高压连接器选料，我们见过太多这样的开场：
"我们要一个 UL94 V0 的阻燃尼龙。"
需求没错，但只说了三分之一。
UL94 考自熄性，GWIT 考灼热丝起燃，CTI 考漏电起痕。 高压件上真正让安规过不去的，往往是后两个，尤其是 CTI。
这篇把三个指标的分工讲清楚，你就知道高压连接器该往哪个方向选料。
开篇先讲个现场
有家做充电桩配套的客户，曾经拿着两张检测报告来问我们：同一个牌号的阻燃增强 PA66，一家机构测的 CTI 是 600 伏，另一家测出来只有 400 伏出头，是不是有一家测错了。
我们把两份报告的测试条件逐行对，没测错——差别在样品状态：600 伏那份用的是干态样，400 伏那份模拟了湿热处理后测试。而充电桩的真实服役环境，明显更像后者。
这个案例把高压连接器选型的核心矛盾摆上了桌：物性表上漂亮的数字，是干态实验室里的数字；你的产品要在湿热、污秽、温变的环境里跑十年，两个世界之间隔着一整套评价方法。
这篇就专门讲这道鸿沟。先分清 CTI、GWIT、漏电起痕三个指标各管什么——很多招标文件把它们混着写，供应商跟着混着报。然后讲 CTI 是怎么在配方和工况里被一步步“打下来”的，为什么高压件常要往半芳香族走，同一个连接器上不同部位怎么分着选。
最后五个坑加边界。给做高压连接器、充电枪、储能连接的读者：这一篇里的判据，建议直接抄进你们的来料检验标准。
一、先分清三个指标各管什么
这三个指标经常被混在一起说，其实考的是三件不同的事。
| 指标 | 全称含义 | 考什么 | 典型要求 |
|---|
| UL94 | 水平/垂直燃烧 | 材料离开火源后能不能自熄 | V0（最高常见等级） |
| GWIT | 灼热丝起燃温度 | 热源接触时会不会被点燃 | 750℃ / 850℃ / 960℃ |
| CTI | 相对漏电起痕指数 | 电压 + 污渍 + 湿气下会不会形成导电通道 | 600V 档常见于高压件 |
一句话分工：UL94 管"火"，GWIT 管"热"，CTI 管"电"。
三个指标的测试条件也不同，不能互相换算。 UL94 是在标准试样上做的燃烧测试；GWIT 是在特定温度的热丝上做的；CTI 要在特定溶液污染条件下测。
所以"我们 V0 过了"这句话，回答不了 CTI 的问题。 三个指标要分别要数据、分别验证。
高压连接器是电的活，所以CTI 才是它的主场。
很多项目的安规返工，不是因为 V0 没做到，是因为 CTI 差一档。
二、CTI 是怎么被"打下来"的
CTI 失效的机理，值得单独说一段。
条件是三个：电压 + 湿气 + 表面污染。
过程大致是：
1. 件表面吸潮或沾上导电性污渍
2. 在电压作用下，表面产生微小泄漏电流
3. 泄漏电流产生局部高温，把表面碳化
4. 碳化层导电，电流进一步集中
5. 形成永久性的导电通道
最后一步之后，绝缘就永久失效了，而且不可逆。
所以升高 CTI 的思路是两条：
① 让材料不吸潮 —— 这是树脂层面的② 让材料不易碳化 —— 这是阻燃体系层面的
这两条恰好是互相牵制的。 很多提高阻燃性的添加剂（尤其卤系）会让 CTI 下降。这就是为什么"高 CTI + V0"是一个配方难题，不是买一个现成牌号那么简单。
一个容易被忽略的参数：吸湿
PA6 / PA66 吸湿之后，体积电阻率会明显下降。
也就是说，同一个牌号，在干燥条件下 CTI 达标，在南方梅雨天里可能就掉档。
这一点对出口到高湿地区的产品尤其重要。选料时要求供应商给"调湿态"的电气数据，不要只看干态。
爬电距离不能替代 CTI
有一种常见的"补救"做法：CTI 不够，就把结构上的爬电距离拉长。
这在设计上有用，但替代不了材料，原因在于：
爬电距离解决的是"表面路径够不够长"- CTI 解决的是"表面会不会被碳化"
如果材料本身容易碳化，距离再长也只是把失效点挪个地方。 一旦某处被碳化，导电通道会从碳化区往外扩展，而不是沿设计路径走。
所以正确顺序是：先选对材料的 CTI 档位，再用爬电距离做设计余量。 反了，就是拿结构去补材料的短板。
三、为什么高压件常要往半芳香族走
把上一节的两个要求放在一起看：
高 CTI：要低吸湿、不易碳化- 高阻燃：要 V0、有时还要求无卤- 高耐温：SMT 件要过回流焊，汽车件要长期 120-150℃
三条叠加，PA66 就很难兼顾了。
半芳香族尼龙（PA6T、PA9T、PA10T、PPA 家族）的优势正在这里：
| 特性 | PA66 | PA6T / PA9T |
|---|
| 平衡吸水率 | 8-9% | 明显更低（PA9T 极低） |
| 熔点 | 265℃ | 320℃ / 306℃ |
| 耐回流焊 | 一般 | 好 |
| CTI 基线 | 中等 | 高（PA9T 常被提到 600V 档） |
| 尺寸稳定 | 一般 | 好 |
| 成本 | 基准 | 高 |
这里最强的性价比项通常是 PA6T，CTI 与尺寸稳定性最好的是 PA9T。
代价是加工温度高——PA6T 熔点在 320℃ 以上，注塑机料温和模具都要跟着调整，不能拿 PA66 的工艺参数直接套。
一句话：高压件的贵料，买的不是强度，是"电性能 + 尺寸 + 耐温"三者的同时达标。
四、同一个连接器，不同部件要分着选
高压连接器不是一个件，是一组件。它们的受力、耐温、电气要求都不同。
| 部件 | 材料方向 | 关键指标 |
|---|
