If you’re designing a high-power LED board and you’re still trying to manage junction temperatures with copper pours and thermal vias on FR4, you’re fighting the material instead of working with it. Standard FR4 has a thermal conductivity of roughly 0.25–0.35 W/m-K. The dielectric layer in Bergquist HPL-03015 delivers 3.0 W/m-K — nearly ten times better — at a thickness of just 38 µm (1.5 mil). That combination of ultra-thin dielectric and high conductivity is what makes HPL-03015 the go-to MCPCB material for lighting engineers who need to extract every degree of thermal headroom from their design.

This guide covers the full verified specifications from the official Henkel Bergquist Technical Data Sheet, a thorough comparison against other Thermal Clad materials, practical design and fabrication guidance, and an honest picture of where HPL-03015 excels and where it doesn’t.

What Is Bergquist HPL-03015?

The Bergquist HPL-03015 is a High Power Lighting (HPL) dielectric in Henkel’s Thermal Clad metal core PCB family. It is an insulated metal substrate (IMS) material specifically engineered for high-density LED applications where achieving the lowest possible thermal resistance is the primary design constraint.

The part number follows the same Thermal Clad naming convention: “03” encodes a nominal 3-mil dielectric specification class, and “015” refers to the thermal resistance of 0.015 °C-in²/W — though the measured value on the datasheet is 0.02 °C-in²/W (0.13 °C-cm²/W). Understanding this shorthand helps you compare HPL-03015 directly to other Thermal Clad products at a glance.

The Three-Layer Construction of HPL-03015

Like all Thermal Clad IMS products, the HPL-03015 is a three-layer composite in its base form:

Copper circuit layer — The top layer, available in standard copper weights (1 oz or 2 oz), carries the circuit pattern. It is patterned by standard subtractive etch processes.

Proprietary dielectric layer — This is where the material’s value lives. The HPL dielectric is a polymer-ceramic composite blend, engineered to conduct heat phonons efficiently while maintaining electrical isolation. At just 0.0015″ (38 µm), it is the thinnest dielectric in the Bergquist Thermal Clad line. The ceramic filler concentration is higher than in standard Thermal Clad dielectrics, which drives up thermal conductivity while slightly increasing dielectric constant.

Aluminum base layer — The structural foundation of the board, typically 1.0 mm or 1.6 mm thick, using 5052 or 1100 alloy aluminum. This layer acts simultaneously as a heat spreader and mechanical support. It can be directly attached to a heatsink, enclosure wall, or luminaire housing without any additional thermal interface material between the PCB and the cooling structure in many designs.

Bergquist HPL-03015 Complete Specifications

All values below are taken directly from the official Bergquist / Henkel Technical Data Sheet (PDS_HPL_0414) and the Reliance EMS TDS archive.

Thermal Properties

Property	Value	Test Method
Product Thermal Conductivity	7.5 W/m-K	MET 5.4-01-40000
Dielectric Thermal Conductivity	3.0 W/m-K	ASTM D5470
Thermal Resistance	0.02 °C-in²/W (0.13 °C-cm²/W)	ASTM D5470
Thermal Impedance	0.30 °C/W	MET-5.4-01-40000
Glass Transition Temperature (Tg)	185°C	ASTM E1356
Maximum Operating Temperature	140°C	UL 796
Maximum Soldering Temperature	325°C	UL 796

Important note on the two thermal conductivity figures: The 7.5 W/m-K product value is the system-level measurement that includes the aluminum base metal and copper foil in the thermal path. The 3.0 W/m-K dielectric-only value is what matters for calculating thermal resistance in your design — the dielectric is always the thermal bottleneck. Use 3.0 W/m-K for your junction-to-case calculations, not 7.5.

