The Complete Guide to Bergquist Thermal Clad PCB Materials [2025]

Power electronics design has a thermal problem that FR-4 simply cannot solve. A 0.3 W/m-K epoxy-glass laminate works fine for a low-power microcontroller. It completely falls apart — thermally — the moment you mount a power FET dissipating 20 W in a 1 cm² footprint, or a 10 W LED that needs to run cool enough to maintain lumen output over 50,000 hours. The junction temperature rises, the device throttles or fails, and the product design that looked good on paper turns into a warranty problem.

Bergquist Thermal Clad PCB materials were developed precisely for this class of problem. Thermal Clad is an Insulated Metal Substrate (IMS) technology — a three-layer system consisting of a copper circuit layer, a proprietary ceramic-polymer dielectric, and an aluminum or copper metal base — where the dielectric thermal conductivity is 3.7× to 25× higher than FR-4 depending on the specific product. The result is a substrate that conducts heat to the metal base and on to the heatsink or chassis efficiently enough to keep power components cool using nothing more than a direct solder mount, eliminating the mica washers, thermal grease, clips, and springs that traditional FR-4 designs require.

This guide covers the complete Bergquist Thermal Clad PCB family — how the technology works, every product with official specifications, how to choose the right dielectric for your application, design and assembly rules, and where Thermal Clad fits versus FR-4, ceramic DBC, and generic aluminum MCPCB alternatives. For Bergquist PCB sourcing and fabrication, the information here gives you the technical foundation to specify the right material and ask the right questions of your fabricator.

How Bergquist Thermal Clad PCB Technology Works

The Three-Layer Construction

Every Thermal Clad board is built from three layers in a specific order:

Circuit Layer: Electrolytic copper foil, typically 1 oz to 10 oz (35–350 µm) depending on current requirements. This is the standard PCB circuit layer where components are soldered, traces are etched, and surface finishes are applied. Thermal Clad supports the same circuit layer processes as conventional PCB — ENIG, lead-free HASL, OSP, immersion silver — along with surface finishes specific to IMS applications like ENEPIG for aluminum wire bonding.

Dielectric Layer: The ceramic-polymer composite that is the core technology of Thermal Clad. This proprietary blend of ceramic filler (for thermal conductivity and dielectric strength) and polymer resin (for electrical isolation, adhesion, and mechanical integrity) provides the thermal path from the circuit layer to the metal base while maintaining electrical isolation between them. Bergquist’s dielectric ranges from 1.5 mil (38 µm) to 9 mil (225 µm) in thickness depending on the product, with thermal conductivities from 1.1 to 7.5 W/m-K. All Thermal Clad dielectrics are glass-free (with the exception of CML-11006, which uses a glass carrier for the prepreg format) — a design choice that avoids the thermal conductivity penalty that glass fiber imposes in conventional FR-4 laminates.

Base Layer: Most commonly 5052 or 6061 aluminum in standard thicknesses of 0.8 mm, 1.0 mm, 1.5 mm, 1.6 mm, or 2.0 mm. Copper base is also available for applications requiring higher bulk thermal conductivity (400 W/m-K for copper versus 150 W/m-K for aluminum) or lower CTE for solder joint reliability on large-area components. In some applications — particularly two-layer multi-circuit assemblies and ultra-thin circuit (UTC) configurations — no metal base is used at all, and the Thermal Clad dielectric bonds to the external heatsink or chassis directly.

Why the Dielectric Is the Critical Variable

Thermal impedance — the temperature rise per watt of heat flow — is determined by the ratio of dielectric thickness to thermal conductivity. The formula is straightforward: Thermal Resistance (°C·in²/W) = Thickness (in) ÷ Thermal Conductivity (W/in·K), adjusted for units. What this means in practice is that a thicker dielectric and a lower thermal conductivity both increase thermal resistance and therefore junction temperature for a given power level. Bergquist designs each Thermal Clad product by choosing a dielectric thickness and ceramic filler loading that achieve the thermal performance needed for the target application class, while also meeting electrical isolation (breakdown voltage) and mechanical integrity requirements.

The Bergquist Selection Guide positions this directly: “Thermal impedance is the only measurement that matters in determining the watt density capability of your application because it measures the temperature drop across the stack-up for each watt of heat flow.”

