154 车载充电机与DC-DC壳体用什么改性尼龙
OBC 和 DC-DC 的工况
车载充电机（OBC）和 DC-DC 变换器是新能源汽车的功率电子部件。
共同工况：内部功率器件发热（壳内温度 70-100℃）、要求 IP67 密封、要电磁屏蔽、要阻燃、长期振动。
这些要求叠加在一起，让壳体成为设计难点——既要散热又要密封，本身就是矛盾。
现场还原：一次散热和密封的拉锯战
去年年初，一家做车载充电机的企业为新平台选壳体材料，会上吵了三个小时。散热派主张用导热塑料，把发热元件的热量直接带走；密封派提醒导热填料会破坏熔体流动性，壳体的密封面质量难保障。两个方向都对，矛盾在怎么同时成立。
最终的方案是个折中样本：壳体主体用常规阻燃增强牌号扛下密封和强度，发热集中区设计一块嵌入式导热板，用螺钉和壳体连接。塑料壳体负责密封绝缘，导热板负责把热点温度拉下来，各干各的活。
装机测试热点温度比全塑料导热方案低两度，密封合格率还高了一截。这家企业的硬件负责人总结：散热和密封不是对手，是分工问题，强迫一种材料干两件事，两件都干不好。
方案定型后还有个插曲：导热板的紧固孔在振动测试里出现松动，补了一道螺纹胶和防松垫片。壳体件选型的最后一步永远是振动，车载环境没有例外。
散热和密封的矛盾怎么解
密封要求壳体不能有开孔，散热要求热量散出去。工业上有三个解法：一是壳体本身导热（走导热改性尼龙或金属）；二是外壳做散热筋片（增大散热面积，但受空间限制）；三是内部灌胶导热 + 外壳散热（灌胶把热量导到壳壁）。主流方案是第三种——导热灌封胶 + 金属或导热塑料外壳。纯塑料外壳通常只用于小功率机型。
阻燃和电气要求
功率电子部件的壳体要 UL94 V-0 阻燃，且要低烟无卤（车内密闭空间）。
电气上要关注 CTI（虽然电压低于高压连接器，但仍要求 400V 以上）和耐电弧性。
另外，壳体如果做屏蔽，走导电体系或金属化涂层——导电填料会影响阻燃等级，要复配验证。
耐湿热和密封
OBC 通常安装在车内或底盘，要过 IP67 和湿热交变。
PA 吸湿膨胀会影响密封面平面度，要走低吸水体系或矿物填充。
密封条的压缩永久变形是关键（长期压缩后密封失效），要做 1000 小时压缩永久变形测试，通常要求 < 25%。
另外，温度交变会让壳体内产生负压，要装透气阀平衡压力。
振动要求
OBC 和 DC-DC 要过随机振动测试（按整车或部件规范，通常是数十小时的随机振动）。
塑料壳体在这个测试中的失效模式是固定点开裂和螺纹滑牙。
三个应对办法：一是固定点加金属嵌件；二是固定点做局部加厚和加强筋；
三是内部重件（变压器、电感）要有独立支撑，不能让壳体承受全部重量。
深一层：OBC 壳体的振动规范背后的整机逻辑
车载充电机壳体的振动要求听着是机械指标，背后是整机的可靠性逻辑。行车振动是宽频随机振动，壳体上的焊点、端子、磁芯都随壳体一起晃，壳体刚性不足，晃动被放大传递到内部元件，焊点疲劳寿命打折。
行业数据里充电机售后故障的相当比例来自焊点开裂，根因链的起点常是壳体刚性不够。所以壳体料的模量指标要按整机振动规范反推，玻纤含量三成到四成是常见落点。
阻燃和绝缘是壳体的法规面。充电机在车内有专门的安装规范，壳体阻燃要求垂直燃烧等级，绝缘配合按工作电压定电气间隙和爬电距离，这两个距离由壳体的结构兜住，材料的 CTI 等级决定爬电距离可以缩短多少。
CTI 高一档，壳体可以做小一号，小型化的收益有时候比材料差价更值钱——这是把材料指标翻译成设计收益的典型例子。
耐湿热则关系到寿命。充电机工作时壳内温升明显，停机后冷却，壳内空气反复呼吸，湿气随之进出，壳体材料在湿热循环里的尺寸稳定性和密封圈的压缩永久变形共同决定十年后的密封状态。验证时把整机做湿热循环加振动双叠加，是最接近实车寿命的考法。
延伸判断：OBC 壳体的隐性变量
有三件最容易漏掉的隐性变量。一是灌胶和壳体的粘接——灌封胶与 PA 的粘接性一般，要选配套的底涂或做表面处理。
二是冷凝水——湿热环境下壳内会结露，要有排水或干燥设计。
