Where are composite heat sinks generally installed in lamps? Installation recommendations
In luminaires, composite heatsinks are most commonly found where heat is most concentrated, which is near the LED chip, module, or body heat source. Different lamps have different internal structures and working environments, and the installation position of composite heat sinks is also different. Why do you pretend to be like this? Is it good to have it here? Are there alternatives? Let’s break it down together.
In fixtures with a particularly high concentration of heat, such as COB floodlights or stage lights, composite heatsinks are often mounted under the LED chips and attached directly to the base. This is done to dissipate the heat as quickly as possible, especially if you are using copper blocks, columns or short heat pipes, which can conduct heat faster and bring the chip temperature down. This not only makes the lamp more stable, but also extends its life. However, it also has minor troubles, such as rust between copper and aluminum or failure due to poor contact. So sometimes, you can also replace it with a pure aluminum large-volume radiator (low cost but not so strong thermal conduction), or use graphite sheets to spread the hot spot (light and thin, but not too deep).
In street lamps or large outdoor lamps, the lamp body is large and heat-intensive, but more importantly, it disperses the heat. At this time, the heat pipe is often buried in the “skeleton” of the lamp body – such as the bottom or middle of the fins. It works like an underground water pipe: it carries heat from the chip to the fin and is blown away by natural wind. The advantage of this design is that it is stable and durable, but special attention should be paid to the tight fit when assembling, otherwise the heat pipe will not play a role and will “drag back”. If heat pipes are not installed, the alternative is to use a large area of aluminum profiles or add a fan, but this may add bulk or noise.
For thin and compact lamps such as panel lights or line lights, thick copper blocks or heat pipes cannot be used. At this time, we will use graphite heat conductive sheets or ultra-thin vapor chambers to spread the heat evenly like a “hot towel” to avoid local overheating. Its advantages are light, thin, and have good uniform temperature effect, making it suitable for ultra-thin designs. But graphite will conduct electricity, so remember to insulate it when installing. If you have a high budget or are particularly strict about heat dissipation, you can also choose a more advanced vapor chamber, but the cost will be much higher.
In the lights or car size group, the heat must be controlled very stably, otherwise it will affect the life and even safety. Composite heat dissipation structures (such as heat pipes and vapor chambers) are often placed behind the module and hidden in the shell to direct heat to a position where heat can be dissipated. The advantages of this method are high space utilization, uniform heat dissipation, and no problem in passing vehicle standards. In contrast, assembly is complex and requires vibration and sealing tests. Alternatives are to use ceramic substrates or split heatsinks with high thermal conductivity, but these options are often more costly.
Finally, for some landscape lights or decorative lights, sometimes the composite heat dissipation module is made inside the lamp body, and the shell is responsible for “secondary heat dissipation”. This is done so that the appearance is not ruined, and at the same time the light body is modular and easy to replace. However, if the design is not good, the shell will block the airflow and affect the heat dissipation efficiency. Some designs simply expose the fins, which dissipates heat well, but may affect the overall shape or easily accumulate dust.
How to install it more stable?
Regardless of where they are installed, the goal of composite heatsinks is the same: to allow heat to flow away smoothly and not accumulate at the source of heat. Therefore, there are a few common recommendations for installation:
The contact should be tight: the heat sink should be tight and flat, and the cleaner and smoother the contact surface, the better the thermal conductivity effect. A layer of thermal conductive material (such as thermal adhesive, phase change sheet) can be added to fill the small gaps.
- The force should be uniform: when fixing with screws, it should be gradually tightened diagonally to avoid pressing too tightly and not pressing firmly on the other. It is best to have a standardized torque standard or compression force control.
Don’t distort the position: Before dry installation, “try” whether the position is aligned and stuck, and make sure there is no problem before installing the official piece.
Anti-corrosion and anti-conductivity: The contact between copper and aluminum should be protected against corrosion, and the graphite sheet should be insulated and hemmed to avoid short circuit or corrosion problems over time.
How to judge whether a good outfit is good?
A well-installed composite heat sink should not only look tight and clean in appearance, but also have good thermal performance. You can check in the following ways:
Use a thermal imager to see the heat distribution of the whole lamp when it works, and there should be no obvious “hot spots”.
Measure whether the key temperature points (such as near the chip, on the surface of the heat sink) are below the target temperature.
Sample and measure the thickness of the thermal conductive material to see if it affects the performance due to too tight or too loose pressure.
Do salt spray, thermal cycling and other tests (if outdoor or automotive) to see if the interface is blistering, discolored or delamination.
In short, the position of composite heat sinks in different types of lamps is different, but the principles are the same: close to the heat source, efficient thermal conduction, and reliable assembly. Don’t use copper when you should use it, but don’t use all copper; The heat pipe should be used to ensure that it is firmly installed and attached. To save costs, there are also reasonable alternatives; The key is to know “why do you pretend to be like this” in order to choose a design that is both appropriate and stable.
Frequently Asked Questions FAQ
Q1: Does the composite heatsink have to be installed directly under the chip?
Not necessarily, but it is recommended to be as close to the heat source as possible. The shorter the path the heat takes, the faster it disperses. If the structure is limited, you can place heat pipes or vapor chambers on the side to “draw out” the heat and then dissipate it, the key is not to let the heat block at the source.
Q2: The graphite sheet conducts heat very well, is the thicker the better?
Not necessarily. Graphite has strong thermal conductivity “in-plane”, and the thinner it is, the better the fit; Thicker will increase thermal resistance. Generally, 0.1~0.3mm is enough, and the key depends on whether the pressing is flat and whether there is insulation protection.
Q3: Copper conducts heat faster than aluminum, why not use copper for the whole radiator?
Thermal conductivity is indeed strong, but copper is heavy and expensive, and processing is troublesome. Most lamps only use copper in hot spots, and other parts use aluminum to diffuse heat, which can be used and the cost is controlled.
Q4: What is TIM? Can you not use it?
TIMs are thermal interface materials, such as thermal adhesives, thermal pads, and phase change materials, which are used to fill the small gaps between the heat sink and the substrate. It is not necessary, but TIM can greatly reduce thermal resistance if the contact surface is not treated very flat, making it a simple and practical auxiliary material.
Q5: I used a heat pipe, but the temperature is still very high, is it installed incorrectly?
It’s very likely. If the heat pipe is not tightly attached to the aluminum tank, or is only in contact with the point and no thermal conductive glue is added, the thermal conductivity effect will be discounted. Check whether there are gaps, whether the pressing force is enough, and whether it is installed in the wrong direction (some heat pipes have evaporation end and condensation end).
Q6: How to confirm the effect after assembly? Do I have to use a thermal camera?
Thermal cameras are the fastest way to visualize whether there are hot spots. If not, you can also use thermocouples to measure the temperature at several key points, as long as the temperature near the heat source is stable and within the safe range, it is basically OK. It is recommended to do a steady-state test before mass production.
Q7: Will copper and aluminum “rust” when contacted?
It is not rust like rust, but copper and aluminum contact is indeed prone to electrochemical reactions in a humid or salt spray environment, leading to corrosion. Therefore, it is recommended that the copper and aluminum contact surfaces be nickel plated, anodized or separated by insulating sheets.