Technical Library
The housing material decides whether a connector survives reflow, whether it holds its dimensions in a humid engine bay, and whether it can be moulded thin enough for the pitch you want. It is usually the first thing to get wrong and the most expensive to change later.
| Material | Temperature | Moisture absorption | Flow / thin wall | Where it fits |
|---|---|---|---|---|
| PBT polybutylene terephthalate |
Good | Low, ~0.1% | Good | The automotive workhorse. Stable dimensions, good electrical properties wet or dry, easy to mould. Default choice unless something pushes you off it. |
| PA66 nylon 6/6 |
Good | High, 1.5-2.5% | Very good | Tough and cheap with excellent chemical resistance. The moisture uptake is the catch: parts grow and electrical properties shift as they condition. |
| PA6T / PA9T / PA46 / PA4T high-temperature polyamides |
Very good | Lower than PA66 | Very good | Developed for lead-free reflow. Survives 260°C peak SMT profiles where PA66 will not. |
| LCP liquid crystal polymer |
Excellent | Very low, <0.02% | Excellent | Fine-pitch SMT connectors and very thin walls. Inherently flame retardant. Anisotropic, so weld lines are weak - design the gating deliberately. |
| PP polypropylene |
Limited | Negligible | Good | Low cost, excellent chemical resistance, low temperature ceiling. Covers, caps, non-critical housings. |
| TPE thermoplastic elastomer |
Varies by grade | Low | n/a | Seals, grommets, strain relief and overmoulded boots rather than the housing itself. |
Properties vary substantially with glass fill and specific grade. Treat the table as a shortlist tool and confirm against the datasheet for the grade actually quoted.
A lead-free SMT profile peaks around 260°C. That rules out standard PA66 and pushes you to a high-temperature polyamide or LCP. Through-hole and wire-to-board parts are not constrained this way, and PBT is usually the better commercial answer.
Below roughly 2 mm pitch the wall sections get thin enough that flow decides whether the part can be moulded at all. LCP fills thin sections that PBT will short-shot, which is why it dominates fine-pitch board connectors despite the cost.
PA66 can take up 1.5 to 2.5% water, and the part grows and softens as it does. For a sealed automotive connector held to tight dimensional tolerance, that conditioning behaviour is usually the reason to specify PBT instead.
On flame rating. UL 94 V-0 is achievable in most of these families, but it is a property of the specific grade, not of the polymer. Put the rating on the drawing with the wall thickness it applies at - a grade rated V-0 at 1.5 mm is not automatically V-0 at 0.8 mm.
How to use these tables. The values here are standard reference figures published to help you specify and compare parts. They are guidance, not a substitute for your own engineering standard, and several of them (torque above all) depend on assumptions about friction, lubrication and joint material that will differ in your application. Where a number matters, confirm it against the governing specification and against the part drawing. We will supply the plant's actual test data with any quotation.