Thermal Clad vs FR-4: The Numbers That Matter

Parameter	Standard FR-4	Bergquist LTI/HT-04503	Bergquist HPL-03015
Dielectric Thermal Conductivity	~0.3 W/m-K	2.2 W/m-K	3.0 W/m-K
Dielectric Thermal Resistance	~0.76 °C·in²/W at 3 mil	0.05 °C·in²/W	0.02 °C·in²/W
Temperature Rise (10 W / 1 cm² device)	~5°C across dielectric alone	~0.3°C across dielectric	~0.1°C across dielectric
Breakdown Voltage (3 mil)	~1.5–2.0 kVAC	6.0–6.5 kVAC	5.0 kVAC
Base Metal Heat Spreading	None (epoxy-glass)	Aluminum: 150 W/m-K	Aluminum: 150 W/m-K
UL Flammability	V-0	V-0	V-0
Multi-layer Capability	Yes (standard)	Limited (CML-11006 only)	No

The numbers tell the story: at the same 3 mil dielectric thickness, Bergquist HT-04503 delivers 15× lower thermal resistance than standard FR-4. Multiply that by the number of power devices on a board and the difference in junction temperatures — and therefore device reliability and lifetime — is substantial in every real-world power electronics application.

Complete Bergquist Thermal Clad PCB Dielectric Family: All Products and Specifications

The official Bergquist Thermal Clad Selection Guide (Bergquist document Q-6019) is the authoritative specification source for every product listed below. Specifications are taken directly from the published dielectric summary table.

Master Specifications Table: All Bergquist Thermal Clad Dielectrics

Product	Family	Thickness	Conductivity	Thermal Resist.	Impedance	Breakdown	Proof Test	Dk	Tg	UL RTI	Peel
HPL-03015	HPL	1.5 mil / 38 µm	3.0 W/m-K	0.02 °C·in²/W	0.30 °C/W	5.0 kVAC	—	—	185°C	140°C	5 lb/in
LTI-04503	LTI	3 mil / 75 µm	2.2 W/m-K	0.05 °C·in²/W	0.45 °C/W	6.5 kVAC	1500 VDC	7	90°C	130/130°C	6 lb/in
HT-04503	HT	3 mil / 75 µm	2.2 W/m-K	0.05 °C·in²/W	0.45 °C/W	6.0 kVAC	1500 VDC	7	150°C	140/140°C	6 lb/in
MP-06503	MP	3 mil / 75 µm	1.3 W/m-K	0.09 °C·in²/W	0.65 °C/W	8.5 kVAC	1500 VDC	6	90°C	130/140°C	9 lb/in
LTI-06005	LTI	5 mil / 125 µm	2.2 W/m-K	0.09 °C·in²/W	0.60 °C/W	9.5 kVAC	2000 VDC	7	90°C	130°C	6 lb/in
HT-07006	HT	6 mil / 150 µm	2.2 W/m-K	0.11 °C·in²/W	0.70 °C/W	11.0 kVAC	2500 VDC	7	150°C	140/140°C	6 lb/in
LTI-07006	LTI	6 mil / 150 µm	2.2 W/m-K	0.11 °C·in²/W	0.70 °C/W	11.0 kVAC	2500 VDC	7	90°C	130°C	6 lb/in
HT-09009	HT	9 mil / 225 µm	2.2 W/m-K	0.16 °C·in²/W	1.0 °C/W	20.0 kVAC	—	7	150°C	150/150°C	6 lb/in
CML-11006	CML	6 mil / 150 µm	1.1 W/m-K	0.21 °C·in²/W	1.1 °C/W	10.0 kVAC	2500 VDC	7	90°C	130/130°C	10 lb/in

HPL-03015: Maximum Thermal Performance for High-Power LEDs

The HPL (High Power Lighting) dielectric is the performance leader in the Thermal Clad family. At 1.5 mil (38 µm) dielectric thickness and 3.0 W/m-K dielectric thermal conductivity, it delivers 0.02 °C·in²/W thermal resistance — 2.5× better than HT-04503 and the best thermal performance in the family. The Tg of 185°C is the highest in the family, making HPL-03015 one of the few Thermal Clad products where AuSn eutectic die attach (280–320°C process) is feasible. HPL-03015 also achieves a 7.5 W/m-K product thermal conductivity figure (combining dielectric and adjacent copper layers) in Bergquist’s composite measurement.

