The upper photograph shows a glossy film around a group of through-hole solder joints. Residue extends between adjacent joints and across the dark solder mask.<\/p>\n\n\n\n
The lower photograph shows a reduction in the broad surface film. Individual solder joints and the surrounding traces are easier to distinguish.<\/p>\n\n\n\n
The contamination is concentrated on an open, relatively flat solder-side area that appears accessible to the cleaning brushes.<\/p>\n\n\n\n
Dry ice fits when the customer requires local waterless cleaning around the exposed joints or when liquid cleaner and subsequent drying are not preferred.<\/p>\n\n\n\n
Use DEZ-C743 when:<\/strong> the same contamination extends to both sides or the complete assembly requires washing and DI-water rinsing.<\/p>\n\n\n\nSample 2: Fine-Pitch IC Leads<\/h2>\n\n\n\nBefore cleaning, visible residue surrounds both rows of IC leads. Small glossy deposits can be seen between the closely spaced metal terminations.<\/p>\n\n\n\n
After cleaning, the spaces between the leads are clearer and less surface residue is visible.<\/p>\n\n\n\n
The residue is exposed around the component leads and can potentially be treated with a focused dry ice nozzle. Spray pressure, distance and angle must be validated on the actual package.<\/p>\n\n\n\n
Choose the aqueous route if contamination may extend beneath the component or if the process requires chemical dissolution followed by DI-water rinsing.<\/p>\n\n\n\n
DEZ-C758 is not recommended<\/strong> for this populated component-side area because direct brush contact is unsuitable.<\/p>\n\n\n\nSample 3: Small SMD Components<\/h2>\n\n\n\nThis area contains a chip resistor, a small integrated circuit and nearby soldered terminations.<\/p>\n\n\n\n
The upper image shows visible deposits around the pad edges. In the lower image, the component boundaries and soldered areas are more clearly defined.<\/p>\n\n\n\n
Dry ice is suitable when the contamination is limited to exposed surfaces around these components and local waterless cleaning is required.<\/p>\n\n\n\n
Use aqueous batch cleaning when several PCBA models require complete washing, rinsing and drying or when residue occurs in multiple areas of the board.
Sample 4: Three-Lead SMD Package<\/h2>\n\n\n\nVisible residue surrounds all three soldered pads of the small SMD package. The film extends from the component body onto the nearby solder mask.<\/p>\n\n\n\n
After cleaning, the pads appear more clearly separated from the surrounding PCB surface.<\/p>\n\n\n\n
This is a strong dry ice application because the contamination is local, exposed and positioned around an accessible component package. It resembles the type of residue produced during component replacement or local soldering work.<\/p>\n\n\n\n
Select batch aqueous cleaning when the same residue is distributed across the complete PCBA rather than limited to one repair area.<\/p>\n\n\n\n
Sample 5: LED Component Terminations<\/h2>\n\n\n\nThe upper photograph shows residue around the LED leads and package edges. After cleaning, the broad surface film is reduced.<\/p>\n\n\n\n
Some colour variation remains on the metal terminations. Surface cleaning does not restore plating or reverse every colour change caused by soldering.<\/p>\n\n\n\n
Dry ice provides direct access to the exposed leads without introducing liquid. The LED package, seals and surrounding materials must tolerate the selected pressure, nozzle and working distance.<\/p>\n\n\n\n
Use aqueous cleaning when the complete LED assembly requires washing and rinsing and all components are compatible with the cleaning chemistry and drying conditions.
