Vertrel^® products are the best choice in the industry for cleaning difficult shapes and awkard pieces. The reason for this success is the very low surface tension of the Vertrel^® products.

A low surface tension means the solvent can get into tight spaces more easily than cleaning processes using solvents with high surface tensions (like aqueous systems). Vertrel^® products can clean those spaces more effectively and more quickly without the time, expense and hassle of high-pressure pumps, extra heating costs and other complications of aqueous systems. In fact, the surface tension of the new Vertrel^® products compares very favorably with the benchmark "safety solvent" of all time, Freon^® TMS, but without any of the environmental problems.

Today's advanced BGA chips cause special cleaning problems. This photo shows the tight spacing beneath the chip where fluxes, pastes and other contamination can accumulate. The Vertrel® products, due to their low surface tension and high wetting index, can easily clean in these difficult circumstances. Photo courtesy Branson Ultrasonics

Here are the specifics:

Category	Solvent	Surface Tension in dyn/cm
HFC	MicroCare CF	15.0
	Vertrel® CHD	19.4
	MicroCare CMS	19.2
	MicroCare CCA	18.8
	Vertrel® MCA	15.2
	Vertrel® MCA PLUS	16.1
	Vertrel® SMT	15.5
	Vertrel® XF	14.1
	Vertrel® XM	14.1
	Vertrel® XMS Plus	14.9
	Vertrel® XDA	14.1
	Vertrel® XP	15.1
	Vertrel® XP10	14.1

But there is a better measurement of the cleaning efficiency of a solvent. A smarter, more comprehensive approach is to combine the three most critical factors into a single index. DuPont recommends using the density of the solvent, the viscosity of the solvent and the surface tension into a cleaning index. DuPont calls this the wetting index. With the wetting index, a higher score produces better cleaning.

Type of Solvent	Name	Density	Surface Tension in dyn/cm	Viscosity	Wetting Index
CFC-113	Freon® TF	1.48	17.3	0.70	122
Chlorinated	TCA	1.32	25.9	0.79	65
Alcohol	IPA	0.79	21.7	2.40	15
Aqueous	DI Water	0.997	72.8	1.00	14
	DI Water + Surf	0.998	29.7	1.08	31
HFC	Vertrel¨ XF	1.58	14.1	0.67	167
	Vertrel¨ XP	1.53	14.2	0.68	158

As mentioned above, when comparing wetting indices the higher score will deliver better cleaning. The formula for computing the wetting index is:

Wetting Index = (Density x 1000)/( Surface Tension x Viscosity)

So here's a great answer: when it comes to tough cleaning problems, Vertrel^® specialty fluids are the ideal choice. These are great replacements for ozone-depleting solvents such as CFC-113, 1,1,1-trichloroethane, HCFC-141b, n-propyl bromide (nPB), HFE solvents and HCFC-225, as well as high-global-warming solvents such as perfluorocarbons (PFCs).

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