Protecting the semiconductor components from damages triggered by external factors is the major function of a metal can package. But it doesn’t end there. The package can do more than that, but first, you want to be sure that you are picking the right package.
With an array of options out there, deciding on the best metal can package may seem a herculean task. We have made it simpler for you to choose one of these packages. We are recommending the TO18 metal can package, not only because of the improved device protection but also because of the specialty in that area.
In this article, you will learn the major facts you always wanted to know about working with the TO18 metal can package.
What is TO18?
It is a metal can package or metal header package designed for semiconductor devices. The primary function is to prevent the overt exposure of the semiconductor components to damages.
If you are working on a device requiring three (3) leads, using the TO18 metal case to protect it is good investment. As a metal can package, TO18 is ideal for such devices (requiring 3 leads) and can provide different variants to fit the job.
General Information about the TO18 Metal Can Package
A few points are worth expressing about the TO18, one of which is the case’s design. Primarily made of metal, it provides the much-needed insulation to protect semiconductor devices from environmental factors, including contaminants and moisture.
The next point to note about the package is that its protective design includes placing the microchip atop the semiconductor component’s die before using a high-wielding current to seal the metal cap.
TO18 is called a “3-terminal” metal can package because it uses three (3) terminals. Devices or applications where it is to be mounted for semiconductor component protection also need to use a maximum of 3 leads.
Features of the TO18 Metal Can Package
Let’s now talk about some of the features or the properties that distinguish the TO18 from the other metal can packages out there.
1. Hermetic Sealing
Protecting a semiconductor component needs to be done the right way and that includes ensuring that the component’s package is well-protected.
The hermetical sealing of the TO18 goes a long way to prevent the semiconductor components from getting affected by the two common environmental hazards – contaminants and moisture.
2. Considerations for Leads
TO18 metal can package is the favorite for devices and applications using three (3) leads. That is why it is one of the best packages for transistors.
Besides that, the package is also ideal for applications that have lower lead counts, anything between 1 and 3 is fine.
3. TO18 has Varying Packages
The TO18 metal can package has an array of options for you to choose from. Note that these variants tend to stick to the 3-lead count, even though some may be flexible enough to accommodate devices with one or two leads.
Interestingly, variations also extend to the different semiconductor components to be protected. Thus, you will find TO18 metal can package variants for the following:
- Light Emitting Diodes (LEDs)
- Diodes
- Photodiodes
TO18 also has variants that may accommodate up to eight (8) leads, though, they are rare.
Technical Properties of the TO18 Metal Can Package
Below is a tabular representation of the technical properties of the TO18 package:
| Technical Properties | Description |
| Cap Diameter | 4.7mm |
| Base Diameter | 5.6mm |
| Minimum Lead Length | 12.7mm |
| Lead Diameter | 0.45mm |
| Lead Arrangement (in circle diameter) | 2.54mm |
| Maximum Lead Pitch | 2.97mm |
Variations of the TO18 Metal Can Package
Here is a detailed breakdown of some of the variants of the TO18 package.
1. TO-206
The TO18 variant was introduced to replace the former circular arrangement of leads in the package. In the place of that, the TO-206 package offers an outlined diameter that is not only maintaining a cap height (diameter) of 1.40mm but doesn’t stick to a minimum diameter for the leads.
2. TO-71
This is also a variant of the TO18, only that the package has a 45-degree minimum angle between the two (2) adjacent leads. It also supports up to 8 leads, though, in reality, it appears to be a 5-leaded TO18 package because up to three (3) of the leads might be omitted.
3. TO-46 & TO-52
This are also a TO18 variant, only that they spot significant changes. Unlike the TO18 metal can package with a cap diameter of 4.7mm, that of the TO-46 is 1.90mm while that of the TO-52 package is 3.30mm.
The only similarity between the TO-46 and the TO-52 packages with the TO18 is that they all have the same support for three (3) leads.
4. TO-72
This is a TO18, but with some changes, especially in the lead count. It doesn’t support 3 leads, but rather supports four. Although the three leads are used just as they are on the TO18 package, the other additional lead is put to a better use.
The fourth lead is typically connected to the package’s case, from where it provides thermal or electromagnetic shielding or protection for the radio frequency-specific applications.
Benefits of Working with a Metal Can Package
Besides the device protection, metal can package like the TO18, can also be beneficial in the following ways:
1. Metal Can Packages Provided Additional Protection for the Devices
The additional protective functions of the metal can package include the prevention of electromagnetic waves from penetrating of getting into the device. We can see that on the TO-72 package that uses the fourth wire (lead) to provide electromagnetic shielding for radio frequency-specific applications.
2. Metal Can Packages Block Disruptive Mechanisms
Blocking contaminants and moisture is the basic function of a metal can package. The additional functions include protecting the device from ultraviolet light, oxygen, water, air and carbon dioxide.
Conclusion
The TO18 metal can package is a great choice for high-frequency devices, which require protection for the components and the device in general.
A good rule of thumb is to buy the TO18 package that does not only fit your device, but also provides additional protective mechanisms.
Generally, TO18 is expensive when compared to the plastic-based TO-92 package. So, you want to draw up a decent budget before shopping for it.
