Bergquist HPL-03015: Ultra-Thin High Power LED PCB Material Guide

There is a point in every high-power LED design where the thermal math stops working on MP-06503 or HT-04503. You’ve maximized copper weight, optimized the heatsink, reduced current, and the junction temperature is still too high. The problem isn’t the heatsink — it’s the dielectric. Every watt that has to travel through the dielectric layer is slowed by thermal resistance, and at 3 mil thickness, even Bergquist’s best HT formulation can only do so much.

That’s the engineering problem Bergquist HPL-03015 was built to solve. The HPL in the part number stands for High Power Lighting, and the 030 and 15 encode the key specification: 0.0015 inch, or 38 µm. Half the thickness of HT-04503’s 76 µm dielectric. The result is a thermal resistance of 0.02 °C·in²/W — one quarter that of HT-04503 — packed into an insulated metal substrate that still maintains a 185°C glass transition temperature, 3.0 W/m-K dielectric thermal conductivity, UL 94 V-0 flammability rating, and compatibility with lead-free and eutectic AuSn solder processes.

The tradeoff is voltage. At 38 µm, HPL-03015 is rated for 120 VAC continuous, 170 VDC continuous, and 260 VDC peak recurring. That is not a drawback for the LED lighting applications this material was designed for — it’s the right engineering tradeoff: maximum thermal performance in exchange for modest voltage capability, in an application domain where low-voltage LED current is the load and thermal management is the binding constraint.

This guide covers the complete HPL-03015 specifications, the applications it serves, the voltage and layout design rules you must follow to use it correctly, and the full context of where it fits in the Thermal Clad family.

What Is Bergquist HPL-03015? Engineering Context Before the Numbers

Bergquist PCB materials follow the same fundamental Thermal Clad architecture across every product: copper circuit foil on top, a glass-free polymer-ceramic dielectric in the middle, and an aluminum or copper metal base below. What differentiates HPL-03015 from every other Thermal Clad product is not a different dielectric chemistry — it is a different dielectric thickness strategy. Where the rest of the Thermal Clad family uses dielectric thicknesses from 3 mil to 9 mil to balance voltage isolation against thermal resistance, HPL-03015 presses the dielectric down to 1.5 mil (38 µm), accepting a lower voltage ceiling in exchange for thermal resistance so low it approaches the performance of direct-bond copper on alumina ceramic at a fraction of the cost.

The part number decoding: HPL = High Power Lighting formulation, 030 = Bergquist internal impedance class reference, 15 = 0.0015 inch (1.5 mil / 38 µm) dielectric thickness. The “030” designation — identical to the “045” in HT-04503 and “065” in MP-06503 — is a Bergquist internal reference tied to the thermal impedance class, not a standard numerical specification.

Bergquist introduced HPL-03015 as a dedicated product for the LED market, explicitly stating in the product TDS that it “introduces a new high thermal performance dielectric into its comprehensive Thermal Clad MCPCB line” and that HPL is “specifically formulated for high power lighting LED applications with demanding thermal performance requirements.” That focus is visible in every specification: every engineering choice in HPL-03015 prioritizes LED thermal performance within the voltage envelope of low-voltage LED systems.

Bergquist HPL-03015 Complete Datasheet Specifications

All values below are from the official Bergquist Thermal Clad HPL-03015 Technical Data Sheet (Bergquist / Henkel) fetched from the Henkel-authorized mclpcb.com PDF archive, cross-referenced with the earlier Bergquist TDS and Thermal Clad Selection Guide for operating voltage parameters.