The application focus is exactly what the name says: high-brightness LED chip-on-board (COB) assemblies, bare-die LED direct attach, automotive headlamp modules, concentrator photovoltaic (CPV) mounts, and any application where squeezing maximum heat out of minimum substrate area is the primary design objective. The tradeoff is voltage: at 38 µm, HPL-03015 is rated for 120 VAC / 170 VDC continuous operating voltage. It is not a high-voltage product.

HT-04503 and HT-07006: The High-Temperature Workhorses

The HT (High Temperature) dielectric family uses 2.2 W/m-K ceramic filler in a high-temperature polymer matrix with a Tg of 150°C — the highest Tg in the non-HPL Thermal Clad family. The UL RTI of 140°C/140°C makes HT products the correct choice for automotive under-hood applications, high-temperature industrial equipment, and any design where the substrate must maintain mechanical and electrical stability at sustained temperatures approaching 140°C.

HT-04503 (3 mil, 6.0 kVAC) is the standard specification for high-density power electronics requiring both thermal performance and high-temperature capability. The 150°C Tg is also the critical enabler for thermosonic gold wire bonding — the substrate must be in its glassy state at wire bond temperature (120–150°C) for the ultrasonic energy to couple effectively. HT-07006 (6 mil, 11.0 kVAC) extends breakdown voltage to 11.0 kVAC for applications requiring isolation up to approximately 690 VAC. HT-09009 (9 mil, 20.0 kVAC) reaches 20 kVAC breakdown for the highest voltage isolation requirements in the family.

LTI-04503, LTI-06005, LTI-07006: High Performance at Standard Operating Temperatures

The LTI (Low Thermal Impedance) family delivers the same 2.2 W/m-K ceramic filler thermal conductivity as HT at the same dielectric thicknesses, but in a polymer chemistry with 90°C Tg and 130°C/130°C UL RTI rather than 150°C Tg and 140°C RTI. The thermal performance is identical to the HT products — 0.05 °C·in²/W for LTI-04503 matching HT-04503, and 0.11 °C·in²/W for LTI-07006 matching HT-07006. LTI-04503 actually has a slightly higher 6.5 kVAC breakdown voltage compared to HT-04503’s 6.0 kVAC at the same 3 mil thickness.

Choose LTI over HT when: the design operates within the 130°C UL RTI; standard SAC305 lead-free reflow is the assembly process; thermosonic gold wire bonding is not required; and working voltage is within the safe operating range for the chosen LTI thickness. For most DC-DC converters, SSR assemblies, LED driver boards, and standard industrial motor controls operating below 130°C, LTI-04503 is the efficient and appropriately specified choice.

MP-06503: The Voltage Isolation Specialist at 3 Mil

The MP (Multi-Purpose) dielectric at 3 mil thickness is the highest-voltage 3 mil product in the Thermal Clad family at 8.5 kVAC breakdown — 42% higher than HT-04503 at the same thickness. It achieves this with 1.3 W/m-K thermal conductivity (lower than the 2.2 W/m-K LTI/HT formulation) and 0.09 °C·in²/W thermal resistance (1.8× higher than HT-04503). The 9 lb/in peel strength is also the highest among the single-layer laminate products.

MP-06503 fills the gap for designs that need more than 480 VAC isolation but want to stay at 3 mil dielectric thickness rather than moving to a 6 mil product. Solid-state relay assemblies with higher working voltages, industrial drives at 600 VAC bus, and medical equipment requiring reinforced insulation at 3 mil are typical MP-06503 applications. The thermal performance is adequate for moderate power densities but not for the highest-watt-density LED or power semiconductor designs.

CML-11006: The Only Prepreg — Multi-Layer IMS Enabler

CML-11006 (Circuit Material Laminate) is the sole prepreg product in the Thermal Clad family and the only one that enables genuine two-layer and multi-layer IMS circuit constructions. At 6 mil thickness with 1.1 W/m-K dielectric conductivity, its 0.21 °C·in²/W thermal resistance is the highest in the family. The peel strength of 10 lb/in is the highest in the family.