| 外壳 | 阻燃 PA66 / PA6T | V0、CTI、机械强度 |
| 胶芯 / 绝缘体 | PA6T / PA9T / PPA | CTI、耐温、尺寸稳定 |
| 端子座 / 固定件 | PA66-GF / PA6T-GF | 强度、耐温 |
| 密封圈 / 防尘件 | 弹性体 / TPE | 回弹、耐候 |
| 屏蔽 / 结构支架 | PA66-GF 或有屏蔽功能材料 | 强度、装配 |
胶芯是最挑材料的一块。
因为它同时要满足：高 CTI、薄壁成型、高尺寸精度、耐温。这就是为什么高压连接器胶芯经常直接用 PA9T 或 PPA——其他位置可以省，这里省不了。
一个工艺上的连坐关系
CTI 不只是配方的事，还受注塑工艺影响。
熔体温度过高 → 材料局部降解 → 表面更容易碳化- 模温过低 → 表面粗糙、内应力大 → 更容易吸潮积污- 料筒滞留时间长 → 同样导致降解
所以同一个牌号，工艺没调好的件和调好的件，实测 CTI 可能不在一个档。 这一条在送安规检测之前，值得先自己打样测一次。
还有一个位置经常被漏掉：金属嵌件与塑料的配合
高压连接器里通常要埋金属端子或螺母。金属和塑料的线膨胀系数差一大截。
温度循环之下，界面处会产生应力。做温度循环试验时，如果件在嵌件位置开裂，多半是这个原因，不是材料强度不够。
处理办法通常是两条：让嵌件设计有足够的咬合结构，或者选线膨胀系数更接近的树脂体系。这类问题必须在设计早期解决——改材料改不动它。
顺带说一个细节：连接器里的密封圈槽口。
密封圈的压缩率，是由槽口尺寸决定的。塑料件吸湿后会涨，槽口尺寸跟着变，压缩率就跟着变。
所以密封槽的关键尺寸，一定要用调湿后的数据来定。否则装配时是好的，用一段时间才开始渗。
半芳香族不是万能升级
CTI 不达标就上半芳香族，这个升级路径在行业里快被说成公式了，但公式有适用边界。半芳香族的电气表现确实好，CTI 六百档常见，耐温也高半档；代价是三个：单价高一截、加工窗口窄、韧性比脂肪族低，低温装配的场合要小心脆断。
所以升级前先做三件事：确认湿态 CTI 真的不达标，很多项目用干态数据吓自己；确认结构侧爬电距离已经优化到位，距离加一毫米可能就不用换料；确认温升和装配温度在半芳香族的舒适区。
三件事做完再升级，钱花得踏实。材料升级解决不了结构偷懒的问题，这个原则在高压件上尤其明显。
五、五个坑
坑 1：只问 V0，不问 CTI。 全文在说这件事。高压件要三个指标一起提。
坑 2：用干态电气数据做设计。 吸湿会拉低体积电阻率。要求调湿态数据。
坑 3：为了阻燃牺牲加工性。 无卤阻燃体系加量大，流动性差、薄壁难打。胶芯薄壁件要提前确认流动性和成型窗口。
坑 4：忽略 CTI 的时效性。 CTI 会随吸湿、老化下降。认证通过不等于长期稳定。
坑 5：拿 PA66 的工艺打 PA6T。 高温尼龙的料温、模温、干燥要求都不同，工艺不换等于白选料。
一个常被忽略的验证项：老化后的机械强度
CTI 会随老化下降，机械性能同样会。高压连接器在整车寿命里要经历温度循环和振动，卡扣的强度不能只看初始值。
要求供应商提供热老化后的强度保持率，比提供常温拉伸强度有用得多。尤其是长期 130℃ 以上的位置，这一项比初始强度更能说明问题。
六、边界
| 场景 | 结论 | 说明 |
|---|
| 800V 平台高压件 | 半芳香族方向 | PA6T / PA9T / PPA |
| 400V 平台通用件 | PA66 阻燃体系可覆盖 | 需验证 CTI |
| 长期 >150℃ 电气件 | PA6T / PA46 / PPA | 按温度定 |
| 高 CTI + 薄壁 + 无卤 | 难度最高 | 建议早期做配方验证 |
| 强电弧场合 | 需专门方案 | 可能需要热固性或陶瓷化材料 |
行业里的一条实感
高压连接器询盘里，我们最常听到的一句话是：
"我要 V0 的料，你们有几种？"
这句话问出来，基本可以判断客户是第一次做高压件。
因为做过高压件的客户，问法是这样的："V0、CTI 600V、长期 150℃，有没有方向？"——三个指标一起提。
我们通常会追问三句：这个件是高压平台的哪一档，400V 还是 800V？长期工作温度多少？有没有薄壁位置？
三句问完，方向基本就定了。如果客户只答得出"要 V0"，那说明项目还停在选料的最前面——这时候选任何牌号都是碰运气。
我们宁可在这时候多问几句，也不愿意等客户送完安规检测再来找我们换料。换料的钱是小事，耽误认证周期的钱是大事。
读者追问两则
追问一：CTI 数据采购时怎么核查才不被忽悠？ 三个动作：看黄卡对应厚度，CTI 数值只在标注厚度以下有效，壁厚更薄要降档；看测试状态，写明是干态还是湿热后，招标文件统一按湿热后判定；
看批次一致性，让供应商提供近两年的第三方复测记录，只有一张历史黄卡、再无跟踪数据的，要打个问号。三步走完，CTI 上的水分基本挤干。
追问二：往半芳香族升级时最容易被忽略的验证项是什么？ 低温装配冲击。半芳香族的韧性比脂肪族低一档，常温装配没问题，冬季北方产线或低温物流场景下，卡扣装配脆断率会冒出来。
升级方案定稿前，把最低装配温度下的卡扣插拔试验加进验证清单，这一项能拦住升级后最常见的售后类型。一句话收尾：升级是在换性格，不是换参数，先把新性格的脾气摸清，再让它上岗。
还有一条给方案评审会的提醒：高压连接器的材料方案，别只让材料工程师签字。结构、工艺、品质三方都要过目——结构看爬电距离留没留够，工艺看注塑能不能稳定做到那个薄壁，品质看来料检验有没有对应的检测手段。
