The stock BCU1525 come with a passive cooler. This passive cooler is nothing like the passive cooler on a low end GPU that will keep the GPU cool enough under load. The BCU passive cooler is designed for being installed in the airflow of a fan with massive static pressure to push large amounts of air through the heat sink. This type of airflow is often associated with server chassis but at the levels of power that the BCU run at care needs to be taken even when installing it into a server chassis. This may sound daunting but there are several more or less simple strategies to get enough cooling for your card.
Air Cooling strategies
You can get an active upgrade from SQRL, there are both a factory installed option and a kit for cards already delivered.
You can use a powerful 120 mm fan and use cardboard or a 3D printer to create a duct to force the air into the card. Cardboard has proven to be about equally effective as 3D prints, your performance will vary with how the duct i shaped but there is generally not a problem to get a working setup. Some leakage to create some airflow around that card can have a positive effect on cooling. The type of fan used needs to be very powerful >200 CFM and >1 inch water static pressure. Regular PC case fans are of no use at all. Powerful fans often works over 5000 rpm, these fans are LOUD.
You can install the card into a server case. You need to make sure there is good airflow in the case and you need to block of any paths that are unused to prevent air from escaping around the card.
To have a quieter setup you can use water cooling. There is a community guide over at the fpga forum about water cooling that has a lot of information on the subject. Water cooling has a lot of products available and has been used in PC builds for over 15 years. Water cooling has the potential for a higher max performance ceiling compared to air.
A more experimental way of cooling is immersion cooling where you keep your card in a dielectric (non conductive) liquid. The liquid is circulated and the heat is removed by radiators or heat exchangers. This technique has the highest cool potential since it cools the card on all surfaces. Although immersion cooling has been used for different kinds of applications before, it has not really had a wide scale adoption in the PC industry yet. Several companies are working on products in the field, most with complete solutions. So far no one has demonstrated a system that works and are outperforming more established solutions like water cooling.
If you need any assistance feel free to submit a ticket or contact us in the #allmine-inc channel on the fpga discord https://discord.gg/PKGtx8b
Allmine support team