HPL-03015 Thermal Properties

Parameter	HPL-03015 Value	Test Method
Product Thermal Conductivity	7.5 W/m-K	Bergquist 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	Bergquist 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 / 60 seconds	UL 796

The dielectric thermal conductivity of 3.0 W/m-K is the highest of any standard Thermal Clad product. In context: HT-04503 and HT-07006 achieve 2.2 W/m-K with their HT polymer-ceramic formulation, and MP-06503 reaches 1.3 W/m-K. HPL-03015 exceeds the HT family by 36% on dielectric thermal conductivity — but the more important number is the thermal resistance of 0.02 °C·in²/W, which is 2.5× lower than HT-04503 (0.05 °C·in²/W) and 4.5× lower than MP-06503 (0.09 °C·in²/W). That 2.5× advantage over HT-04503 is the core technical reason to use HPL-03015.

The product thermal conductivity of 7.5 W/m-K (measured by Bergquist’s internal MET method including copper foil and aluminum substrate) is more than 3× higher than the 2.4 W/m-K product thermal conductivity of MP-06503. As discussed in our MP-06503 guide, this figure should not be used for dielectric comparisons — but it does reflect the system-level thermal conductance improvement that the ultra-thin dielectric and higher dielectric conductivity combine to deliver.

The glass transition temperature of 185°C is the highest of any Thermal Clad product — higher than the HT family at 150°C and MP-06503 at 90°C. This is somewhat counterintuitive: HPL-03015 is a low-voltage dielectric, but it achieves the best thermal aging stability in the family. The 185°C Tg means that the dielectric maintains its glassy mechanical state through virtually any LED application operating environment, and the storage modulus remains high (18 GPa at 25°C, 12 GPa at 150°C) even at temperatures that would push MP-06503 well into its elastomeric state. CTE below Tg is 35 µm/m·°C — lower than MP-06503 (40 µm/m·°C) and comparable to HT-04503 (25 µm/m·°C).

HPL-03015 Electrical Properties and Operating Voltage Limits

Parameter	HPL-03015 Value	Test Method
Dielectric Constant (Dk)	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	2,000 V/mil (75 kV/mm)	ASTM D149
AC Breakdown Voltage	5.0 kVAC	ASTM D149

The breakdown voltage of 5.0 kVAC requires careful interpretation. The dielectric strength of 2,000 V/mil is impressive — it means the 1.5 mil dielectric can theoretically withstand 3,000 V. In practice, the working voltage must be substantially lower than breakdown due to voltage derating factors, defect probability, and safety margins. Bergquist’s published operating voltage limits for HPL-03015 in the earlier TDS version are specific and must be observed:

Voltage Mode	HPL-03015 Continuous Limit
Continuous AC	120 VAC
Continuous DC	170 VDC
Peak Recurring	260 VDC

These are not conservative suggestions — they are the published working voltage limits for continuous operation on HPL-03015. The 120 VAC continuous limit means HPL-03015 is appropriate for LED driver output circuits, low-voltage DC power rails feeding LED strings, and LED arrays on the output side of isolated drivers — but not for PCBs where the aluminum base may be at chassis potential with mains-referenced conductors on the circuit layer. Designs where the circuit layer operates at mains voltage (230 VAC, 277 VAC, 480 VAC) must not use HPL-03015 as the substrate dielectric.

The capacitance of 140 pF/cm² is by far the highest in the Thermal Clad family (compare to HT-04503 at 85 pF/cm² and HT-07006 at 43 pF/cm²). This is a direct consequence of the 38 µm dielectric thickness — capacitance increases inversely with thickness, and at 1.5 mil versus 3 mil, the capacitance doubles. In LED lighting circuits where operating frequencies are low (PWM dimming at 400–1000 Hz, or DC operation), this is not a functional concern. In switching power supply designs where the substrate capacitance can couple switching noise to the chassis, the higher capacitance of HPL-03015 would be a design consideration — another reason this material belongs on the LED side of an isolated driver topology, not the mains primary side.

