The radio frequency coaxial connector (hereinafter referred to as the RF connector) is usually regarded as a component installed on the cable or installed on the instrument as a component for electrical connection or separation of the transmission line. It belongs to mechatronics products. Simply speaking, it mainly serves as a bridge.

Compared with other electronic components, the development history of RF connectors is relatively short. The UHF connector that appeared in 1930 was the earliest RF connector. During the Second World War, due to the urgent needs of the war, with the development of radar, radio and microwave communications, medium series such as N, C, BNC, TNC, etc. were produced.

After 1958, small products such as SMA, SMB, and SMC appeared. In 1964, the US military standard MIL-C-39012 “General Specification for Radio Frequency Coaxial Connectors” was formulated. Since then, RF connectors have begun to develop in the direction of standardization, serialization and generalization.

In more than sixty years, through the joint efforts of experts from various countries, the RF connector has formed an independent and complete professional system and has become an important part of the connector family. It is an indispensable key component of the coaxial transmission system.

The research and development technology of RF connectors in the United States, Britain, France and other countries are in a leading position. Its design, production, testing and use technologies have been completed and tended to be perfect. Not only has it formed a complete standard system, but also raw materials, auxiliary materials, testing systems, Assembly tools have also been standardized, and specialized scale production has been carried out.

1. BNC Characteristic impedance
The characteristic impedance of BNC radio frequency connectors is 50Ω and 75Ω. Many series of connectors have both 50Ω and 75Ω specifications. Generally speaking, 50Ω connectors are mostly used for high-frequency and high-performance products; 75Ω connectors are mostly used for products with lower frequencies, and the frequency is mostly below 4GHz, especially for consumer electronic video. Users should choose a connector that matches their impedance according to their own products. If the user uses a 75Ω RG 59 Cable, he should choose a 75Ω connector.

BNC Connector for RG174 Cable Plug Crimp Type

BNC Connector for RG174 Cable Plug Crimp Type

2. BNC Frequency
Each type of radio frequency connector has a frequency range, and the user should understand the working frequency of his product to choose the connector. Choosing a connector lower than the required operating frequency will affect the electrical performance of the whole machine; or choosing expensive, high-precision and high-frequency connectors will cause waste. It should be noted that the frequency of use of connectors designed by different companies is quite different, and the frequency of use of inferior products is far from reaching the industry standard. When selecting the connector, the user should confirm the electrical performance description of the product.

BNC Connector for Coaxial Cable for RG178 180 Degree Male to N Type Female 4 Hole Square Flange Female

VSWR is one of the most important performance indicators of RF connectors. It is a measure of the amount of signal returned from the connector. It is a vector unit including amplitude and phase components. The VSWR of the same type of connector is different at different frequency of use. Generally speaking, the higher the frequency of use, the higher the VSWR. If the user wants to know the VWSR of the connector at a certain frequency, he can ask the manufacturer.

The quality of soldering has a huge impact on the overall quality of the PCB. Through soldering, different parts of the PCB are connected to other electronic components to make the PCB work properly and achieve its purpose. When industry professionals evaluate the quality of electronic components and equipment, one of the most prominent factors in the evaluation is the ability to work in soldering.

To be sure, welding is very simple. But this does require practice to master. As the saying goes, “practice can be perfect.” Even a novice can make functional solder. But for the overall life and function of the equipment, clean and professional welding work is necessary.

What is a perfect solder joint?

It is difficult to include all types of solder joints in a comprehensive definition. Depending on the type of solder, the PCB used or the components connected to the PCB, the ideal solder joint may change dramatically. Nevertheless, most perfect solder joints still have:

  • Completely wet
  • Smooth and shiny surface
  • Neat recessed corner

In order to obtain the ideal solder joints, whether it is SMD solder joints or through-hole solder joints, an appropriate amount of solder must be used, and the appropriate soldering iron tip must be heated to an accurate temperature and be ready to contact the PCB. Oxide layer removed.

The following are the nine most common problems and errors that can occur when welding by inexperienced workers:

  1. Solder bridge

PCBs and electronic components are getting smaller and smaller, making it difficult to manipulate around the PCB, especially when trying to solder. If the tip of the soldering iron you use is too large for the PCB, an excess solder bridge may be formed. Soldering bridge refers to when the soldering material connects two or more PCB connectors. This is very dangerous. If it goes undetected, it may cause the circuit board to short circuit and burn. Make sure to always use the correct size soldering iron tip to prevent solder bridges.

  1. Too much solder flux

Novices and beginners often use too much solder flux when soldering, and large bubble-shaped solder balls are formed at the solder joints. In addition to what looks like a weird growth on the PCB, if the solder joint is functioning properly, it may be difficult to find. There is a lot of room for errors under the solder balls. The best practice is to use solder sparingly and add solder if necessary. The solder should be as clean as possible and have a good concave angle.

