For the majority of companies moving to Lead Free we would like to suggest the following as a need to do list.
Time frame 2 to 4 months |
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To do: review BOM. |
| Check what you are currently supplied, are being offered or are being forced to take for the following properties; |
| Type of lead free finish. |
| MRT rating (moisture resistance to temperature) to new higher temperatures. JEDEC-020 |
| Type of plastic used for components and connectors: can they withstand higher temperatures? |
| Check that flame-retardants in components are not PBB or PBDE and if they will survive higher Temperatures (260 C) |
| PWB Laminate choice. It will be necessary to change unless it is a simple low thermal demand assembly. |
| Check capability of existing equipment to handle Lead Free assembly. |
| Place purchase orders for necessary upgrades to equipment |
| Determine requirements for UL or other such approval. |
| Determine the type of Alloy and Flux to be used for Wave, reflow and Hand soldering. |
| Inform all customers of plan to change to Lead free assembly, discuss time frame and price increases. |
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Time frame 2 to 4 months |
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To do: Trial run. |
| Review BOM for either your most complex assembly or the assembly requiring the highest reliability level. |
| Assemble BOM to build this assembly Lead free. |
| Verify the performance of new or existing equipment to meet Lead free assembly |
| Build a statistically significant sample size of assemblies. |
| Resolve all processing issues. |
| Determine all reliability, cleanliness and corrosion requirements. |
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Time frame 1 to 2 months |
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To do: Reliability Testing. |
| Place assembly through required testing. |
| Schedule compliance laboratory to begin testing at end of reliability test presuming sample will pass in house testing. |
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Time frame 1 month |
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To do: Document process. |
| Send sample to compliance laboratory to begin testing. |
| Inform all customers of success of changeover and start filling pipeline with Lead free product. |
As can be seen from the above a best-case scenario will take between six (6) to eleven (11) months depending on the complexity and size of the operation.
Running into any problems only extends the timeline.
It could be said that if you are only starting now you are too late.
There is a solution.
We can help jump start the process and cut some time from the process by offering a Starter Kit for Lead Free Assembly.
The Starter Kit will offer the following.
We will show you how to choose and specify the correct laminate for your process, how to verify that suppliers meet We will recommend bare board surface finishes suitable for your process and show you how to set up monitoring process to keep suppliers on track.
Components.
For most companies the prospect of checking each component for process compliance is so daunting that it has stopped them from moving forward with Lead free assembly.
We will show you how to sort your components into groups that can be ranked from highest to lowest impact on the process.
We can show you what characteristics can be ignored and what can hurt.
Based on your process capabilities we will recommend a selection of fluxes and alloys that give you the greatest flexibility for Reflow, wave and hand soldering.
We will show the impact of using various flux types on the reliability of the finished assembly.
Reliability and Work environment
We will give a concise review on corrosion testing and cleanliness requirements, how to test and how to comply.
Intermetallics. Silver contamination in Solder joint causes similar failures to Gold Tin intermetallic at lower concentrations
MRT Rating on Chip. At higher assembly temperatures there is a potential for chip damage (from micro cracking to popcorning)
Residues on PC board. As a result of the higher assembly temperature, certain residues once considered benign can become active initiating corrosion.
Third party certification. If you are required to have UL, CE or other such approval to sell your product you will need to submit the new Lead free module for approval.
Here in the USA, Underwriters Laboratories (UL) may not have sufficient capacity to qualify every module submitted before the RoHS deadline