Complete Bergquist LTI-04503 specs, thermal properties, design guide & FAQ. Engineer’s reference for this low temperature dielectric MCPCB material — datasheets included.

If you’ve been sourcing Metal Core PCB (MCPCB) substrates for mid-range thermal applications, there’s a good chance you’ve come across the Bergquist LTI-04503. It occupies a well-defined niche in the Thermal Clad lineup — not the maximum-temperature beast that the HT series is, but also not the barebones general-purpose option. The LTI-04503 is the dielectric you reach for when your operating environment is moderate, your budget matters, and you still need genuine thermal performance backed by Bergquist’s decades of engineering credibility.

This guide walks through everything a PCB engineer actually needs to know: what LTI means in Bergquist’s naming convention, full material specifications, how it compares to sibling dielectrics, which applications it genuinely fits, and how to design with it effectively.

What Is the Bergquist LTI-04503?

Understanding the Thermal Clad Platform

Bergquist’s Thermal Clad Insulated Metal Substrate (IMS) was developed as a thermal management solution for higher watt-density surface mount applications where heat issues are a major concern. The entire platform is built around a three-layer construction: a copper circuit layer on top, a proprietary dielectric layer in the middle, and a metal base (typically aluminum) underneath.

The dielectric is a proprietary polymer/ceramic blend that gives Thermal Clad its excellent electrical isolation properties and low thermal impedance. The polymer is chosen for its electrical isolation properties, ability to resist thermal aging and high bond strengths. The ceramic filler enhances thermal conductivity and maintains high dielectric strength.

What “LTI” Means

In Bergquist’s product naming system, the prefix identifies the dielectric family. LTI stands for Low Temperature Insulator — a dielectric engineered specifically for applications that operate at moderate temperatures, as distinct from the HT (High Temperature) family, which is rated for far more aggressive thermal cycles. Bergquist references the LTI dielectric alongside FR-4 in comparative current-carrying capability charts, meaning it’s positioned as a step up from standard FR-4 in thermal performance while remaining suitable for standard temperature environments.

The 04503 suffix follows Bergquist’s standard numbering: “045” refers to the approximate total laminate stack, and “03” denotes the 3-mil (0.003″, approximately 76 µm) dielectric layer thickness.

Bergquist LTI-04503 sits within the broader Thermal Clad family alongside materials such as MP-06503, HT-07006, ML-11006, and HPL-03015, each targeting a different thermal performance tier and application environment.

Bergquist LTI-04503 Full Specifications

Core Physical & Thermal Properties

The table below summarizes the key properties of the LTI-04503 dielectric as used in the Bergquist Thermal Clad platform:

Property	Value	Test Method
Dielectric Thickness	3 mil (76 µm / 0.003″)	Physical measurement
Thermal Conductivity	~1.5 W/m-K	ASTM E1461
Thermal Resistance	~0.20 °C·in²/W	Bergquist internal method
Peel Strength @ 25°C	≥ 1.0 N/mm	ASTM D2861
Glass Transition Temperature (Tg)	~130°C	ASTM E1356 (DSC)
Dielectric Breakdown (AC)	≥ 3.0 kV	IEC 60243
Volume Resistivity	> 10⁹ Ω·cm	ASTM D257
Flammability Rating	UL 94 V-0	UL 94
RoHS Compliance	Yes	EU RoHS Directive
Lead-Free Solder Compatible	Yes	IPC J-STD-001

Note: Verify current specifications directly against the Bergquist/Henkel official datasheet before design lock-in, as formulations can be updated.

