While reading a series of articles posted on www.pcb007.com relating to IPC and Jedec Standards, I was surprised to see the results of a survey they carried out with regards to the new and updated MSD (moisture sensitive devices) standards release late last year. These standards are J-Std-020, J-Std-033 and the new J-Std-075.  While two of these are updated revisions of the old standards they still do hold a lot of new valuable information, especially when it comes to higher reflow and wave soldering temperatures.  However, the J-Std-075 is new and one can expect this to change and be updated as the industry evaluates this further.  Or perhaps not, as the results of the survey showed that these standards are currently not really being conformed to. Baking parts before use can be a costly and time consuming exercise and one that may be seen to have to real benefit.  However, when you consider that not putting simple processes in place to prevent damage can decrease yields, not to mention wasting what could be valuable components, the cost of not doing so can soon add up. What this shows me is that you can't just give an assembly house a bunch of parts, some PCB's and expect them to deliver functional and reliable products with high yields.  (Although this is exactly what everyone would like to see happen.) Any electronic design house needs to know what standards their suppliers adhere to and what consequences may occur if their chosen production facility does not apply these standards.  This does require a design house to keep up to date with manufacturing standards. This is especially true when you consider MSD damage to devices.  The units may pass any production testing bu fail later in the field.  This puts the failure back into the hands of the design house who then needs to deal with the RMA returns and upset customers. Another important question not to be overlooked is how widely known are these standards?  Do IPC and Jedec need to do more to promote the use of these standards within the industry?  Based on the results of the survey, it seems more in the court of the customer, i.e. any design house.  Once a customer starts to request compliance to the standards, component manufacturers/suppliers and contract manufacturers will put the required processes in place.

The RoHS EU directive that came into affect in July 2006 banned 6 substances from being used in electrical and eletronic equipment. However, since then, others have come on board with their own version of the directive. Look at China for instance.  Although China bans the same materials, they do it in a different way and in some areas they are more strict on what is required for compliance. See http://www.rohscompliancedefinition.com/china-rohs.html California also has laws that prohibit 4 of these substances since January 2007. These being:

• Cadmium
• Hexavalent Chromium
• Lead
• Mercury

These directives to nee to be regularly checked to insure that any changes to these are adhered to. This is particularly important if your product currently falls under an exemption as the requirements may change. It is also important for each company selling into these markets to make a statement on what is considered due diligence. That way, its employees know what is expected of them and what the ramifications are for not following the required process. A good description can be found here: http://www.rohscompliancedefinition.com/due-diligence-rohs.html

While working on a project for the UK market, the issue of Printed Circuit Board material came up. As this product was required to be RoHS compliant (Restrictions of Hazardous Substances Directive), it must be able to withstand the higher re-flow temperatures associated with lead free soldering, which can peak at 260C. A common misconception with this is that using just a higher TG (Glass Transition Temperature) will be acceptable. However, you will also need to ensure your base material is also of a higher TD (Decomposition Temperature). The TG value is where the resin changes from rigid to soft material and TD is the value where the material weight changes by 5%. Exceeding the TD value will cause permanent damage to the circuit board, which can result in loss of adhesion and delamination. See the link below for a more detailed and in depth read. www.isola-group.com/images/media/ReengineeredFR4Materials.pdf So when selecting PCB material for the lead free solder process, a good guide is to use material with TD above 340C and TG above 170C.