Introduction
In the internal interconnection of electronic devices, board-to-board (BTB) connectors play a critical role in connecting different PCB boards and transmitting signals and power. From smartphones to industrial control equipment, from automotive electronics to communication base stations, BTB connectors are found almost everywhere. However, faced with the vast array of specifications and parameters on the market, engineers often find themselves confused during selection: What pitch should I choose? What stacking height is appropriate? How do I determine the pin count? Starting from the core parameters, this article provides a systematic guide to BTB connector selection.
1. Pitch: The Fundamental Parameter Determining Density and Current-Carrying Capacity
Pitch is one of the most core parameters of BTB connectors, referring to the distance between the centers of adjacent contact terminals, usually measured in millimeters (mm). The choice of pitch directly affects the connector’s pin density, current-carrying capacity, manufacturing difficulty, and cost.
Currently, common BTB connector pitch specifications on the market mainly include: 0.4mm, 0.5mm, 0.8mm, 1.0mm, 1.27mm, 2.0mm, 2.54mm, and others. Among these, 0.4mm and 0.5mm are high-density fine-pitch specifications, mainly used in consumer electronics such as smartphones, tablets, and wearables; 0.8mm and 1.0mm are the mainstream specifications in the industrial field, balancing density and reliability; pitch specifications of 1.27mm and above are more commonly used for power connections or in industrial and automotive fields with extremely high reliability requirements.
When selecting pitch, the following factors should be considered comprehensively: First, PCB routing space-space-constrained applications require finer pitch; second, signal transmission rate-high-speed signals have higher requirements for pitch consistency and shielding design; third, current-carrying demand-larger pitch generally means thicker terminals and higher current-carrying capacity; fourth, processing and assembly precision-fine-pitch connectors require higher SMT placement precision, with relatively higher defect rates.
For scenarios with high reliability requirements such as industrial control and communication equipment, RXSY recommends prioritizing BTB connectors with 0.8mm pitch and above, ensuring performance while reducing production and maintenance difficulty.
2. Stacking Height: The Key Dimension Matching Structural Design
Stacking height, also known as mated height, refers to the total distance between two PCB boards after the male and female connectors are mated. Stacking height is the parameter most closely related to structural design in BTB connector selection, directly determining the space utilization inside the device.
Common stacking heights range from ultra-low profile 0.9mm to specifications of several tens of millimeters. Consumer electronics generally pursue thinness and lightness, with stacking heights typically between 1.5mm and 5mm; industrial and automotive fields, due to the need to consider vibration, heat dissipation, and other factors, have a wider range of stacking heights, with applications from 5mm to over 20mm.
The following points should be noted when selecting stacking height: First, it must precisely match the overall structural design-excessive error will lead to assembly difficulties or connection failure; second, consider tolerance accumulation-PCB thickness, component height, housing tolerances, etc., all affect the actual stacking height requirement, and a certain margin should be reserved during selection; third, low-stacking connectors usually mean smaller terminal contact area and lower mating/unmating life, requiring a trade-off between thinness and reliability; fourth, for applications with floating requirements, BTB connectors with floating mechanisms should be selected to absorb assembly deviations and vibration displacement.
In addition, stacking height is closely related to the connector’s vibration resistance. Generally speaking, the lower the stacking height, the better the overall rigidity of the connector and the stronger its vibration resistance; the higher the stacking height, the more prone it is to fretting wear due to vibration. Therefore, high-stacking specifications should be carefully selected for high-vibration scenarios such as automotive and rail transit applications.
3. Pin Count and Arrangement: Balancing Signal Integrity and Cost
Pin count, the number of contact terminals in a connector, is another important parameter in BTB connector selection. The choice of pin count depends on the number of signal and power paths required by the application, but it is not simply a matter of “selecting exactly how many are needed.”
