In all methods, the following considerations must be taken into account:
- Coating. All Elmo assembled PCBs are coated by a conformed coating that results in a significantly higher resistance to humidity and polluted environments (Elmo’s standard coating is the acrylic HumiSeal - 1B31)
- Some cleaning methods involve cleaning with solvents and then dipping in water (or other “conducting” liquids) to get rid of the residues and the solvents
Such a cleaning method may cause:
- The acrylic protective coating to dissolve thus exposing the product to higher sensitivity to humidity
- Water (or any other conductive liquid) to be trapped in the product. Even though the cleaning process has a drying stage for the product, the drying process may never fully dissipate the liquid completely allowing the wetness to remain within the product.
The scenario above, of stripping off the conformal coating plus the “trapped water” might cause destructive short circuits on "Power On".
The Best and Recommended Assembly Process options are:
Method 1: No Cleaning Required
- No cleaning at all by using “Non-Clean” soldering pastes
Remark: Using “Non-Clean” soldering paste and operating at high temperatures such as “higher than 60ºC” may cause “re-activating” of the Non-Clean Flux residues. In very extreme cases, this may result in conduction paths. Therefore, when the product operates at high temperatures it is recommended to also clean the “Non-Clean” paste residues. The simplest method is by hand brushing.
- No need to clean when using a Nitrogen “environment” (hand station or Nitrogen wave soldering) with fluxless soldering pastes
Remark: The world is becoming “greener and greener’ and the “clean” (no fluxes, no residues, no pollution) Nitrogen soldering (Hand and wave soldering) will become more and more popular. In addition, the Nitrogen soldering environment ensures the high quality of the soldering process. Elmo is gradually implementing this “Clean and Qualitative” soldering method to all Elmo products.
Method 2: Clean Simply
This method is used when cleaning is required after soldering with flux solder paste:
The cleaning process should be done by hand using a soft brush. Simply and gently brush the cleaning agent on the area needing to be cleaned.
Remark: If the Interface Board is “heavily” populated with components it recommended to:
- Wave soldering the whole assembly including the Elmo drive
- Hand cleaning of the whole assembly
- Wave soldering of the assembly without the Elmo drive
- Clean the assembly using any method
- Hand soldering the Elmo drive onto the interface board
- Hand clean the Elmo drive soldering pins if required
An example of Nitrogen hands soldering station
Immersion of the boards in cleaning baths or spray cleaning of any kind are absolutely forbidden by all means.