Laminate Stack Construction

Layer	Standard Specification
Circuit Layer (Copper)	1 oz to 3 oz (35–105 µm); custom weights available
Dielectric Layer	3 mil (76 µm) LTI polymer/ceramic blend
Base Metal	Aluminum (most common) or Copper
Base Thickness	0.8 mm, 1.0 mm, 1.57 mm (0.062″), 2.0 mm (standard offerings)
Surface Finish Options	HASL LF, ENIG, OSP, FST
Solder Mask	White, black, or none

Electrical Properties

Electrical Parameter	Typical Value
Dielectric Constant (Dk) at 1 MHz	~4.0–4.5
Dissipation Factor (Df) at 1 MHz	< 0.03
Insulation Resistance	> 10⁹ Ω
Breakdown Voltage (DC)	≥ 1500 VDC
Breakdown Voltage (AC)	≥ 3.0 kVAC

How the LTI-04503 Fits Within the Bergquist Thermal Clad Family

One of the most common questions when selecting a Bergquist substrate is: which dielectric variant do I actually need? The table below helps clarify where the LTI-04503 lands relative to the other core options.

Bergquist Thermal Clad Dielectric Comparison

Material	Thermal Conductivity	Max Temp. Focus	Best Use Case
LTI-04503	~1.5 W/m-K	Standard/Moderate	Consumer electronics, standard LED, audio
MP-06503	2.4 W/m-K	Multi-purpose	General power, LED lighting, mid-range thermal
HT-04503	2.2 W/m-K	High temperature	LED lighting, power supplies, amplifiers
HT-07006	Higher performance	High temperature, high-reliability	Motor drives, solar receivers, solid state relays
HPL-03015	Highest Thermal Clad	High-Power Lighting	High-watt LED lighting systems

The LTI-04503 is the most cost-conscious of the group. For designs where junction temperatures will comfortably stay below the Tg (~130°C) and there’s no requirement to withstand extreme thermal cycling, the LTI-04503 offers a compelling balance of performance and economics. If your device sits at a higher steady-state temperature or goes through aggressive thermal shock testing, you’ll want to step up to the MP or HT series.

Key Advantages of the Bergquist LTI-04503

Proven Thermal Management Over FR-4

The single biggest reason to move to the LTI-04503 from conventional FR-4 is thermal conductivity. Standard FR-4 delivers approximately 0.2–0.3 W/m-K. Bergquist materials allow heat to be transferred more efficiently with thermal conductivity up to 9.0 W/m-K across the product range, and even the entry-level LTI-04503 at ~1.5 W/m-K is roughly five times better than FR-4. In real-world terms, this means substantially lower junction temperatures for the same power dissipation, which directly translates to longer component life.

UL-Recognized Dielectric

The dielectric layer has UL recognition, simplifying agency acceptance of final assemblies. For products destined for consumer markets in North America and Europe, this matters during safety certification — your UL file for the end product can reference the recognized dielectric rather than requiring a full re-test of the substrate material.

Automated Assembly Compatibility

Thermal Clad can reduce production costs by enabling automated pick-and-place equipment for SMDs. Unlike some ceramic or thick-film alternatives, the LTI-04503 plays nicely with standard SMT assembly lines. Standard stencil printing, reflow ovens, and automated optical inspection (AOI) all apply without special process accommodations.

RoHS and Halogen-Free Compliance

Thermal Clad substrates are RoHS compliant and halogen-free. The LTI-04503 meets current EU RoHS directives and supports lead-free solder processes, making it appropriate for products entering EU, UK, and other regulated markets.

Board Size Reduction and Hardware Elimination

Thermal Clad greatly reduces board space while replacing other components including heat sinks. It offers the opportunity to eliminate mica and grease or rubber insulators under power devices by using direct solder mount to Thermal Clad. By eliminating this hardware, heat transfer is improved. For a design that previously used a TO-220 device with mica washer, thermal grease, and a discrete finned heatsink, migrating to an LTI-04503 board can eliminate all that hardware and still achieve equal or better thermal performance.

Typical Applications for the Bergquist LTI-04503

The LTI-04503 hits its stride in applications where thermal performance needs to exceed what FR-4 can offer, but where the operating environment is not demanding enough to justify the premium of the HT or HPL series.

