RoHS FAQ's
Click on Questions to show Answers.
Q: Which process do you recommend (cost and reliability) and why?
A: Prior to responding with specific board information, we would require an RFQ detailing your requirements including your preference for board finish knowing the requirements of your product. Generally, based on cost and reliability we recommend immersion tin or immersion silver, which has a higher initial board cost compared to some of the other Lead free finishes but the reduced manufacturing costs help to offset the initial price differential. One of the potential drawbacks to an immersion tin finish is a greater percentage of tin in the final product which can lead to an increased potential for tin whiskers. The immersion silver finish helps to keep the percentage of tin lower, but is subject to a shorter shelf life and other pre assembly handling concerns. As you can see there are pros and cons to each board finish.
Q: What are the costs associated with each process?
A: Costs will depend on board finish and quantity. We work with several competent board houses and will source the most competitive price, quality, and delivery.
Q: Do we have to specify any requirements for the boards going through the ovens?
A: No additional requirements are needed. IPC specifies tolerance for PCB warp, and most drawings already include tolerances. Each assembly built at EE Technologies also has its own unique reflow oven profile. These profiles are created using modern profiling techniques and the KIC thermal profiling system, which helps to ensure that the temperatures on the surface of the board are within the process window specified by the solder paste manufacturer and that excessive heat is not unnecessarily applied to the PCB. Single sided PCB’s are reflowed on the flat surface of the oven conveyor and double sided boards are stiffened with titanium supports and run on an elevated conveyor system to ensure weight induced warp does not occur during the reflow process.
Q: Is it possible to have one process for all our PWBs, or will we require more than one process?
A: Regarding finishes of the board – design will impact finish selected (immersion silver, immersion tin, and gold are all available lead free) and EE Technologies can work with all finishes. So you can have one or multiple processes depending on your needs.
Q: Will the regulations affect how our PWB boards are called out and manufactured?
A: Yes, finish should be specified on documentation (prefer to receive smart CAD data with specifics). The glass epoxy specified for the assembly should be able to withstand the higher temperatures (see component temperature section) that the PCB will encounter during any Lead free reflow or wave process.
Q: Are there any issues with single sided, double sided, or multilayer boards with the RoHS process?
A: The components selected for placement on the PCB will need to be able to withstand a second reflow, and all epoxies selected in the manufacturing of the raw PCB must be selected for their ability to handle the higher temperatures for more than one thermal cycle. The concerns for double sided PCB's built with the Tin Lead process apply to Lead free process as well.
Q: What temperature do the components need to be rated at? Duration time?
A: The components selected for the Lead free processes should be able to withstand a minimum of 260 degrees Celsius for 30 seconds and a total time above 200 degrees Celsius of 150 seconds. There may be some conflict with the parts manufactured with a Tin Bismuth alloy, these parts are Lead free but have a much lower reflow temperature. The lower melting point of Tin Bismuth (138 degrees Celsius) may indicate that the material selected by the component manufacturer for the component package is not compatible with the hotter SAC 305 Lead free process used at EE Technologies.
Q: Will you verify our BOM for components and call out any DNI’s (do not install) for potential temperature issues?
A: Yes, we have a Green BOM review process to confirm customer BOM’s for RoHS compliance. Assembly drawings should call out parts with temperature or moisture constraints.
Q: Which lead-free solder alloy will be used? Temperature range?
A: SAC 305 (Tin 95.5%, Silver 3.0%, Copper 0.5%) will be used for the SMT process. The standard specifications for this family of alloys call for a 0.5-2.0 degree Celsius linear ramp rate, a soak time of 40-120 seconds at 200-210 degrees Celsius, and a peak temperature of 230-260 degrees Celsius for 30-90 seconds. When the specifications for the oven profiling equipment are created for the particular Lead free paste to be utilized, the lower end of the temperature spectrum will be used except in the situations where quality will be compromised. The wave soldering process will use the SN 100 C alloy. SN 100 C is a patented nickel stabalized tin/copper alloy that operates at 250-260 degrees Celsius.
Q: What assembly equipment will be used for assembly (Please include model numbers)?
A: All equipment listed below is Lead-free capable, the ERSA EWS 500 F Wave Solder machine is dedicated strictly to Lead free production due to the nature of the wave solder process.
- MPM Ultraprint 1500 Printer (Model #UP1500)
- Assembleon Topaz X (Type PA131201)
- Assembleon Emerald X (Type PA131302)
- Vitronics Soltec XPM2-940 (Model XPM2-940)
- ERSA Wave Solder machine (Model EWS 500 F)
Q: How will the board be identified for RoHS compliance?
A: Fab board designs should have an identifier as part of silkscreen on the board. Finished assemblies plan will be to identify with a green part number label (currently use white part number label). Looking into availability/cost of green thermal labels. Also, we are using an internal part number with a RoHS1 prefix.