First, the type and quantity of signals need to be clarified. Signals are divided into different types such as high-speed signals, low-speed signals, power, and ground, and different types of signals have different requirements for terminal positions and shielding. High-speed signals usually require adjacent ground pins to ensure impedance continuity, while power pins need to consider current-carrying capacity, and multiple pins can be paralleled to increase current capacity if necessary.
Second, the arrangement of pin count is also important. Common arrangements include single-row, double-row, four-row, and others. Single-row structures are simple and low-cost, suitable for applications with fewer pins; double-row is the most common structure, balancing density and reliability; four-row and above are high-density structures, suitable for scenarios with large pin count requirements and limited space, but with higher processing difficulty and cost.
Reserve margins should also be considered during selection. For mass-produced products, it is recommended to reserve 10%-20% spare pin positions to cope with subsequent product iterations or functional expansion, avoiding the need for re-selection and board redesign due to insufficient pin count. Of course, excessive reserves also cause cost waste, which needs to be reasonably judged based on product planning.
4. Other Key Selection Factors
In addition to the three core parameters of pitch, stacking height, and pin count, the following factors also need attention during selection:
Mounting Method: BTB connectors mainly have two methods: SMT surface mount and DIP through-hole mount. SMT is currently the mainstream, suitable for automated mass production with high placement density; DIP has better mechanical strength, suitable for scenarios that need to withstand large insertion/extraction forces or vibration.
Material and Plating: Insulating bases commonly use engineering plastics such as LCP, PA6T, and PBT, which should be selected based on operating temperature and soldering resistance requirements. Terminal materials are mostly phosphor bronze or brass, and plating options include gold plating, tin plating, nickel-gold plating, and others. Gold plating has low contact resistance and corrosion resistance, suitable for high-reliability and low-level signal scenarios; tin plating is low-cost and has good solderability, making it the mainstream choice for industrial applications.
Environmental Adaptability: Includes operating temperature range, vibration and shock resistance, protection rating, and more. Automotive-grade connectors typically require an operating temperature range of -40C to 125C and must meet corresponding vibration test standards; industrial outdoor applications may require IP67 or higher protection ratings.
Locking Mechanism: For applications with vibration risk or requiring high retention force, BTB connectors with latches or locking mechanisms should be selected to prevent loose connections due to vibration.
Conclusion
BTB connector selection is a systematic project that requires comprehensive consideration from multiple dimensions including electrical performance, mechanical performance, environmental adaptability, and cost. Pitch determines the foundation of density and current-carrying capacity, stacking height affects structural matching and vibration resistance, and pin count relates to signal integrity and expansion space. Only by deeply understanding the meaning of each parameter and their interrelationships can the most suitable product solution be selected.
Board-to-Board Connector Key Parameters Comparison
| Pitch | Stacking Height | Typical Pin Count | Current Rating | Application Area |
|---|---|---|---|---|
| 0.4mm | 2.5~8.0mm | 20~120P | 0.3~0.5A/pin | Smartphones, wearables, miniaturized products |
| 0.5mm | 3.0~10.0mm | 10~100P | 0.5~1.0A/pin | Consumer electronics, tablets, laptops |
| 0.8mm | 4.0~12.0mm | 10~80P | 1.0~2.0A/pin | Industrial control, communication equipment |
| 1.0mm | 5.0~15.0mm | 6~60P | 2.0~3.0A/pin | Power-signal mix, industrial equipment |
| 1.27mm | 6.0~20.0mm | 6~50P | 3.0~5.0A/pin | High-current, industrial power, test equipment |
| 2.0mm | 8.0~25.0mm | 2~40P | 5.0~10A/pin | Power connections, high-current apps |
RXSY offers BTB connector products in various specifications, covering multiple pitches from 0.5mm to 2.54mm, with different stacking heights and pin counts available, widely used in industrial control, communication equipment, consumer electronics, and other fields. For high-quality BTB connector solutions, please refer to the RXSY product series. Our engineering team can provide professional selection support and customized services.