三是导热填料的取向——导热填料在注塑中沿流动方向取向，导致不同方向导热系数差异可达 2-3 倍，散热设计要考虑这一点。
工程实测：4 条强制测试
测试1：导热系数。导热改性 PA 1.8 W/(m·K)，通用 PA66 0.25——差 7 倍，但各向异性明显。
测试2：IP67 + 湿热交变。低吸水体系 + 弹性密封通过，通用 GF30 在 40 次交变后漏气。
测试3：压缩永久变形 1000 h。硅橡胶密封条 18%，普通橡胶 38%（要求 < 25%）。
测试4：随机振动。固定点加金属嵌件的方案通过，纯塑料固定点在第 12 小时开裂。
边界声明
| 工况 | 推荐材料 |
|---|
| 小功率机型外壳 | 导热阻燃 PA66（V-0 + 无卤） |
| 大功率机型 | 金属壳 + 导热灌封胶 |
| 密封面 | 低吸水体系 + 硅橡胶密封条 |
| 固定点 | 金属嵌件 + 局部加厚 |
| 压力平衡 | 装透气阀（防负压） |
工程备忘
OBC 壳体散热和密封本身就是矛盾——主流解法是导热灌封胶 + 金属或导热塑料外壳，纯塑料只用于小功率机型。
振动测试中固定点开裂是主要失效，要靠金属嵌件。
实战案例：常见踩坑与正解
踩坑一：按传统汽车的思路选料，忽略了电气安全要求。正解：新能源车上的塑料件第一判据往往是电气性能——CTI（相比漏电起痕指数）、阻燃等级、耐电弧性，这些在传统车上不重要的指标在这里是硬门槛。踩坑二：只看阻燃等级，忽略了长期湿热下的电痕化。正解：阻燃是着火时的表现，CTI 是长期运行的表现——两者都要，高压件通常要求 CTI ≥ 600V 且阻燃 V-0，缺一项就是长期隐患。踩坑三：把电池的工况简单理解为"高温"，忽略了冷热交变和湿热。正解：电池包内是温度交变 + 湿度变化 + 冷却液的复合环境，验证要做温度冲击 + 湿热 + 冷却液相容性的组合测试。这三个坑都是量产前必须自查的清单。
追问三连：充电机壳体读者的三个高频问题
第一问：导热塑料值得用吗？看热流密度。低功率模块的壳体可以直接用导热塑料，省掉导热板；高功率方案里导热塑料的导热率上限不够，嵌入式金属板更实际。先测热流密度再选路线，别被材料商的参数表牵着走。
第二问：壳体的阻燃等级怎么定才不浪费？按安装位置的整车规范定，充电机所在的舱位多数要求垂直燃烧，更高等级只在规范明示时选。等级每高一级，材料成本上一个台阶，过度阻燃是壳体成本里最常见的浪费。
第三问：密封圈和壳体材料怎么配套？氯丁、硅橡胶、氟橡胶对 PA66 系壳体的相容性各有差异，配套验证要把密封圈泡在壳体材料的标准试片上做老化，确认互相不析出不溶胀。这个配套测试便宜且快，很多团队却漏做，漏的都在售后找回来。
反向案例：一台没做振动复测的新壳体
有家企业为降本把壳体玻纤含量从四成降到三成，振动规范只做了初版的正弦扫频，没做随机振动复测。装车半年后磁芯异响投诉出现，拆机发现焊点疲劳提前。降下的材料成本不到十元一台，召回返工花了六位数。
壳体改动后，振动验证要从头走一遍，这条红线不能省。
增补：另外三个读者的实际问题
第四问：壳体壁厚对材料等级有影响吗？有。薄壁化让注塑难度上升，对材料的流动性和热稳定性要求同步提高。壁厚从二点五降到二点零，能选的牌号范围会窄一圈，结构设计先定壁厚再定材料，顺序别反。
第五问：充电机壳体的温升测试怎么做才实？按满载工况跑温升曲线，热点位置贴热电偶实测。仿真给方向，实测定结论，两者差超过十度时先怀疑仿真的边界条件。
第六问：壳体件的年降空间在哪？大宗填料的配比优化、副牌料的合规使用、模具效率提升三条线是行业常规。硬压材料单价会压出批次波动，波动成本最后都回到整机厂手里，合理的年降节奏对双方都是保护。
一组现场的判断
判断一，充电机的售后故障有一半能在壳体上找到线索。拆机先看密封面状态和紧固件松紧，这两处的异常往往早于电气故障出现。
判断二，材料升级和结构优化要联动评估。单独换材料或单独改结构都容易顾此失彼，把两者放进同一个验证计划里走，一轮试验解决两件事。
