Stable grids need cool electronics, with as little maintenance as possible

In power supplies, air cooling typically reaches its limit above roughly 5 to 10 W/cm² of heat flux density. What matters is not the absolute power but the area over which it has to be dissipated. An IGBT module with 3 kW of losses on a large base plate is manageable with air cooling; the same 3 kW on a SiC module with a quarter of the area is not. The second limit is installation space: air cooling needs fin height and air volume, a cold plate does not. A practical guide from customer projects: from around 2 kW per assembly, or where heat sink temperatures below 60 °C are required at 40 °C ambient, liquid cooling is usually the simpler solution. Conversely, as long as air is enough, air is cheaper and needs less maintenance, so you should not switch to liquid.

A specified thermal resistance comes from three quantities: the internal structure of the cold plate, the volume flow and the position of the heat sources. For targets around 0.02 K/W with several heat sources, a tube-based cooler usually will not get there; an internally structured plate with the channel directly beneath the source will. Important for your enquiry: Rth cannot be verified without stating volume flow, inlet temperature and reference area. The same plate achieves a far better value at 8 l/min than at 2 l/min. We calculate the design by thermal simulation and state the value achieved together with the corresponding boundary conditions. Limit: below certain values the pressure drop rises so steeply that the pump becomes the cost driver, and we check that as well.

A heat sink can be at potential. That is a regular case in power electronics, and it mainly affects the choice of coolant and connections. With coolers at potential you work with insulating hose sections of defined length, deionised water or insulating interlayers; the clearances follow insulation coordination (DIN EN 60664-1, EN 50124 in rail applications). For partial discharge testing in the kilovolt range, edge rounding and surface quality matter too, because field peaks form at burrs. COOLTEC manufactures and tests the mechanical side; the insulation design and the partial discharge test of the overall assembly lie with the system manufacturer, because they depend on the complete environment. For that we supply drawing data on radii and surfaces and match the connection geometry to it.

With a good design, the transition between module and cold plate is the largest single resistance in the entire path, not the cold plate itself. Three things are decisive: flatness of the mounting face, surface roughness and a uniform bolt tightening pattern. For power modules we machine the contact face flat to 0.05 mm across the module area and state the values achieved in the drawing. Thermal paste or foil only compensates residual unevenness; a thick layer of paste degrades the transition rather than improving it. Limit: with very large module areas, distortion of the module itself limits the result. Even better flatness of the plate then adds nothing, and you work via the bolt pattern and contact force.

Single pieces and small series are the norm, not the exception: a large share of our enquiries begins with 1 to 10 units, often as a prototype ahead of a series decision. For customer-specific cold plates there is no minimum quantity in the classic sense. The unit price falls with quantity because set-up and programming effort is spread. It is different with a dedicated extrusion profile: that requires tooling which only pays off above a certain annual volume; until then you work with an existing profile from the profile database and adapt it mechanically. Limit: for single pieces the set-up effort dominates the price so strongly that the unit price is not comparable with a series calculation. That is set-up time, not pricing policy.

COOLTEC is certified to DIN EN ISO 9001:2015 (TÜV Thüringen), scope: development, production and sale of heat sinks and cold plates plus accessories for the electronics industry. For industry-specific requirements (fire behaviour in rail vehicles or material certificates in aviation, for example) we provide evidence through material and test certificates from our suppliers plus our own test records, not through our own system certification to the respective industry standard. In practice that means: we supply material certificates, leak and pressure test records and dimensional reports, and we know the requirements of the relevant standard. The declaration of conformity for the end product is issued by the system manufacturer. If you have a specific certification as a supplier requirement, tell us early, and we will clarify before the quotation whether we can meet it.

We start from your load case: heat load, distribution across the area, permissible component temperature, inlet temperature, volume flow and installation space. This yields the Rth budget. We test it in thermal simulation against variants of the channel routing before design work begins.

We calculate with the load profile rather than the data sheet maximum and plan reserve for contamination and ageing of the circuit. We also consider load-cycle endurance, which determines the service life of the joints.

We work in copper, copper-nickel, stainless steel and aluminium. The choice follows three criteria: thermal conductivity, media compatibility and mechanical requirement. We frequently combine materials: conductive material at the heat source, resistant material at the medium.

Pressure testing of every part is our standard; for demanding applications we additionally test with a helium leak test and document the leak rate per part. We set the target leak rate before design.

We build everything from a 30 mm microchannel cooler to a 3 m (30,000 mm) cold plate, right up to a fully cooled large precision part. Size alone does not decide what is possible; material, design and tolerance do. Give us your dimensions and we will tell you in which design we can produce them.

Yes. Part lengths up to around 3 m and large-area cold plates are part of our standard range.

The most common cause is the material pairing, not the part itself. We agree material, medium and inhibitor together; for mixed installations we recommend separate circuits.

Samples in around 6-8 weeks as standard, 2-4 weeks by express. For series production we manufacture in a highly automated plant in Germany; cost-sensitive standard parts come from our joint ventures in Asia.

Yes, that is the norm for us. We sign your non-disclosure agreement or provide ours. We never pass on customer projects or application details.