Electrical Properties

Property	Value	Test Method
Dielectric Constant	6.6	ASTM D150
Dissipation Factor @ 1 kHz	0.003	ASTM D150
Dissipation Factor @ 1 MHz	0.005	ASTM D150
Capacitance	925 pF/in² (140 pF/cm²)	ASTM D150
Volume Resistivity	10¹⁴ Ω·m	ASTM D257
Surface Resistivity	10¹³ Ω/sq	ASTM D257
Dielectric Strength	2000 V/mil (75 kV/mm)	ASTM D149
Breakdown Voltage	5.0 kVAC	ASTM D149

Operating Voltage Ratings

Voltage Type	Rating
Continuous AC	120 VAC
Continuous DC	170 VDC
Peak Recurring	260 VDC

Mechanical Properties

Property	Value	Test Method
Dielectric Thickness	0.0015″ (38 µm / 1.5 mil)	Visual
Color	Off-white	Visual
Peel Strength @ 25°C	5 lb/in (0.9 N/mm)	ASTM D2861
CTE XY/Z Axis Below Tg	35 µm/m·°C	ASTM D3386
CTE XY/Z Axis Above Tg	85 µm/m·°C	ASTM D3386
Storage Modulus @ 25°C	18 GPa	ASTM D4065
Storage Modulus @ 150°C	12 GPa	ASTM D4065

Chemical Properties

Property	Value	Test Method
Water Vapor Retention	0.11 wt%	ASTM E595
Out-Gassing Total Mass Loss	0.15 wt%	ASTM E595
Collect Volatile Condensable Material	<0.01 wt%	ASTM E595

Agency Ratings and Compliance

Property	Value	Standard
UL Maximum Operating Temperature	140°C	UL 796
UL Flammability Rating	V-0	UL 94
Comparative Tracking Index (CTI)	0 / 600	ASTM D3638 / IEC 60112
Solder Limit Rating	325°C for 60 seconds	UL 796
RoHS Compliance	Yes	—
Lead-Free Solder Compatible	Yes	—
Eutectic AuSn Compatible	Yes	—

Key Specification Callouts for Designers

The 5.0 kVAC breakdown voltage is the most important limitation to internalize before selecting HPL-03015. Compared to HT-07006 at 11 kVAC, HPL-03015 offers just under half the isolation headroom. The trade-off for that lower voltage rating is dramatically better thermal performance. For 120 VAC mains-connected LED driver circuitry with proper clearance and creepage distances, 5.0 kVAC is typically sufficient. For industrial motor drives or solid-state relays operating at higher bus voltages, it is not.

The 185°C Tg is the highest in the standard Thermal Clad lineup, which is counterintuitive given that the material is rated for only 140°C maximum continuous operation. The gap exists because UL 796 rates maximum operating temperature conservatively relative to Tg. The 185°C Tg means the dielectric has excellent thermal stability through the 140°C rated range with meaningful margin — it won’t soften or lose adhesion at rated conditions the way a lower-Tg material would.

The 0.9 N/mm peel strength is noticeably lower than the 1.1 N/mm in the HT series. This is a direct consequence of the ultra-thin dielectric. Thinner adhesive bond line means less mechanical peel resistance. In practice, HPL-03015 peel strength is sufficient for standard surface mount assembly and reflow, but it is something to be aware of if your assembly process involves aggressive handling or rework.

HPL-03015 vs. Other Bergquist Thermal Clad Dielectrics

This is the comparison table that should drive your material selection conversation with your fabricator:

Parameter	MP-06503	HT-04503	HPL-03015	HT-07006	HT-09009
Dielectric Thickness	3 mil / 76 µm	3 mil / 76 µm	1.5 mil / 38 µm	6 mil / 152 µm	9 mil / 229 µm
Dielectric Thermal Conductivity (W/m-K)	1.3	2.2	3.0	2.2	2.2
Product Thermal Conductivity (W/m-K)	—	—	7.5	4.1	—
Thermal Resistance (°C-cm²/W)	0.65	0.45	0.13	0.71	0.90
Breakdown Voltage (kVAC)	8.5	8.5	5.0	11.0	20.0
Glass Transition Temp. Tg (°C)	90	150	185	150	150
Max Operating Temp. (°C)	130	140	140	140	150
Peel Strength (N/mm)	1.6	1.1	0.9	1.1	1.1
CTE Below Tg (µm/m·°C)	—	25	35	25	25
Primary Use Case	General LED, consumer	High-power, industrial	High-density LED	Isolated power, relays	Very high isolation

