Comparing SMD Capacitors vs. Electrolytic Capacitors

Key Takeaways

  • An overview of capacitor form factors.

  • SMD capacitor characteristics and advantages.

  • The advantages of electrolytic capacitors using through-hole technology.

 SMD capacitor

The SMD electrolytic capacitor specification is designated using capacitance value and working voltage

Capacitors are irreplaceable elements in electronics circuits. The function of a capacitor, whether it be filtering, coupling, decoupling, energy storage, impedance matching, or snubber action, varies from one circuit to another. Capacitor form factor, size, and dielectric material are all important characteristics when selecting capacitors. The form factor of a capacitor is determined based on its capacitance value and circuit board space availability. The dielectric material influences the capacitance value and adds more stability to the capacitor under various environmental conditions.

Depending on the circuit and function, a capacitor can be polarized or non-polarized. You can find polarized and non-polarized capacitors in different form factors. For example, if you are in need of electrolytic capacitors in a miniaturized circuit board, surface-mount device (SMD) capacitors are the best choice. On the contrary, if the circuit application is at a high temperature, the best choice would be electrolytic capacitors with through-hole mounting technology.

Comparing SMD capacitors vs. electrolytic capacitors using through-hole technology is challenging, especially when there are space constraints in circuit designs for applications that must withstand high temperatures, extreme acceleration, or collisions. In this article, we will explore the capacitor form factor and compare SMD capacitors vs. electrolytic capacitors with leads. 

Capacitor Form Factor

Downsizing circuit boards to save space is a common trend in electronics. As circuits are miniaturized with high power density, great attention is given to conserving operational reliability. Component form factors or sizes are selected according to circuit sizing and space availability. Manufacturers have invested in different form factors of passive components, as there is a huge demand for various sizes. Some capacitor form factors available include:

  1. Through-hole capacitors/ leaded capacitors: Capacitors with leads are called through-hole capacitors. Through-hole mounting technology is applicable to all capacitor types based on dielectric materials such as paper capacitors, ceramic capacitors, or electrolytic capacitors. These are inserted into holes in a PCB and soldered on the opposite surface. Through-hole electrolytic capacitors are commonly used in prototype circuits. Electrolytic capacitors using through-hole technology offer resilience due to their niche reliability and distinctive advantages. 
  2. Screw terminal capacitors: Screw terminal capacitors come with threaded studs and are mounted on the board with screws. 
  3. Snap-in capacitors: The lead configuration of snap-in capacitors is designed for easy mounting onto PCBs. 
  4. Press-fit capacitors: Press-fit capacitors have pins that exert a lateral force on the holes where they are inserted. This type of capacitor eliminates production issues, quality problems, and the soldering process. It also provides the fast exchange of capacitors on the board. 
  5. Axial capacitors: In a radial capacitor, the leads come out on one side of the capacitor, whereas in axial capacitors, leads run parallel to the capacitor body and come out at opposite ends. 
  6. Surface-mount device (SMD) capacitors: SMD capacitors are soldered to the assigned pads in the PCB and occupy a space on the PCB. 

These classifications can be combined; if you search an electronic distributor’s website, you can filter the search by capacitor type based on dielectric material and capacitor form factor. You may find combinations like snap-in tantalum capacitors, through-hole electrolytic capacitors, SMD electrolytic capacitors, etc.

Next, let’s compare SMD capacitors vs. electrolytic capacitors using through-hole technology.

SMD Capacitors vs. Electrolytic Capacitors Using Through-Hole Mounting Technology

SMD Capacitors

For dense, high-performing, and compact circuits, SMD capacitors are best. They do not require drilled holes to make connections and are secured by solder on the board surface. SMD electrolytic capacitors usually consist of an electrolytic can and are measured by the can’s diameter. The polarity of SMD electrolytic capacitors is usually marked at one of the device terminals by a line in either white or black. SMD electrolytic capacitor specifications are designated using capacitance value and working voltage. There are two methods to represent the SMD capacitor specification:

  1. The first method defines the capacitance value in microfarad and its working voltage in Volts. 
  2. The second method uses a code of three figures: the first letter indicates the working voltage in Volts, and the other two represent the capacitance value in picofarad. For example, J106 indicates 10 microfarad capacitors with a working voltage of 6.3 V.

Advantages

SMD electrolytic capacitors are well known for their large capacitance to footprint ratio and are very economical. To build high-frequency or high-speed circuits with minimal parasitic inductance and capacitance, SMD capacitors rank the highest among capacitor form factors. 

Electrolytic Capacitors

Whenever polarized capacitors are required, electrolytic capacitors should be used. Most commonly, electrolytic capacitors are used as through-hole devices. Through-hole electrolytic capacitors have a positive terminal and negative terminal with a minus sign marked closer to it. The leads of through-hole electrolytic capacitors can withstand environmental stress to a great extent since they make stronger mechanical bonds with the layers of a circuit board in comparison to SMD capacitors. 

Applications

The reliability of the connection makes through-hole electrolytic capacitors the best choice in aerospace and military applications where the probability of experiencing high temperatures, collisions, and extreme acceleration is greater. The manual replacement and adjustment capabilities provided by through-hole electrolytic capacitors lead to their use in prototyping and testing applications as well. The capacitance value and voltage rating of through-hole electrolytic capacitors are marked on the body of the capacitor. 

Disadvantages

Unfortunately, through-hole technology is heavier, costlier, and more voluminous than SMD capacitors. Usually, the size of through-hole electrolytic capacitors makes it difficult to match the space constraints of the design. Consider your PCB space availability to determine whether you should use SMD capacitors vs. electrolytic capacitors using through-hole technology in your circuit design.

To design circuit boards with active and passive components of different form factors, you can depend on Cadence’s PCB design software. Leading electronics providers rely on Cadence products to optimize power, space, and energy needs for a wide variety of market applications. If you’re looking to learn more about our innovative solutions, talk to our team of experts or subscribe to our YouTube channel.

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Cadence PCB solutions is a complete front to back design tool to enable fast and efficient product creation. Cadence enables users accurately shorten design cycles to hand off to manufacturing through modern, IPC-2581 industry standard.

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