Press Fit Technology in the field of PCB (printed circuit board) is an interconnect technology that establishes reliable electrical and mechanical connections on PCBs without the need for soldering.
The following is key information about the crimping process:
Table of Contents
1. Core principle:
Utilize precision designed Press Fit pins or connector terminals.
These pins typically have special elastic deformation areas (the most common being the “eye shaped hole” design, but there are also other shapes such as swallowtail, C-shaped, etc.).
The pins are vertically pressed into the corresponding plated through holes on the PCB with precisely controlled pressure.
During the pressing process, the elastic deformation area of the pin undergoes plastic deformation, resulting in a high-strength interference fit with the coating (usually copper) on the PTH hole wall.
This close contact has formed:
Reliable electrical connection: low resistance, stable signal transmission path.
Secure mechanical connection: The pins are firmly fixed in the holes and can withstand vibrations, impacts, and insertion and extraction forces.
2. Main advantages:
No thermal stress: avoids high temperature thermal stress caused by welding, protects temperature sensitive components (such as connectors under BGA chips) and PCB substrates (especially thick or multi-layer boards). This is particularly important for high-frequency, high-power, or complex PCBs.
High reliability: The connection is based on mechanical stress and is not affected by welding defects such as solder fatigue, virtual welding, and cold welding. It performs excellently in vibration, impact, and temperature cycling environments. Long term reliability is high.
Environmental Protection: No need for solder, flux, or cleaning agents, complying with RoHS and other environmental requirements, simplifying the process flow, and reducing environmental treatment costs.
Repackability: The crimped pins can usually be unplugged without damage using specialized tools or equipment, making it convenient for rework, replacement, or upgrading of components.
Suitable for high-temperature applications: The connection itself does not involve solder with a lower melting point, so it can maintain stability at higher operating temperatures.
Excellent high-speed and high-frequency performance: The crimping point usually has more consistent electrical characteristics (impedance, inductance), and there are no signal integrity issues caused by solder bumps or voids, making it very suitable for high-speed digital and RF applications.
Simplified process flow: eliminates welding (wave soldering, reflow soldering), cleaning and other steps, shortens production cycle, reduces equipment investment and energy consumption.
Suitable for thick/large plates: When welding thick or large-sized plates, uniform heating is difficult, but there is no problem with crimping.
Airtight connection: Some precision crimping designs can achieve a connection close to airtightness, preventing moisture or pollutants from entering.
3. Main drawbacks/challenges:
High cost: The design and manufacturing cost of crimped connectors/pins themselves is usually higher than that of soldered types. Crimping equipment and molds (especially automated crimping) may also have higher costs.
PCB design requires high precision: the dimensional tolerance, positional accuracy, and hole wall quality (coating thickness, uniformity, roughness) of PTH holes are very strict. It is necessary to strictly follow the design specifications of the connector manufacturer.
Crimping equipment and process control: Specialized crimping machines (manual, pneumatic, or servo electric) and precisely matched crimping molds (Anvil) are required. The crimping force and crimping depth must be precisely controlled to ensure the reliability of the connection and avoid damaging the PCB or connector. Process monitoring, such as force displacement curve monitoring, is crucial.
Risk of hole wall damage: Improper crimping parameters or poor hole quality may cause tearing of the hole wall coating or damage to the inner layer connection.
Pull out force requirement: The connection requires a sufficiently large pull out force to ensure mechanical strength, but excessive pull out force may make repair difficult or damage the PCB.
Application limitations: Mainly used for through-hole connectors (such as backplane connectors, power connectors, high pin number connectors, test points, etc.), not suitable for surface mount components.
4. Typical application scenarios:
Backplane/daughter card connection: High density connectors are the most common application in high-speed data transmission backplane systems (such as AdvancedTCA, MicroTCA, VPX).
Power connector: A high current power connector that needs to withstand high mechanical and thermal stresses.
Automotive electronics: modules such as engine control units and transmission controls that require high reliability and resistance to harsh environments.
Industrial control and automation: PLC, servo drives, etc.
Rail Transit: Train Control System.
Aerospace and Defense: A field that requires extremely high reliability and no thermal stress.
Medical equipment: equipment that requires high reliability.
High pin number connector: Avoid yield issues caused by large-scale soldering.
Test point/debugging point: convenient for plugging and unplugging test probes.
5. Key points of process control:
PCB quality: PTH aperture tolerance, hole position accuracy, hole wall copper thickness (usually required to be ≥ 25 μ m, even above 35 μ m), and quality are key factors.
Quality of crimping parts: The dimensional accuracy, material elasticity, and surface treatment (oxidation resistance) of the pins must be qualified.
Crimping equipment and molds: The accuracy of the equipment and the matching degree between the mold and the connector are crucial.
Crimping parameters: Crimping force, crimping stroke/depth must be accurately set and monitored according to connector and PCB specifications.
Process monitoring: Using a crimping machine with force displacement curve monitoring function is the best practice in the industry, which can detect in real time whether the crimping process is normal (such as missing pins, blocked holes, insufficient or excessive crimping force, etc.).
Cleanliness: PCB holes and crimping areas should be kept clean to avoid contamination affecting contact.
Summary:
The crimping process is an important solderless connection technology in PCB assembly, which has significant advantages in applications that require high reliability, no thermal stress, high signal integrity, repairability, and environmental protection. Despite high requirements for PCB design, component quality, and process control, as well as relatively high costs, its long-term reliability and performance advantages make it an irreplaceable connection solution in high-end communication, computing, industry, automotive, aerospace, and other fields, especially in backplane interconnection where it is almost a standard choice. It is a powerful supplement and alternative to traditional welding processes.