CML-11006 is used in three construction types: a two-circuit-layer board bonded to an aluminum base (power circuit on top, control circuit on bottom, CML-11006 as interlayer); a replacement for FR-4 prepreg in mixed multi-layer constructions (3.7× better thermal conductivity than FR-4 prepreg at the interlayer); and metal-base-free ultra-thin circuits for ceramic submount replacement. Thermal via arrays are mandatory for high-power CML-11006 designs to compensate for the 0.21 °C·in²/W dielectric thermal resistance.

Bergquist Thermal Clad PCB Dielectric Selection: Decision Framework

The selection logic follows from four application parameters evaluated in sequence.

Step 1: Establish the Operating Temperature Requirement

This single question divides the family into two branches:

Operating Temperature	Dielectric Family
Above 130°C continuous, or automotive under-hood (up to 140°C ambient)	HT only (UL RTI 140/140°C)
Above 130°C with extreme high-voltage (>11 kVAC)	HT-09009 (UL RTI 150°C)
Up to 130°C continuous	LTI, MP, CML (UL RTI 130°C)
High-brightness LED, COB bare die, photovoltaics	HPL-03015 (Tg 185°C, lowest thermal resistance)

Step 2: Determine the Required Voltage Isolation

Working Voltage	Recommended Dielectric	Min Breakdown
Up to 120 VAC / 170 VDC (LED systems)	HPL-03015 or any 3 mil product	5.0 kVAC
Up to 480 VAC (standard industrial)	HT-04503 or LTI-04503 (3 mil)	6.0–6.5 kVAC
480–600 VAC or reinforced isolation at 3 mil	MP-06503	8.5 kVAC
480–690 VAC (high-voltage industrial)	HT-07006 or LTI-07006 (6 mil)	11.0 kVAC
Above 690 VAC or high-voltage industrial	HT-09009 (9 mil)	20.0 kVAC

Bergquist’s own guidance states that for applications with expected voltage over 480 VAC, dielectric thickness greater than 3 mil (75 µm) is recommended.

Step 3: Assess Thermal Performance Requirement

If the design passes Steps 1 and 2 with both LTI/HT options remaining viable, select based on watt density:

Application Power Density	Preferred Dielectric at 3 mil	Notes
Maximum (LED COB, CPV, AuSn die attach)	HPL-03015	0.02 °C·in²/W, Tg 185°C
High (DC-DC, power modules, SSR)	HT-04503 or LTI-04503	0.05 °C·in²/W
Moderate (HVAC, lighting drivers)	MP-06503	0.09 °C·in²/W
Multi-layer construction needed	CML-11006	Thermal vias required

Step 4: Assembly Process Compatibility

Assembly Process	Compatible Dielectrics	Restriction
SAC305 lead-free reflow (peak 245–260°C)	All products	Stay below each product’s solder limit
AuSn eutectic die attach (280–320°C)	HPL-03015, HT-04503, HT-07006, HT-09009	HT products rated 325°C / 60s; CML-11006 limited to 260°C
Thermosonic gold wire bonding	HT-04503, HT-07006, HT-09009	Requires Tg ≥150°C for substrate modulus at 120–150°C bond temperature
Aluminum wire bonding	All HT, LTI products with ENIG/ENEPIG	Lower process temperature than gold bonding

Bergquist Thermal Clad PCB Base Metal Selection

Aluminum vs Copper Base

Parameter	Aluminum (5052 / 6061)	Copper
Thermal Conductivity	~150 W/m-K	~400 W/m-K
CTE	~25 ppm/°C	~17 ppm/°C
Density	2.7 g/cm³	8.9 g/cm³
Cost	Lower	Higher
Electrical Connection to Base	Requires special scheme	More compatible
Best Application	General power electronics, LED, weight-sensitive	High localized heat loads, solder joint CTE matching

Aluminum 5052 and 6061 are the standard base materials. The Bergquist Selection Guide notes a useful cost equivalence: 1.0 mm (0.040″) copper costs approximately the same as 3.2 mm (0.125″) aluminum, so copper base can be cost-neutral when thinner base metal is acceptable in the design. For applications requiring electrical connection to the base plate, copper is the more compatible choice. Standard aluminum base thicknesses for Thermal Clad are 0.8 mm, 1.0 mm, 1.5 mm, 1.6 mm, and 2.0 mm.