HPL-03015 Mechanical Properties

Parameter	HPL-03015 Value	Test Method
Color	Off-white	Visual
Dielectric Thickness	0.0015″ (38 µm)	Visual
Peel Strength @ 25°C	5 lb/in (0.9 N/mm)	ASTM D2861
CTE (XY/Z, below Tg)	35 µm/m·°C	ASTM D3386
CTE (XY/Z, above Tg)	85 µm/m·°C	ASTM D3386
Storage Modulus @ 25°C	18 GPa	ASTM D4065
Storage Modulus @ 150°C	12 GPa	ASTM D4065

The peel strength of 0.9 N/mm (5 lb/in) is the lowest in the Thermal Clad family — compared to 1.1 N/mm for HT-04503 and 1.6 N/mm for MP-06503. This reflects the challenge of achieving high bond strength with an ultra-thin dielectric layer: there is simply less polymer-ceramic material adhering the copper foil to the aluminum base. The lower peel strength does not typically cause issues in LED assembly using standard reflow processes, but it does mean HPL-03015 is more sensitive to mechanical stress — aggressive depaneling methods, board bending, and improper handling can delaminate the thin dielectric if the process isn’t controlled. Fabricators experienced with HPL-03015 will know this and adjust their handling procedures accordingly.

HPL-03015 Chemical Properties

Parameter	HPL-03015 Value	Test Method
Water Vapor Retention	0.11% wt.	ASTM E595
Outgassing Total Mass Loss (TML)	0.15% wt.	ASTM E595
Collected Volatile Condensable Material (CVCM)	< 0.01% wt.	ASTM E595

HPL-03015 achieves the best outgassing performance of any standard Thermal Clad dielectric. At 0.15% TML, it is lower than HT-07006 (0.23%), MP-06503 (0.29%), and HT-04503. For standard LED luminaire applications, outgassing is rarely a design constraint, but for sealed optics, clean room lighting, or LED systems in precision optical instruments where condensable volatile materials could fog lenses or contaminate optical surfaces, HPL-03015’s low outgassing is a useful secondary specification advantage.

HPL-03015 Agency Ratings

Parameter	HPL-03015 Value	Standard
UL Maximum Operating Temperature	140°C	UL 796
UL Flammability	V-0	UL 94
Comparative Tracking Index (CTI) — ASTM	0	ASTM D3638
Comparative Tracking Index (CTI) — IEC	600	IEC 60112
UL Solder Limit Rating	325°C / 60 seconds	UL 796
Lead-Free Compatible	Yes	—
AuSn Eutectic Compatible	Yes	—
RoHS Compliant	Yes	—

CTI 600 under IEC 60112 gives HPL-03015 Material Group I classification — the same as HT-04503 and HT-07006 — providing the best possible tracking resistance for creepage distance calculations in safety-certified products. The 325°C/60-second solder limit enables AuSn die attach, which is relevant for bare-die COB (Chip-on-Board) LED assemblies where direct die mounting on HPL-03015 provides the lowest possible thermal resistance from LED junction to substrate.

Where HPL-03015 Sits in the Complete Thermal Clad Family

Full Family Comparison: Performance vs Voltage Capability

Parameter	HPL-03015	MP-06503	HT-04503	HT-07006	HT-09009
Dielectric Thickness	1.5 mil / 38 µm	3 mil / 76 µm	3 mil / 76 µm	6 mil / 152 µm	9 mil / 229 µm
Dielectric Thermal Cond. (W/m-K)	3.0	1.3	2.2	2.2	2.2
Thermal Resistance (°C·in²/W)	0.02	0.09	0.05	0.11	0.16
Thermal Impedance (°C/W)	0.30	0.65	0.45	0.70	0.90
Breakdown Voltage (kVAC)	5.0	8.5	6.0–8.5	11.0	20.0
Continuous AC Working Voltage	120 VAC	~300 VAC	~480 VAC	~480 VAC+	~1000 VAC+
Dielectric Constant (Dk)	6.6	6	7	7	7
Glass Transition Tg (°C)	185	90	150	150	150
UL Max Operating Temp (°C)	140	130	140	140	150
Capacitance (pF/cm²)	140	65	85	43	—
Peel Strength (N/mm)	0.9	1.6	1.1	1.1	1.1
Outgassing TML	0.15%	0.29%	—	0.23%	—
AuSn Compatible	Yes	Yes	Yes	Yes	Yes

HPL-03015’s position in this table tells the complete selection story: it occupies the top-left corner on thermal performance and the bottom-left corner on voltage capability. When those two vectors align with your design — maximum thermal efficiency at low working voltage — HPL-03015 is the right specification. When voltage requirements exceed 120 VAC, the rest of the family handles it with progressively thicker dielectrics.

