Aluminum PCB vs FR4: A Real Thermal Imaging Test on a 3.3V LDO Regulator (with Video)

Watch the Experiment

The full real-time thermal color-change sequence — from power-on to 5-minute steady state — is captured on video below.

If the player above doesn’t load, watch it directly on YouTube ▶

Test Setup

Because both modules were powered from the same source at the same time, under the same load, any difference in the rate or pattern of color change can be attributed directly to the PCB substrate material — not to the regulator IC, load, or ambient conditions.

Step-by-Step Observations

In every photo below, the FR4 module is the green-PCB board (top-left) and the Aluminum (MCPCB) module is the white/silver board (bottom-right). Both are powered, loaded, and photographed at the same time.

T = 0s — Power ON (Baseline)

Both modules begin solid red/pink — confirming both boards start at the same ambient temperature, with no pre-existing thermal bias. This is the control reference point for the rest of the test.

T = ~11s — The Hotspot Forms on FR4

• FR4 PCB (top): The coating directly under the LDO package begins fading toward white almost immediately. The fiberglass-resin substrate has very low thermal conductivity (roughly 0.2–0.3 W/m·K), so heat generated by the regulator has nowhere to go but straight up into the coating — it can’t spread sideways through the board.
• Aluminum PCB (bottom): The coating remains solid red/pink with no visible change. The aluminum core begins acting as a heat spreader from the very first seconds, conducting heat away from the package footprint laterally through the metal base.

T = ~40s — The Escape Phase

• FR4 PCB (top): The white “hotspot” zone is now clearly formed and well-defined around the LDO. Because the heat is trapped locally, the regulator’s junction temperature climbs quickly toward its thermal limit.
• Aluminum PCB (bottom): Still predominantly red/pink, with only a very subtle lightening starting to appear. Heat is escaping into the aluminum base rather than concentrating at the source.

T = ~100s — Thermal Saturation

• FR4 PCB (top): The coating across most of the board has now turned transparent/white — indicating the area has been at or above the threshold temperature for some time. Heat is dissipating inefficiently, mostly through still air at the board surface.
• Aluminum PCB (bottom): Has lightened from deep red to a pale pink, but is nowhere near as faded as the FR4 module. The metal core is actively absorbing thermal energy from the hotspot and distributing it across a much larger surface area, keeping the peak temperature lower.

T = 5 minutes — Steady State (300mA Continuous Load)

• FR4 PCB (top): The coating has gone fully transparent/”deep white” across nearly the entire board — the highest temperature state observed in the test. The fiberglass substrate has no further capacity to move heat away from the component.
• Aluminum PCB (bottom): Remains a clearly pink/salmon shade — visibly cooler than the FR4 module at the same point in time. The metal core continues to wick heat away from the regulator and spread it across the board, confirming a lower and more stable junction temperature under the same electrical conditions.

The Full Sequence at a Glance (T0 → 5 min)

Frame-by-frame composite from the recorded experiment. Watch the FR4 board (top of each frame) progressively wash out to white, while the Aluminum PCB module (bottom of each frame) stays comparatively pink throughout the same 5-minute window.

Summary: FR4 vs Aluminum PCB Under Identical LDO Load

Why This Matters for LDO-Based Designs

Linear regulators dissipate the voltage difference between input and output as heat — P = (VIN − VOUT) × ILOAD. For a 5V-to-3.3V LDO at 300mA, that’s roughly 0.5W dissipated directly in the regulator package, with nowhere to go except through the PCB.

On a standard FR4 board, that 0.5W stays concentrated under the package because FR4’s thermal conductivity is roughly 0.2–0.3 W/m·K — close to an insulator. The result, as this test shows visually, is a fast-forming localized hotspot. Sustained operation at elevated junction temperature accelerates thermal stress on the regulator die, nearby ceramic capacitors, and solder joints — a well-documented driver of long-term field failures in compact, densely-packed modules.

An aluminum (metal-core) PCB inserts a high-conductivity layer directly beneath the copper circuit layer. Instead of acting like a thermal “wall,” the board becomes part of the cooling path — spreading heat across the entire board area, lowering peak junction temperature, and often eliminating the need for an external heatsink altogether.

How This Applies to the TrueVolt-74033

The TrueVolt-74033 is a 3.3V / 300mA ultra-low-noise LDO module built on exactly this principle — an Aluminum (Metal-Core) PCB paired with a genuine Texas Instruments TLV74033 regulator and Samsung MLCC capacitors. The thermal behavior demonstrated in this experiment is the same mechanism that gives the TrueVolt-74033 its steady-state thermal advantage over conventional FR4-based LDO modules:

• Lower steady-state junction temperature at the same load current
• No fast-forming hotspot under the regulator package
• Reduced thermal stress on the LDO and surrounding components — supporting longer operating life
• Often no external heatsink required in space-constrained embedded, IoT, or imaging applications

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