COMPOUNDS | THERMALLY CONDUCTIVE
PA9T, PA6T, LCP Show Low Weld Line Strength Base Polymer GF Content
Mechanical Property Weld Line Strength
[-] [%] [MPa]
Stanyl® 20 60
Source: Envalior NOTE: Weld line strength measurement is based on UL tensile bar
provides a strong bonding force whilst resisting high temperatures and high humidity environments must be used. Often, contaminants such as dust and moisture collect inside connector housings which causes insulating plastics to break down. Liquid crystal polymer (LCP) has long been used to manufacture micro-USB connectors. However, this material demonstrates low resistance to tracking when applied to electronics with thin walls. As USB-C connectors move to higher power throughputs, they require materials with high safety profiles. Envalior describes its Stanyl range as a “best-in-class polyamide” with high amide density, engineered for demanding electrical and electronic applications. With outstanding thermal and electrical properties and creep resistance, it offers 500V CTI to reduce tracking by 50% in thin-walled parts. It also comes in certified halogen- free UL94 V-0 grades, boasts high flow, is compatible with high-speed signal transfer, facilitates lead-free reflow soldering without blistering, has level 1 JEDEC moisture sensitivity level (MSL), comes in halogen and red phosphorous-free grades, and promotes excellent bonding.
Weld line Over its lifetime, a USB-C connector has to withstand thousands of insertions and removals. This requires durable materials that strike the right balance between toughness and stiffness. When
USB-C plug housings are moulded, a weld line is formed on the front of the receptacle. To help absorb the impact of plugging and unplugging devices, the inside of the receptacle is moulded with thin ribs requiring a material with high-flow properties. If the weld line is weak, cracking can occur. When comparing the strength of type C tensile bars made from different materials, Stanyl demonstrated the strongest weld lines. Scientists at Envalior conducted an experiment to compare the bonding performance of LCP and competitive PPA against Stanyl, where a cross- section of each connector was observed under an optical microscope. The results showed clear cracks and gaps with the PPA and LCP, while Stanyl showed better bonding capabilities. To minimise the risk of arc tracking, an insulating material with a high CTI rating should be used, the performance of which can be determined by placing 50 droplets of an electrolyte solution onto the insulating material and measuring the rate at which a tracking path is produced on the material’s surface. After being exposed to 12 saltwater droplets, the LCP connector showed burn marks and electrical breakdown but after dropping 60 saltwater droplets on the Stanyl connector, the insulation material remained structurally intact.
Thin walls
Envalior says that in a bonding experiment on USB-C connectors, results showed cracks and gaps in versions with PPA and LCP, while its Stanyl material showed better bonding capabilities Source: Envalior
46 COMPOUNDING WORLD | September 2024
Nowadays USB-C connectors are designed with a much tighter pitch to house its 24 connector pins. Envalior said to prevent short circuits from forming between the pins, a thin-walled insulating material is required that can demonstrate superior resistance to electrical tracking in high voltage environments. The terminal pitch of the latest USB-C connector version is 0.5 mm, meaning the insulation material width is only 0.3 mm. The thinnest wall on both sides of the USB-C receptacle connector may go down to 0.1 mm in the overmoulding process. To achieve this level of thinness, it is crucial to use a thermal plastic with good flowability, another quality attributed to Stanyl. A proliferation of batteries and charging systems
means that demand has increased for plastics that can be integrated in existing material combinations to achieve an enhanced thermal management
www.compoundingworld.com
PA46 35 50
PA9T 45 22
PA6T/66 35 40
LCP 35 17
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