What jumps out immediately: HPL-03015 has the lowest thermal resistance of any standard Thermal Clad product — 0.13 °C-cm²/W versus 0.45 for HT-04503 and 0.71 for HT-07006. This is achieved through a combination of thinner dielectric (half the thickness of the HT series) and higher dielectric thermal conductivity (3.0 vs. 2.2 W/m-K). The trade-off is isolation voltage: at 5.0 kVAC, HPL-03015 is the lowest in the family.

The highest Tg (185°C) combined with the lowest thermal resistance is what makes HPL-03015 uniquely suited for high-power LED applications. More LED watts mean more heat, which pushes dielectric temperatures higher. You want a material whose Tg margin is as wide as possible above the actual dielectric operating temperature — and HPL-03015 delivers the best of both metrics simultaneously.

When to Use Bergquist HPL-03015 in Your LED PCB Design

High-Watt-Density LED Arrays

This is HPL-03015’s home turf. Any LED array exceeding approximately 5–10 W/cm² of surface power density will generate junction temperatures on FR4 that force you to either derate the LEDs, add external heatsinking that increases system cost and size, or accept shortened LED lifespan. HPL-03015’s 0.13 °C-cm²/W thermal resistance reduces the temperature rise across the dielectric to a fraction of what FR4 or even standard IMS materials produce. For a 10 W device on a 10 cm² footprint, that difference can translate to a 30–50°C lower die temperature compared to FR4 with thermal vias — directly translating to longer L70 lumen maintenance life.

Automotive Exterior Lighting

Automotive headlamps, daytime running lights (DRL), and rear combination lights are among the most thermally stressed LED applications. Under-hood and front-fascia ambient temperatures can reach 85–105°C continuously, and LED packages in these fixtures must maintain consistent luminous flux over 15,000+ hours. HPL-03015’s 185°C Tg and 140°C maximum operating temperature give adequate thermal margin in most automotive exterior lighting thermal budgets. The material is also eutectic AuSn compatible, making it suitable for die-attach processes used in automotive-grade LED modules.

High-Bay Industrial Luminaires and Street Lighting

Industrial high-bay luminaires running 200–600W LED arrays present one of the most challenging thermal environments in the lighting industry. Enclosure temperatures are often elevated, airflow is limited, and thermal cycling from on/off switching stresses the dielectric repeatedly over years of service. HPL-03015’s combination of low thermal resistance and high Tg produces a design that runs cooler under continuous load and survives more thermal cycles than standard IMS materials before dielectric microcracking and adhesion degradation become reliability issues.

Projector and Display Backlighting

Projector lamp replacement with high-power LED engines requires extremely dense LED packing with managed thermal uniformity. Backlight applications for large-format displays share the same requirements: high heat flux in a constrained area, with tight tolerances on operating temperature to maintain color consistency and flux stability. HPL-03015’s thin dielectric geometry also means lower capacitance variation across the board area, which helps in applications where consistent electrical impedance matters.

Headlamp and Specialty Lighting Applications

Beyond automotive, HPL-03015 is regularly specified for marine, aviation, and military lighting applications where luminaires operate in elevated ambient environments and are expected to deliver long service intervals without thermal-degradation failures.

When HPL-03015 Is Not the Right Material

Being specific about the limits of a material is as important as understanding its strengths.