材料方案从来不是材料一个人的决定，四方签字齐了，方案才算立得住，落地才没有死角。这个流程看起来慢，实际上是三电项目里最省时间的一环。
招标条款里的 CTI 模板
把 CTI 要求写进招标文件，推荐这样成段：高压电气件用工程塑料，相比电痕化指数按 IEC 60112 测试，判定状态为湿热处理后测得，PTI 不低于四百伏（八百伏平台件不低于六百伏），测试厚度不高于产品最小壁厚，随报告附黄卡对应档位截图；
供应商需提供近两年内第三方复测记录，无跟踪数据者须随样品同步送检。这一段抄进去，三件事就锁死了：判定状态锁死，堵住干态数据蒙混；厚度绑定，堵住高档位低厚度的错配；跟踪数据，堵住一次性报告。
招标文件多写这五行，来料环节的 CTI 纠纷基本绝迹。条款是上游管理，比下游扯皮便宜太多。
再把招标谈判中的一个常见场景补上：供应商报了一个 CTI 很高的新牌号，价格也漂亮，要不要切？切之前要三样东西：第三方完整报告而不只是宣传页数字、近半年的量产供货记录、以及同行业类似工况的使用案例。
三样齐了做小批量试产，试产件全部送检复测。新牌号的性能陷阱往往不在平均值，在批间波动——宣传数字是挑过的最好一批，你的产线拿到的是随机批次。波动这一课，供应链上每家都要补，早补早安心，晚补的学费单都不少。
结语
高压连接器选料，记住三个词的顺序：
先 CTI，再 GWIT，最后看 UL94。
因为高压件是"电的活"，UL94 只是入场券。顺序反了，就会在送检时才发现了问题。
再加上一条：所有电气数据，都要问调湿态的。
最后补一句：高压连接器选料，本质上是在"电性能、耐温、成本"三个角上找一个能同时站住的位置。三个角都要，就是贵料；能省一个，才有余地。这句话留给你下次和研发开会时用，比十页资料都管用。
For high-voltage connector material selection, we have seen too many openings like this:
We want a flame-retardant nylon with UL94 V0 rating.
The demand is not wrong, but it only covers one-third.
UL94 tests for self-extinguishing properties, GWIT tests for glow wire ignition, and CTI tests for tracking resistance. For high-voltage components, what truly causes safety standards failures are often the latter two, especially CTI.
This article explains the division of the three indicators clearly, so you will know which direction to choose materials for high-voltage connectors.
Let's start with a live scene
There is a client who makes charging pile accessories. They once came to us with two test reports and asked: For flame-retardant reinforced PA66 of the same brand, one institution measured a CTI of 600 volts, while another measured just over 400 volts. Is it possible that one of them made a mistake?
We compared the test conditions of the two reports line by line and found no testing errors—the difference lies in the sample condition: the 600-volt test used dry samples, while the 400-volt test simulated testing after damp-heat treatment. And the actual service environment of the charging pile is obviously more like the latter.
This case puts the core conflict of high-voltage connector selection on the table: the beautiful numbers on the physical property sheets are numbers from dry laboratory tests; your product has to operate for ten years in humid, dirty, and temperature-changing environments, and a whole set of evaluation methods separates these two worlds.
