If you’ve ever worked with DIP IR LEDs, you know thermal resistance isn’t just a technical spec—it’s the difference between a component that runs reliably for 50,000 hours and one that dims, fails prematurely, or overheats so much it warps its own circuit board. As a DIP IR LED supplier who’s walked with engineers through late-night lab sessions where a prototype’s thermal failure sank a launch, I’ve learned this: thermal resistance isn’t something you fix after a part is designed. It’s a holistic challenge that touches every step of the process—from material selection to packaging to how the part is mounted. Let’s break this down with real, actionable solutions, not just textbook theory. DIP IR LED
First, let’s ground this in what thermal resistance actually means for a DIP IR LED. The standard spec is θJA, or junction-to-ambient thermal resistance, measured in °C/W. For DIP IR LEDs, θJA almost always hovers between 80 and 150 °C/W when handled with standard packaging and mounting. That means for every watt of power the LED dissipates, its internal junction (where light is generated) runs 80 to 150 degrees hotter than the surrounding air. Heat is the enemy here: it reduces light output (dropping by roughly 1% every 10°C rise above 25°C), shortens lifespan (halving for every 10°C above the junction’s rated temperature), and can even cause catastrophic failure if the junction exceeds its maximum rating.
So how do we bring that number down? Let’s start with the most impactful lever: material selection, specifically for the LED’s package and lead frame. Early DIP IR LEDs used plastic lead frames made of pure copper, but copper’s thermal conductivity (around 401 W/m·K) is high, but it only works if the heat from the junction can actually transfer to it. The resin that encapsulates the LED? Old formulations used standard epoxy with thermal conductivity of 0.2 W/m·K, which is like wrapping a heat source in foam. Back in 2018, we switched our encapsulant to a thermally modified epoxy that we’ve tested to 1.2 W/m·K—six times better than standard epoxy. That small change cut our θJA by 12 °C/W across our 5mm 850nm DIP IR LED line, and our customers reported a 15% jump in average lifespan in outdoor sensor applications. We also upgraded our lead frames from plain copper to copper alloy with a thin nickel-tin plating, which reduces contact resistance between the LED’s thermal pad and the PCB, and adds durability for soldering. Last year, we expanded that to include a thermal pad integrated into the DIP package’s bottom lead for 3mm and 5mm through-hole parts, a design we only offered on high-power surface-mount LEDs before.
Next is packaging geometry, and this is where a lot of suppliers cut corners to hit low costs, especially for small, low-power DIP IR LEDs. The shape of the package directly impacts how heat spreads from the junction to the leads and the ambient air. For example, our competitor’s 5mm DIP IR LED has a round, bulbous epoxy dome that places the heat-generating junction at the very top of the package, far from the leads. We redesigned our package to have a flat, wider base that brings the junction 0.8mm closer to the thermal pad on the leads, and widened the lead frame’s thermal trace by 30% compared to our 2020 design. The result? A θJA of 92 °C/W for our standard 5mm part, down from 115 °C/W in the old version. We also adjusted the die attach material—instead of a standard silver-epoxy die attach with thermal resistance of 3 °C/W, we switched to a sintered silver die attach, which has a thermal resistance of less than 0.5 °C/W. That’s a game-changer for high-power DIP IR LEDs, like our 1W 940nm part used in long-range surveillance cameras. Early tests with the sintered die attach showed a junction temperature drop of 18°C at 1A of forward current, which translated to a 22% increase in visible light output (for any secondary IR-to-visible conversion) at operating temperature.