Application	Why HPL-03015 Is Wrong for This Job	Better Alternative
Motor drives and solid-state relays	5.0 kVAC breakdown is insufficient for high-bus-voltage isolation	Bergquist HT-07006 (11 kVAC)
High-voltage power conversion (>120 VAC)	Continuous AC voltage rating is only 120 VAC	HT-07006 or HT-09009
Multi-layer routing boards	HPL-03015 is a single-dielectric IMS; multilayer not standard	HT-09009 multi-layer configurations
General-purpose LED (low watt density)	Cost premium not justified; thermal margin isn’t the bottleneck	MP-06503 or standard FR4
Extreme-isolation military/aerospace power	5.0 kVAC breakdown is marginal	HT-09009 (20 kVAC), Arlon PCB CE/BT systems
RF or high-frequency signal circuits	Dk of 6.6 and Df of 0.005 at 1 MHz are unsuitable for GHz-range signals	Rogers RO4003C, RO4350B

HPL-03015 PCB Design Considerations

Thermal Resistance Calculation in Practice

The standard junction-to-ambient thermal model for an LED on HPL-03015 on an aluminum chassis follows this chain:

θ(total) = θ(j-s) [package] + θ(dielectric) [HPL-03015] + θ(base-metal) [Al] + θ(mounting interface) + θ(heatsink)

The HPL-03015 contribution (θ dielectric) at 0.13 °C-cm²/W is typically the smallest resistive element in this chain when the board is properly mounted. In many direct-mount configurations to aluminum extrusions or housings, the mounting interface can actually become the dominant thermal resistance — making proper mounting surface finish and contact pressure as important as the PCB material selection itself.

Pad Layout and Thermal Pad Design

Because the dielectric layer is only 38 µm thick, the thermal footprint of an LED’s thermal pad directly drives heat into the aluminum base very efficiently. There’s less lateral spreading in the dielectric itself — the heat path is highly directional. This means you don’t need large copper spreading areas under LED packages to achieve good thermal performance. The aluminum base distributes the heat laterally once it passes through the dielectric. Design your copper thermal pads to match the package recommendations from the LED manufacturer, then let the base metal do the spreading work.

Copper Weight Selection

Standard copper weights for HPL-03015 are 1 oz (35 µm) and 2 oz (70 µm). For LED arrays with individual device currents under 1A at standard trace widths, 1 oz is sufficient. For designs running multi-amp LED strings or high-current bus traces, 2 oz copper reduces I²R heating in the circuit layer, which compounds nicely with the thermal performance of the dielectric. The base metal also helps, as heat generated in copper traces conducts down through the dielectric into the aluminum almost as efficiently as heat from the LED packages themselves.

Surface Finish Compatibility with HPL-03015

Surface Finish	Compatible	Notes
HASL (Lead-Free)	Yes	Most common; good for through-hole and SMD
ENIG	Yes	Preferred for fine-pitch LED packages and wire bonding
Immersion Silver	Yes	Good solderability; check shelf life for LED assembly
OSP	Yes	Lowest cost; 12-month shelf life typically
Hard Gold	Yes	For edge contacts and connectors on same panel
Eutectic AuSn	Yes	325°C solder limit directly supports 280°C AuSn process

Assembly and Solder Process Notes

HPL-03015 is fully compatible with lead-free SAC305 reflow at standard peak temperatures of 245–260°C — well below the 325°C solder limit. The thin dielectric requires slightly more care during rework because local heating during hot-air rework can cause localized delamination if the heat dwell time is excessive. Standard rework practice for MCPCB applies: use a regulated rework station, minimize dwell time, and pre-warm the board before component removal.

For high-volume LED assembly using pick-and-place reflow, HPL-03015 processes like any standard aluminum MCPCB. The solder mask is typically white (to improve LED lumen extraction via reflection), though black solder mask is available for applications where contrast between the board and LED is needed. Confirm your fabricator’s solder mask ink compatibility with the HPL dielectric surface before specifying unusual solder mask colors.

