholes, we recently completed a short R&D trial on copper arrays for a customer requiring thin-wall, densely packed features. Within a brief two-iteration development cycle using our standard production electrolytes, we produced:
~700 µm holes with ~100 µm walls at 1 mm depth, before refining the process to
~360–370 µm holes with walls approaching 50 µm.
Even in this benchtop environment, hole diameters were highly consistent, and wall-thickness variation was traced to fixture limitations rather than the PECM physics. Voxel's engineers also ensured no stray entrance etching existed between the first and second trials.
As these features did not require custom chemistry or extended parameter tuning, they are a great example of PECM’s ability to generate dense, uniform microholes and thin-wall structures far faster and more predictably than heat or force-based machining methods like laser drilling or CNC.
Applications
Let’s now discuss key areas across critical industries that require dense, large arrays of tight-tolerance microhole features, from semiconductors and power electronics to drug delivery devices, and how PECM’s aforementioned capabilities can be applied to each.
Semiconductor Cooling
For a robust deep-dive on this topic, see our recent article on direct-to-chip cooling infrastructure enabled by PECM.
In the demanding world of semiconductor and data center cooling infrastructure, manufacturers must account for increasingly high heat-flux environments as chip power increases at a seemingly exponential rate. Industry reporting suggests AI energy usage will triple by 2028 with cooling infrastructure alone accounting for roughly 40% of that. Without complex, compact cooling infrastructure, data center lifespan (a market worth hundreds of billions of dollars) plummets and technological progress becomes physically limited as high temperature-flux wears down both chips and server racks.
On the semiconductor level, manufacturers are exploring direct-to-chip cooling methods using both liquid and gas channels that enables robust heat dissipation “at the source” via complex microhole arrays. These sub-millimeter hole arrays must remain dimensionally precise (as internal surface irregularities can affect cooling distribution) and arrays must remain extremely uniform (as this allows a predictable tolerance to heat flux when chips are/aren’t being used).
PECM’s unique internal finishing capabilities on dense, microhole arrays at-scale can enable better coolant flow, minimized pressure drops, and ultimately maximize heat transfer efficiency for a variety of semiconductor/data center cooling infrastructures. PECM’s non-contact and non-thermal nature allows tight tolerances, and its usage of multi-tooled cathodes allow excellent uniformity across arrays, and scalability for the unprecedented scale-outs of data centers.
Gas Delivery Showerheads
For a robust deep-dive on this topic, see our recent article on gas delivery infrastructure for semiconductor fabs enabled by PECM.
On the topic of semiconductor manufacturing, a key aspect of the fabrication process includes a complex web of corrosive-gas delivery systems such as “showerheads” used to deposit thin layers of material across wafers utilizing thousands of microholes. These showerhead arrays can have thousands of sub-millimeter diameter holes, and superfinished internal surfaces are essentially mandatory. Near-perfect gas distribution is essential for semiconductor efficiency, microscopic debris can affect wafer performance, and the toxic nature of certain gases can take advantage of microscopic surface irregularities to cause damage to the products, equipment, and even human health.
Laser drilling is still the dominant process for producing these arrays, but often suffers from tapering, recast layers, and HAZ, which can ultimately produce internal particle and debris. PECM, however, can produce the complete internal geometry in one operation, down to ~0.13 µm Ra (and in some cases better), without recast, HAZ, or tool-induced microcracks. This enables dense, thin-walled showerhead arrays in nickel alloys and other difficult materials at scalable part volumes, while significantly reducing the mechanisms that generate particles inside gas-delivery hardware.
Power electronics
Akin to the cooling infrastructure found in modern AI data centers, a variety of different power electronics infrastructures, such as those found in EVs or E-aircraft, also utilize unique cooling channels and microhole arrays to limit extreme temperature-flux that can damage or degrade the equipment over time.
Power devices using more heavy-duty semiconductor materials like SiC (Silicon Carbide) or GaN (Gallium Nitride) must deal with more concentrated pockets of heat hotspots, sometimes millimeter-sale regions with heat flux 10-20x higher than a typical GPU’s. Power electronic cooling infrastructure deals with this in unique ways, such as micro-jet plates directly under individual dies or tighter arrays of microholes to fine-tune coolants between inverters (to target hotspots more efficiently).
