The short answer
For automotive and appliance connectors that are not reflow soldered, start with glass-filled PBT (low moisture, steady dimensions) or nylon 66 (tougher, higher heat, high CTI). For surface-mount connectors that go through lead-free reflow, use LCP, or PPS, high-temperature PPA or PA46 kept dry. Then check the grade's flame rating at your thinnest wall, its CTI, and glow-wire values if the connector goes into an appliance.
A connector is a small, thin-walled part that has to hold metal terminals in exact positions, insulate them from each other, survive heat and sometimes a soldering oven, and pass the flame and electrical tests of the product it goes into. For larger enclosures, see best plastic for electrical housings.
What a connector resin has to do
- Fill thin walls: walls between terminals can be well under 0.5 mm. The resin must fill them without short shots, flash or warpage.
- Flame rating: V-0 at thin wall is a common requirement; the rating holds only at the thickness and colors listed for the grade. See UL 94 flame ratings explained.
- Tracking (CTI): resistance to surface tracking under wet, contaminated conditions. A higher CTI can permit shorter creepage distances.
- Glow wire: appliance standards such as IEC 60335-1 call for glow-wire values (tested under IEC 60695-2-12 and -13) on parts supporting live connections.
- Long-term heat (RTI): the relative thermal index under UL 746B should sit above the connector's operating temperature, including heating from current flow.
- Dimensional stability: pitch, mating force and seal fit depend on low warpage and low moisture growth.
- Terminal retention: the plastic must hold the terminal latch for years at temperature without creeping or relaxing.
- Reflow survival: for surface-mount parts, no blistering or distortion through the solder oven.
- Color and marking: color coding for keying, and laser-markable grades for codes and polarity marks.
Connector resins compared
| Resin | Flow / thin wall | Heat and reflow | CTI (typical) | Moisture uptake | Typical connectors |
|---|---|---|---|---|---|
| PBT, glass-filled (15–30%) | Very good | Not for reflow (melts ~223–225°C / 433–437°F); GF30 HDT ~200–210°C | Non-FR and high-CTI grades often 400–600 V; standard FR grades lower | Very low | Automotive harness and sensor connectors, appliance terminals |
| PA66, unfilled or glass-filled | Very good | Not for SMT reflow (melts ~260–265°C / 500–509°F); GF30 HDT ~240–255°C | High in many grades, often 600 V non-FR | High; dimensions and properties change with humidity | Harness connectors, terminal blocks, glow-wire appliance parts |
| PET, glass-filled | Good | Not for reflow (melts ~250–255°C / 482–491°F); GF30 HDT ~220–230°C | Moderate; varies by grade | Very low | Larger housings, bobbins, relay parts |
| PA46, glass-filled | Very good | Reflow possible with dry-packed parts (melts ~295°C / 563°F) | High in many grades | Higher than PA66; blister risk if moist | High-heat and some SMT connectors, automotive parts near the engine |
| PPA, glass-filled | Good | High-temperature grades handle reflow if kept dry; HDT ~260–295°C | Moderate to high; varies by grade | Lower than PA66 | SMT connectors, high-voltage and e-mobility connectors |
| PPS, glass-filled | Good; tends to flash | Survives reflow (melts ~280°C / 536°F); GF40 HDT ~260–270°C | Low to moderate (often ~125–175 V); higher in special grades | Very low | Hot sensor connectors, coil bobbins, sockets |
| LCP, glass or mineral filled | Excellent; fills walls of a few tenths of a mm | Best reflow performance of the group | Low to moderate on many grades | Very low | Fine-pitch board-to-board, memory and card sockets, SMT connectors |
Typical values and behavior; grades vary widely. Flame-retardant packages, glass level and color all change CTI and flow. Read flame rating, CTI, glow wire and RTI from the listing for the specific grade at your wall thickness.
PBT vs. nylon 66
Glass-filled PBT absorbs very little water, so a PBT connector keeps its size and electrical properties from a dry winter to a humid summer. It flows well into thin walls and crystallizes quickly for short cycles. FR grades reach V-0 at thin walls, down to about 0.4 mm on some grades. Standard PBT can degrade in long hot, wet service, so look at hydrolysis-resistant grades for under-hood connectors. See PET and PBT.