Aluminum Base Thickness Options

The aluminum base is typically available in 1.0 mm, 1.2 mm, 1.6 mm, and 2.0 mm standard thicknesses. The choice depends on mechanical rigidity requirements, thermal spreading performance, and how the board mounts into its enclosure:

Base Thickness	Application Context	Notes
1.0 mm	Compact luminaires, strip LED modules	Lighter; may require support features for large panel formats
1.2 mm	Standard LED downlights, retrofit modules	Common balance of weight and rigidity
1.6 mm	High-power arrays, commercial lighting engines	Most common specified thickness
2.0 mm	Industrial high-bay, heavy-duty luminaires	Maximum rigidity; best thermal spreading for large boards

HPL-03015 vs. FR4 with Thermal Vias: The Real Comparison

The argument for using FR4 with copper-filled thermal vias on LED boards comes down to familiarity and cost. It’s a valid approach for low-power LEDs. But let’s quantify the thermal difference at higher power levels.

Parameter	FR4 (0.25 W/m-K) with Thermal Vias	HPL-03015 (3.0 W/m-K dielectric)
Effective dielectric conductivity	~0.6–1.0 W/m-K (with vias)	3.0 W/m-K (uniform)
Thermal resistance (typical LED pad)	~5–15 °C/W depending on via density	~0.3–0.8 °C/W
Thermal uniformity across array	Variable (hot spots between vias)	Uniform (continuous dielectric)
Junction temperature rise at 5W per LED	~20–50°C above board	~3–6°C above board
Heatsink required	Typically yes, often large	Often reduced or eliminated
Board fabrication complexity	High (via drilling, filling, plating)	Low (standard MCPCB process)
Material cost (bare laminate)	Lower	Higher

For anything above 3W per LED in a dense array, the thermal via approach on FR4 loses the cost argument because the system cost of the heatsink and the reduced LED lifetime more than compensate for the higher material cost of HPL-03015.

Useful Resources for Bergquist HPL-03015 Designs

These references belong in your library if you are evaluating or qualifying HPL-03015 for a design:

Official HPL-03015 TDS (MCL PCB hosted) — Full technical data sheet with all measured properties: https://www.mclpcb.com/wp-content/uploads/2021/05/Bergquist-HPL-03015.pdf

Bergquist Thermal Clad Selection Guide (Mouser hosted) — Complete dielectric comparison table and thermal impedance charts: https://www.mouser.com/catalog/additional/Bergquist_PDS_HPL_0414%20v6.pdf

Henkel Electronics Product Portal — Current product availability, SDS documents, and regional contacts: https://www.henkel-adhesives.com/us/en/products/thermal-management.html

Digikey HPL-03015 Listing — Distributor availability and cross-reference: https://www.digikey.com (search: “HPL-03015 Bergquist”)

ASTM D5470 — Standard Test Method for Thermal Transmission Properties of Thermally Conductive Electrical Insulation Materials (the basis for the thermal resistance figures in the TDS): https://www.astm.org/d5470-17.html

IPC-2221B — Generic Standard on Printed Board Design (covers IMS design rules): https://www.ipc.org/ipc-2221

US DOE EERE Solid-State Lighting Program — LED thermal management resources and application guides: https://www.energy.gov/eere/ssl/solid-state-lighting

GlobalSpec HPL-03015 Datasheet Archive — Secondary archive of HPL specifications: https://datasheets.globalspec.com/ds/4336/HenkelElectronics/84D18505-B814-46F3-873F-D7E744FB83D1

Frequently Asked Questions About Bergquist HPL-03015

Q1: What is the difference between Bergquist HPL-03015 and HT-04503?

Both are high-performance Thermal Clad IMS dielectrics for high-temperature applications, but they target different design requirements. HPL-03015 is thinner (38 µm vs. 76 µm for HT-04503), has higher dielectric thermal conductivity (3.0 vs. 2.2 W/m-K), lower thermal resistance (0.13 vs. 0.45 °C-cm²/W), and a higher Tg (185 vs. 150°C). The trade-off is that HPL-03015 has lower breakdown voltage (5.0 vs. 8.5 kVAC) and lower peel strength (0.9 vs. 1.1 N/mm). HPL-03015 is the right choice when maximum thermal performance and LED lifespan extension is the priority. HT-04503 is better when you need higher isolation voltage along with good thermal performance, such as in motor drives or power supplies where the LED circuit is not isolated by other means.

