本文是System Design系列：ROHS和关键材料
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What you’ll learn:
- 哪些SVHC金属和非金属目前没有商业上可行的替代品？
- Issues with meeting EPEAT certifications and maintaining product design performance.
- 电子回收的基本原理。
这European Union (EU) led the way to enforcing collection and recyclability goals back in 2003 with its WEEE Directive (Waste Electrical and Electronic Equipment). Shortly thereafter, the EU’s Eco-Design Directive of 2008 published guidelines for product designs that consider the entire product lifecycle. These measures were further solidified with the 2018 amendment to the EU Waste Framework Directive (WFD), which began to strongly promote the development of a Circular Economy.
循环经济的一些关键目标包括减少可能通过支持关注物质的替代物质，并提供有关废物处理运营商和回收者可用的产品内容的信息的危险物质。这数字显示了从原材料到设计和生产，产品使用，重复使用的产品生命周期，然后收集并回收回同一圆圈。左侧仅显示一个小的残余废物输出。
来源：https://ec.europa.eu/easme/en/news/r2-supporting-transition-circular-cormonomy。在没有修改的情况下重印http://creativecommons.org/licenses/4.0/。©欧盟，1995-2021
对于某些产品的自愿环境认证计划也已经存在 - 如果客户需要遵守采购，则实际上根本不是自愿的。其中是Epeat全球电子委员会管理的高科技电子设备计划。目前涵盖了以下类型的设备，并列出了其相关行业标准。
- 计算机和显示：IEEE 1680.1
- 成像设备：IEEE 1680.2
- 电视：IEEE 1680.3
- 手机：UL 110
- 光伏模块和逆变器：NSF/ANSI 457
- 服务器：NSF/ANSI 426-2018
这se types of certifications use a series of evaluations that allow the manufacturer to earn points to meet minimum criteria. The questions include attention to materials selection during product design to avoid toxic substances and materials, and consideration for other types of negative environmental impact. Ability of the product to be reused and then recycled at end-of-life is another category earning points toward certification.
欧盟的ROHS指令（危险物质的限制）已经将十组的物质受到小于0.1％（镉及其化合物的0.01％）的调节。由于许多制造商在全球运营，因此主要OEM已广泛采用这些限制。
但是，对于那些不在欧盟市场开展业务的公司，实际上所有需要使用ROHS豁免来进行产品性能和可靠性的人，仍然可能存在一些危险物质。实际上，大多数剩余物质不能简单地设计或用当今产品设计师可用的选择而替代。
截至2021年1月，进入欧盟市场的产品现在必须在一个名为SCIP的新数据库中公开宣布非常关注的物质（SVHC）（产品中包含的物质）（请参阅“请参阅“请参阅“请参阅“请参阅”新的欧盟报告要求非常关注的物质”）。
Most electronics engineers will probably avoid looking up the fullSVHC list of some 211 such substancesunder the EU REACH Directive (European Chemicals Agency Registration, Evaluation and Authorization of CHemicals). But chances are that someone in your company will, and what follows is offered as practical information that you should know now.
A Closer Look at SVHC Candidates
Two metals in particular—lead and cadmium—are both banned by RoHS and listed as SVHC under REACH. However, they’re still needed in small amounts for specific types of device performance and reliability that may be allowed under specific RoHS Exemptions. Here’s a short list of some of the more common usages of these metals in component parts for which there are presently no commercially viable substitutes:
- 每种均匀材料的可加工钢合金中的铅最高为0.35％。
- Lead in machinable aluminum alloys up to 0.4% per homogenous material.
- 铜合金中的铅（如铜合金），每种均匀材料高达4.0％。
- 在玻璃中的铅，在这种情况下，铅以氧化形式与玻璃内结合的其他物质结合在一起。
- 高温焊料的铅，用于电源半导体等组件的可靠性，以及需要进行两次焊接过程的应用。
- 铅中的铅含量，如铅锆 - 钛酸盐（PZT）压电传感器和传感器。
- 合金中的镉，如氧化镉，用于高电流开关和中继触点。
在某些应用中也可以找到SVHC的非金属：
- Remaining non-RoHS restricted phthalate plasticizers in soft materials and polymers like polyvinylchloride (PVC). These may typically include wire and cable insulation and gaskets.
- Various plastics may require the use of flame retardants for fire safety that are SVHC but not the RoHS-restricted type. Dechlorane Plus is one example.