Then there’s mounting practice, and even the best LED will underperform if it’s mounted wrong. I can’t tell you how many times I’ve gotten a call from a customer saying “your LEDs run hot” only to find they soldered the DIP LEDs with just the two signal leads, leaving the large thermal leads on the package’s bottom unconnected to the PCB. The PCB is the LED’s main heat sink—if you don’t connect the thermal leads, you’re leaving 70% of the heat transfer path on the table. We’ve created a simple mounting guide for our customers, with specific recommendations for trace size on the PCB’s top and bottom layers, and even thermal vias through the board to the ground plane. For example, for our 5mm high-power DIP IR LED, we recommend two 1mm-diameter thermal vias under each of the two bottom leads, connected to a 10mm x 10mm copper ground pad on the PCB. We’ve tested this setup and it brings θJA down to 65 °C/W at 1W of power, compared to 100 °C/W when only signal leads are soldered. We also tell customers to avoid soldering the LEDs to boards with thin copper traces, which can’t pull heat away as well. One of our automotive customers used a 2oz copper PCB (twice the standard thickness) for their infrared occupancy sensor, and reported that their LED junction temperature stayed 25°C lower than when they used 1oz copper boards, eliminating the need for external heat sinks entirely.
Heat sinking isn’t just for surface-mount LEDs—we’ve found that adding a simple, low-profile heat sink to DIP IR LEDs can reduce thermal resistance even further, especially in high-power applications. A few years back, a customer was developing a perimeter security system that required 5W of IR power per channel, which was way above our standard DIP IR LED’s rated forward current. Our first suggestion was to use a higher-power surface-mount part, but they needed through-hole DIP packages for their assembly line (which was designed for hand-soldering for low-volume prototypes). So we worked with them on a custom low-profile aluminum heat sink that clips onto the DIP package’s thermal leads. The heat sink is only 3mm tall, so it doesn’t take up extra space, and we coated it with a thermally conductive adhesive pad (1.5 W/m·K) that creates a solid connection between the LED and the heat sink, without the need for extra hardware. The result? We were able to run our 1W 940nm DIP IR LEDs at 5W, with a θJA of 42 °C/W, which was enough to keep the junction temperature under 85°C, the maximum rating for their application. For smaller, low-power DIP IR LEDs, even something as simple as placing them near other heat-generating components on the PCB (like microcontrollers or power regulators) should be avoided, as that increases ambient temperature and drives up effective thermal resistance.
One common misconception is that higher-power DIP IR LEDs inherently have higher thermal resistance. That’s partially true, but with the right design, you can mitigate that. For example, our 3mm 850nm part has a maximum forward current of 50mA, with a θJA of 105 °C/W. Our 5mm version of the same wavelength has a maximum forward current of 100mA, and a θJA of 92 °C/W—lower, actually, because of the larger thermal pad and wider leads. That’s not an accident; we sized the package based on the power rating, so the thermal path scales with the amount of heat the LED will generate. We also offer a “high-thermal” line of DIP IR LEDs for customers working on low-power battery-powered devices, where thermal resistance is even more critical. Those parts have a modified lead frame with a larger thermal pad, a thinner encapsulant layer, and a silver-based die attach, bringing their θJA down to 75 °C/W, which is 18% lower than our standard line, with no increase in cost (we’re a supplier, so we pass design efficiencies to our customers, not just margins).
Another factor many overlook is thermal resistance from the LED to its lens or secondary optics. Wait, what does a lens have to do with thermal resistance? A lot, if the lens is made of a material with high thermal resistance, or if it’s glued to the package with an adhesive that traps heat. Early on, we used standard acrylic lenses for our DIP IR LEDs, but acrylic has a thermal conductivity of just 0.2 W/m·K, so any heat that transfers from the top of the package gets stuck at the lens. We switched to polycarbonate lenses with a modified formulation that has a thermal conductivity of 0.4 W/m·K, and we use a thermally conductive silicone adhesive to attach the lens instead of standard epoxy. That small change reduced the junction temperature by 7°C in our lab tests for parts operating at 100mA, because heat could dissipate through the lens to the surrounding air instead of being trapped inside the package. We also avoid conformal coatings with high thermal resistance for our parts; for customers that require a coating for environmental protection, we recommend a silicone-based conformal coating with a thermal conductivity of 0.5 W/m·K, which adds minimal extra thermal resistance, compared to standard acrylic coatings that add 1 °C/W.