Bergquist HPL-03015 Applications: Where Ultra-Thin Dielectric Changes the Design

High-Power COB LED Modules and Chip-on-Board Assemblies

Chip-on-Board LED assemblies mount bare LED dice directly on the substrate — no package, no lead frame, just die-to-substrate direct attach followed by wire bonding. Thermal resistance in standard packaged LEDs includes the junction-to-solder-point thermal resistance of the package itself, which can be 2–10 °C/W depending on package type. In COB on HPL-03015, that package thermal resistance is eliminated: the die sits directly on the copper circuit layer, solder-attached or epoxy-attached, with only the HPL-03015 dielectric between the die and the aluminum heatsink base. The total junction-to-heatsink thermal resistance drops dramatically.

COB LED engines for high-bay industrial lighting, stadium floodlights, grow light arrays, and architectural spot lighting use HPL-03015 as the standard substrate for premium performance modules. The combination of the 185°C Tg (which stabilizes the substrate mechanically even as LED junctions operate at 100–130°C), the 0.02 °C·in²/W thermal resistance, and the AuSn solder compatibility for highest-reliability die attach makes HPL-03015 the platform choice for COB LED modules that need to maintain lumen output over a 50,000+ hour product lifetime.

Automotive Headlamp LED Modules

Automotive LED headlamp assemblies are among the most demanding LED thermal management environments. Headlamp assemblies operate at high ambient temperatures (up to 85°C under hood), in a confined space with limited airflow, driving high-luminance LEDs continuously during night driving. LED junction temperatures in headlamp modules directly affect lumen output (lower junction = higher flux) and L70 lifetime. The Bergquist TDS explicitly lists “Headlamps” as an application for HPL-03015, which is notable — it is one of the few Thermal Clad products with headlamp listed directly.

In a projector-style or matrix LED headlamp module, LED dies or packaged LEDs are mounted on HPL-03015 on an aluminum heat spreader, with the aluminum base in thermal contact with the headlamp housing. The 140°C UL maximum operating temperature rating of HPL-03015 covers the operating envelope, and the 185°C Tg ensures the dielectric stays in its glassy state even under worst-case thermal events. Lead-free and AuSn solder compatibility satisfies AEC-Q requirements for automotive assembly processes.

High-Intensity LED Backlighting for Large-Format Displays and Projectors

Direct-lit LED backlighting for large LCD displays (commercial signage, video walls, cinema screens) and high-lumens projector light engines drives LEDs at high current density with tight thermal management requirements. Color uniformity and long-term lumen maintenance in display applications depend directly on keeping LED junction temperatures controlled, making the substrate thermal resistance one of the primary specifications. HPL-03015 is listed in the Bergquist TDS under both “Backlighting” and LED applications, and its 0.30 °C/W thermal impedance means that a 5 W LED die in a 1 cm² footprint produces only 1.5°C of temperature rise across the dielectric — a fraction of what alternative MCPCB substrates deliver.

Concentrator Photovoltaic (CPV) and Solar Cell Assemblies

High-concentration PV uses optical systems to focus sunlight at 100–1000× concentration onto tiny, high-efficiency III-V solar cells. These cells generate enormous current density at a few volts — exactly the operating voltage profile that HPL-03015’s 170 VDC continuous limit covers. The thermal load on the CPV cell mount substrate is severe, and the aluminum IMS base integrates directly with the CPV module’s cooling system. HPL-03015’s extreme thermal performance (0.02 °C·in²/W) and low outgassing make it a natural fit for CPV receiver substrates.