补一组现场数字
数字一，关于壳体温升的空间。充电机满载工况下壳体热点温升普遍控制在四十度以内，超过这个数字，内部电解电容的寿命折损进入加速区。壳体材料的耐热等级按热点加二十度富余选，是常见的稳态。
数字二，关于振动寿命的折算。整车十五年的振动工况，台架上按强化系数压缩到几百小时，强化系数每家定义不同。壳体件的振动验证一次做足，比市场端返修便宜两个数量级。
数字三，关于密封的十年考题。密封圈压缩永久变形加壳体蠕变，两份曲线叠加算出十年后的密封余量。余量低于三成就值得重新设计密封槽，这条经验值由多个售后案例反推得来。
结束前多说一句
充电机壳体是典型的小批量多品种件，功率档位多、平台迭代快。这类件最吃供应商的快速响应和小批量柔性，选供应商时把打样周期和最小起订量写进评估表，比只比单价更贴近实际。
末尾一记
最后补一条冷知识：充电机壳体的接地连续性也和材料有关，塑料壳体上的接地弹片接触位置要避开脱模剂残留区，弹片和壳体的接触电阻超标会让整机过不了安规。模具和材料两头都对这一处多看一眼。
结语
样品寄出去之后——选料这件事，越早问越省事。
这类件的选料与试模，可以一起聊。
What type of modified nylon is used for the housing of the 154 vehicle charger and DC-DC converter?
Operating conditions of OBC and DC-DC
On-board chargers (OBC) and DC-DC converters are power electronic components of new energy vehicles.
Common operating conditions: internal power devices generate heat (case temperature 70-100℃), require IP67 sealing, need electromagnetic shielding, need flame retardancy, long-term vibration.
These requirements combined make the casing a design challenge—it needs to provide both heat dissipation and sealing, which is inherently contradictory.
On-site Reenactment: A Tug-of-War Between Heat Dissipation and Sealing
At the beginning of last year, a company that makes in-vehicle chargers spent three hours arguing in a meeting over the casing material for a new platform. The heat-dissipation camp advocated using thermally conductive plastic to directly carry away the heat from the heating components; the sealing camp reminded them that thermal fillers can compromise melt flow and make it difficult to ensure the quality of the casing's sealing surfaces. Both sides were correct, and the contradiction lay in how to satisfy both requirements at the same time.