This article specifically discusses this gap. First, clarify what the three indicators CTI, GWIT, and tracking resistance each cover—many tender documents mix them together, and suppliers report mixed values accordingly. Then it explains how CTI is gradually 'brought down' through formulations and working conditions, why high-voltage components often have to move toward semi-aromatic types, and how different parts of the same connector are selected differently.
Add the last five pits and boundaries. For readers making high-voltage connectors, charging guns, and energy storage connections: the criteria in this article are recommended to be directly copied into your incoming material inspection standards.
1. First, distinguish what each of the three indicators measures
These three indicators are often mixed up when discussed, but in fact, they measure three different things.
| Indicator | Full name meaning | What exam | Typical requirements |
|---|
| UL94 | Horizontal/Vertical Burning | Can the material extinguish itself after being removed from the fire source? | V0 (Highest Common Level) |
| GWIT | Incandescent wire ignition temperature | Will it ignite when in contact with a heat source? | 750℃ / 850℃ / 960℃ |
| CTI | Comparative Tracking Index | Will voltage, dirt, and moisture form a conductive path? | The 600V range is commonly used for high-voltage components. |
Division in one sentence: UL94 handles 'flammability', GWIT handles 'heat', CTI handles 'electricity'.
The test conditions for the three indicators are also different and cannot be converted into each other. UL94 is a combustion test conducted on standard specimens; GWIT is done on a hot wire at a specific temperature; CTI needs to be measured under specific solution contamination conditions.
So the phrase 'we have V0' cannot answer CTI's question. The three indicators each require separate data and separate verification.
High-voltage connectors involve electricity, so CTI is their main field.
Many projects require safety rework, not because V0 wasn't achieved, but because the CTI is one grade lower.
2. How CTI was 'brought down'
The mechanism of CTI failure is worth discussing separately.