Circuit Flatness: The 10% Rule

A practical design rule from the Bergquist Selection Guide: to achieve a flat circuit on aluminum base, maintain the copper circuit layer thickness at 10% or less of the aluminum base thickness. If the copper circuit layer is thicker relative to the base, the copper’s internal stresses will cause warping. As an example: 1.5 mm aluminum base with 1 oz (35 µm) copper is within the 10% ratio; switching to 4 oz (140 µm) copper on the same 1.5 mm base approaches the boundary. When heavy copper is required, use a thicker aluminum base or switch to copper base to maintain flatness.

Bergquist Thermal Clad PCB Applications

Power Conversion and DC-DC Modules

The Bergquist Selection Guide explicitly calls out power conversion as the application that drove original Thermal Clad adoption: “Due to the size constraints and watt-density requirements in DC-DC conversion, Thermal Clad has become the favored choice.” High-density brick converters, telecom rectifiers, server power delivery modules, and point-of-load converters all benefit from Thermal Clad’s ability to manage heat from high-frequency switching FETs and rectifiers without separate heatsinks, clips, or thermal interface materials for each device.

High-Brightness LED Lighting

LED applications have become a major Thermal Clad segment. The key relationship is direct: lower substrate thermal resistance → lower LED junction temperature → higher forward current for same junction temperature → more lumens per LED → fewer LEDs needed or brighter fixture. Bergquist developed HPL-03015 specifically for this market as COB packaging pushed power densities beyond what HT-04503 could optimally handle. The Bergquist Selection Guide states: “Mounting high-brightness LEDs on T-Clad assures the lowest possible operating temperatures and maximum brightness, color and life.”

Motor Drives and Variable Frequency Drives

Compact, high-reliability motor drives are cited in the Bergquist Selection Guide as one of the applications where Thermal Clad has set the benchmark for watt density. VFD power modules for HVAC compressors, industrial conveyors, servo drives, and automotive traction control all mount power transistors on IMS boards. The ability to combine the power stage and gate driver on a single Thermal Clad board (using CML-11006 multi-layer for two-circuit assemblies) eliminates one complete PCB from the design.

Solid State Relays and Power Switches

SSR designs mount thyristors, TRIACs, or MOSFETs directly on IMS substrates for direct solder thermal contact to an external heatsink. Thermal Clad eliminates the mica wafer and thermal compound that traditional power device mounting uses, reducing thermal resistance at the interface and simplifying assembly automation. The voltage isolation provided by the Thermal Clad dielectric — 6.0 to 11.0 kVAC depending on product — satisfies SSR agency requirements for standard industrial voltage classes.

Automotive Electronics

Automotive electronics use Thermal Clad across multiple application domains. Body electronics — LED lighting, seat heaters, mirror motors, HVAC blower controls — typically use LTI-04503 or HT-04503 depending on under-hood vs. cabin temperature environments. Under-hood applications require HT-04503 (140°C UL RTI) as a minimum, and HT-09009 (150°C UL RTI) for the harshest thermal locations. Automotive designs also leverage Thermal Clad’s forming capability: the metal base can be stamped, bent, and shaped into three-dimensional thermal management structures, which the Bergquist Selection Guide illustrates in a motor control heat-rail application.

Heat-Rail and Formed Thermal Structures

Thermal Clad’s mechanical formability is a capability that distinguishes it from ceramics and from many competing IMS materials. The aluminum base can be formed into rails, brackets, and custom shapes after circuit fabrication, creating integrated thermal management structures without separate heatsink hardware. Applications include audio amplifier chassis-integrated circuit boards, automotive heat rails, and motor control assemblies where the board itself becomes the thermal path to the environment.

Bergquist Thermal Clad PCB Design Rules and Assembly Guidance

Solder Joint Thickness: The 100 µm Rule

The Bergquist Selection Guide is explicit on this point: “No other decision will affect the reliability of the solder joint as much as the thickness of the solder to be used. A minimum of 0.004 inch (100 µm) is recommended (after reflow).” On Thermal Clad, the metal base conducts heat away from the solder joint much more efficiently than FR-4 — which means the joint cools faster on Thermal Clad. Faster cooling increases solder joint stress from CTE mismatch during thermal cycling. Thicker solder joints (100 µm minimum) absorb CTE mismatch stress through plastic deformation rather than crack propagation through the joint itself.