  1. Cold stitch

When the temperature of the soldering iron is lower than the optimal temperature, or the heating time of the solder joint is too short, a cold solder joint will occur. Cold seams have a dull, messy, pock-like appearance. In addition, they have a short life and poor reliability. It is also difficult to evaluate whether cold solder joints will perform well under current conditions or limit the functionality of the PCB.

  1. Burnt out node

A burnt joint is the exact opposite of a cold joint. Obviously, the soldering iron works at a temperature higher than the optimal temperature, the solder joints expose the PCB to the heat source for too long, or there is still a layer of oxide on the PCB, which hinders the optimal heat transfer. The surface of the joint is burnt. If the pad is lifted at the joint, the PCB may be damaged and cannot be repaired.

  1. Monument

When trying to connect electronic components (such as transistors and capacitors) to the PCB, tombstones often appear. If all sides of the component are properly connected to the pads and soldered, the component will be straight. Failure to reach the temperature required for the welding process may cause one or more sides to lift up, creating a tomb-like appearance. The tombstone falling off will affect the life of the solder joints and may have a negative impact on the thermal performance of the PCB. One of the most common problems that cause tombstone cracking during reflow soldering is uneven heating in the reflow oven, which may cause premature wetting of solder in certain areas of the PCB relative to other areas. The self-made reflow oven usually has the problem of uneven heating. Therefore, it is recommended that you purchase professional equipment.

  1. Insufficient wetting

One of the most common mistakes made by beginners and novices is the lack of wettability of solder joints. Poorly wetted solder joints contain less solder than the solder required for proper connection between the PCB pads and the electronic components connected to the PCB by solder.

Poor contact wetting will almost certainly limit or damage the performance of electrical equipment, reliability and service life will be poor, and may even cause a short circuit, thereby seriously damaging the PCB. This situation often occurs when insufficient solder is used in the process.

  1. Jumpwelding

Jump welding may occur in the hands of machine welding or inexperienced welders. It may happen due to lack of concentration of the operator. Similarly, improperly configured machines may easily skip solder joints or part of solder joints. This leaves the circuit in an open state and disables certain areas or the entire PCB. Take your time and check all the solder joints carefully.

  1. Pad lift

Due to the excessive force or heat exerted on the PCB during the soldering process, the pads on the solder joints will rise. The pad will lift up the surface of the PCB, and there is a potential risk of short circuit, which may damage the entire circuit board. Be sure to reinstall the pads on the PCB before soldering the components.

  1. Webbing and splash

When the circuit board is contaminated by contaminants that affect the soldering process or due to insufficient use of flux, webbing and splashing will occur on the circuit board. In addition to the messy appearance of the PCB, webbing and splashing are also huge short-circuit hazards, which may damage the circuit board.


Radio-frequency connector is mainly consisted of outer conductor, inner conductor,insulating support medium,The mainly material are as below:

Outer conductor:Passivation for stainless steel. copper alloy gold plating,copper alloy nickel plating,copper alloy ternary alloy three-partalloy ect,

Inner conductor: copper alloy gold plating,copper alloy silver plating ect,

Insulating support medium:PTFE、PEI、LCP ect,

The main specification of the RF coaxial connector.

Impedance:almost all of the RF coaxial connectors and electric cable have the standard impedance of 50Ohm.The only one exception is the 75Ohm system is usually used for cable TV installation,It is also an important RF coaxial cable connector have the characteristic impedance of a matched cable,If not like this,A discontinuity is brought into and the damage can be caused.

VSWR(voltage standing wave ratio):In the ideal case ,it should be unity,good design and carry out to keep them within 1.2.

Frequency range:Nowadays,the most RF coaxial connectors works among DC-10GHz,As to the connectors work among 10-40GHz ,They will be more expensive.

Loss:This is connector loss in the normal frequency range,Losses are usually 0.1 and 0.3 decibels,

Operating cycle:How many the circle of connect and disconnect they can withstand,It’s usually 500-1000 times.

Power:Power supply is consisted with two resistance losses(heat) and insulation breakdown,

Characteristics of rf coaxial connectors:

1.Multiple specifications and varieties:More than 20 names in the international general purpose department,more varieties and specifications.

2.Products are reliable,failure mode and failure mechanism are complex.

3.Electrical characteristics are guaranteed by mechanical structure,It is an electromechanical integration product,There are essential differences with other low-frequency connectors,

4.Parts processing is mainly turning machine processing,There are many manual assembly operations, so it is difficult to carry out automatic assembly.

5.Product update is slow.

Connector is named as plug and socket,Usually means electric couple,They connect two active device,transmit current or signals.

The connectors are the components electronics engineers usually meet,Their usage is Between blocked or isolated circuits within a circuit,build bridges,So that the current is flowing.The connector is an indispensable part in the electronic equipment.Observe along the path of current flow,You’ll always find one or more connectors.