The conditions are three: voltage, moisture, surface contamination.
The process is roughly as follows:
1. The surface of the part absorbs moisture or gets contaminated with conductive dirt
2. Under the action of voltage, a small leakage current occurs on the surface
3. Leakage current generates local high temperatures, causing the surface to carbonize.
4. The carbonized layer is conductive, and the current is further concentrated
5. Form a permanent conductive path
After the final step, the insulation will fail permanently and irreversibly.
So there are two approaches to increasing CTI:
① Make the material moisture-resistant — this is at the resin level ② Make the material less prone to charring — this is at the flame-retardant system level
These two happen to counteract each other. Many flame-retardant additives (especially halogen-based ones) can cause the CTI to drop. This is why 'high CTI V0' is a formulation challenge, not something that can be solved by simply buying an off-the-shelf grade.
A parameter that is easily overlooked: hygroscopicity
After absorbing moisture, the volume resistivity of PA6 / PA66 will significantly decrease.
In other words, the same grade may meet the CTI standard under dry conditions, but it might fail during the plum rain season in the south.
This is especially important for products exported to high-humidity areas. When selecting materials, suppliers should provide electrical data in the 'conditioned' state, not just in the dry state.
Creepage distance cannot replace CTI
There is a common 'remedial' practice: when the CTI is insufficient, the creepage distance in the structure is lengthened.
This is useful in design, but it cannot replace materials, for the following reasons:
Creepage distance addresses whether the 'surface path is long enough' - CTI addresses whether the 'surface will be carbonized'
If the material itself is prone to carbonization, increasing the distance only shifts the failure point elsewhere. Once a certain area is carbonized, the conductive path will expand outward from the carbonized region, rather than following the designed path.
So the correct order is: first choose the CTI rating of the right material, then use the creepage distance to design the safety margin. If reversed, it means using the structure to compensate for the material's shortcomings.
3. Why high-pressure components often tend to move toward semi-aromatic
Look at the two requirements from the previous section together:
High CTI: requires low moisture absorption and resistance to carbonization - High flame retardancy: requires V0, and sometimes also halogen-free - High temperature resistance: SMT components must withstand reflow soldering, automotive components must withstand long-term 120-150°C
With three combined factors, PA66 becomes very difficult to handle.
The advantages of semi-aromatic nylons (PA6T, PA9T, PA10T, PPA family) are here:
| Feature | PA66 | PA6T / PA9T |
|---|
| Balanced water absorption | 8-9% | Significantly lower (PA9T extremely low) |
| Melting point | 265℃ | 320℃ / 306℃ |
| Reflow solder resistant | general | Good |
| CTI Baseline | Medium | High (PA9T is often mentioned in the 600V range) |
| Dimensional stability | general | Good |
| Cost | Benchmark | Tall |
The item with the best cost-performance ratio here is usually PA6T, while PA9T has the best CTI and dimensional stability.
The drawback is the high processing temperature—PA6T has a melting point above 320°C, so both the injection molding machine’s material temperature and the mold need to be adjusted accordingly; you cannot directly apply the process parameters of PA66.
In one sentence: The expensive material of high-voltage components is not bought for its strength, but for the simultaneous compliance of 'electrical performance, dimensions, and temperature resistance'.
4. For the same connector, different components should be selected separately
A high-voltage connector is not a single part, it is an assembly. Their stress, temperature resistance, and electrical requirements are all different.
| Component | Material direction | Key indicators |
|---|
| Shell | Flame-retardant PA66 / PA6T | V0, CTI, Mechanical Strength |
| Rubber core / Insulator | PA6T / PA9T / PPA | CTI, temperature resistance, dimensional stability |
| Terminal block / Fastener | PA66-GF / PA6T-GF | Strength, temperature resistance |
| Sealing ring / Dust-proof part | Elastomer / TPE | Rebound, weather resistance |
| Shield / Structural Bracket | PA66-GF or materials with shielding capabilities | Strength, assembly |
The rubber core is the most particular piece of material.
Because it needs to simultaneously meet: high CTI, thin-wall molding, high dimensional accuracy, and temperature resistance. This is why high-voltage connector resin cores often directly use PA9T or PPA—other areas can economize, but here it cannot be spared.
A vicarious liability in craftsmanship
CTI is not just a matter of the formulation; it is also affected by the injection molding process.