Consumer and Commercial Electronics

Standard LED driver circuits, power supply boards, and audio amplifier output stages are natural homes for the LTI-04503. If you’re building a class-D amplifier with MOSFETs running at moderate switching frequencies, or a 30–50W LED driver for commercial lighting, LTI-04503 gives you good heat spreading without paying for thermal headroom you’ll never use.

LED Lighting (Standard Output)

Metal core PCB and standard FR-4 are commonly used circuit board materials in conjunction with Power LEDs. Bergquist’s Thermal Clad dielectric is a thin, thermally conductive layer bonded to an aluminum or copper substrate for heat dissipation. The key to Thermal Clad’s superior performance lies in its dielectric layer — it offers electrical isolation with high thermal conductivity and bonds the base metal and circuit foil together. For LED luminaires where the LED junction temperature target is in the 85–100°C range and the ambient is well below 50°C, LTI-04503 is well-suited without overkill.

Power Conversion (Low-to-Mid Power Range)

Due to the size constraints and watt-density requirements in DC-DC conversion, Thermal Clad has become the favored choice. It is available in a variety of thermal performances, is compatible with mechanical fasteners and is highly reliable. For telecom PSU boards, industrial 24V power supplies, and battery management systems (BMS) operating at moderate power levels, the LTI-04503 offers an efficient and cost-effective substrate.

Automotive Ancillaries (Non-Powertrain)

For automotive interior electronics — ambient lighting drivers, seat heater controllers, climate control modules — where temperatures are moderate and the primary driver for moving off FR-4 is lifespan and reliability, the LTI-04503 checks the boxes. Bergquist PCBs are widely used for sparker and modifiers on fire for mobile and motorcycle, soundbox, power LED, acoustic shielding system and power supply modules.

Solid State Relays and Switching Devices

The implementation of Solid State Relays in many control applications calls for thermally efficient and mechanically robust substrates. Thermal Clad offers both. The material construction allows mounting configurations not reasonably possible with ceramic substrates.

Design Considerations When Using Bergquist LTI-04503

Circuit Flatness and Copper Thickness Ratio

Circuit flatness can be a concern when the base layer is aluminum. To achieve a flat circuit, maintain the proper ratio of circuit layer thickness to base. If the thickness of the copper circuit layer is kept at 10% of the base layer thickness or thinner, the aluminum base will mechanically dominate, keeping the circuit flat. In practice, with a 1.57 mm (0.062″) aluminum base, your copper circuit layer should stay at or below approximately 157 µm — roughly 4.5 oz copper — to maintain flatness. Most designs using 1 oz or 2 oz copper are well within this range.

Voltage Ratings and Dielectric Thickness

For applications with an expected voltage over 480 Volts AC, Bergquist recommends a dielectric thickness greater than 0.003″ (75 µm). The LTI-04503’s 3-mil dielectric is right at this threshold. If your design operates above 480 VAC, consider either using a thicker dielectric variant or applying additional creepage and clearance spacing in the PCB layout to remain within safety agency requirements.

Solder Process Compatibility

The LTI-04503 is compatible with standard lead-free reflow profiles (SAC305 alloys, peak temperatures around 260°C). The typical application technique for solder is a metal stencil. Dispensing of solder to specific locations is used for secondary operations or special attachment requirements. For the base metal, avoid excessive heat soaking — prolonged exposure above 260°C at the board level can stress the polymer-ceramic dielectric bond.

Proof Testing and Dielectric Integrity

Any micro-fractures, delaminations or micro-voids in the dielectric will break down or respond as a short. Due to the capacitive nature of the circuit board construction, it is necessary to control the ramp-up of the voltage to avoid nuisance tripping of the failure detect circuits in the tester and to maintain effective control of the test. When doing production hipot (high-potential) testing, use a controlled voltage ramp rate. A sudden step to the full test voltage on a Thermal Clad board will frequently cause false failures due to displacement current in the capacitive dielectric structure.

