Problem Solved: TE NanoMQS Miniature Automotive Connectors
TE’s NanoMQS miniature automotive connectors address the need for increased density and reduce the footprint on the PCB by about 50%.
TE Connectivity expanded its MQS product group, which is used by most European vehicle manufacturers as well as others worldwide, with a miniaturized version. The NanoMQS system’s capability for small wire cross sections down to 0.13mm2 paves the way for harness weight-saving measures. At the same time, NanoMQS is also an interconnection system with an exceptional level of vibration resistance (for instance, up to 400g sinus for the sealed version). The robust miniaturized terminals (contacts), connectors, and headers address the increasing density of electronics in the vehicle. They reduce the footprint on the printed circuit board (PCB) by roughly 50%, and still offer up to three amps of nominal current-carrying capacity. The TL version offers up to 32 contact positions, while the even more compact SL version has up to 20 positions.
Original MQS Development
The original MQS interconnection system was designed in the mid ’90s as an automotive termination solution with high packing density, robust design, two locking levels, and compact dimensions. This MQS system for wire-to-wire and wire-to-board contacts, with its 2.54mm pitch, proved very successful: In 2011, TE Connectivity manufactured 13 billion MQS terminals. Over the years, the original MQS series has been expanded with the Micro-Power Quadlok (MPC) and the Power Quodlok (PQ) series, among others, to carry higher currents (Figure 1).
Driven by the continuously rising share of electronics in the car, there is a need for miniaturizing components. As the scope of functions grows, the PCB in electronic control units (ECUs), for instance, has to be as compact as possible. This trend is also valid for the interconnection technology. In some cases — sensors in the engine bay, for example — the connector has become the limiting factor for miniaturization. So TE expanded the MQS product family again with the miniaturized NanoMQS interconnection system. The terminals along with the first generic headers and connector housings, are available in production numbers and are being used in vehicles.
Components of the NanoMQS Interconnection System
The single-piece crimp terminal (contact) forms the very core of the NanoMQS family (Figure 2).
In the standard version, the receptacle contact is made from tin-plated copper. It is available in two sizes for wire cross sections of 0.13mm2 to 0.22mm2, and for wires measuring up to 0.35mm2. The receptacle contacts are designed for rectangular contact blades measuring 0.5 by 0.4 millimeters.
The connectors with tin-plated terminals are approved for ambient temperatures between -40°C and up to 105°C. A silver-plated version permits usage at up to 170°C – conditions which can be found in the engine bay, for instance. The nominal current carrying capacity is up to 3A; however, short peaks of up to five times the nominal limit are possible. When mated, the receptacle contact establishes two electrical points of contact to the blade via a robust L-shaped spring that exerts a high normal force.
Among the quality features of the NanoMQS receptacle contacts is the closed box design of the contact chamber. Combined with comparatively large lead-in chamfers on the housing, which ensure a smooth guiding-in, this design prevents the blade from colliding with the receptacle contact during mating (no “stubbing”), which could otherwise deform and damage the contacting lance. An incorrect insertion is prevented by the design.
A locking lance on top of the contact, which audibly and tangibly latches into the plastic housing when the terminal is fully inserted, provides the primary locking mechanism within the two-level contact retention (Fig. 3).
A cutout provides visual access to the locking hole and thus permits visual confirmation of the correct insertion. At a maximum insertion force of 5N, this primary locking device already gives a minimum retention force of 30N. The independent secondary locking device, which latches into an undercut on the housing, provides a retention force greater than 50N.
Polarization Prevents Incorrect Insertion
To ensure an excellent level of safe and convenient handling despite the terminal’s small dimensions, its cross section is polarized, as are the contact cavities in the housings. Incorrect insertion is thus effectively ruled out. Just like the MQS series, the NanoMQS series is designed for 20 mating cycles. Customers can freely choose their preferred way of loading the terminals into the plastic connector housings: Options include manual assembly as well as fully automated population of the receptacle contacts.
Spatial Envelope Nearly Halved
The NanoMQS series terminals are designed for a nominal pitch of 1.8mm. Therefore, the same number of positions on a NanoMQS header only requires roughly half the board space, which an MQS header needs (Figure 4).
Such a dense nominal pitch requires thin-walled housings, which in turn can only be manufactured in production numbers with a wealth of injection molding know-how. All of TE’s main production processes, including injection molding, are united under one roof.
Obviously, high-position interconnections will benefit most from the NanoMQS interconnection system’s great packing density: In Figure 4, the header footprint drops from 840mm2 with MQS to a mere 411mm2 with NanoMQS.
