A Comprehensive Guide to Liquid-Cooled Leak Testing Solutions: From Testing Principles and Industry Standards to Automated Mass Production

Power consumption in AI servers is reaching new limits. As the thermal dissipation of a single GPU approaches 700W, air cooling is proving inadequate, and liquid cooling has naturally emerged as the primary choice for thermal management in data centers, new energy vehicles, and industrial applications.

However, liquid-cooling systems have one critical weakness that is often overlooked:LeakThe

Brazed joints on liquid-cooled plates, O-rings on quick-connect fittings, and welded joints in piping—even the slightest leak in any of these areas can allow coolant to come into contact with electrical components, causing short circuits and equipment downtime. No matter how efficient the cooling system is, the cost of a seal failure is enough to negate all its advantages.

That's why.Air tightness testingIt should not merely be the final step before shipment, but rather a process that spans the entire chain—from product design verification and component manufacturing to assembly and traceability during mass production.

So.Should the liquid-cooled plate use the direct-pressure method or the differential-pressure method? When is helium mass spectrometer leak detection required? How should the test pressure, hold time, and leak limits be set?This article breaks down each aspect in detail, combining JCGK Jingcheng Engineering's equipment solutions with industry standards.

I. Leakage Risks Lurk in Every Joint of a Liquid-Cooling System

The liquid cooling system consists of a liquid cooling plate, cooling piping, quick-connect fittings, a manifold, and a coolant distribution unit (CDU); each component has a different structure, and the sources of leakage risk vary accordingly.

Liquid-cooled plateThe risks are concentrated in the welded areas: brazing, friction stir welding, laser welding, and the integrity of the seal between the internal flow channels and the outer wall.Cooling Piping and Copper Tube AssembliesThe weak points are at the welded joints and pipe bends.Quick-Connect FittingsThe sealing rings and connection points—in particular, the deterioration of sealing performance after repeated insertion and removal—require special attention.Fractionator and CDU It is then necessary to verify the overall seal integrity of the welds, flanges, valves, and pipe connections after the assembly is complete.

The consequences of a leak follow a clear hierarchy:In mild cases, coolant loss can lead to reduced cooling capacity; in severe cases, contact between the coolant and electrical components can cause a short circuit, which in turn can result in a systemic safety incident.. For mass-production facilities, airtightness testing must provide traceable data, rather than simply yielding a pass or fail result.

II. Four Testing Methods: What Can Each One Do?

There is no one-size-fits-all solution for liquid-cooled leak testing. The four mainstream methods—direct pressure, differential pressure, helium mass spectrometry leak detection, and water immersion bubble testing—each have their own limitations.

Direct Pressure Method and Differential Pressure Method: Core Tools for Mass Production

direct pressureThis is the most direct method of detection:Gas at a specified pressure is introduced into the workpiece; after a stabilization period, the pressure change is measured, and if it exceeds the set threshold, the workpiece is deemed nonconforming.. The principle is simple, making it suitable for the initial screening of cooling tubes, copper tube welded assemblies, and parts with relatively regular shapes in batch production. It should be noted that the measurement results are sensitive to temperature changes and elastic deformation of the workpiece; the settings for gas filling, equilibration, and testing time directly determine the reliability of the results.

differential pressureThe approach is more ingenious. Rather than observing the pressure of the test piece in isolation, itGas is introduced simultaneously into the test specimen and the reference chamber, and leaks are detected by measuring the pressure difference between the two sides.. This “Electronic Balance"This logic can, to a certain extent, offset the interference caused by fluctuations in ambient temperature, making it particularly suitable for liquid-cooled plates, precision-welded parts, and components that require high measurement repeatability. However, the differential pressure method cannot eliminate all temperature drifts—the quality of the reference chamber and the thermal equilibrium of the workpiece remain key variables affecting accuracy."

Helium Mass Spectrometry Leak Detection: A Specialized Tool for Extreme Conditions

Helium Mass Spectrometry Leak DetectionUsing helium as a tracer gas,By detecting helium ion concentration, this method determines the presence, location, and magnitude of a leak, with sensitivity far exceeding that of the air pressure drop method.. Its applications include R&D validation requiring extremely low leak rates, as well as product verification requiring precise detection of micro-leaks.

However, helium testing is not a panacea. Helium is expensive, the supply chain is subject to volatility risks, and the investment in equipment and processes is substantial. More importantly,Helium test results cannot be directly converted to values obtained using the air pressure drop method.—These two methods measure different physical quantities and cannot be used interchangeably when applying standards.

Water-Immersion Bubble Method: A Tool for Verification, Not for Mass Production

Water-Immersion Bubble MethodIts advantage lies in its intuitiveness:Submerge the workpiece in water; if bubbles appear, there is a leak, and the location is immediately obvious.. However, it relies on manual observation, so minor leaks may not always be reliably detected, and it also faces challenges related to subsequent processing, such as water ingress, drying, and cleaning. This method is more suitable for process validation and fault localization than for online mass-production inspection.