Trace Width and Current Capacity

Current carrying capability is a key consideration because the circuit layer typically serves as a printed circuit, interconnecting the components of the assembly. The advantage of Thermal Clad is that the circuit trace interconnecting components can carry higher currents because of its ability to dissipate heat due to I²R loss in the copper circuitry. Compared to FR-4, trace temperature rise for a given current is lower on LTI-04503, meaning you can effectively use slightly narrower traces for equivalent thermal performance — a useful benefit in space-constrained designs.

Manufacturing Process Overview for LTI-04503 PCBs

Getting a quality LTI-04503 board made requires working with a manufacturer who stocks genuine Bergquist material and understands MCPCB fabrication. The key process steps differ meaningfully from standard FR-4 manufacturing.

Step 1 – Material Procurement and Incoming Inspection

The raw laminate (copper foil + LTI dielectric + aluminum base) arrives in panel form. Incoming inspection should verify the dielectric thickness and visual integrity of the laminate.

Step 2 – Circuit Imaging and Etching

Standard photo-imaging and wet chemical etching applies. The aluminum base is masked to prevent attack during etching. Pattern tolerances follow standard IPC-2221 guidance.

Step 3 – Surface Finish Application

Common surface finish options include HASL (Hot Air Solder Leveling) — a 63/37 Pb/Sn or lead-free equivalent coating with excellent shelf life and solderability. OSP (Organic Solderability Protectant) is a thin coating to protect the copper with a shelf life of 3–6 months. FST (Flow Solderable Tin) is a relatively new planar coating with a long shelf life. ENIG (Electroless Nickel Immersion Gold) is also widely used for LTI-04503 boards, especially in applications requiring wirebonding or very fine pitch SMD.

Step 4 – Mechanical Fabrication

Routing, drilling, and scoring are performed using CNC equipment. Aluminum-base MCPCB requires carbide tooling and controlled feeds. V-scoring is a common option for panel depaneling.

Step 5 – Electrical and Dielectric Testing

Every Bergquist Thermal Clad board should undergo a hipot test to verify dielectric integrity. Production proof-test voltage is typically applied at a controlled ramp rate.

Bergquist LTI-04503 vs. Competing MCPCB Materials

While other manufacturers produce aluminum-base PCB laminates with comparable claimed specs, Bergquist’s Thermal Clad family — including the LTI-04503 — carries decades of field reliability data, UL recognition, and a rigorous qualification program. New Bergquist materials undergo a rigorous 12 to 18 month qualification program prior to being released to the market, with extensive testing on all thermal materials for electrical integrity, including mechanical property validation, adhesion, temperature cycling, and thermal and electrical stress testing to 2000 hours.

For engineers who want to compare LTI-04503 against other Insulated Metal Substrate (IMS) platforms, it’s worth noting that comparable alternatives exist from manufacturers such as Arlon PCB and others in the IMS laminate space. Arlon’s IMS products are worth evaluating if design requirements push outside the Bergquist standard range, though the LTI-04503 remains one of the most widely supported and documented IMS dielectrics in production worldwide.

Useful Resources and Datasheets for the Bergquist LTI-04503

Resource	Description	Link
Bergquist Thermal Clad Selection Guide (Digikey PDF)	Complete dielectric comparison, design guidelines, assembly recommendations	Download PDF
Bergquist (Henkel) Official Product Page	Current product catalog, datasheet access, regional contacts	henkel.com/bergquist
Bergquist Thermal Clad Selection Guide (TJK PDF Mirror)	Alternate hosted version of the full selection guide	TJK Mirror PDF
IPC-4101 – Specification for Base Materials	Industry standard governing laminate materials including IMS	IPC.org
IPC-2221B – Generic Standard on PCB Design	Design guidelines covering trace width, clearance, and dielectric considerations	IPC.org
Digikey Product Listing – Bergquist Thermal Clad	Stocked parts, pricing, availability	Digikey Bergquist
Mouser Electronics – Bergquist PCB Materials	Alternate distributor sourcing	Mouser.com
RayPCB Bergquist PCB Guide	Practical guide on Bergquist material applications	RayPCB Bergquist Article

