Three basic properties of RF connectors
1.Mechanical
Mechanical properties as far as connection function is concerned, plug and pull force is an important mechanical property. Plug and pull force is inserted force and pull out force, the requirement of both is different.The maximum insertion force and minimum separation force are specified in the relevant standards, which indicates that the insertion force is small from the point of view of use (hence the structure with low insertion force LIF and no insertion force ZIF), small separation force will affect the reliability of the contact.
Another important mechanical property is the mechanical life of the connector.Mechanical life is actually a durability index, in the national standard GB5095 called it mechanical operation.It is based on a cycle of one insert and one pull out, and is judged by whether the connector can normally complete its connection function (such as contact resistance value) after the specified plug and pull cycle.
The insertion force and mechanical life of the connector are related to the structure of the contact piece (positive pressure) and the coating quality of the contact part (sliding friction coefficient) as well as the dimension accuracy of the contact piece arrangement (alignment degree).
2.Electrical properties
Including contact resistance, insulation resistance and electrical strength.
(1)Contact resistance
High quality electrical connectors should have a low and stable contact resistance.The contact resistance of the connector varies from a few to tens of milliohms.
(2) Insulation resistance
I tis measurement of electrical connector contacts and contacts and shell insulation performance index, its order of magnitude is hundreds of megohm to thousands of megohm.
(3) the electrical strength, or voltage resistance, medium voltage resistance, it is to characterize the connector contacts between or between the contacts and the shell withstand rated test voltage.
(4) other electrical properties.
Electromagnetic interference leakage attenuation is to evaluate the shielding effect of the connector, and electromagnetic interference leakage attenuation is to evaluate the shielding effect of the connector, which is generally tested in the frequency range of 100MHz~10GHz.
3.Common environmental properties
Including the resistance to temperature, humidity, salt spray, vibration and shock.
At present, the highest working temperature of rectangular connector is 140℃ (except a few high temperature special connector), and the lowest temperature is -45℃.Since the connector works, the current generates heat at the contact point, resulting in a temperature rise, it is generally considered that the operating temperature should be equal to the sum of the ambient temperature and the contact temperature rise.In some specifications, the maximum allowable temperature rise of the connector at the rated working current is specified.
(2) moisture intrusion will affect the connection h insulation performance, and corrosion of metal parts.The constant humidity and heat test condition is relative humidity 90%~95% (up to 98% according to product specifications), temperature +40±20℃, and the test time is at least 96 hours according to product regulations.Alternating humidity and heat tests are more rigorous.
(3) when the salt mist connector works in the environment containing moisture and salt, its metal structure parts, contact parts surface treatment layer may produce electrochemical corrosion, affecting the physical and electrical properties of the connector.Salt spray tests are prescribed to evaluate the ability of electrical connectors to withstand this environment.It is to suspend the connector in a temperature-controlled test chamber, and spray the specified concentration of sodium chloride solution with compressed air to form a salt fog atmosphere. The exposure time is specified by the product specification for at least 48 hours.
(4) vibration and impact resistance vibration and impact is the important performance of electrical connectors, in the special application environment such as aviation and aerospace, railway and road transport is particularly important, it is an important index to test the robustness of electrical connector mechanical structure and electrical contact reliability.There are clear rules in the relevant test methods.The peak acceleration, duration and pulse waveform of the shock, as well as the time of interruption of electrical continuity, shall be specified in the shock test.
(5) other environmental performance according to the use of requirements, the other environmental performance of the electrical connector are sealing (air leakage, liquid pressure), liquid immersion (resistance to specific liquid vice), low pressure and so on.
RF Connector Selection
1. Frequnency range: The selected RF connector should conform to the actual frequency range.
2. Generally, the straight type connector's electrical performance is better than the right angle type connector's, so we can select according to actual use situation.
3. VSWR: Select the low VSWR's connector
4. Insertion loss: Select the low insert loss's connector
5. Impedance: The selected RF connector should match the impedance of the matched RF connector or cable.
6. The EMC of the thread RF connector is better than any bayonet type or push-pull type RF connector.
7. When IM is required, the material and coating of RF connector should be considered.
8. When the ordinary RF connector meets the requirements, we do not need to select high-performance RF connector.
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