Written by Priyank Kishor, Global Product Manager
Branson Welding and Assembly – Emerson (all images courtesy of Emerson)
The sophistication of today’s automobiles is remarkable, with thousands of low-resistance connections of sensors, cameras, and high-tech lighting inside and out. With the private and governmental mandates for the development of electric vehicles (EVs) and autonomous vehicles, electronic complexity will only increase.
New uses for materials, including reinforced plastics in car manufacturing, require rethinking the use of conventional joining technologies, such as glues and screws. Fortunately, plastics joining technologies are advancing to meet these challenges.
Widespread use of EVs and, especially, autonomous cars is likely a few years away yet, however, they’re already changing the way that designers approach automotive electronics. Today’s vehicles are far more “connected” than ever before.
Ten years ago, the typical car had a relatively small number of sensors, aimed at monitoring the combustion engine and drivetrain components. Today, the average number of electronic devices in a car surpasses 200 — sensors, radar, and cameras — which are intended to connect the driver (human or automated) to information about the vehicle and its surroundings. This includes lane markings, other vehicles, objects, and people or animals that may be on the side of the road or crossing a street.
These electronic components, which are typically tiny, printed circuit boards and related wiring, are typically housed in, attached to, and protected by plastic structures. But the fragility of these devices poses an assembly challenge.
In EVs and hybrids, the batteries are highly powerful and rechargeable, requiring weathertight enclosures. These housings, often made of highly engineered and reinforced polymers, are unique in terms of form, fit, and function. They carry their own set of welding and assembly challenges.
Smarter exterior and interior automotive lighting now use organic LED (light-emitting-diode) lamps, which include electronic control components. These lamps require precise yet gentle welding methods to avoid damage. More modern headlamps use connected sensor technology that illuminates the road ahead and warns of any hazards. Tail lamps also are advancing. Small individual structures are being replaced by new designs that integrate LEDs and sensors, and that span the entire width of a car. They’re built into assemblies that are primarily made of plastics.
Driver-information displays are now a key design element in automobile interiors. From dashboard instruments to interactive maps and satellite radio selections, these displays are connected to almost every possible sensor and camera in the car. The outer plastic housings require joining, as do many of the circuit boards and wired assemblies inside the console. Even a driver’s key fob makes use of plastics in sealed assemblies.
As auto designers push toward lighter and more fuel-efficient vehicles — and components become smaller, more complex, and incorporate solid-state and LED technologies — the welding of the plastic enclosures and assemblies has become more sophisticated.
Plastic welding offers more than one technology to meet these demands. In fact, the term encompasses a range of joining technologies that continue to evolve. Here are a few techniques that are ideally suited to these new automotive assemblies.
Ultrasonic welding – creates a high-frequency, heat-generating motion between the components to be bonded. It has been used to join thermoplastics for more than 70 years. Historically, it was used when parts were too complex or costly to be molded in one piece. Instead, they were molded in multiple parts, which allowed for more efficient and cost-effective welding.
Several automotive components are already ultrasonically welded. However, the precision required for today’s delicate sensors, cameras, and lighting components has led to the need for advanced technology.
For example, “dynamic mode” welding can automatically adjust to respond to part-to-part variabilities and unique materials. This technique can safely weld small, thin, or complex plastic parts onto plastic structures directly atop sensors or delicate electronics without damage. It can also weld parts atop plastic assemblies containing compressible internal elements, such as elastomeric seals or cores. Plus, it can handle materials that vary in hardness or structural consistency, such as composites.
Additional benefits include:
• Short cycle time (usually < 1 sec)
• Cost efficiency
• Creates a strong hermetic seal
• No curing time; creates an immediate strong assembly
• No consumables required
• Outstanding repeatability
Laser welding – useful for fast and accurate assembly of small to large structures, such as the plastic housings that surround hybrid and EV batteries. Laser welding is also precise enough for use on the smallest of structures with critical or complex geometries.
This means pre-assembled parts can be joined without vibration or high-temperature heat sources, which could otherwise damage delicate, internal components. This allows for 3D joint configurations and more flexible part designs.
The resulting weld joint has little flash and virtually zero particulates, making laser welding ideal for applications that cannot tolerate contamination. Battery housings fall into this category since batteries are extremely sensitive to any contaminant.
Other benefits of laser welding include:
• Short cycle times
• Homogeneous, reliable, repeatable welds
• Strong hermetic seals (tight/waterproof assembly)
• Excellent aesthetics
• Design freedom to allow for contoured visible weld joints
• Greater material compatibility, including soft materials
• No curing time
• No consumables required
PulseStaking – a new advancement in staking technology. Unlike traditional staking tips, which radiate heat at all times, PulseStaker tips are independently and instantaneously heated and cooled, and localized within the heating effect. Therefore, pulsing tips can be positioned more closely to heat or vibration-sensitive electronic components (such as printed circuit boards), soldered components, or sensors, with no risk of radiant heating.
This technology also offers extremely small welds, which can secure four corners of a circuit board inside a plastic housing.
Additional benefits include:
• Advanced, blended, glass-reinforced, or chromed/metalized plastics
• Complex 3D part designs with varied surface contours
• Multiple, closely aligned post or flap features
The plastic welding technologies required to take automobiles to the next level already exist, with manufacturers continually working on improvements. As advances in electronics for the auto industry develop, so will assembly technologies to help make designers’ visions a reality.