- 在垫片和密封剂中可以发现多硅氧烷聚合物生产的低水平残基的Siloxanes（称为D4，D5和D6）。
- 全氟化合物，如全氟丁烷磺酸（PFB）。少量可能会产生不粘的，自润滑的塑料或包含氟聚合物的其他最终产品。
环境空白的设计
Environmental product certifications like EPEAT require that the lifecycle aspects of the product be considered, including end-of-life and materials recovery. At the product level, the designer is faced with limited choices when it comes to ensuring that, first, the product will perform as intended in the field and meet its stated reliability goals. Even basic consumer electronics goods must withstand some shock and vibration, variations in temperature, and so on.
这引起了根本的工程挑战：如何确保产品在使用过程中的完整性，但可以轻松将其拆卸并通过回收材料将其分离成单独的材料。
在组件级别上，除了“无铅”终止之外，类分，离散的半导体和ICS，以及某些本质上根本不包含SVHC的设备，没有真正的绝佳选择。考虑集成电路本身的性质：多种材料沉积在薄膜中，该薄膜被沉积在基材上，该基材进一步包装在热固性塑料的外壳中，或者最少以可售的颠簸提供。至少现在没有，这里没有实用的设计选择，即“可回收”芯片。
同样,设计师几乎没有选择printed wiring board (PWB) selection. Some choices are available in the flame retardant used that may avoid bromine or other halogens. Research has been done on expensive processes to separate the glass filler and metals from the PWB itself to chemically recycle the laminate, but these possible approaches aren’t yet widely adopted, and even so are intended to work on today’s materials. Flexible circuits may be mounted directly to a metal housing, which has disassembly problems of its own. And a traditional hybrid has the same problems with diverse materials typically adhered to an alumina substrate.
即使可以使主要的PWB组件本身可以移除，但在实用的大容量回收操作中，手动拆卸也不太可能发生，尤其是对于较小的产品。当今的带有玻璃显示器的产品还提出了回收玻璃本身的问题，更不用说薄膜半导体（如LED）是不可或缺的。
使用视觉透明的二键蛋白氧化触摸传感器，使用触摸屏存在类似的困境。从可能将可能分离为有用的回收流的角度来看，在进一步处理之前，只有具有单独金属外壳的较大产品会更好。
今天还不错
可回收电子设备的基本问题实际上是同时拥有同时存在导体（或半导体）和绝缘体的必要性。一个没有另一个没有使基本的电力甚至无法安全工作。对于实用产品，它们必须通过内部制造工艺，成型，挤压或带有焊料或粘合剂的组装来紧密而牢固的接触。
Conductors tend to be based on metals, while insulators are generally carbon-based (defined as “organic” by chemists). What if the conductive materials could also be based on carbon? In fact, such materials are being researched and include candidates like carbon nanotubes; polymers like polyacetylene, polypyrrole, polyaniline, polyphenylene sulfide, PEDOT (polyethylenedioxythiophene); and TCNQ (tetracyanoquinodimethane).
Besides the fact that those are generally not ready to be picked up and used by the designer, they would bring another even worse outcome—now they could not readily be separated at all for recycling, unlike metallic and organic materials. Plastic materials with conductive properties would have limited reuse potential.
基本原则和建议
今天回收的关键基于一些实际有效的基本原则：
- 密度：硬件被切碎和缩小的能力可以分类成有用的部分，可以进一步处理以恢复材料。然后可以将非常低密度的材料（如标签和填充剂）漂浮到顶部，或从其余的溪流中捡起。
- 温度：Metals melt only at high temperature above which most organics can’t survive without burning. The different melting properties of different metals further enables their separation back to useful pure metals or alloys by dedicated metal smelters. An all-carbon-based assembly could not take advantage of this.
- 特殊属性：铁合金可以用磁铁排序。铝和其他分数可以通过涡流技术进行排序。在某些情况下，光学分选可用于将其他材料（例如塑料）分类为有用的部分。
简而言之，将金属作为导体和碳，玻璃或陶瓷作为绝缘体并不是一个坏主意。金属废品的运行速度可以带来正财务回报。
考虑到所有这些，似乎我们今天只为电子产品设计师提供了一些建议：
- 尽可能继续寻找具有关注内容和最低环境足迹的组件和材料。
- 向您的供应商索取此类组件和材料以创造需求。
- 可能可以在原材料中添加小替代品；例如，一些用于增强对性能并非至关重要的聚合物产品的SVHC实际上可能有可用的替代方法。
- 考虑一下您的产品如何使用全新的方法；例如，考虑加法过程，例如3D打印，而不是减去加工等减法过程。
- 由于作者目前没有其他大魔术子弹可以提供，因此前进的每一步都是有价值的。但是，不要以这篇简短的文章为最后一句话。面对挑战，并帮助朝着循环经济发展更大的步伐。