LED Street Lighting Premium Modules

While MP-06503 handles the cost-sensitive mainstream LED streetlight market, HPL-03015 is specified for premium high-power streetlight modules where maximum LED efficacy and maintained output over the luminaire lifetime are priorities. At the driver current levels used in modern 150–250 W streetlight modules, the difference in junction temperature between MP-06503 and HPL-03015 as the substrate can be 8–15°C — enough to push a design from marginal to comfortable in the thermal budget, or to allow a higher drive current (higher lumens per fixture) with the same thermal headroom.

HPL-03015 Design Tips: Using Ultra-Thin Dielectric Correctly

The Non-Negotiable Voltage Rule

Every HPL-03015 design must be evaluated against the published operating voltage limits before any other design work begins. The Bergquist operating voltage specification is:

120 VAC continuous / 170 VDC continuous / 260 VDC peak recurring

These are not suggestions. At 38 µm dielectric thickness, voltage gradients across the dielectric are steep — the 5.0 kVAC breakdown voltage provides theoretical headroom, but real-world operation at elevated temperatures, after thermal cycling, and in the presence of humidity requires the working voltage margin that these limits encode. Any design that places the circuit layer at a potential above 120 VAC relative to the aluminum base (which is typically at chassis or heatsink potential) should not use HPL-03015. Mains-referenced circuit traces on an HPL-03015 substrate are a safety violation.

LED Current Feed and Circuit Topology

For a standard isolated LED driver topology — mains input, isolated transformer, constant-current LED output — the HPL-03015 LED board lives entirely on the output side of the isolation barrier. The LED string voltage is typically 12–48 VDC for mid-power LEDs, or up to 150 VDC for long series strings in AC phase-dimmable circuits. All of these are well within HPL-03015’s 170 VDC continuous limit. The driver primary side PCB (which operates at mains potential) should be on a different, appropriately rated substrate — and the two boards should be physically separated by the required safety creepage distance for the isolation barrier between them.

Pad Design for LED Die and Package Mounting on HPL-03015

For packaged LED components (SMD LEDs with exposed pad thermal slug):

The thermal pad of the LED must make full contact with the copper circuit layer — any voids in the solder joint under the thermal pad directly increase effective thermal resistance by forcing heat to travel around the void. For high-power LED pads, consider a stencil aperture pattern that promotes void-free solder joints: typically a 70–80% aperture coverage ratio with multiple smaller apertures rather than a single solid opening, allowing solder paste outgassing during reflow. Void levels above 20% of the thermal pad area measurably increase thermal resistance.

For COB bare-die mounting on HPL-03015: AuSn solder (280°C process) or silver-filled die attach film provides the lowest thermal resistance from die to substrate. The 325°C/60-second solder limit rating of HPL-03015 covers the AuSn reflow process. Gold or aluminum wire bond to the circuit layer pads requires ENIG (gold wire) or ENEPIG (aluminum wire) surface finish — confirm with your wire bond equipment supplier on the surface finish requirement for their bonder settings.

Copper Weight, Trace Design, and Current Handling

Copper Weight	Thickness	Current Capacity (10°C rise, 1 cm trace)	Notes
1 oz (35 µm)	35 µm	~3.5 A	Standard LED module, COB wire bond substrates
2 oz (70 µm)	70 µm	~5.0 A	High-current LED arrays, improved lateral spreading
3 oz (105 µm)	105 µm	~6.5 A	Premium COB modules, high-current strings

Because HPL-03015’s thermal conductance is so high, the substrate conducts heat away faster than thicker MCPCB materials — which means trace temperatures for a given current are lower than on MP-06503 or HT-04503. This can allow narrower traces for the same current rating versus IPC-2221 tables, though the IPC standard should be used as the baseline and the HPL-03015 thermal advantage treated as additional headroom rather than an excuse to undersize traces.

Avoid sharp 90° corners on high-current LED feed traces. Current crowding at sharp corners creates localized hot spots that accelerate copper fatigue under thermal cycling. Route power traces with 45° chamfers or smooth arcs at direction changes.