Figure 5 shows an engine ECU header study. In this application NanoMQS could save 60% of the ECU’s spatial envelope. Comparable projects for 254- and 284-position engine ECUs are currently being implemented.
Its 1.8mm nominal pitch makes NanoMQS a perfect option for hybrid connectors as every contact of the MQS family can be integrated in a grid as an integer multiple of the next size up (Figure 6). To make this possible, the secondary locking device is on the same level on all housings.
NanoMQS housings (headers and connectors), made from a high-grade thermoplastic, are available in two versions, called Top Latch (TL) and Side Latch (SL), both of which are available with a perpendicular or parallel orientation to the PCB. The most striking difference between the two versions is the position of the locking device, which is located centrally on top of the housing of the TL versions (Figure 7). With the locking device positioned in the middle, it is easier to mount connectors side by side. This increases flexibility: For instance, if three generic connectors are initially mounted side by side to establish a high-position interconnection with up to 96 pins during the ramp-up of a new model, the switch to a single customer-specific part can be made any time later without change of technology.
In contrast, the locking device is located at the side of the slightly more compact SL version housings (Figure 8). In the case of the TL versions with two to 32 positions, the housing stiffness is further increased by reinforcing ribs, which primarily serve to raise the stiffness level of the versions with 20 positions and more. The SL versions do not require stiffening ribs, as the locking is ensured without ribs at up to 20 positions.
As the plastic locking and latching profiles have compact geometries, the overlap between the connector and header fronts, for instance, was given in a new wedge shape. During connector mating, this provides a smooth guiding-in of the two halves. When fully mated, the overlap results in a strong, positive connection formed by two wedge shapes securing each other (Figure 9).
High Vibration Resistance Up to Level 4
Vibration and shock resistance are core requirements that electric connections in the vehicle must meet. Corresponding test levels are defined in the standard LV 214 for the EMEA region. According to this standard, the regular versions of the NanoMQS series meet level 2 without any further measures (level 2 is around 3g effective random and 30g shock). This is quite remarkable in so far as this level is already met by an unsealed NanoMQS system, although level 2 was specified for sealed systems.
If an additional seal is included in the connector, the high contact normal force of NanoMQS will make it possible to achieve level 3 for an installation close to components as well as level 4 for direct engine mounting (Figure 10). NanoMQS systems can even achieve the extremely harsh 400g sinus requirement, which was identified as a trait of injection valves.
Fully Designed for Automatic Handling
From day one, NanoMQS has been designed for the production number and quality requirements of the automotive industry. To terminate wires with cross sections between 0.13 and 0.35mm2, the options include manual crimp tools and automated applicators, which can have a pneumatic or servo-driven crimp terminal feed. The quality control and verification of the automated crimping process can be done via standard crimp monitoring systems, which are suitable for fine wires. Using the manual crimp tool delivers exactly the same crimp connection quality that results from automated wire termination. In addition, the manual tool’s good ergonomics permit its use within confined spaces.
Headers have all the features necessary for automated handling: Grippers can grab the offset surfaces while suction caps can use the middle section of the surfaces. On the PCB side, where the most flexibility is needed, it is always the same main element that is used for contacting the PCB. Currently the pins are designed either for thru-hole, wave soldering, or the pin-and-paste process (reflow soldering). A press-fit version is currently under development. The version for surface mounting (SMD) also ensures level alignment with the PCB. To facilitate a test procedure before soldering, a sheet metal bracket for a board lock is also available. A strain relief can be integrated either via grooves in the housing or via the collar on the rear of the header.
Guide posts provide a minimum positioning aid for placing the header on the PCB. The posts ensure that the gripper can place the header force-free, and that the header stays in the correct position on the PCB.
The NanoMQS series provides a new miniaturized solution to terminate signal circuit wires in the vehicle. Depending on the application, the compact system with its 1.8mm nominal pitch can reduce the PCB footprint or the spatial envelope of the connector by up to 50%. Add to this the mass reduction of the connector, and the wire size, which can be reduced down to 0.13mm2 with NanoMQS. On top of that, NanoMQS supports the design of high-position hybrid connectors for power and signal as NanoMQS terminals can be seamlessly integrated at half the grid measure of the larger MQS terminals. As far as mating cycles, ambient temperatures, extraction forces, and vibration resistance are concerned, the NanoMQS interconnection system does not only offer the strengths of the MQS versions, which have proven themselves billions of times, but even goes beyond them in some respects. The first NanoMQS applications can be found in the vehicle interior (roof module) and as sealed systems.
SJ Kim is product manager terminal and connectors, TE Connectivity in Bensheim, Germany.