Surface Finish Selection

Finish	Properties	Best Application
ENIG (Electroless Nickel Immersion Gold)	Flat, long shelf life (up to 12 months), supports Al wire bonding	General SMT, fine-pitch, wire bond substrates
Lead-Free HASL	Slight surface topology, good solderability, long shelf life	Cost-sensitive production, large thermal pads
OSP (Organic Solderability Preservative)	Flat, short shelf life (3–6 months)	Immediate-assembly production
Immersion Silver	Flat, high reflectivity	LED boards requiring high optical reflectivity
ENEPIG	Nickel-palladium-gold, supports gold wire bonding	COB wire bond applications requiring gold wire

The Selection Guide specifies that use of soldermask on Thermal Clad is mandatory. Soldermask prevents copper oxidation and protects the dielectric layer from environmental exposure that could degrade electrical isolation properties over time.

Electrical Design: Hipot Testing and Creepage/Clearance

The proof test voltages specified in the Bergquist Selection Guide — 1500 VDC for 3 mil products, 2000 VDC for LTI-06005, 2500 VDC for 6 mil products — are the standard fabrication-level electrical integrity tests. The Bergquist Selection Guide notes that the proof test must be performed with a controlled ramp rate to avoid capacitive nuisance trips: “It is necessary to control the ramp up of the voltage to avoid nuisance tripping of the failure detect circuits in the tester.” The board being tested must be fully discharged before removal from the test fixture — an important safety consideration for the high capacitance of large IMS panels.

Creepage and clearance distances on the circuit layer are independent of the dielectric breakdown voltage and must comply with the applicable product safety standard (IEC 60950, IEC 61010, IEC 60335, UL 508, or the relevant product-specific standard). Circuit design is the most important consideration for determining safety agency compliance — the dielectric breakdown value alone does not determine whether a design passes agency review.

Selective Dielectric Removal and Pedestal Formation

A unique Thermal Clad process capability: the dielectric can be selectively removed from specific areas of the board, exposing the bare metal base. This creates “pedestals” — raised copper circuit areas surrounded by exposed metal base — used for direct mechanical mounting of power devices to the base plate through a hole in the circuit layer, or for forming electrical vias directly from circuit to base metal. This capability is documented in the Bergquist Selection Guide and enables packaging configurations not possible with standard PCB or ceramic substrates.

Bergquist Thermal Clad PCB vs Competing Substrate Technologies

Thermal Clad vs Generic Aluminum MCPCB

This comparison is the most important one for procurement decisions, because the market is full of generic aluminum MCPCB manufacturers whose products look identical to Bergquist Thermal Clad in dimension and construction but use generic 1–2 W/m-K dielectrics rather than Bergquist’s qualified ceramic-polymer system at 2.2–3.0 W/m-K. The gap in thermal resistance between a 2.2 W/m-K Bergquist dielectric and a 1 W/m-K generic dielectric at the same thickness is a factor of 2.2× — a power electronics designer who specifies Bergquist HT-04503 and receives a generic 1 W/m-K substitute has a board that runs significantly hotter than the thermal model predicted. Require a Certificate of Conformance with Bergquist/Henkel lot number traceability.

Thermal Clad vs Ceramic DBC

Parameter	Bergquist Thermal Clad (HT-04503)	Alumina DBC	AlN DBC
Dielectric Thermal Conductivity	2.2 W/m-K	24 W/m-K	180 W/m-K
Form Factor	Large panel, any shape, punched/routed	Ceramic tile, limited size	Ceramic tile
Mechanical Fragility	Ductile, impact-resistant	Brittle	Brittle
Current Carrying (Copper)	1–10 oz copper, high current	Limited by Cu thickness	Limited
Relative Cost	Medium	High	Very high
SMT Assembly Compatibility	Full SMT, reflow, wave	Limited	Limited
Multi-layer Capability	CML-11006 available	No standard	No standard

Ceramic DBC dominates at very high power density per unit area — bare SiC and GaN power semiconductors at 100+ W/cm² require the bulk thermal conductivity of AlN or alumina because no via compensation approach comes close to 180 W/m-K. For power densities below 30–50 W/cm² where mechanical robustness, large-format panels, SMT compatibility, and cost matter, Thermal Clad is the practical choice. The Bergquist Selection Guide explicitly includes “DBC Replacement” as a documented application area: Thermal Clad can replace large-area ceramic substrates and provides higher current carrying capability than thick-film ceramic technology.