Layout Rules: Clearance to Board Edge and Slot Edges

The minimum distance between any electrically active copper feature and the routed board edge must account for the aluminum base being at chassis potential. A minimum edge-to-conductor clearance of 0.5 mm is a starting point, but the actual required clearance depends on the working voltage and the creepage/clearance requirements of the applicable safety standard. For HPL-03015 designs at 12–48 VDC LED string voltage, clearance to the aluminum base edge is a secondary concern after the primary isolation being provided by the driver. Avoid routing conductors over milled slots or cutouts in the aluminum base — these create thermal expansion discontinuities that stress the copper traces and dielectric during cycling.

White Solder Mask and Optical Reflectivity

HPL-03015 is specified as off-white in appearance. White solder mask over off-white dielectric provides maximum optical reflectivity for LED applications — reflecting light that would otherwise be absorbed into the PCB surface back into the luminaire optics. For LED COB modules where optical efficiency is closely managed, specifying white solder mask with LRV (Light Reflectance Value) above 80% is standard practice. The dielectric color itself also contributes if it is exposed in the inter-LED spaces between solder mask openings.

Surface Finish Selection for HPL-03015 LED PCBs

Surface Finish	Best Application	Notes
ENIG	COB wire bonding, fine pitch, long shelf life	Required for gold wire bond; standard for premium LED modules
ENEPIG	Aluminum wire bonding, highest reliability	Palladium barrier prevents gold embrittlement in Al wire bond
Lead-Free HASL	Standard packaged LED SMT, cost-sensitive	Good for larger thermal pads; less precise on fine features
OSP	Immediate-assembly production environments	Short shelf life; not recommended for HPL-03015 long-storage panels
Immersion Silver	Optical reflectivity, premium surface	High reflectivity under LED package openings; oxidation management required

ENIG is the standard surface finish for HPL-03015 COB LED substrates. Its flat, consistent surface improves solder joint formation under small die attach and LED package pads, and it provides a bondable surface for gold wire bonding without additional process steps.

HPL-03015 vs Competing Ultra-Thin LED Substrate Options

Substrate Option	Thermal Resistance	Working Voltage	Process Compatibility	Relative Cost
Bergquist HPL-03015	0.02 °C·in²/W	120 VAC / 170 VDC	Standard MCPCB, wire bond	Medium-high
Bergquist HT-04503	0.05 °C·in²/W	~480 VAC	Standard MCPCB	Medium
Bergquist MP-06503	0.09 °C·in²/W	~300 VAC	Standard MCPCB	Medium-low
Generic MCPCB 1 W/m-K (3 mil)	~0.6 °C/W per cm²	Varies	Standard MCPCB	Low
Alumina (Al₂O₃) DBC	Very low	Very high	Ceramic specialist	High
AlN DBC	Extremely low	Very high	Ceramic specialist	Very high
Silicon Carbide submount	Extremely low	Medium	Specialized	Very high

For the cost bracket where MCPCB competes, HPL-03015 is at the performance limit for polymer-ceramic IMS technology. Alumina and AlN DBC provide lower thermal resistance, but at ceramic process costs and with the fragility and size constraints of ceramic. HPL-03015 processes on standard MCPCB equipment, can be fabricated in large panel formats, accepts standard surface finishes, and can be punched or routed without cracking — advantages ceramics cannot match at any price point.