Nylon 66 is tougher, takes more heat and has high CTI in many grades, which is why it is common for terminal blocks and glow-wire appliance parts. It absorbs water: a dry-as-molded part grows slightly and gets tougher and less stiff as it conditions, and moisture lowers its insulation resistance. Design latches and fits for both the dry and conditioned states.
Surface mount and reflow soldering
Lead-free reflow profiles typically peak around 260°C (500°F). That is above the melting point of PBT (about 223–225°C / 433–437°F) and PET, and about at the melting point of PA66, so none of them is used for connectors that go through the oven.
- LCP: the usual choice for fine-pitch SMT connectors. Very high flow, very low warpage, low moisture uptake and inherent flame resistance.
- PPS: survives reflow and is inherently V-0, but flashes easily in thin, tight tools. See PPS.
- High-temperature PPA and PA46: tougher than LCP and PPS, but they absorb moisture. Water in the part turns to steam in the oven and causes blisters, so parts are kept dry and often shipped in moisture-barrier packaging. See PPA.
Qualify any SMT connector against the actual reflow profile and moisture-sensitivity level the board assembler uses.
Appliance connectors and glow wire
Under IEC 60335-1, insulating parts supporting connections that carry more than 0.2 A in unattended appliances (washers, dryers, dishwashers, refrigerators) generally need GWFI of at least 850°C (1562°F) and GWIT of at least 775°C (1427°F), or the finished part must pass a 750°C (1382°F) glow-wire test. FR nylon 66 and FR PBT grades with published glow-wire values are common here. A V-0 grade does not automatically pass. See electrical and electronics.
What to send us for a quote
- The grade on the drawing, or the connector type and wall thickness
- Flame rating, CTI, glow-wire and RTI values required, and the product standard
- Whether the part is reflow soldered, and the peak temperature
- Color, laser marking, annual volume and ship-to location
Common questions
What plastic are electrical connectors made of?
Glass-filled PBT and nylon 66 (filled and unfilled) are the workhorse connector resins in automotive and appliance work. PA46, PPA, PPS and LCP are used where heat, reflow soldering or very thin walls rule those out.
Which plastics survive lead-free reflow soldering?
Lead-free reflow peaks around 260°C (500°F), above the melting point of PBT and PET and at about the melting point of PA66. LCP is the usual choice, and PPS and high-temperature PPA and PA46 grades can work if the parts are kept dry, because absorbed moisture causes blisters.
Why is LCP used for fine-pitch connectors?
LCP flows extremely well, so it fills very thin walls and long, narrow cores, it shrinks and warps very little, and it withstands reflow soldering. It is also inherently flame retardant. Its downsides are weak weld lines, strong flow-direction anisotropy and a relatively low CTI on many grades.
What CTI does a connector need?
The end-product standard and the creepage distances in the design decide. A higher CTI can allow shorter creepage distances at a given voltage, which is why high-CTI PBT and PA66 grades (often 400–600 V) are used in compact, higher-voltage connectors.
Do appliance connectors need glow-wire testing?
Usually, yes. Under IEC 60335-1, insulating parts supporting connections that carry more than 0.2 A in unattended appliances generally need a material with GWFI of at least 850°C (1562°F) and GWIT of at least 775°C (1427°F), or the finished part must pass a 750°C (1382°F) glow-wire test. Check the edition that applies to your product.
PBT or nylon 66 for connectors?
PBT absorbs far less moisture, so it holds dimensions and electrical properties in humid service and warps less in thin sections. Nylon 66 is tougher, takes higher heat and has high CTI in many grades, but it grows slightly as it absorbs water and its properties change between the dry and conditioned states.
Does a UL 94 V-0 connector pass glow wire?
Not necessarily. UL 94 and glow-wire tests measure different things, and a V-0 grade can fail GWIT. Check the glow-wire values listed for the grade at your wall thickness.
Tell us the connector and its ratings
A polymer chemist reviews every request, then matches your grade or finds a qualified equivalent and prices it.
What to send for an accurate quote
- The grade name, from any supplier, or a data sheet
- Color (natural, black or a custom match)
- Fill type and percentage, if any
- Melt flow, if you know it
- Quantity for this order and what you use in a year
- Ship-to city and state or province