Melt temperature too high → Local material degradation → Surface more prone to carbonization - Mold temperature too low → Rough surface, high internal stress → More prone to moisture absorption and contamination - Long residence time in the barrel → Also leads to degradation
So for the same grade, parts with an unadjusted process and parts with an adjusted process may have different measured CTI values. It is worth doing a test sample measurement yourself before sending it for safety certification testing.
There is one more spot that is often overlooked: the fit between metal inserts and plastic.
High-voltage connectors usually need to embed metal terminals or nuts. The thermal expansion coefficients of metal and plastic differ significantly.
Under temperature cycling, stress occurs at the interface. When performing temperature cycling tests, if a part cracks at the insert location, it is mostly due to this reason, not because of insufficient material strength.
There are usually two ways to deal with it: design the insert with sufficient interlocking structures, or choose a resin system with a coefficient of linear expansion that is closer. This kind of problem must be solved early in the design stage—you can't fix it by changing the material.
By the way, a small detail: the groove for the sealing ring in the connector.
The compression rate of the sealing ring is determined by the groove size. After absorbing moisture, the plastic part will expand, the groove size will change accordingly, and the compression rate will change accordingly.
Therefore, the key dimensions of the sealing groove must be determined using data after humidity adjustment. Otherwise, it may fit well during assembly, but leakage will start after a period of use.
Semi-aromatic is not a universal upgrade
If the CTI standard is not met, we go for semi-aromatic; this upgrade path has almost become a standard formula in the industry, but formulas have applicable limits. The electrical performance of semi-aromatics is indeed good, CTI of 600 is common, and the temperature resistance is also half a level higher; the costs are threefold: higher unit price, narrower processing window, and lower toughness compared to aliphatics, so caution is needed for brittle failure in low-temperature assembly.
So before upgrading, do three things: confirm that the wet CTI really does not meet the standard, as many projects scare themselves with dry data; confirm that the creepage distance on the structural side has been optimized, as adding one millimeter might mean no need to change the material; confirm that the temperature rise and assembly temperature are within the comfortable range for semi-aromatic.
Finish these three things before upgrading, and you'll spend money with peace of mind. Upgrading materials cannot solve the problem of cutting corners in the structure, and this principle is especially evident in high-stress components.
Five, five pits
Pitfall 1: Only ask about V0, not CTI. The whole text is talking about this. For high-voltage components, all three indicators need to be mentioned together.
Pitfall 2: Designing using dry-state electrical data. Moisture absorption will lower the volume resistivity. It is necessary to use conditioned (moisture-adjusted) data.
Pitfall 3: Sacrificing processability for flame retardancy. Halogen-free flame retardant systems require high loading, resulting in poor flow and difficulty in molding thin walls. For thin-walled parts with a plastic core, it is necessary to confirm flowability and molding window in advance.
Pitfall 4: Ignoring the timeliness of CTI. CTI declines with moisture absorption and aging. Passing certification does not mean long-term stability.
Pitfall 5: Using the process for PA66 to process PA6T. The material temperature, mold temperature, and drying requirements of high-temperature nylon are all different, so not changing the process is equivalent to choosing the material in vain.
A commonly overlooked verification item: the mechanical strength after aging
CTI decreases with aging, and mechanical properties will also decline. High-voltage connectors are subjected to temperature cycling and vibration throughout the vehicle’s life, so the strength of the latch cannot be judged solely by its initial value.
It is much more useful to ask suppliers to provide the strength retention after thermal aging than to provide the tensile strength at room temperature. Especially for locations above 130°C over the long term, this parameter explains the issue better than the initial strength.
6. Borders
| Scene | Conclusion | Explanation |
|---|
| 800V platform high-voltage components | semi-aromatic direction | PA6T / PA9T / PPA |
| 400V platform standard parts | PA66 flame-retardant system can cover | CTI verification required |
| Electrical components >150℃ long-term | PA6T / PA46 / PPA | According to temperature |
| High CTI, Thin Wall, Halogen-Free | The most difficult | It is recommended to conduct formula verification early |
| High-power arc situations | Requires a specialized plan | May require thermosetting or ceramic materials |
A real feeling in the industry
In high-voltage connector inquiries, the sentence we hear most often is:
I want V0 materials, how many types do you have?
If this question is asked, it can basically be judged that the customer is dealing with high-pressure components for the first time.