Useful Resources for Bergquist HPL-03015 Design and Procurement

Resource	Content	Link
Bergquist HPL-03015 Official TDS (mclpcb.com PDF)	Complete thermal, electrical, mechanical, chemical, and agency specifications — primary reference	mclpcb.com PDF
Bergquist Thermal Clad Selection Guide (Digikey)	Full family comparison including HPL-03015 thermal chart, dielectric thickness vs performance graphs, LED application guidance	Digikey PDF
Bergquist HT-04503 TDS (Henkel)	Reference comparison: 3 mil HT dielectric — use to quantify HPL-03015 thermal improvement for your design	mclpcb.com PDF
Henkel Electronics Portal	Current Bergquist Thermal Clad product documentation, SDS (Safety Data Sheets), technical support	henkel.com/electronics
IPC-2221B	PCB design standard — current capacity, clearance, trace design baseline rules for MCPCB	ipc.org
IPC-2152	Standard for determining current-carrying capacity in PCB conductors — more accurate than IPC-2221 for high-current LED traces	ipc.org
ASTM D5470	Thermal conductivity test method — used for all HPL-03015 dielectric thermal values	astm.org
Digikey — Bergquist Thermal Clad	HPL-03015 stock, pricing, and panel ordering from Bergquist/Henkel	digikey.com

FAQs: Bergquist HPL-03015

Q1: HPL-03015 has a 5.0 kVAC breakdown voltage but only 120 VAC continuous operating voltage. Why is the derating so severe, and is it really necessary?

The derating from 5.0 kVAC breakdown to 120 VAC continuous is not a conservative safety factor applied on top of a comfortable margin — it reflects the engineering reality of a 38 µm dielectric layer in real-world operating conditions. The 5.0 kVAC ASTM D149 breakdown test is conducted on a clean, flat, room-temperature sample under controlled conditions designed to measure intrinsic dielectric strength. Real-world operating conditions include: thermal cycling that stresses the dielectric and can introduce micro-fractures or micro-voids (which reduce local breakdown voltage dramatically), humidity exposure that can degrade surface and bulk resistivity, and the capacitive effects at the ultrathin dielectric that create high field gradients at even moderate voltages. Bergquist publishes the 120 VAC / 170 VDC operating limits as the continuous working voltage for which the material is designed, tested, and qualified — not as a conservative estimate. Exceeding these limits in a product is both a safety risk and a violation of the design intent for which the material’s agency certifications were obtained. The derating ratio from breakdown to working voltage is approximately 40:1, which is substantially larger than the HT family (roughly 14:1 for HT-04503 at 6 kVAC breakdown and 300-plus VAC working voltage) — and this reflects the fundamental physics of ultra-thin dielectric design.

Q2: Can HPL-03015 be used for a 48 VDC LED lighting system? What about a 150 VDC long-series LED string?

48 VDC is well within the HPL-03015 continuous DC operating limit of 170 VDC — this is a straightforward application. 150 VDC is also within the 170 VDC continuous limit, and is a common operating point for AC phase-dimmable LED systems using long series strings. The 260 VDC peak recurring limit accommodates transient overvoltages above the 150 VDC steady-state level. For a 150 VDC design, verify that transient overvoltage protection (TVS diodes or varistors) limits the peak recurring voltage on the LED string to below 260 VDC. The 170 VDC limit is for continuous steady-state operation; brief transients within the 260 VDC peak recurring limit are acceptable. Confirm these limits against the specific Bergquist TDS for the version of HPL-03015 you are procuring, as early and later versions of the datasheet list slightly different values for maximum operating temp (140°C vs 150°C) and these should be reconciled with the current Henkel production specification.

Q3: What is the practical difference between HPL-03015 and HT-04503 for a 10 W, 1 cm² LED package in terms of junction temperature?

For a 10 W LED in a 1 cm² package footprint, the dielectric thermal resistance contribution for each substrate is: HPL-03015: 0.02 °C·in²/W ÷ 0.155 in²/cm² = 0.129 °C/W × 10 W = 1.29°C across the dielectric. HT-04503: 0.05 °C·in²/W ÷ 0.155 in²/cm² = 0.32 °C/W × 10 W = 3.2°C across the dielectric. The difference is approximately 1.9°C per 10 W for a 1 cm² device — or about 0.19°C per watt per cm². That may sound modest, but for a high-power LED array with multiple devices (say, a 150 W COB module with 15 × 10 W devices in parallel), the total thermal resistance improvement across the assembly is multiplied by total power dissipation. More importantly, for LED luminaire design, the LED junction temperature budget is typically 60–80°C above ambient, and a 2–5°C improvement at the substrate level translates directly into either higher allowable drive current (higher lumen output) or longer lifetime at the same drive current. In a product competing on efficacy per fixture, that is a meaningful engineering advantage.