The final solution is a compromise sample: the main body of the casing uses a conventional flame-retardant reinforced grade to handle sealing and strength, and a thermal-conductive embedded plate is designed in the heat-concentrated area, connected to the casing with screws. The plastic casing is responsible for sealing and insulation, while the thermal-conductive plate is responsible for lowering the hotspot temperature; each handles its own job.
The hotspot temperature during machine installation testing is two degrees lower than that of the all-plastic thermal conductivity solution, and the sealing pass rate is also significantly higher. The company's hardware manager summarized: heat dissipation and sealing are not opponents; it's a matter of division of labor. Forcing one material to do two things results in neither being done well.
After the scheme was finalized, there was still an interlude: the fastening holes of the heat-conducting plate became loose during the vibration test, so a layer of thread-locking adhesive and anti-loosening washers were added. The final step in selecting housing components is always vibration, and the in-vehicle environment is no exception.
How to resolve the contradiction between heat dissipation and sealing
Sealing requires that the casing have no openings, while heat dissipation requires that the heat be released. There are three industrial solutions: first, the casing itself conducts heat (using thermally conductive modified nylon or metal); second, the outer casing is equipped with heat-dissipating fins (to increase heat dissipation area, but limited by space); third, internal potting with thermally conductive material and outer casing heat dissipation (the potting conducts heat to the casing wall). The mainstream solution is the third one—thermally conductive potting glue with metal or thermally conductive plastic casing. Pure plastic casings are usually only used for low-power models.
Flame retardant and electrical requirements
The housings of power electronic components must be UL94 V-0 flame retardant and low-smoke halogen-free (for closed spaces inside vehicles).
Electrically, attention should be paid to CTI (although the voltage is lower than high-voltage connectors, 400V or above is still required) and arc resistance.
In addition, if the casing is to provide shielding, using a conductive system or metallized coating – conductive fillers will affect the flame retardant rating, and combination verification is required.
Moisture and heat resistant and sealed
OBC is usually installed inside the vehicle or on the chassis and must pass IP67 and alternating humidity and heat tests.
PA moisture absorption and expansion can affect the flatness of the sealing surface, so a low water absorption system or mineral filling should be used.
The compression set of the seal strip is key (seal failure after long-term compression), and a 1,000-hour compression set test should be conducted, usually requiring less than 25%.
In addition, temperature changes can create negative pressure inside the casing, so a vent valve must be installed to balance the pressure.
Vibration requirements
OBC and DC-DC need to pass random vibration testing (according to the whole vehicle or component specifications, usually several tens of hours of random vibration).
The failure modes of the plastic housing in this test are fixed-point cracking and thread stripping.
Three countermeasures: first, add metal inserts at fixed points; second, locally thicken and add stiffeners at fixed points;
Third, heavy internal components (transformers, inductors) must have independent support and should not let the enclosure bear the entire weight.
A deeper look: The overall machine logic behind the vibration specifications of the OBC housing
The vibration requirements for the car charger housing sound like mechanical specifications, but behind them is the reliability logic of the whole device. Vehicle vibrations are broad-frequency random vibrations, and the welds, terminals, and magnetic cores on the housing all shake along with the housing. If the housing lacks rigidity, the shaking is amplified and transmitted to internal components, reducing the fatigue life of the welds.
A considerable proportion of after-sales failures of chargers in industry data comes from solder joint cracks, with the starting point of the root cause chain often being insufficient rigidity of the casing. Therefore, the modulus index of the casing material should be deduced according to the vibration specifications of the complete machine, with a common range for glass fiber content being 30% to 40%.
Flame retardancy and insulation are the regulatory aspects of the housing. In-vehicle chargers have specific installation regulations, and the housing's flame retardancy requires a vertical burning rating. The insulation coordination is determined by the working voltage to set the electrical clearances and creepage distances. These two distances are accommodated by the structure of the housing, and the material's CTI rating determines how much the creepage distance can be reduced.
CTI is high-level, and the casing can be made one size smaller. Sometimes the benefits of miniaturization are more valuable than the material price difference—this is a typical example of translating material specifications into design gains.
