# Board-to-board connector selection guide: spacing, height, pin number full resolution
In the internal interconnection of electronic devices, Board-to-Board (BTB) connectors play a key role in connecting different PCB boards, transmitting signals and power supplies. From smartphones to industrial control devices, from automotive electronics to communication base stations, board-to-board connector applications are virtually ubiquitous. However, in the face of the dazzling range of specifications on the market, engineers are often confused when selecting models: how large is the spacing? How high is appropriate? How to determine the pin number? This article will provide you with a guide to the selection of board-to-board connectors for your system, starting with the core parameters.
# # I. Pitch: Determine the basic parameters of density and current carrying
Spacing is one of the core parameters of the board-to-board connector, which refers to the distance between two adjacent contact terminal centers, usually in millimeters (mm). The choice of spacing directly affects the connector’s pin density, current carrying capacity, processing difficulty and cost.
At present, the common board-to-board connector spacing specifications on the market are: 0.4mm, 0.5mm, 0.8mm, 1.0mm, 1.27 mm, 2.0mm, 2.54 mm, etc. Among them, 0.4mm and 0.5mm belong to high-density small-pitch specifications, which are mainly used in consumer electronics such as smartphones, tablets, and wearable devices; 0.8mm and 1.0mm are the mainstream specifications in the industrial field, which take into account both density and reliability; 1.27 mm and above large-pitch specifications are more used for power connection or industrial and automotive fields with extremely high reliability requirements.
When selecting the type, the choice of spacing needs to consider the following factors comprehensively: First, the wiring space of the PCB, and the space-constrained application scenarios require smaller spacing; second, the signal transmission rate, the consistency of high-speed signals to the spacing and the shielding design requirements are higher; third, the current carrying requirements, large spacing usually means thicker terminals and higher current carrying capacity; fourth, the processing and assembly accuracy, small pitch connectors require higher SMT mounting accuracy, and the defect rate is relatively higher.
For industrial control, communication equipment and other scenarios with high reliability requirements, Ruixin Shengye recommends that board-to-board connectors with a spacing of 0.8 mm or more be preferred to ensure performance while reducing production and maintenance difficulties.
# # II. Stacking Height: Key Dimensions to Match Structural Design
Height, also known as stacking height, refers to the total distance between the two PCBs after the male and female seats are paired. The height is the most closely related parameter to the structural design in the selection of board-to-board connectors, which directly determines the space utilization rate inside the equipment.
Common heights range from a very low profile of 0.9mm to specifications up to tens of millimeters. The consumer electronics field generally pursues lightness and thinness, and the total height is usually between 1.5mm and 5mm; in the industrial and automotive fields, due to the need to consider factors such as vibration and heat dissipation, the total height range is wider, from 5mm to more than 20mm.
The choice of height needs to pay attention to the following points: First, it must be accurately matched with the structural design of the whole machine, and excessive errors will cause assembly difficulties or connection failures; second, considering the accumulation of tolerances, PCB thickness, device height, shell tolerances, etc. will affect the actual high demand, and a certain margin should be reserved for selection; third, low height connectors usually mean smaller terminal contact area and lower plugging life, which requires a trade-off between lightness and reliability; fourth, for applications with floating requirements, board-to-board connectors with floating mechanisms should be selected to absorb assembly deviations and vibration displacements.
In addition, Hogao is closely related to the vibration resistance of the connector. In general, the lower the closing height, the better the overall stiffness of the connector, and the stronger the vibration resistance; the higher the closing height, the easier it is to produce fretting wear due to vibration. Therefore, strong vibration scenarios such as automobiles and rail transit should be carefully selected to meet high specifications.
# # III. Number and Arrangement of Pins: Balancing Signal Integrity and Cost
the number of pins, which is the number of contact terminals of the connector, is another important parameter for board-to-board connector selection. The choice of the number of pins depends on the number of signals and power paths required for the application, but it is not simply “how much to choose”.
First, it is necessary to clarify the type and number of signals. The signal is divided into different types such as high-speed signal, low-speed signal, power supply, ground, etc. Different types of signals have different requirements for terminal position and shielding. High-speed signals usually require pins in close proximity to ensure continuous impedance, and power pins need to consider current carrying capacity. If necessary, multi-pin parallel connection can be used to increase current carrying.
Secondly, the arrangement of the number of pins is also important. Common arrangement methods are single-row, double-row, four-row, etc. Single-row structure is simple and low-cost, suitable for applications with fewer pins; double-row is the most common structure, taking into account both density and reliability; four rows and above are high-density structures, suitable for scenarios with large pin number needs and limited space, but processing difficulty and cost are also higher.
Reserve margin should also be considered when selecting models. For mass-produced products, it is recommended to reserve 10% -20% of spare pins to meet the needs of subsequent product iterations or feature expansion, and avoid re-selection and plate modification due to insufficient pins. Of course, reserving too much will also cause cost waste, which needs to be reasonably judged according to product planning.
# # IV. Other key selection factors
In addition to the three core parameters of spacing, closing height and pin number, the following factors need to be paid attention to when selecting models:
* * Installation method * *: The board-to-board connector mainly has SMT surface mount and dip through hole insertion. SMT is currently the mainstream, suitable for automated mass production and high mounting density; dip has better mechanical strength and is suitable for scenarios that need to withstand large plugging forces or vibrations.
* * Material and coating * *: Engineering plastics such as LCP, PA6T, PBT, etc. commonly used in insulated base, should be selected according to the use temperature and weld resistance requirements. The terminals are mostly made of phosphor bronze or brass, and the plating has a variety of options such as gold plating, tin plating, and nickel gold plating. Gold plating has small contact resistance and corrosion resistance, which is suitable for high reliability and weak signal scenarios; tin plating has low cost and good solderability, which is a mainstream choice for industrial applications.
* * Environmental adaptability * *: including operating temperature range, vibration shock resistance, protection level, etc. Automotive-grade connectors usually require an operating temperature range of -40 ℃ ~ 125 ℃ and meet the corresponding vibration test standards; industrial outdoor applications may require IP67 and above.
* * Locking mechanism * *: For applications where there is a risk of vibration or where a high holding force is required, a board-to-board connector with a locking clasp or locking mechanism should be selected to prevent loose connections due to vibration.
Conclusion
The selection of board-to-board connectors is a system project, which requires comprehensive consideration of electrical properties, mechanical properties, environmental adaptability, costs and other multidimensional considerations. The spacing determines the basis of density and current-carrying, the combination of high impact structure matching and vibration resistance, and the pin number is related to signal integrity and expansion space. Only by thoroughly understanding the meaning of each parameter and its interrelationships can the most suitable product plan be selected.
Rui Xin Sheng Ye provides a variety of specifications of board-to-board connector products, covering 0.5mm to 2.54 mm a variety of spacing, different height and pin number options, widely used in industrial control, communication equipment, consumer electronics and other fields. For high-quality board-to-board connector solutions, refer to Rui Xin Sheng Ye’s product range, and our engineering team can provide professional selection support and customized services.
