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TO268: A Bigger Version of the D2PAK Package

Motorola made the headlines as one of the companies to venture into the production of a different kind of package for semiconductor devices. The package known as Decawatt Package or DPAK soon became a household name, helping semiconductor consumers get additional protection for their device.

Although other manufacturers like Infineon Technologies soon came aboard to produce different variants, the DPAK remains one of the best protective mechanisms for semiconductor devices.

Today, in this article, we are going to talk about the TO268, a bigger version of the D2PAK package.

What is the D2PAK Package?

Motorola started with the launch of the Decawatt Package, which is simply called DPAK. The production of subsequent variants came with numbers, such as the D2PAK, being the second variant of the D2PAK.

The Decawatt Package 3 (D3PAK) came after the D2PAK. The D3PAK is what we know as the TO268 package.

Therefore, the D2PAK is the TO268’s predecessor and the latter (the TO268 package) improve on the D2PAK’s design and functions.

Attributes of the TO268 Package

TO268

TO268 or the D3PAK package shares similar attributes as the previous versions of the Decawatt Packages (DPAKs), especially the mounting style. It is a surface-mounted, plastic-molded package, relying on the Surface Mount Technology (SMT) to place the semiconductor components in their respective positions atop the circuit board.

1. TO268 Package Variations

It is generally assumed that any Decawatt Package (DPAK) with three (3) leads is a DPAK, while those with five (5) leads are the D2PAK. The TO268 or D3PAK can have up to seven (7) leads.

As much as that calculation is considerably right, it is not the entire fact. The TO268 or D3PAK package can have a minimum of three (3) leads. Depending on the variant, the lead count could be up to seven (7), which is typically the maximum.

2. Terminal Spacing

To ensure that the leads and all the other semiconductor components are well-placed in the circuit board, the TO268 provides flexible spacing to accommodate those. That is why the terminal pitch extends up to 215 mils.

Technical Properties of the TO268/D3PAK Package

Below is a tabular representation of the technical composition of the D3PAK/TO268 package:

Number of TerminalsBody Sizes (including the heatsink)Body ThicknessTotal Length (including the leads)Terminal Pitch (the distance between the terminals)
3650 x 590 mils198 mils745 mils215 mils
5400 x 390 mils175 mils600 mils67 mils
7400 x 390 mils175 mils600 mils50 mils

Features of the TO268 Package

Below are some of the common features you can see in the TO268 or D3PAK package:

1. High-Power Uses

The TO268 is commonly used with applications in the following areas:

  • Microsemi power IGBTs
  • Microsemi power MOSFETs
  • Power diodes (Microsemi)

2. Improved Thermal Resistance

Heat dissipation is one important factor to consider when investing in or buying a DPAK. In the case of the TO268, the package offers an improved thermal resistance of up to 40-degeree Celsius/W.

Below is a list of the supported thermal resistances of the package:

  • 18˚C/W
  • 0.24 to 1.18˚C/W
  • 21.9˚C/W
  • 40˚C/W

Note that the lower thermal resistance of the TO268 is to help model the package for high-powered applications, especially for MOSFETs and power diodes.

3. Less Power Dissipation

Heat or power dissipation has to do with the process of removing or moving (excessive) heat out of the package. TO268’s heat dissipation is less because of the larger die capacity, which in turn, influences a decrease in the MOSFETs’ RDS(ON) values.

4. Flexible Soldering

Soldering or attaching the TO268 package to the Printed Circuit Board (PCB) is easy because of the flexibility of soldering it by hand. It is also possible to solder the package with other processes, including reflow techniques and infrared.

You however, want to have in mind that hand-soldering the TO268 package needs to be done with precaution. To get the best results, consider using a functional soldering iron when working on the package’s central thermal pad.

Quick Facts about Heatsinks for DPAK Packages

By design, a three-tied Decawatt Package (DPAK), such as the D3PAK or TO268 ought to have the following compositions:

  • Resistor: The resistor of the D3PAK is formed through the two (2) surface-mounted leads.
  • Heatsink: The heatsink of the package is derived from the squared body design of the package.

Noteworthy is that a heatsink helps in heat or thermal dissipation in the TO268, and indeed any other DPAK package. It may be a bit confusing to understand how the entire dissipation process works, so here is how it is done.

Heatsink Thermal Dissipation Process in TO268 Package

For heat or thermal energy to be moved or dissipated on the TO268, there must be a heatsink. In the package, the heatsink works by a process called conduction, which is an indirect, yet effective way to remove (excessive) heat from the package.

The amazing thing about “conducting” heat via the TO268’s heatsink is that the entire process doesn’t involve or require a direct contact to the Surface Mount Technology (SMT) device.

The conducted heat or thermal energy moves from the TO268 package into the Printed Circuit Board (PCB). From there, it is transported down to the copper drain pad, which picks it up and transports the same to the device’s heatsink.

The heat would then make its out way out of the heatsink via the opening and is then released into the immediate environment.

With that in mind, you want to be intentional when choosing a heatsink for your TO268 package. Here are some of the factors to consider when doing that:

Matching Dimensions

The dimensions of the heatsink should match the PCB. That way, there will be a lot of space through which the heat would be conducted from the circuit board and dissipated into the surrounding environment.

Surface-Mountable

As the TO268 is a surface-mounted, plastic-molded package, it makes sense to use it with Surface Mount Technology (SMT) devices.

In extension, the heatsink should also be surface-mountable.

That is also a good reason why the selected heatsink shouldn’t have attachment holes, because it is meant to be mounted.

Last but not least, the heatsink should be compatible with the Surface Mount Technology (SMT) operations, as that simplifies the process of mounting it on the Printed Circuit Board (PCB).

Conclusion

TO268 is a bigger version of the D2PAK package, and not only is it bigger – it also has a convenient spacing among the terminals and has the heatsink strategically located at the back for high-power/heat dissipations.

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