Resistance to heat and humidity is related to lifespan. When the charger is working, the temperature inside the casing rises significantly, and after shutdown, it cools down, causing the air inside the casing to repeatedly move in and out, along with moisture. The dimensional stability of the casing material in heat and humidity cycles, along with the permanent compression deformation of the seals, together determine the sealing condition after ten years. During testing, subjecting the entire unit to combined heat and humidity cycles and vibration is the method closest to assessing the actual vehicle lifespan.
Extended Judgment: Hidden Variables of the OBC Housing
There are three hidden variables that are easiest to overlook. The first is the bonding between potting and the housing—potting adhesive generally has ordinary adhesion with PA, so a matching primer should be selected or surface treatment should be applied.
Second is condensate — in a hot and humid environment, condensation will form inside the enclosure, so drainage or drying design is required.
Third is the orientation of the thermal conductive filler — in injection molding, the thermal conductive filler aligns along the flow direction, resulting in differences in thermal conductivity in different directions by 2-3 times. This should be taken into account in heat dissipation design.
Engineering Test: 4 Mandatory Tests
Test 1: Thermal conductivity. Modified thermal PA 1.8 W/(m·K), general PA66 0.25 — a difference of 7 times, but the anisotropy is obvious.
Test 2: IP67 Wet heat alternation. Low water absorption system - elastic seals passed, general GF30 leaked after 40 cycles of alternation.
Test 3: Compression set 1000 h. Silicone rubber sealing strip 18%, ordinary rubber 38% (requirement < 25%).
Test 4: Random vibration. The scheme with metal inserts at the fixed points passed, while the pure plastic fixed points cracked at the 12th hour.
Boundary Declaration
| Operating condition | Recommended materials |
|---|
| Small power model casing | Thermally conductive flame-retardant PA66 (V-0, halogen-free) |
| High-power model | Metal casing thermal conductive potting adhesive |
| Sealing surface | Low Water Absorption System Silicone Rubber Sealing Strip |
| Fixed point | Metal insert Locally thickened |
| Pressure balance | Install a breather valve (anti-negative pressure) |
Engineering Memo
OBC housing heat dissipation and sealing are inherently contradictory — the mainstream solution is thermally conductive potting adhesive, with metal or thermally conductive plastic housings, while pure plastic is only used for low-power models.
In vibration testing, cracking at the fixed point is the main failure, requiring metal inserts.
Practical Case Study: Common Pitfalls and Correct Solutions
Pitfall 1: Choosing materials according to traditional automotive thinking ignores electrical safety requirements. Correct answer: The primary criterion for plastic parts in new energy vehicles is often electrical performance—CTI (compared to trace index), flame retardant rating, arc resistance. These unimportant indicators in traditional cars are hard thresholds here. Pitfall 2: Only looking at flame retardant rating, ignoring the electric marks caused by long-term damp heat. Correct answer: Flame retardant is the behavior during fire, CTI is the result of long-term operation—both are needed. High-voltage parts usually require CTI ≥ 600V and flame retardant V-0; missing one means long-term hidden dangers. Pitfall 3: Simply interpreting battery conditions as "high temperature" ignores alternating hot and cold and damp heat. Correct answer: The battery pack is a composite environment of temperature alternating + humidity changes + coolant. Verification requires a combination test of temperature shock + damp heat + coolant compatibility. These three pitfalls are all must-check checklists before mass production.
Follow-up triple question: Three frequently asked questions from charger case readers
First question: Is thermal conductive plastic worth using? Look at the heat flux density. For low-power modules, thermal conductive plastics can be used directly, eliminating the thermal conductive plate; In high-power solutions, the upper limit of thermal conductivity for thermal plastic is insufficient; embedded metal plates are more practical. First measure the heat flux density before choosing the route; don't be led astray by the material supplier's spec list.