Guidelines for Selecting Among Four Methods

Detection Methods	core value	The Most Suitable Task
direct pressure	Simple structure, fast mass production cycle	Batch Pre-screening, Routine Seal Validation
differential pressure	Precise differential pressure measurement with strong resistance to interference	Liquid-cooled plates, precision-welded components
helium mass spectrometry	Extremely high sensitivity, capable of locating leak points	Extreme Leak Rate Verification, R&D Validation
Water-Immersion Bubble Method	Visualization of Leak Locations	Leak Detection Support and Process Validation

The ultimate basis for selecting a method isTarget Leakage Rate, Test Conditions, and Physical Verification Results...rather than because a certain method sounds more advanced.

III. Which industry standards deserve special attention from 2024 to 2026?

There is a common misconception in the liquid cooling industry:Copy test parameters directly from other projects. A test pressure of 200 kPa, a pressure drop of no more than 50 Pa, and a leakage rate of no more than 2.5 mL/min—these figures are not tied to specific products or testing methods and cannot serve as a universal standard for all liquid-cooled products. The following four standards currently constitute the most important reference framework:

QC/T 1206.2—2024《Thermal Management Systems for Electric Vehicle Power Batteries—Part 2: Liquid-Cooling Systems》Effective January 1, 2025, this standard specifically addresses liquid-cooling systems and components for electric vehicle power batteries. The standard specifies three methods for verifying seal integrity: wet testing(No visible bubbles), Dry Inspection(Leakage rate ≤ 2.5 mL/min), Helium Test(Leakage rate ≤ 2 × 10⁻⁶ Pa·m³/s)TheThese three paths correspond to different testing methods and should not be regarded as interchangeable values under the same conditions.

GB/T 44556—2024《Evaluation of the Leak Tightness of Components and Fittings in Refrigeration Systems and Heat Pumps》Effective April 1, 2025, this standard applies to the evaluation of the leak tightness of components related to refrigeration systems and heat pumps. Whether it applies to liquid-cooled products depends on the specific application and the scope of the standard.

GB/T 48023—2026《Technical Specifications for Cold Plate Liquid Cooling Systems in Data Centers》was published on July 30, 2026, and is scheduled to take effect on February 1, 2027. Manufacturers and integrators of liquid-cooling systems for data centers can review the requirements in advance.

YD/T 7105—2026《Test Methods for Cold-Plate Liquid-Cooled Data Centers》is scheduled to take effect on November 1, 2026, and primarily covers equipment testing, acceptance testing, and operations and maintenance testing for cold-plate liquid-cooled data centers.

A key determination:Liquid-cooling systems for new energy vehicles and cold plate-based liquid-cooling systems for data centers are two distinct types of products.(math.) genusJust because all systems use liquid cooling technology doesn't mean the same set of test parameters should be applied across the board.. When formally developing the plan, the official texts of the applicable standards, product drawings, customer technical specifications, and risk assessment results shall serve as the basis.

IV. How Should Test Pressure, Duration, and Leakage Limits Be Scientifically Determined?

This is the issue engineers are most concerned about, and it’s also the area where they’re most likely to run into problems.

Test Pressure: Higher Isn't Always Safer

Test pressure must be determined in conjunction withProduct Rated Operating Pressure, Design Pressure Rating Requirements, Sealing Configuration, and Applicable StandardsTo be determined jointly. Setting the pressure too high may cause deformation of thin-walled structures or subject seals to abnormal stress, thereby introducing new failure risks; setting the pressure too low, on the other hand, may fail to meet validation requirements. Without deviating from the specific product, “General Test Pressure"The

Test Duration: The compressed stabilization phase poses the greatest risk

A complete dry-type airtightness test procedure consists of four stages:Inflate(Reaches the set pressure)→ equilibrium(Wait for the temperature and pressure to stabilize)→ sensing(Measure the change)→ Determination and Recording(Output)The

The internal flow channels of liquid-cooled plates are complex and have a large volume, and the material may also undergo elastic deformation. When the balancing time is shortened to meet production cycle requirements, the gas enters the testing phase before its temperature has stabilized, causing pressure changes resulting from thermal expansion to be mistakenly interpreted as leaks.Test times must be repeatedly verified using合格件, samples with known leak rates, and不合格件....to strike a true balance between testing reliability and mass production efficiency.

Leakage Limit: The pressure drop is not equal to the leakage rate

This is the most confusing part. Just because the instrument shows a pressure drop of 50 Pa does not mean the product meets a particular standard. The relationship between the pressure change and the actual leak rate also depends on the workpiece volume, test pressure, gas temperature, test duration, and the equipment’s algorithm.

Companies need to clarify four things:Which physical quantity should be used as the basis for determination?(Pressure change, differential pressure, or flow rate).;In what units should the result be expressed?.;Which standard or customer specification provides the acceptance limits?.;Has the equipment been thoroughly calibrated so that it can reliably distinguish between conforming and nonconforming products?. During the R&D phase, it is essential to verify whether the method is applicable; during the mass production phase, it is essential to verify whether the results can be consistently reproduced—both are indispensable.