Q4: Does HPL-03015 need special fabrication equipment or handling, and what should I ask a new fabricator about their HPL-03015 experience?

HPL-03015 does not require fundamentally different equipment from other Thermal Clad materials, but the 38 µm dielectric thickness introduces process sensitivities that require controlled handling. Key questions for a new fabricator: (1) Have you fabricated HPL-03015 specifically — not just generic MCPCB? (2) What is your minimum conductor-to-edge clearance practice for HPL-03015, and how do you handle depaneling to avoid dielectric delamination? (3) How do you verify dielectric integrity — do you perform 100% electrical hipot testing, and at what test voltage? (4) What surface finish processes do you run on HPL-03015, and have you qualified ENIG on HPL specifically for COB wire bond applications? (5) What is your solder mask printing process for HPL — specifically the squeegee pressure, which needs adjustment for the aluminum-backed substrate versus standard FR-4? A fabricator who has processed HPL-03015 in production will be able to answer these concretely. One who has not may substitute generic MCPCB or may attempt HPL-03015 without the process controls its thin dielectric requires. For safety-certified LED products, request a fabrication traceability record showing the Bergquist HPL-03015 lot number used in your boards.

Q5: How does HPL-03015’s 185°C Tg affect long-term reliability in an LED module that runs at 80°C substrate temperature continuously?

The 185°C Tg of HPL-03015 is a significant reliability advantage for continuous operation at 80°C substrate temperatures, compared to MP-06503 (Tg 90°C) or even HT-04503 (Tg 150°C). At 80°C operating temperature, HPL-03015 is 105°C below its Tg — the dielectric is firmly in its glassy, mechanically stable state. Storage modulus remains at or near the 18 GPa room-temperature value through most of the operating range (it drops to 12 GPa at 150°C, showing good retention). The CTE below Tg is 35 µm/m·°C, and since operation never approaches Tg, the dielectric never transitions to its higher CTE, higher-stress elastomeric state. Thermal cycling between cold start (say, -20°C or -40°C outdoor) and 80°C continuous operation will exercise approximately 100 µm/m·°C × temperature range in dimensional change — the low CTE of HPL-03015 below Tg limits this and reduces thermal fatigue stress on solder joints and wire bonds over the product lifetime. The practical conclusion: HPL-03015’s 185°C Tg, combined with its mechanical stability data, supports high confidence in long-term reliability for LED modules operating in the 80–120°C junction temperature range that characterizes high-power LED lighting.

Conclusion

Bergquist HPL-03015 occupies a unique and precisely defined position in MCPCB design: it is the highest-performance polymer-ceramic insulated metal substrate in the Thermal Clad family for thermal resistance, achieving 0.02 °C·in²/W through a combination of ultra-thin 38 µm dielectric and 3.0 W/m-K dielectric thermal conductivity that no thicker Thermal Clad product can approach. The 185°C Tg is the highest in the family, and the outgassing performance (0.15% TML) is the best in the family. These properties come with a well-defined and non-negotiable voltage constraint: 120 VAC / 170 VDC continuous, 260 VDC peak recurring.

For engineers designing high-power LED modules — COB assemblies, automotive headlamps, high-bay luminaires, premium streetlight engines, LED backlights, CPV receivers — where the circuit operates at LED output voltages and the thermal budget is the binding design constraint, HPL-03015 is the material answer. Design it correctly (observe the voltage limits absolutely, implement proper pad design for void-free solder joints under LED thermal pads, specify ENIG for COB wire bonding, manage creepage at board edges), and it delivers thermal performance that closes thermal budgets other MCPCB substrates cannot reach.