In-house Joining Process · Capabilities
TLP (Transient Liquid Phase) diffusion bonding is one of ToneCooling's in-house cold plate joining processes, available to Australian engineering teams through the Carlton, Victoria customer engineering office. The Carlton VIC team coordinates DFM review, process selection, and AS/NZS-aligned validation documentation for Australian buyers. Unlike conventional vacuum brazing — which leaves a braze-filler interface layer — TLP forms a continuous metallurgical joint across the bonded plane, without a filler-metal interface. That makes it well suited to copper cold plates that see heavy thermal cycling. Bonded joints are checked by ultrasonic C-scan inspection. The process is carried out at our own IATF 16949-aligned manufacturing facility in Huizhou, and process selection is confirmed per programme at DFM review and quotation.
Capability Snapshot
Engineering Reference & Standards
Process
Mating surfaces machined flat and cleaned to remove oxide and organic contamination.
Proprietary melting-point-depressant alloy interlayer placed between mating surfaces.
Assembly heated under controlled atmosphere; interlayer melts and wets both surfaces under uniform pressure.
Depressant diffuses into bulk metal; liquid phase isothermally solidifies; continuous grain structure forms.
Controlled cooling; ultrasonic C-scan inspection of the bonded interface; leak testing to the programme specification.
Comparison
| Attribute | TLP diffusion bonding (ToneCooling) | Vacuum brazing (industry standard) | Why it matters |
|---|---|---|---|
| Microstructure | Continuous metallurgical grain | Discrete braze-filler interlayer | Eliminates the braze-filler weak point under thermal cycling fatigue |
| Joining temperature | Below bulk melting; interlayer melts and isothermally solidifies at temperature | Above filler-metal liquidus; below bulk solidus | TLP operates closer to bulk melting; tighter thermal control required |
| Bond verification | Ultrasonic C-scan | Ultrasonic C-scan (industry-best practice) | Same NDI method; both processes verified non-destructively |
| Dimensional control | Tighter (no filler-thickness variation) | Filler thickness contributes to the tolerance stack | TLP enables tighter post-bond flatness for high-precision applications |
| Equipment cost | Higher (precision pressure-temperature control) | Lower (mature furnace technology) | Weighed against part volume and reliability target per programme |
| Suitable materials | Copper cold plates (primary application) | Wide range (mature process) | Material and interlayer chemistry determine whether TLP is viable; confirmed at DFM review |
Thermal cycling
Inference and training load swings cycle processor dies through repeated temperature swings. For copper cold plates in sovereign-cloud and HPC deployments, TLP is one of the joining options evaluated per programme.
Australian BESS sites cycle daily on AEMO ISP / CIS-aligned despatch profiles. Cold-plate thermal cycling lifetime is a primary BESS reliability constraint; aluminium BESS plates are typically joined by CAB, with the process confirmed per programme.
Mining truck inverters, electric bus traction drives, and marine electrification systems put power modules through heavy duty cycling. The joining process for their cold plates is selected per programme at DFM review.
Verification
Non-destructive inspection of the bonded interface using a focused ultrasonic transducer scanning across the cold plate surface. The output is a two-dimensional image of the bonded plane. Performed at our own manufacturing facility in Huizhou before shipment.
Per ASTM E2375-22 NDI methodologyHelium mass-spectrometer leak testing to the acceptance level specified for the programme.
Acceptance level per programmeLot-sample cross-sectioning, polishing, and etching to reveal grain structure at the former bonding interface. Optical or SEM microscopy confirms continuous grain across the bonded plane — no discrete filler interlayer visible.
Per process qualification cycleLot-sample shear strength testing during process qualification. Testing performed at our Huizhou QA laboratory, and at accredited third-party laboratories on customer request.
Third-party verification available
Application fit
| Application category | Material | Typical joining approach |
|---|---|---|
| Copper cold plates for AI server and HPC processors | Copper | Brazing, vacuum brazing, or TLP — confirmed per programme |
| Copper cold plates for high-reliability industrial equipment (medical imaging, laser sources, semiconductor process tools) | Copper | TLP considered where thermal cycling is heavy — confirmed per programme |
| Battery and BESS cold plates | Aluminium | Controlled atmosphere brazing (CAB) |
| EV and heavy-EV battery cold plates | Aluminium | Friction stir welding (FSW) |
Frequently Asked
TLP diffusion bonding removes the braze-filler interlayer, which is a common fatigue initiation site in brazed cold plates under thermal cycling. The joint is a continuous metallurgical structure rather than a filler-metal interface, which is why TLP suits copper cold plates that see heavy thermal cycling, such as those exposed to AI server load swings or power-electronics duty cycling. Whether it is the right process for a given programme is confirmed at DFM review and quotation, and thermal cycling validation scope is agreed per programme.
Bonded joints are checked by ultrasonic C-scan inspection of the bonded interface. The C-scan output is a two-dimensional image of the bonded plane: uniform colour indicates a void-free bond, dark patches indicate voids or unbonded zones. C-scan evidence is supplied with the validation documentation. Additional checks used during process qualification, such as cross-section metallurgy, shear testing and leak testing, are agreed per programme.
TLP is available for copper cold plates in high thermal-cycling applications, confirmed per programme. Aluminium cold plates are typically joined by controlled atmosphere brazing (CAB) or friction stir welding (FSW), which are the appropriate processes for aluminium-alloy joining. The DFM review covers process selection and trade-offs for your specific application.
Cost depends on material, geometry, volume, and qualification scope, so there is no single rule for which joining process is cheaper. The DFM review compares the candidate joining processes for your specific programme, and the process is confirmed at quotation.
Continue Exploring
Joining-process comparison for liquid cold plates.
PRODUCTGB200 / GB300 / H200 — copper micro-channel kits with tested datasheets.
View product → PRODUCTAMD EPYC SP5 / Intel Birch Stream cold plates; joining process confirmed at quotation.
View product → CAPABILITYUltrasonic C-scan and helium leak testing, scoped per programme.
View capability → RESOURCE12-section engineering reference — direct-to-chip channel topology and joining process.
Read the guide →Send your TDP map, target ΔP and flow rate, qualification scope, and reliability target. The Carlton VIC team coordinates the engagement and the Huizhou design and engineering team provides a process recommendation (TLP / vacuum braze / FSW / CAB), CFD output, and a draft quote in AUD.
Discuss your TLP application Email [email protected]
