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PROCESS VARIATIONS AND HOW THEY AFFECT THE EVS PROCESS

A brief summary of various wave soldering (common) combinations & options is summarised below together with the effect on the EVS process.

Fluxes -

Low Rosin

No problem possible

 

High Rosin

NEW HS HIGH SOLIDS Filter needs to be bought when you order the machine.

Cylinder maintenance needs to be regularly performed.

 

No Clean

Should be no problem

 

No Clean (rosin)

Depending on solids content %.

Contact EVS before ordering a machine.

 

Organic Acid
(water sol)

Watch the fumes! Minimise exposure when lifting loading flap. Ensure regular filter maintenance. Cylinder maintenance needs to be regularly performed.

Waves -

Single Lambda

Standard machine used for soldering PTH

 

Single Oscillating

Adaptation of above in attempt to solder SMD - produces slightly more dross than single Lambda

 

Dual/Chip

Most common way of wave soldering SMD's. The "chip" wave by its nature produces large amounts of dross. A common problem is dross blockage of the chip wave producing an uneven solder wave. This can be exaggerated by leaving dross on the surface of the solder wave. Regular de-drossing is important.

 

Kirsten

Don't bother. Small volume machine uses oil to lubricate wave.

Treatments -

Wave Oil

Do not load oil laden dross into the EVS. The EVS will allow companies to stop using oil. To be effective they have to be added to the solder pot every 4 hours and are very expensive.

Paying large amounts per month to reduce dross does not make sense.

 

De-drossing Powders

Do not load dross in to the EVS that has had dross reducing powders mixed in. Dross reducing powders are only effective when mixed in to the solder pot for 20-30 minutes.

This may increase shorts, bridging and rework a mixing these powders in to the solder may cause an increased exposure to fumes that can be dangerous to the operator and the people around.

 

Open Nitrogen

Otherwise known as a contour wave it is not that effective in reducing dross - typically 15% less dross. Nitrogen can cost up to £1000 a month to run. The traditional argument for Nitrogen is that it is required to run a no clean process. No longer true. The modern formulations are more than capable of supporting NC technology in atmospheric conditions (try our NC213 & NW85!). The EVS can easily be justified by switching off the Nitrogen!

 

Closed Nitrogen

Produces much less dross, but equipment is very costly. Some customers have still bought EVS to handle the dross produced by the closed N2 system. This was not done on ROI however.

 

Hot air knife

Used to debridge pcbs the hot air knife can actually produce serious amounts of dross. The cost of reworking is such that the cost of producing the dross can be discounted. With the EVS the customer can have the best of both worlds!

 

 

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