Useful Resources for Bergquist Thermal Clad PCB Design and Procurement

Resource	Content	Link
Bergquist Thermal Clad Selection Guide (tjk.com.au)	Complete family specification table, dielectric selection logic, base metal selection, circuit design rules, assembly recommendations — the primary engineering reference for all Thermal Clad products	PDF
Bergquist Thermal Clad Selection Guide (Digikey)	Alternate hosted version with full family data	PDF
Bergquist HT-04503 TDS (Henkel/mclpcb)	Full individual TDS for the flagship 3 mil HT dielectric	PDF
Bergquist HT-07006 TDS (Henkel/mclpcb)	Full individual TDS for the 6 mil HT dielectric	PDF
Bergquist HPL-03015 TDS (Henkel/mclpcb)	Full TDS for the ultra-thin high-power LED dielectric	PDF
Bergquist MP-06503 TDS (Henkel/mclpcb)	Full TDS for the multi-purpose high-voltage 3 mil dielectric	PDF
Henkel Electronics Portal	Current product documentation, SDS sheets, technical support request	henkel.com/electronics
IPC-2221B	PCB design standard — creepage/clearance, trace width, via design	ipc.org
IPC-6012	Qualification standard for rigid PCBs including IMS	ipc.org
ASTM D5470	Standard test method for thermal conductivity of dielectric materials — basis for Thermal Clad thermal resistance specifications	astm.org
Digikey — Bergquist Thermal Clad	Stock, pricing, and panel ordering	digikey.com

FAQs: Bergquist Thermal Clad PCB

Q1: Can Bergquist Thermal Clad PCB be used with through-hole components, or is it SMT only?

Thermal Clad is fundamentally an SMT substrate — the metal base and the dielectric construction mean conventional plated-through holes (PTH) connecting circuit to base plate are not part of the standard process. The Bergquist Selection Guide shows (66) through-hole FETs as a documented application example, however, where through-holes are used as mounting holes rather than electrical plated-through connections. Components with leads can be soldered to surface pads, with the lead bent and the joint made at the surface. For designs requiring electrical connection from the circuit layer to the metal base plate, the selective dielectric removal process creates a direct-connect pad to the exposed metal. Full PTH with plated barrels connecting multiple circuit layers (as in standard FR-4 multilayer) is not applicable to standard single-layer Thermal Clad; it becomes relevant only in CML-11006 two-layer constructions where thermal vias are drilled and copper-plated through the interlayer.

Q2: What is the correct reflow solder profile for Bergquist Thermal Clad PCB, and does it differ from FR-4?

The reflow profile for Thermal Clad differs from FR-4 in one important way: the metal base acts as a heat sink during reflow, so the board heats up more slowly and more uniformly than an equivalent FR-4 board. This can require a longer preheat and soak stage in the reflow profile to bring the board and components to activation temperature before entering the reflow zone. For SAC305 (lead-free) assembly: use peak temperature of 245–260°C, staying within the solder limit of the specific Thermal Clad product (260°C for CML-11006 and LTI/MP products, 325°C for HT products — HT’s higher limit is relevant for AuSn die attach, not SAC305 reflow). Time above SAC305 liquidus (217°C) should be 30–60 seconds. The minimum solder thickness of 100 µm (0.004″) after reflow is a Thermal Clad-specific requirement that may mean specifying more solder paste than you would on FR-4. Solder paste volume recommendations from the stencil design should be reviewed with this 100 µm minimum in mind.

Q3: Why do some fabricators offer “Bergquist equivalent” IMS material? Is it actually equivalent?

