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The Knowledge and Know-how Connection
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June 19, 2013
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Views: 3129
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There is another situation: The product is lead-free soldered due to availability of BGA with lead-free balls. Now, we have few parts to rework, the product does not need RoHS label but was soldered with SAC305.
Now, we need to touch up the joint using regular 63/37 Tin-Lead solder alloy. The reworked parts are discrete and ICs. (if BGA reworked, it is with SAC305 only)
Do you see any problem with mixing of alloys when RoHS label is not required by the customer?
Ashok Dhawan, P. Eng., Manufacturing Specialist, Parker Hannifin Canada
Let's start with the premise that the assembly must meet the print requirements. The solder alloy to be used is listed on the drawing, including any exceptions (for example, Note 1. "Use Sn63Pb37 solder, except BGA U1 which may have SAC305 solder balls").
In order to rework the assembly back into compliance with the print requirement, you should always be able to get a copy of the original assembly print from the customer to determine the solder alloy requirements and exceptions, and rework accordingly. If the assembly print no longer exists, then an appropriate waiver from the customer is needed before mixing alloys or removing old solder and reworking with different alloys.
You can't just fly by the seat of your pants with issues such as solder alloys. These are critical items and must be kept controlled. It doesn't really matter if it is a stereo component or a flight control. If you rework solder on 1,000 stereo amplifiers with the wrong alloy and reliability issues result, you will be getting The Call from your friends at Davidowitz, Davidowitz, and Davidowitz, Attorneys at Law!
Richard Stadem