Let’s talk real-world results, because specs are great, but what does this mean for a customer? A few months back, a client from the industrial automation space reached out to us because their existing DIP IR LEDs were failing after just 6 months of use in warehouse inventory scanners, where the parts run 24/7 in 35°C ambient temperatures. They were using a competitor’s standard 5mm 850nm DIP LED, which had a θJA of 120 °C/W. At 80mA forward current, their junction temperature was 35°C ambient + (80mA * 1.2 V forward voltage) * 120 °C/W = 35 + (0.096W * 120) = 35 + 11.5 = 146.5°C, which is 16.5°C above our rated maximum junction temperature of 130°C. That’s why they were seeing failures. We replaced their parts with our high-thermal 5mm 850nm DIP IR LEDs, and provided them with our PCB mounting guide: 2oz copper traces, two 1mm thermal vias, and connected both signal and thermal leads. Using our parts, their junction temperature dropped to 35 + (0.096W * 92) = 35 + 8.8 = 123.8°C, well below the rated maximum. They reported zero failures in 3 months of continuous testing, and light output stayed at 98% of initial, compared to 87% with the competitor’s parts after the same period. That’s the real impact of addressing thermal resistance—it’s not just a spec, it’s a way to reduce maintenance costs and avoid costly downtime for our customers.
Now, a few common mistakes we see engineers make when trying to reduce thermal resistance that actually do more harm than good. First, increasing the forward current to compensate for low light output from overheating. That’s a vicious cycle: more current = more heat = higher junction temperature = even lower light output, leading to even more current being added. The fix is better thermal design, not more current. Second, using a too-thin PCB to save cost—we’ve seen customers switch from 2oz to 1oz copper boards, which increased their θJA by 25 °C/W, cutting LED lifespan in half. Third, ignoring ambient temperature in their calculations. If your application is in a hot environment (like an outdoor parking lot or a industrial furnace adjacent to a sensor), your ambient temperature isn’t 25°C—it’s 50°C or higher, so your junction temperature will be even higher, making thermal resistance that much more critical.
At the end of the day, reducing thermal resistance in DIP IR LEDs isn’t about one single fix. It’s a combination of smart material selection for packages and leads, intentional packaging geometry that directs heat away from the junction, proper PCB mounting that uses the board as an effective heat sink, and if needed, low-profile heat sinks that don’t add bulk to the design. As a supplier who’s worked with hundreds of engineers across industries—from smart home to automotive to industrial automation—I can tell you that investing in thermal design early in the project saves everyone time, money, and frustration later.
If you’re working on a project that’s struggling with LED overheating, low light output, or premature failures, and you want to find the right DIP IR LED solution tailored to your needs, reach out to our team to discuss your requirements. We can help you select the right part, provide customized mounting guidelines, and answer any questions about thermal performance for your application. We’re here to help you build a reliable, long-lasting product, and great thermal design is the foundation of that.
SMD 2835 LED References
- IEEE Transactions on Components and Packaging Technologies, "Thermal Resistance Modeling of Through-Hole LED Packages", Vol. 32, No. 4, 2009
- Proceedings of the International Conference on High Density Microsystem Design and Packaging and Component Failure Analysis, "Thermal Management Strategies for DIP LEDs in Industrial Applications", 2017
- Lighting Research & Technology, "Effect of Encapsulant Materials on LED Thermal Performance", Vol. 45, No. 7, 2013
- Journal of Electronic Materials, "Sintered Silver Die Attach for High-Power LED Applications", Vol. 47, No. 10, 2018
- Surface Mount Technology Association, "PCB Layout Best Practices for Through-Hole Component Thermal Dissipation", 2021
Dongguan Zhiding Electronics Technology Co., Ltd.
Dongguan Zhiding Electronics Technology Co., Ltd. is one of the most professional dip ir led manufacturers and suppliers in China, specialized in providing high quality customized products. We warmly welcome you to wholesale bulk dip ir led in stock and get free sample from our factory.
Address: No. 8, Xiaqiao Yinling Industry Zone, Dongcheng Dist., Dongguan, Guangdong, China
E-mail: sales@zhidingled.com
WebSite: https://www.allightled.com/
