How to choose the right power connector?

2022-02-20
How to choose the right power connector?
Correct choice of power connector

System design is becoming smaller and smaller, but the demand for power supply is growing, which brings great challenges to design engineers. This means that the power connector must accommodate two contradictory necessary conditions at the same time, that is, in addition to increasing the power supply, the design must be more compact, and I don't know how to start when screening a wide range of power connectors in the market. Take the key feature - rated current as an example, which contains a lot of knowledge.

Rated current refers to the amount of current that promotes the specific temperature rise of the female terminal, generally 20 ℃ or 30 ℃. To use this data correctly, we must not only understand its test method, but also pay attention to its test environment. For example, some simply test a pair of female terminals and male pins connected but not installed in the shell. As we all know, the factors affecting the temperature rise of the connector include contact resistance, current and heat dissipation channel. In practical application, the male and female terminals are installed in the shell. As a result, the number of cooling channels has decreased dramatically. In addition, multiple contact pairs are generally used at the same time, and the rated current peak cannot be set as the working current of the connector.

From the manufacturing point of view, most of the traditional power connectors are processed by lathe. Based on the increasingly mature stamping technology, a new generation of stamping power connector is derived. In contrast, the lathe processing process is relatively simple and the setting time of abrasives is short, which is a more flexible production technology. Although the stamping forming process is expensive, its cost is equal to that of lathe processing when it is put into mass production. In particular, the stamping forming technology allows local electroplating, which is an option that lathe processing cannot provide. From the perspective of quality, under the condition of long-term mass production, stamping forming can ensure a certain quality stability, which can not be compared with lathe processing.

From the perspective of assembly, the methods of circuit board assembly include crimping, surface pasting or welding; The methods of cable assembly include screw connection, welding, winding, rolling and IDC (commonly known as puncture connection or insulation displacement connection). To choose a suitable connector, we should not only consider the price of the connector, but also the appropriate assembly technology. Welded connectors are naturally cheaper than surface pasted and crimped connectors, because there is no need for high temperature resistant plastic shell and special crimping area of pins. However, if there are surface mount components on the single board, it is more cost-effective to choose a surface mount power connector. In terms of wiring, screw connection, welding and winding must be assembled manually, and assembly equipment on the market can be selected for grinding and IDC to assemble connectors and cables quickly and accurately. Compared with the grinding connection, IDC has strict requirements on the size of the cable. The size and soft hardness of the cable conductor and insulating layer must meet the specifications of the relevant IDC connector to avoid damaging the connector and ensure the ideal electrical connection between the cable and the connector. If it is used in the working environment with high vibration, the ground cable connector shall be selected. Other factors to be considered include the consideration of whether to use high-temperature resistant cables due to the working ambient temperature.

Current derating curve of ermet power module

In fact, the key design of the connector is the contact formed by the female terminal and the male pin. Poor design, process, unsuitable base materials and electroplated coatings can lead to unsatisfactory contact or even failure to form contact. On the contrary, excessive clamping positive force will lead to excessive wear of the surface coating of the connector and shorten its mechanical life, that is, the number of plugging. The contact design includes lathe [industrial electrical network cnelc] circular pin and terminal, such as European din41612 and ermet 2mm m power terminal, stamping double rod terminal and pin, such as 2mm HM power module, SMC connector, male and female same double rod terminal, such as microstac, etc. The surface coating materials include gold, palladium, nickel, silver, tin, etc. Silver has high conductivity, but it is easy to change color, especially in sulfur-containing environment. Slight will only affect the appearance, and serious will reduce the conductivity. Palladium nickel has high hardness and low porosity, so it has good corrosion resistance. Gold has high chemical stability, low hardness and high cost. In contrast, each has its own advantages and disadvantages.

Press formed double rod terminal

In terms of configuration, there are two different power connectors. The signal terminals on the composite connector generally account for the majority, while the power terminals account for the minority. As for the simple power connector or power module, the terminals are high current terminals. Traditionally, power connectors are mostly designed exclusively, and each brand is different. In view of the increasingly demanding demand for power connectors, various standards gradually include power connectors and derive standard power connectors, such as multiple types of D-sub, D, e, F, h and M connectors in European din41612, 2mm HM m connector and power module, and ATCA power connector. Typical examples of composite connectors include M-type European connector, 2mm HM M-type connector and D-sub connector. For example, the ermet 2mm M-shaped female connector provides 55 pins (5 rows of X11 pins) and is equipped with three special pin cavities for placing power terminals or coaxial terminals. This type of connector can be used alone or combined with other types such as a, B, C, l or n. In contrast, ermet M-type vertical male connector has up to 77 pins (7 rows of X11 rows of pins), of which two rows of outer rows (22 pins) will be connected with the shielding plate of the female connector. Accordingly, the male connector also has three special pin cavities for placing power terminals or coaxial terminals. Examples of simple power modules include 2mmhm power module, microspeed power module and ATCA power connector. In addition, there are board to line power connections - minibridge and maxibridge.

Male and female double pole terminals

In order to enable the power connector to provide higher rated current, connector manufacturers have been improving the design of power connector, including selecting new copper alloy based materials with stronger conductivity, innovating the design of female terminal and male pin contact, and improving the heat dissipation performance of connector. In line with various working environment conditions, connector manufacturers have also developed various power connectors suitable for high vibration systems, dust-proof and waterproof, and with latches for special purposes. There are even connectors with different colors meaning different mechanical codes, so as to prevent operators from inserting them by mistake. In view of the increasing automation of PCB assembly process, tape packaging and pre installation grab pads are becoming more and more common.
With the rapid development of electronic technology, it is estimated that there will be more and greater breakthroughs in the design of power connector in the future. As long as appropriate power connectors are selected and good PCB design is adopted, system design engineers will be able to launch higher quality products.