Q2: Can Bergquist HPL-03015 be used for non-LED applications like power MOSFETs and IGBTs?

Technically yes, but with important caveats. The 5.0 kVAC breakdown voltage limits HPL-03015 to applications operating from relatively low bus voltages — 120 VAC and 170 VDC continuous are the rated operating voltages. Many power conversion designs exceed these levels, which makes HT-07006 or HT-09009 more appropriate. For low-voltage, high-current DC applications like synchronous buck converters or low-voltage motor drives where device isolation requirements are modest, HPL-03015’s thermal performance does benefit power semiconductor applications. Always verify the isolation requirements of your specific circuit before specifying HPL-03015 outside of its LED-optimized use case.

Q3: Is the 7.5 W/m-K or 3.0 W/m-K figure the correct thermal conductivity to use for design calculations?

Use 3.0 W/m-K for all thermal resistance calculations in your design. The 7.5 W/m-K product thermal conductivity is a system-level measurement (MET 5.4-01-40000 test method) that includes the aluminum base and copper foil contributions to the overall thermal conductivity. For engineering thermal resistance models, the dielectric-only value of 3.0 W/m-K (measured by ASTM D5470) accurately represents the resistive element you are designing around. The 7.5 W/m-K figure is useful for comparing Bergquist HPL-03015 against competing IMS products where system-level conductivity is the reported metric, but it should never be plugged directly into a dielectric-specific thermal resistance calculation.

Q4: How does HPL-03015’s 185°C Tg affect long-term reliability in LED applications?

Very positively. The 45°C margin between the 140°C maximum operating temperature (UL 796) and the 185°C Tg means the dielectric is always operating well below its transition point during rated continuous use. In FR4 and lower-Tg IMS materials, the dielectric closer to its Tg accelerates polymer chain relaxation and microcracking under repeated thermal cycling, which eventually leads to adhesion loss, delamination, and increased thermal resistance at the LED thermal pad interface. HPL-03015’s wide Tg margin slows this aging mechanism significantly, contributing directly to the extended LED lumen maintenance life that Bergquist positions as a core benefit of the Thermal Clad line.

Q5: What fabricators in China and globally can manufacture PCBs using Bergquist HPL-03015?

HPL-03015 panels and fabricated boards are available through MCPCB-specialized manufacturers globally. In China, companies including Andwin Circuits and Beijing Ruikai Electronic (who maintain a Bergquist Thermal Clad distribution relationship) regularly produce HPL-03015-based boards. In North America and Europe, MCPCB shops that work with the full Bergquist Thermal Clad lineup typically stock HPL-03015 or can source it through Henkel’s distribution channel via Digikey, Arrow, or Mouser. Lead times for prototype quantities are typically 5–10 business days; production runs 2–4 weeks, varying by region. When qualifying a new fabricator for HPL-03015, ask specifically for IPC Class 2 or Class 3 process qualification, material traceability documentation, and confirm they have process validation data for the HPL dielectric — not all MCPCB shops are equally experienced with the ultra-thin 38 µm dielectric layer.

Summary: Is Bergquist HPL-03015 the Right Choice for Your LED PCB?

The HPL-03015 earns its specification when three conditions are present: your LED power density is high enough that thermal management is genuinely the design constraint, your isolation voltage requirement is met by 5.0 kVAC and 120 VAC continuous operating voltage, and the thermal performance improvement justifies the material cost premium over standard FR4 or lower-grade IMS materials.

For high-power luminaire manufacturers, automotive LED module designers, and anyone building a lighting system where LED lifespan and lumen maintenance are commercial differentiators, HPL-03015 delivers a measurable technical advantage that compounds across the product lifetime. Lower dielectric operating temperature, better Tg margin, and reduced thermal resistance to the aluminum heat spreader all translate directly into longer-lasting, more efficient LED products.

The specification decision is straightforward once you run the thermal numbers. If the temperature delta across the dielectric is your performance bottleneck, HPL-03015 is the most effective standard IMS solution available in the Bergquist lineup.