“Bergquist equivalent” typically means a generic ceramic-polymer dielectric IMS product claimed to match Bergquist Thermal Clad’s specifications. In practice, there are three specific concerns. First, thermal conductivity verification: most generic IMS dielectrics are specified at 1.0–2.0 W/m-K, and unless the fabricator can provide third-party ASTM D5470 test data for the specific lot being used, the claim of equivalence is unverified. Second, UL recognition: Bergquist Thermal Clad has UL component recognition under specific file numbers — generic IMS materials may or may not have independent UL recognition, which matters if your product design uses the UL V-0 flammability and RTI ratings of the substrate in the safety certification file. Third, long-term reliability qualification: Bergquist’s 12–18 month qualification program (Q-6019) includes 2,000-hour thermal bias aging, 500-cycle temperature cycling (-40°C to 150°C), and comprehensive mechanical and electrical testing. Generic IMS materials may not have undergone equivalent qualification. If your design permits it and your supply chain requires it, request independent ASTM D5470 thermal conductivity data, UL recognition documentation, and reliability qualification data before accepting a “Bergquist equivalent” substitution.

Q4: How does Bergquist Thermal Clad PCB handle solder joint fatigue in thermally cycled applications?

Solder joint fatigue on Thermal Clad follows the same fundamental mechanism as on any PCB — CTE mismatch between the component and the substrate causes cyclic stress in the solder joint during thermal cycling, which accumulates as plastic deformation until cracks propagate through the joint. What is different about Thermal Clad relative to FR-4 is the CTE of the base metal: aluminum at 25 ppm/°C has a significantly higher CTE than the ceramic components (typically 4–8 ppm/°C for alumina packages) mounted on it. This mismatch is large, which means large devices with wide footprints (large passive components, ceramic capacitors, large-area power modules) are under significant cyclic stress. Bergquist’s mitigation strategies include: the 100 µm minimum solder thickness to provide a compliant joint that absorbs the CTE strain through plastic deformation rather than crack propagation; copper base option for CTE matching to ceramic components (copper at 17 ppm/°C is closer to alumina’s CTE); and Bond-Ply thermally conductive adhesive for bonding assemblies where solder joint fatigue from CTE mismatch is the dominant failure mechanism. For high thermal cycling applications (automotive, industrial with wide temperature swings), the base metal CTE must be factored into the solder joint life calculation explicitly.

Q5: What certifications and agency approvals do Bergquist Thermal Clad PCBs carry, and how do I reference them in my product safety file?

Bergquist Thermal Clad dielectrics have UL component recognition under specific UL file numbers. The relevant certifications are: UL 94 V-0 flammability for all Thermal Clad dielectrics; UL 746E Relative Thermal Index (RTI) ratings as published in the Selection Guide (130°C for LTI/MP/CML, 140°C for HT, 150°C for HT-09009); and UL recognition as a recognized component for use in Listed equipment. When referencing Thermal Clad in a UL or ETL product certification file, the correct approach is to cite the Bergquist UL file number for the specific dielectric being used. The Bergquist Thermal Clad Selection Guide directs readers to obtain current UL file information directly from Bergquist/Henkel, as UL recognition databases are updated continuously. Bergquist’s manufacturing facilities hold ISO 9001 certification, and the qualification program (Q-6019) provides the documented material performance basis for certifying bodies. Always verify current UL recognition status at the time of specification, as certification details can change between guide revisions and product updates.

Conclusion: Matching Bergquist Thermal Clad PCB to Your Application

The Bergquist Thermal Clad PCB family covers the full spectrum of thermally managed power electronics substrate requirements with a portfolio of nine products across five dielectric families. The selection logic is disciplined: operating temperature first (HT if above 130°C, LTI or MP below 130°C, HPL for high-power LED), then voltage isolation (3 mil for standard industrial, 5–6 mil for higher voltages, 9 mil for the highest isolation), then thermal performance within the qualified family (LTI/HT at 2.2 W/m-K, MP at 1.3 W/m-K, HPL at 3.0 W/m-K), then assembly process (HT required for AuSn and gold wire bond).

The consistent performance advantage over FR-4 — 15× lower thermal resistance at the same 3 mil dielectric thickness — is not incremental. It is the difference between a design that requires complex heatsink hardware and manual assembly, and one that delivers the same or better thermal management through a directly soldered, automated SMT assembly. Combined with Bergquist’s 12–18 month qualification program, ISO 9001 manufacturing, UL component recognition, and a global fabrication and distribution network, Thermal Clad is the industrial standard for power electronics IMS substrates.