V. Jingcheng Engineering’s Liquid-Cooling Testing Solution System

For products such as liquid-cooled plates, copper tube assemblies, quick-connect fittings, and CDUs,Selecting the right equipment is just the beginning. Other factors that truly determine the effectiveness of the testing include fixture sealing, pneumatic circuit design, test procedures, and automation integration.

Shenzhen Jingchenggongke Technology Co., Ltd.(JCGK) has developed three main solutions for liquid-cooling applications:

Precision Differential Pressure Measurement:JC-C10005

For liquid-cooled plates, precision-welded components, and sealed housings,JC-C10005 High-precision measurement is achieved using the differential pressure method.Differential pressure range: ±5000 Pa; resolution: 0.1 Pa; nominal test accuracy: 0.075% F.S.... supports multi-channel expansion and is suitable for workstations with strict repeatability requirements.

Dual-Channel Direct Pressure Testing: A Mass Production Solution for Copper Tube Assemblies

For products with relatively well-defined structures, such as cooling tube and copper tube welded assemblies,Dual-channel airtight testing equipment, when used in conjunction with custom fixtures, can effectively improve testing efficiency.. In a certain liquid-cooling component project, in addition to its inspection functions, the equipment also reserved space for fixtures to be used by robotic arms for loading and unloading—Expanding from a simple assessment of leaks to the overall design of tooling, production rhythms, and automation layoutsThe

Multi-Channel Automation Integration: For Mass Production Lines

Designed for mass production,JCGK Jingcheng Engineering can evaluate configurations with two, four, or more stations based on production capacity requirements, and provide customized fixtures, PLC signal communication, automatic loading and unloading, and data traceability capabilities.. For companies with MES management needs, the system can link inspection data to product barcodes, upload results, sort out anomalies, and retrieve historical records. The actual capabilities and production capacity can be confirmed through a project technical review and on-site joint debugging.

VI. The design of tooling and fixtures is just as important as the equipment itself.

Liquid-cooled plates are typically large in size, with fluid inlet and outlet ports located in various positions, and their internal flow channels may feature complex compartmentalization. If one focuses solely on selecting the instrument while neglecting fixture design, issues such as uneven contact at the sealing surfaces, workpiece deformation caused by excessive clamping force, and changes in the sealing position after a tooling change—all of these can directly interfere with the test results.

The criteria for evaluating workwear design are not limited to “The fixture itself does not leak air.", and also verifyClamping repeatability, whether the workpiece deforms while clamped, consistency during changeovers, and whether leaks in the fixture can be effectively distinguished from product leaks. When multiple liquid-cooled products are manufactured on the same production line, a reasonable combination of changeover tooling and multi-channel configurations can significantly reduce changeover downtime.

VII. Passing the airtightness test does not necessarily mean that the liquid-cooled plate meets quality standards.

Air tightness testing verifies sealing performance; it cannot replace comprehensive structural and performance verification.

A liquid-cooled plate that has passed the airtightness test may still have an insufficient welded bond area.(But a continuous leakage path has not yet formed.), partial blockage of internal flow channels by solder or foreign objects, flow resistance exceeding the design range, and new leaks developing after prolonged thermal cycling and vibration.

A comprehensive liquid cooling quality verification system should also take into account, based on product risk,Flow and flow resistance testing, pressure or burst testing, non-destructive testing of weld quality, and re-testing of seal integrity following environmental stress testing. For liquid-cooling systems in new energy vehicle power batteries, QC/T 1206.2—2024 covers a number of validation requirements, including pressure resistance, seal integrity after vibration, weld strength, burst pressure, and high- and low-temperature cycling; airtightness testing is just one of these steps.

A "PASS" result in a leak test confirms that the seal meets the requirements under the current test conditions; it does not serve as proof of the product's reliability over its entire lifecycle.

Conclusion

A suitable liquid-cooled airtightness testing solution begins by determining the testing methods based on product structure and failure risks, and then transforms laboratory testing capabilities into repeatable, traceable mass production quality control capabilities through the design of test pressures, equilibration times, leakage limits, test fixtures, and automation.

If you are planning a liquid-cooled airtightness test procedure, be sure toProduct Type, Target Leak Rate, Test Pressure, and Mass Production Cycle TimeOnce these four parameters have been clearly defined, proceed with prototype testing and solution validation—this is the most efficient way to begin.

Shenzhen Jingchenggongke Technology Co., Ltd.(JCGK) has established partnerships with several leading brands in the liquid cooling industry and has accumulated extensive experience in providing solutions and practical case studies for applications such as liquid cooling plates, copper tube assemblies, quick-connect fittings, and CDUs. If you need assistance with selecting testing equipment or evaluating solutions, please feel free to contact us.

Original Statement: This article was written byShenzhen Jingchenggongke Technology Co., Ltd.Written by the technical team, reproduced with attribution.Data sources: Precision Engineering internal test data and customer cases.