Because the customer has worked with high-voltage components, the question was asked like this: 'V0, CTI 600V, long-term 150℃, is there any direction?' — all three indicators are mentioned together.
We usually ask three follow-up questions: Which tier of the high-voltage platform is this component, 400V or 800V? What is the long-term operating temperature? Are there any thin-walled areas?
After asking three questions, the direction is basically determined. If the client can only answer 'want to V0,' it indicates that the project is still at the very beginning of material selection — at this point, choosing any grade is just a matter of luck.
We'd rather ask a few more questions at this time than wait for the customer to finish safety testing before coming to us for a replacement. The cost of replacements is a minor issue; the cost of delaying the certification cycle is a big issue.
Reader Follow-up Questions Two Questions
Follow-up Question One: How to verify CTI data during procurement without being misled? Three actions: Check the thickness corresponding to the yellow card; CTI values are only valid below the indicated thickness, and lower the notch if the wall thickness is thinner; Check the test status, specify whether it's dry or damp heat, and the tender documents uniformly judge it as damp heat;
Check batch consistency and have suppliers provide third-party retest records from the past two years. If there is only one historical yellow card with no tracking data, leave a question mark. After completing these three steps, the moisture on the CTI is basically squeezed out.
Follow-up question two: What is the most easily overlooked verification item when upgrading to semi-aromatic? Low-temperature assembly impact. The toughness of semi-aromatic is one level lower than that of aliphatic types, so room temperature assembly is fine, but in northern production lines or low-temperature logistics scenarios in winter, snap assembly brittle breakage rates can appear.
Before finalizing the upgrade plan, add the plug-in and unplug test at the lowest assembly temperature to the validation list. This can block the most common after-sales type after the upgrade. In short: upgrading is about changing character, not changing parameters. First, understand the temperament of the new character, then put it into work.
also has a reminder for the proposal review meeting: don't just have material engineers sign the material plan for high-voltage connectors. Structure, process, and quality all need to be reviewed—the structure depends on whether the creepage distance is sufficient, the process depends on whether injection molding can stably achieve thin walls, and on quality, the material inspection has corresponding testing methods.
The material plan has never been a decision made by the material alone; only when all four parties sign together can the plan be established and implemented without dead ends. This process may seem slow, but in reality, it is the most time-saving part of the three-electric project.
The CTI template in the tender terms
Include the CTI requirements in the bidding documents, recommending a segment as follows: High-voltage electrical parts use engineering plastics, compared to the marking index tested according to IEC 60112, determined to be after wet heat treatment, PTI not less than 400V (800V platform parts not less than 600V), test thickness not exceeding the minimum product wall thickness, with yellow card screenshots corresponding to the grade attached with the report;
Suppliers must provide third-party retest records from the past two years; those without tracking data must be sent for inspection synchronously with the samples. Copying this section locks three things: lock the judgment state to block dry data confusion; Thickness binding to prevent mismatches between high levels and low thickness; Track data and block one-time reports.
Write these five lines more in the bidding documents, and CTI disputes in the incoming material stage basically disappear. The clause is managed upstream, much cheaper than downstream disputes.
Here's a common scenario in bidding negotiations: a supplier has submitted a new grade with a very high CTI, and the price is attractive. Should you cut it? Before cutting, you need three things: a complete third-party report, not just the numbers on the flyer, the last six months' worth of mass production and supply records, and usage cases under similar conditions in the same industry.
With all three items together, do small-batch trial production, sending all trial parts for inspection and retesting. The performance trap of new grades is often not the average, but fluctuations between batches—the advertised numbers are the best batch, but your production line gets random batches. Every supplier in the supply chain needs to pay for the fluctuation lesson—the earlier you supplement, the safer you are. The later the lesson, the more you pay for it.
Conclusion
High-voltage connector material selection, remember the order of the three words:
First CTI, then GWIT, and finally UL94.
Because high-voltage components are 'electrical work,' UL94 is just a ticket. If the order is reversed, problems will only be discovered when it's sent for inspection.
Add one more thing: all electrical data must be asked about humidity regulation.
One last note: When selecting high-voltage connector materials, essentially, it's about finding a position that can stand on the three corners of 'electrical performance, temperature resistance, and cost' at the same time. If you want all three parts, it's expensive material; Save one to have room to spare. This saying is useful for your next R&D meeting—it's more useful than ten pages of documentation