Second question: How to determine the flame retardant rating of the case to avoid waste? According to the vehicle specifications for installation location, most charger compartments require vertical combustion, and higher grades are only selected when explicitly specified. Each higher grade raises material costs, and excessive flame retardant is the most common waste in casing costs.
Third question: How do sealing rings and casing materials match? Neoprene, silicone rubber, and fluororubber have varying compatibility with PA66 series casings. Matching verification requires soaking the sealing ring in a standard test piece of the casing material for aging to confirm no precipitation or swelling. This matching test is cheap and fast, but many teams overlook it, and any missing parts are collected after after-sales service.
Reverse Case: A new housing without vibration retesting .
A company reduced the glass fiber content in the shell from 40% to 30% to reduce costs, only did the initial sine sweep in the vibration specification, and did no random vibration retesting. Complaints about abnormal magnetic core noise appeared six months after installation, and disassembly found solder joint fatigue was premature. The material cost was less than ten yuan per unit, and recalls and rework costs six figures.
After the housing was modified, vibration verification had to be done from scratch—this red line can't be skipped.
Supplement: Another practical question from three readers
Fourth question: Does shell wall thickness affect material grade? Yes. Thin-wall design increases injection molding difficulty, and the requirements for material fluidity and thermal stability also increase. Reducing wall thickness from 2.5 to 2.0 narrows the range of grades available. Structural design should determine wall thickness first, then material, and don't reverse the order.
Fifth question: How to conduct a realistic temperature rise test for the charger casing? Run the temperature rise curve under full load conditions, and place the thermocouple at the hotspot for actual measurement. Simulation provides direction, actual measurement determines the conclusion; if the difference exceeds ten degrees, first consider the simulated boundary conditions.
Sixth question: Where is the annual reduction potential for housing components? Optimizing bulk packing ratios, compliant use of sub-brand materials, and improving mold efficiency are industry norms. Hard pressing material unit prices cause batch fluctuations, and the cost of these fluctuations ultimately returns to the manufacturer. A reasonable annual reduction pace protects both parties.
One-on-site judgment
Judgment one: Half of after-sales charger faults can be found on the casing. When dismantling, first check the sealing surface condition and fastener tightness; these two abnormalities often appear before electrical faults.
Judgment two: Material upgrades and structural optimization should be evaluated together. Changing materials or changing structures separately can easily overlook one side; putting both into the same verification plan solves two problems in one round of testing.
Supplement a set of on-site numbers
Number One: regarding the space for housing temperature rise. Under full load conditions, the housing hotspot temperature rise is generally controlled within 40 degrees; exceeding this number, the internal electrolytic capacitor degrades into the accelerated zone. The heat resistance grade of the housing material is selected by the hot spot plus 20 degrees of surplus, which is a common steady-state condition.
Number 2, regarding vibration life conversion. The vehicle's fifteen-year vibration cycle is compressed to several hundred hours on the bench according to the strengthening factor, with different definitions for the strengthening coefficient. Fully validating the vibration of housing components in one go is two orders of magnitude cheaper than market rework.
Number Three, a ten-year test on sealing. The sealing ring compression permanent deformation plus housing creep is superimposed to calculate the sealing margin after ten years. If the margin is below 30%, it is worth redesigning the sealing groove; this experience is derived from multiple after-sales cases.
One more thing before the end
charger casings are typical small-batch, multi-variety parts, with multiple power levels and fast platform iterations. These parts depend most on the supplier's quick response and small-batch flexibility. When selecting suppliers, include the sample production cycle and minimum order quantity in the evaluation sheet, which is more realistic than just unit price.
Final Note
One last fun fact: The grounding continuity of the charger housing is also related to the material. The contact position of the grounding spring on the plastic shell should avoid the release agent residue area. If the contact resistance between the spring piece and the shell exceeds the standard, the whole machine will fail to meet safety standards. Both the mold and the material should pay close attention to this part.
Conclusion
After sending the sample—the earlier you ask about material selection, the easier it is.
For material selection and mold trials for these types of pieces, you can chat together