Copper’s unique thermal properties make it an excellent match for this cooling infrastructure for heavy-duty power electronics, but its machinability (notably with micro-features like these) can be a significant challenge due to its softer, gummy-like properties. Machining microhole features causes burrs, HAZ, recast layers, work hardening, and alignment issues for manufacturers, and these issues become even more pronounced as aspect ratios and part volumes increase.
PECM is uniquely suited to solve these issues by entirely sidestepping problems like work hardening, tool breakage, recast layers, HAZ and more. Voxel has demonstrated the feasibility of machining low-thousands of microholes in one operation, with cycle time primarily tied to hole depth rather than hole count. Recent internal trials (referenced earlier) allowed us to process high-surface-quality microholes in copper with quick turnaround, in high-volume scenarios.
Drug Delivery Devices
For further details on this potential application, see our recent article on “EHAR”.
Another potential application for PECM’s unique ability to make scalable, tight-tolerance arrays of microholes is in drug delivery systems in the medical device industry, such as implantable pumps, microneedle cartridges, and atomizer plates. These devices, loosely speaking, all work to regulate how a liquid drug is administered or metered to a patient. Microscopic arrays of small nozzles ensure patients are receiving proper drug dosages for patient safety and regulatory consistency, and akin to the internal feature requirements in gas delivery systems for semiconductors, these nozzles require superfinished internal surfaces to prevent debris buildup and uniform drug delivery. In fact, small geometric changes can be drastic safety problems: fraction-of-a-percent changes in dosage amount and/or administration rates can lead to tangible risks in patient safety.
PECM may be capable of producing tight-tolerance, high-internal-surface-quality microhole features in drug delivery devices with high repeatability and scalability to meet both patient safety and regulatory standards. As PECM would produce every nozzle in-parallel, all would have near-identical geometries, ensuring uniform droplet size and spray behavior.
Conclusion
Microhole Application | Primary Function | Typical Hole Scale | Material Examples | Why PECM Helps Most |
Semiconductor cooling | Micro-jets / coolant distribution | 100–500 µm | Cu, Cu alloys, Ni alloys | Uniform jets, deep arrays, good internal finish |
Gas delivery showerheads | Gas distribution & mixing | <50–200 µm | Ni, Hastelloy, superalloys | Smooth internals, no recast/particles |
Power electronics | Jetting / throttling / manifolds | 100–500 µm | Cu, Cu alloys | Dense arrays in copper, parallel machining |
Drug delivery | Spray/dose metering | Varies from tens to hundreds of µm | Stainless, Ti, Ni alloys | Burr-free nozzles, repeatable geometry |
Future: microreactors etc. | Reaction/mixing, heat exchange | application-dependent | Ni, Hastelloy, others | Non-LOS channels, thin walls, internal finish |
As demands continue to mount for semiconductors, power electronics, medical devices and more, microhole arrays take a central role in how heat, fluids, gases, and even medicine move through some of the most critical hardware in the world, like data centers and life-saving drug devices.
In this push towards denser, tighter-tolerance and superfinished microholes, conventional processes like laser drilling and CNC have been exposed as inherently limited and unequipped to handle the next generation of microhole arrays for critical industries. Recast layers, tapered holes, tool wear, fixture drift, burrs, and a lack of proper repeatability are actively preventing the next generation of data centers, thermal control infrastructure, and drug delivery devices.
Fortunately, PECM can avoid many of those constraints with its ability to produce dense, tight microhole arrays with high scalability without any heat, contact, or significant tool wear. Recent internal research implies PECM’s ability to produce hundreds to low-thousands of microholes in a single cathode operation with sub-millimeter diameters and micrometer-ra surface finishes in production environments.
Although this article has focused on semiconductors, power electronics and drug delivery, these advantages can translate into a broader array of applications, from heat exchangers to advanced energy systems. If you have any ideas, email us at info@voxelinnovations.com or use the contact forms to speak with an engineer.
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