Connectors come in a variety of forms and structures,With the difference between the application object, frequency, power, application environment, etc,There are different types of connectors.For example,Connectors for lighting and hard drive on the field,And the connector that ignites the rocket is very different.But whatever kind of connector it is.should ensure that the current is flowing smoothly and reliably.In general.The connector is connected to more than just current.In today’s rapid development of optoelectronic technology,In an optical fiber system, the carrier of the signal is light.Glass and plastic instead of wires in ordinary circuits,But connectors are also used in optical signaling pathways,They act as electrical connectors.

The connector is a device that connects two active components and is used to transmit current or signals. Connectors’ is widely used and take important role in it’s application.

Connector category

There are only two basic ways to classify connector products according to their appearance, structure and working frequency. They are divided into Circle and rectangle by the outline structure. The operating frequency can be divided into low frequency and high frequency, and the frequency is bounded by 3MHZ.The rectangle connectors is the majority used in the market.Its cross-section is a trapezoid, which is approximately a rectangle.In addition, it can be divided into many different types according to some other purposes, installation methods, special structures, special performance, etc. At the same time, according to the relevant technical standards of connectors can be divided into low-frequency circular connector, rectangular connector, printed circuit connector, radio frequency coaxial connector, fiber connector and so on.

Use advantages

1、The connectors improve the production process, not only simplifies the assembly process of electronic products, but also simplifies the mass production process.

2、The connectors are very easy to maintain.When some components don’t work, Itis convenient to change the lose efficacy and restore normal operation of the component.

3、They are convenient to upgrade.With the development of technology, the components can be updated when the connectors are installed, and can be replaced with new ones.

4、They are flexible for design.When people use the connectors for the assemble system, they will find it is more flexible.

Dosin hardware electronics, as a professional connector manufacturer, which is focused on rf connector production research and development and sales for thirteen years, precipitated the rich technical experience, strength. Now have gained a good reputation in the national connector market, and the products have been exported to more than 40 countries and regions at home and abroad through the cooperation with the foreign trade team of Renhotec.

Many practitioners may don’t have a good knowledge about the differences about 3.5mm/2.92mm/2.4mm/SMA,As a menber of Dosin Hardware Electronics Co., Ltd.I’m really happy to share the knowledge of these four connectors with you and hope this knowledges will help you. Many users may meet this problem. 3.5mm/2.92mm/2.4mm,  connectors,which one can seamless connect with SMA.First we should learn to tell these connectors apart before answering the question.

At the baginnig.SMA is designed for 0.141semi-rigid coaxial cable.and usually filled with ptfe medium.In the army industries ,they are used as precision connectors for microwave applications.At that condition.since SMA is small in small size and can work in high frequency. (Frequency range of semi-hard cable is DC~18GHz,and the soft cable is DC~12.4GHz)They are popular quickly.Even the Millimeter wave connectors developed later (for example:3.5mm、2.92mm) also take the mechanical compatibility into consideration.

What is 3.5mm connectors? The outer diameter is 3.5mm.The impedance is 50Ω.The bindiny mechanism is 1/4-36UNS-2 English thread Connector.The biggest difference betweem SMA is 3.5mm is use air dielectric.The outer conductor of 3.5mm connectors is thicker than SMA connector.The mechanical strength of 3.5mm connectors is better than SMA connectors.Not only the behaviour of electricity of 3.5mm connectors is better than SMA connectors’ .but also mechanical endurance and repeatability of performance are higher than SMA connectors.So they are suitble for used in testing industries.

The Outer diameter of the 2.92 connectors is 2.92mm.The impedance is 50Ω.The bindiny mechanism is 1/4-36UNS-2 English thread coaxial Connector.the structure of 2.92 connectors are similar with 3.5 connectors.but smaller than 3.5 connectors. 2.92 connectors’ frequency is DC~46GHz.they have good electrical property and can be compatied with SMA connectors and 3.5mm connectors.So 2.92 connectors are soon accepted by manufacturers. And became one of the most widely used millimeter wave connectors in the globle world.

The outer diameter of the 2.4mm connectors is 2.4mm.The impedance is 50Ω.The outer diameter of the 1.85mm connectors is 1.85mm.The impedance is 50Ω.They have smaller inside dimension.and higher working frequency.nominal can up to 50GHz 60GHz,

This two connectors are mechanical compatible and can connect with each other.But please note that they can’t be connected with 2.92mm,3.5mm and SMA connectors.If connect with 2.92mm,3.5mm and SMA connectors.They will be broken down.

After reading the above article.You may have a good idea about the difference among 3.5mm/2.92mm/2.4mm/SMA connectors.If you want to know more information about the connectors of  3.5mm/2.92mm/2.4mm/SMA connectors.Please log in

If Purchase and customize SMA connectors.Please choose Dosin Hardware Electronics Co., Ltd.We have experience in manufacturing SMA connectors for 12 years.All our products are passed ISO certification. We are spoken highly by our peer.and our product sale to 40 countries in the world.and enjoy high recognition.You contact us by 0086 769 81153906.