Frequently Asked Questions About Bergquist LTI-04503

1. What does “LTI” stand for in Bergquist LTI-04503?

LTI stands for Low Temperature Insulator, referring to the specific dielectric formulation used in this Thermal Clad variant. It is designed for applications operating at moderate ambient and junction temperatures, making it distinct from Bergquist’s HT (High Temperature) series, which uses a more thermally robust polymer system rated for sustained high-temperature exposure. The LTI dielectric still significantly outperforms FR-4, but it is not the right choice if your board will see sustained temperatures approaching or exceeding 130°C.

2. What is the thermal conductivity of the Bergquist LTI-04503?

The LTI-04503 dielectric offers a thermal conductivity of approximately 1.5 W/m-K, compared to FR-4’s typical 0.2–0.3 W/m-K. While lower than the HT-04503 (~2.2 W/m-K) or the MP-06503 (~2.4 W/m-K), this figure is still roughly five to seven times better than standard fiberglass laminate. For the thermal loads typical of standard LED drivers, consumer audio, and general-purpose power electronics under 100W, 1.5 W/m-K is generally sufficient.

3. Can I use the Bergquist LTI-04503 for high-voltage applications?

The LTI-04503 with a 3-mil (76 µm) dielectric has a typical AC breakdown voltage of ≥ 3 kVAC and is suitable for many industrial and commercial applications. However, as noted in Bergquist’s own design guidelines, for applications with an expected voltage over 480 Volts AC, Bergquist recommends a dielectric thickness greater than 0.003″. If your application runs above 480 VAC, you should either use a thicker dielectric variant or apply appropriate creepage and clearance margins in the PCB layout per IEC 60664-1.

4. How does LTI-04503 compare to the HT-04503?

Both use a 3-mil dielectric (“03” suffix) but differ significantly in the dielectric formulation. The HT-04503 features a thermal conductivity of 4.1 W/m-K and is rated for high-temperature exposure, with a Tg of approximately 150°C. The LTI-04503 sits below this at roughly 1.5 W/m-K thermal conductivity and a Tg around 130°C. Practically, if your device operates below 100°C steady-state and doesn’t go through aggressive thermal cycling (-40°C to +150°C), LTI-04503 is typically sufficient and more cost-effective. Step up to HT-04503 or HT-07006 for LED high-bay lighting, automotive powertrain, EV chargers, or motor drives.

5. Where can I buy Bergquist LTI-04503 raw material or finished PCBs?

Raw Bergquist LTI-04503 laminate can be sourced through authorized distributors such as Digikey, Mouser, and Arrow Electronics. For fabricated PCBs using LTI-04503 material, many China-based MCPCB manufacturers keep genuine Bergquist stock, including manufacturers able to provide Bergquist LTI-04503, MP-06503, ML-11006, HT-07006, and HPL-03015 material in configurations such as 1.6 mm thick, single-sided, 1 oz, with ENIG surface finish and CNC routed outline. Always confirm your fabricator is using genuine Bergquist laminate if the certification trail matters for your end product.

Conclusion

The Bergquist LTI-04503 is a mature, well-characterized Insulated Metal Substrate dielectric that earns its place in any PCB engineer’s materials toolkit. It isn’t the headline act — that role belongs to the HT or HPL variants for extreme thermal applications — but for the broad middle ground of standard-power electronics where FR-4 falls short, the LTI-04503 delivers genuine thermal improvement, UL-recognized insulation, lead-free solder compatibility, and the backing of Bergquist’s extensive qualification history.

The key is to match the material to the application honestly. If your steady-state board temperature comfortably sits below 100–110°C, your power dissipation is moderate, and your budget is under pressure, LTI-04503 is the pragmatic choice. Push beyond those boundaries and the HT or MP series will serve you better.

All specifications should be verified against the most current official Bergquist/Henkel datasheet prior to use in production design. Material properties can vary by production lot and are subject to revision by the manufacturer.

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