Sample 6: White Process Residue<\/h2>\n\n\n\nThe green PCBA contains extensive white deposits around component pads, unpopulated footprints and printed reference markings.<\/p>\n\n\n\n
After cleaning, the surface is substantially clearer and the pad outlines and markings are easier to inspect.<\/p>\n\n\n\n
The photograph cannot establish whether the deposit is flux, dried cleaning chemistry or another production contaminant.<\/p>\n\n\n\n
A complete chemical wash and DI-water rinse is the safer initial route when the residue chemistry is unknown and the contamination covers a wider board area.<\/p>\n\n\n\n
Dry ice should only be selected if testing confirms that the deposit is an accessible surface material that can be separated without chemical dissolution or rinsing.<\/p>\n\n\n\n
DEZ-C758 is unsuitable<\/strong> if the contamination is on a populated surface or distributed around structures that the brushes cannot reach.Sample 7: Mixed Power Components<\/h2>\n\n\n\nThis sample combines a power inductor, larger solder joints and smaller surface-mounted components.<\/p>\n\n\n\n
A glossy film is visible around the larger joints before cleaning. The lower image shows less visible residue across the same area.<\/p>\n\n\n\n
Dry ice suits local Flux removal around exposed power-component joints when the nozzle can reach the contaminated surface.<\/p>\n\n\n\n
Use aqueous batch cleaning when residue is distributed across the complete assembly or when washing and DI-water rinsing are required.<\/p>\n\n\n\n
DEZ-C758 is less suitable<\/strong> on the populated side because the power inductor and mixed component heights restrict brush access.Product Matching Summary<\/h2>\n\n\n\nSample<\/th> Component Structure<\/th> Primary Product<\/th> Alternative<\/th><\/tr><\/thead> 1<\/td> Open through-hole solder side<\/td> DEZ-C758<\/td> DEZ-C7310 or C743<\/td><\/tr> 2<\/td> Fine-pitch IC leads<\/td> DEZ-C7310<\/td> DEZ-C743<\/td><\/tr> 3<\/td> Small SMD components<\/td> DEZ-C7310<\/td> DEZ-C743<\/td><\/tr> 4<\/td> Local three-lead package<\/td> DEZ-C7310<\/td> DEZ-C743<\/td><\/tr> 5<\/td> LED component leads<\/td> DEZ-C7310 after testing<\/td> DEZ-C743<\/td><\/tr> 6<\/td> Widespread white residue<\/td> DEZ-C743<\/td> DEZ-C7310 after testing<\/td><\/tr> 7<\/td> Mixed power assembly<\/td> DEZ-C7310<\/td> DEZ-C743<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\nProblems Solved<\/h2>\n\n\n\nVisible Flux During Final Inspection<\/h3>\n\n\n\n Glossy residue around joints and components can cause a finished assembly to fail appearance requirements. Removing the film makes the component area easier to inspect under magnification.<\/p>\n\n\n\n
Inconsistent Manual Cleaning<\/h3>\n\n\n\n Manual wiping depends on operator access, pressure, chemical quantity and cleaning time. It is difficult to achieve the same result between narrow IC leads, large through-hole joints and mixed component structures.<\/p>\n\n\n\n
Local Rework Residue<\/h3>\n\n\n\n Component replacement and manual soldering can leave Flux around a limited repair area. Dry ice is relevant when the residue is directly accessible and the complete board should not enter a liquid process.<\/p>\n\n\n\n
Contamination Across the Complete Assembly<\/h3>\n\n\n\n When residue covers several areas or may remain around low-clearance components, an aqueous process provides washing, DI-water rinsing and drying across the assembly.<\/p>\n\n\n\n
Accessible Solder-Side Residue<\/h3>\n\n\n\n When contamination is restricted to one open solder side, brush cleaning can remove visible Flux marks and loose solder balls without washing the populated side.<\/p>\n\n\n\n
Why One Machine Does Not Fit Every PCBA<\/h2>\n\n\n\n The seven samples show that \u201cFlux residue\u201d is not enough information for equipment selection.<\/p>\n\n\n\n
Two PCBAs may contain similar-looking contamination but require different machines because of:<\/p>\n\n\n\n
\nResidue location;<\/li>\n\n\n\n Component height;<\/li>\n\n\n\n Pad spacing;<\/li>\n\n\n\n Surface accessibility;<\/li>\n\n\n\n Chemical compatibility;<\/li>\n\n\n\n Required cleanliness;<\/li>\n\n\n\n Production quantity;<\/li>\n\n\n\n Inline or offline operation.<\/li>\n<\/ul>\n\n\n\nA visible deposit on an open through-hole solder side may suit brushes. The same deposit between component leads may require dry ice or aqueous spray cleaning. Contamination beneath low-clearance packages may require washing and DI-water rinsing.<\/p>\n\n\n\n
Visible Cleanliness and Ionic Cleanliness<\/h2>\n\n\n\n These microscope comparisons demonstrate changes in visible surface contamination. They do not provide ionic-cleanliness data.<\/p>\n\n\n\n
Dry ice and brush cleaning can remove accessible visible residue, but they must not be presented as proof that a numerical ionic-contamination limit has been achieved.<\/p>\n\n\n\n
When the customer specifies ionic cleanliness, provide the test method and acceptance value before the process is confirmed. Aqueous washing, controlled rinsing, drying and subsequent testing may be required.<\/p>\n\n\n\n
Project Result<\/h2>\n\n\n\n The seven comparisons show that visible residue was reduced across different PCBA structures:<\/p>\n\n\n\n
\nThrough-hole solder joints became easier to inspect;<\/li>\n\n\n\n Fine-pitch lead spacing appeared clearer;<\/li>\n\n\n\n Residue around small SMD packages was reduced;<\/li>\n\n\n\n LED and power-component areas showed less surface film;<\/li>\n\n\n\n White deposits across the green PCB were substantially reduced.<\/li>\n<\/ul>\n\n\n\nThe project also demonstrated that equipment should be selected from the contamination location and production requirement\u2014not from the word \u201cFlux\u201d alone.<\/p>\n\n\n\n
Send Your PCBA for Cleaning Evaluation<\/h2>\n\n\n\n Send representative PCBAs with their actual contamination together with:<\/p>\n\n\n\n