Heatsink Screw Size For To-220: A Comprehensive Guide

The TO-220 package is a type of electronic component that requires a heatsink to prevent it from overheating. When mounting a heatsink to a TO-220 package, it is important to use the correct screw size to ensure a secure fit. The screw size for a TO-220 heatsink is usually M3, but some people also use 6-32 or 4-40 screws. The correct screw size will fit into the 0.150-inch hole in the TO-220 package and will be long enough to accommodate the thickness of the heatsink.

Screw size for mounting a heatsink

When it comes to mounting a heatsink, selecting the appropriate screw size is crucial to ensure a secure and functional assembly. The following paragraphs will provide a detailed guide on choosing the right screw size for this task:

The TO-220 package is a standard type of electronic component packaging that requires a specific screw size for mounting a heatsink. The correct screw size for this application is typically M3. This size ensures a secure fit within the designated mounting hole, which usually has a diameter of approximately 3.5 mm. It is important to use a screw that fits snugly without being too tight, as this can damage the component or affect heat dissipation.

When mounting a heatsink, it is recommended to use a pan-headed screw. This type of screw has a flat head that sits flush with the surface of the heatsink, allowing for even contact and efficient heat transfer. Using a matching nut on the other side of the component will help secure the assembly and ensure a stable connection. It is also important to consider the length of the screw. The screw should be long enough to pass through the mounting hole and accommodate the nut, but not so long that it protrudes excessively.

In some cases, you may find that the M3 screws are not readily available from certain suppliers or distributors. In such instances, it is possible to use alternative screw sizes that can still provide a good fit. For example, 6-32 screws have been known to work well with the LM7805 component, and they have a diameter of approximately 4.7625 mm. This option may be more accessible through certain retailers or for those who are more familiar with inch-based screw definitions.

When working with TO-220 packages, it is worth considering the use of an insulating ring, especially if the integrated circuit (IC) needs to be mounted in an isolated manner on the heatsink. In such cases, the 4-40 screw size is a suitable choice as it provides sufficient space for the insulating ring. This option ensures that any necessary electrical isolation is maintained while still allowing for a secure connection between the heatsink and the component.

Screw size for TO-220 packages

The correct screw size for TO-220 packages depends on the size of the mounting hole, which is usually around 3.5mm to 4mm in diameter.

Some common screw sizes that can be used for TO-220 packages include:

• M3 screws: These are mentioned by several sources as a suitable size for TO-220 packages. They are available at most hardware stores and can be purchased by weight, which can be cheaper for hobby projects.
• 6-32 screws: These screws have been used successfully with TO-220 packages and have a major diameter of 0.1380 inches with 32 threads per inch (a thread pitch of 1/32 inch).
• 4-40 screws: This size is also mentioned as a possible option for TO-220 packages, especially if insulation is needed with spacers or shoulder washers.

When choosing a screw, it is important to consider the available space and whether any additional components, such as an isolating ring, need to fit between the IC and the heat sink. The length of the screw should also be considered to ensure it does not protrude excessively.

Screw size for bare PCB

When selecting a screw size for a bare PCB, it's important to consider the specific requirements of your project, such as the size of the mounting hole and the need for insulation or heat dissipation. Here are some recommendations and guidelines for choosing the right screw size:

M3 Screws:

M3 screws are commonly used for mounting PCBs. They are the standard size for motherboard standoffs, PC screws, and nylon PCB screws. The diameter of the mounting hole for an M3 screw should be approximately 3.5mm to ensure a secure fit.

6-32 Screws:

6-32 screws are another option for mounting PCBs. They are often used for ATX motherboards and can also work well with TO-220 packages. The major diameter of a #6 screw is 0.1380 inches, with 32 threads per inch.

4-40 Screws:

4-40 screws are recommended if you need to use spacers or shoulder washers for insulation. They can also be suitable for TO-220 packages. The major diameter of a #4 screw is typically smaller than that of a #6 screw.

Self-Tapping Screws:

If you are mounting a PCB to a 3D printed case or plastic enclosure, consider using self-tapping screws designed specifically for plastic. These screws cut their own threads and provide a secure hold without the need for pre-drilled holes.

Heat Dissipation and Insulation:

When selecting a screw size, consider the need for heat dissipation and insulation. Using a larger screw, such as an M4 or 8-32, can provide more surface area for heat transfer if needed. Additionally, nylon washers or isolating rings can be used with screws to provide electrical insulation.

In summary, the recommended screw sizes for a bare PCB, especially for mounting purposes, include M3, 6-32, and 4-40. It is important to choose the appropriate screw size based on the specific dimensions and requirements of your project, ensuring a secure fit and considering any additional needs for heat dissipation or electrical insulation.

Nut requirements

When mounting a TO-220 package, it is important to use the correct type and size of screw and nut to ensure a secure and safe installation. The size of the mounting hole is typically around 3.5mm in diameter, so the screw and nut must be able to fit within this constraint.

The recommended screw size for a TO-220 package is an M3 screw, which has a diameter of 3.5mm and should fit perfectly within the mounting hole. This screw size is commonly used by hobbyists and professionals alike for their TO-220 projects. It is important to note that the screw should not be too long, as excess length can cause issues.

For the nut, it is recommended to use a matching M3 nut, also known as a "matching nut" for the M3 screw. This ensures that the screw and nut fit together properly and provide a secure hold. The nut should be placed on top of the package, allowing any excess screw length to stick upwards. This placement ensures that the assembly is secure and that there is no interference with other components.

When purchasing the screws and nuts, it may be more cost-effective to buy them in bulk from a hardware store or an online distributor. Some stores charge by weight, so you can often get a better deal for the quantity needed for hobby projects.

Additionally, if you are using a mechanical fastener and are concerned about it coming loose over time, you can consider using a nut with a nylon insert or applying a threadlocker adhesive like Loctite 222. These options provide added security and help prevent the fastener from loosening due to vibration or other factors.

By following these guidelines and using the correct screw size and nut requirements, you can ensure a safe and secure installation of your TO-220 package.

Screw size for mounting a TIP31

When mounting a TIP31 in a TO220 package to a bare PCB, it is recommended to use a pan-headed M3 screw with a matching nut. The mounting hole diameter is approximately 3.5mm, so it is important that the screw fits within this size.

You can purchase machine screws and nuts of similar thickness from a hardware store, which may be more cost-effective.

When mounting the screw, place the nut on top of the package so that any excess screw length sticks upwards.

If you are concerned about the screw coming loose, you can use a nut with a nylon insert or apply Loctite 222 threadlocker for small fasteners.

Additionally, soldering the TO220 tab to a wide pad on the PCB can provide extra security and reduce the number of parts needed.

Frequently asked questions