Many challenges are associated with designing products that are not only safer for the environment but meet the legislative and OEM requirements that are being adopted around the world. To ensure success, you must understand the global requirements and deadlines for the removal of hazardous substances from electronic products. At a more practical level, you must understand how Pb-free devices impact board design. Xilinx® understands these challenges and offers a strategy to ease the transition to Pb-free and environmentally friendly products.

Global Environmental Requirements
To develop products that can be shipped globally, you must comply with global requirements and deadlines for the removal of Pb and other hazardous substances from electronic products. As shown in Figure 1, the most eminent requirement is the European Union (EU) directive for the restriction of the use of certain hazardous substances (RoHS). This directive bans shipments of electronic products into the EU after July 1, 2006 that do not comply with the directive’s restriction on Pb, mercury, cadmium, hexavalent chromium, PBB, and PBDE flame retardants.

Japan recognizes RoHS and also enforces their own green initiatives, driven by recycling/reuse laws in their country. China recently announced plans to adopt legislation that will be more strict than the RoHS legislation – banning, rather than restricting, the named substances by the same July 1, 2006 timeframe. Individual states in the U.S. are also considering bans on the same list of materials – and potentially others.

Pb-Free in Board Designs
How do Pb-free solutions impact board designs? As a rule of thumb, Pb is distributed in electronics in the solder (75%), board (20%), and components (5%), so you must understand the implications to the overall solution. “Green” components in the industry feature new material sets that require changes to solder materials and processes, which in turn affect board selection. The good news is that most Pbfree packages have the same form, fit, and function as standard packages; no special board layout considerations are required from the component side.

Pb-free lead-frame packages (for example, PQG and TQG) that use matte tin plating on the leads are of little concern, since they are considered “backward compatible” to traditional SnPb manufacturing processes. However, many Pb-free BGA package solutions in the industry use a SnAgCu solder ball material that is not backward compatible with traditional manufacturing processes. The SnAgCu material requires higher peak reflow temperatures than those specified for standard packages. This situation makes it difficult for designers to mix Pb-free and standard components on the same board. So the decision must be made up-front as to whether the board will be Pb-free or not.

The BOM for Green Products
Crafting the bill of material (BOM) can be difficult when designing Pb-free solutions. Pb-free devices cannot always be mixed with standard devices on the same board because of differences in the manufacturing process. Therefore, you need to know if a given device is Pb-free or standard when including it in a board design. What makes this complex is that some companies in the industry are simply “converting” standard devices to Pb-free. And because the part number does not change in this scenario, the part type cannot be easily identified.

And what about the BOM cost? Many designers are challenged to create costeffective solutions that can compete in a tough market. Many component companies in the industry are applying cost adders to Pb-free versions of their products to offset the higher costs they may be experiencing. What was already a difficult constraint is now exacerbated by unexpected higher costs.

Availability and Reliability
As a designer, you surely want to know that the parts designed onto a board are available and reliable. You should feel comfortable that the parts you have selected will be available when the board is prototyped or built in production. Component manufacturers in the industry are getting up to speed with green products at different rates, so the simultaneous availability of components is hard to predict.

You will also want to make sure that Pb-free parts are high-quality, reliable devices. Because material sets have changed, it is imperative that the new devices are fully qualified and that the packages can withstand the higher reflow temperatures now required.

The Transition to Pb-Free
To ensure that you can easily develop solutions that support green requirements, Xilinx is committed to providing RoHScompliant products to the market ahead of all directives. Xilinx also stays active in industry consortia to ensure advanced knowledge of any new environmental legislation that may affect electronic products. Xilinx green components will comply with all global requirements.

Pb-free packages from Xilinx have the same form, fit, and function as standard packages. Xilinx and its suppliers have carefully selected material sets for Pb-free components; these material sets are among the most commonly used in the industry. Xilinx Pb-free packages use matte tin plating for lead-frame packages and SnAgCu solder balls for BGA and flip-chip packages. All Pb-free packages from Xilinx are fully RoHS compliant, and in most cases are available at no additional cost over standard products (see Table 1). To simplify Pb-free part identification, Xilinx instituted a special part number (Figure 2). You can easily designate and identify Pb-free products, thus saving time and effort. Furthermore, Xilinx adopted a “dual-line” strategy, which makes both standard and Pb-free products available in parallel so that companies can transition at their own pace.

Conclusion
When designing with Xilinx Pb-free products, you can be assured that all products are qualified and as highly reliable as standard products. Package materials were enhanced to withstand the thermal stress from higher reflow temperatures associated with new Pb-free materials.

For more information regarding quality and reliability, read the Device Reliability Report on the Xilinx website, www.xilinx.com/quality. For more information about Xilinx Pb-free products, visit www.xilinx.com/pbfree.

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