Precision cleaning with a flexible twist

Zestron Europes Stefan Strixner highlights the potential of spray cleaning using real-world automotive applications

Recently, spray cleaning processes have become increasingly popular in Europe. In addition to inline processes, spray cleaning in dishwasher-type systems is frequently used for limited number of boards. Thus, the advantages of a small foot print and economical operation are combined with flexibility.

The cleaning principle of industrial dishwasher equipment is similar to household dishwashers, hence accessible to users. Naturally, the materials are adjusted to industrial cleaning requirements. Also, industrial systems keep the cleaning medium in a closed-loop for multiple use. Spray cleaning and rinsing are gentle and carried out at a relatively low pressure.

Cleaning agent is pumped from the holding tank into the cleaning chamber and heated to the preset operating temperature. Then the cleaning process starts and continues for the set time. After cleaning, the agent is pumped back to the holding tank where it is stored for subsequent cleaning cycles. After rinsing steps with softened or demineralised water, the cleaned parts are dried with hot air. Additional metering channels allow more additives, such as inhibitors or defoamers. If required, different baskets can be used to hold a variety of product geometries and sizes.

Water-based Micro Phase Cleaning is tailored to this system. Compared with traditional surfactant systems, MPC active cleaning components do not bind to removed contaminants. The microphases temporarily retain impurities, then release them to the filter which removes them from the cleaning agent. This offers the following advantages:

Active components are not selectively depleted during cleaning
Collected dirt is easily removed using simple bath treatment processes
Significantly longer bath life compared with solvent or surfactant cleaners

MPC cleaners were developed for precision cleaning of electronic assemblies. They are distinguished by their flux removal capabilities acros a wide range of applications. Given the presence of polar and non-polar components, both organic and inorganic impurities (such as salt-like residues) are removed in a single process. Thanks to the surfactant-free formulation, parts are rinsed and dried residue-free, aiding a compact and reliable process. Lead-free solder pastes have also been tested and removed.

The combination of dishwasher equipment and MPC cleaning agent allows the use of standard solutions for a range of cleaning needs. This illustrated by applications at HL Planartechnik, Dortmund and HE System Electronic, Veitsbronn. Both employ a spray cleaning process for completely different production applications with a Miele IR6001 washer using water-based MPC cleaner Vigon A200.

At HL Planartechnik, inclination sensors are cleaned after soldering. Since the sensors are supplied to the automobile industry, high cleaning standards typical for this sector must be maintained. Colophony residues from the soldering process with a high-lead-containing solder wire must be removed completely.

After cleaning an inkjet barcode is applied, requiring a printable, ink-adhesive surface free from flux. Throughput can reach 3,000 units per day and rising. By introducing and optimising the cleaning process, the desired, reproducible results are achieved.

HE System Electronic cleans 4in by 4in ceramic hybrids and FR4 assemblies after reflow and comb soldering. These products are also mainly manufactured for the automotive industry.

Cleanliness requirements are geared toward the J-Std 001D and subsequent wire bonding process. Approximately four to five system loads are cleaned per day. The water-based spray cleaning process revealed much better results after converting to the lead-free soldering process than the previously used solvent cleaning method. With the evaluated parameters the required thresholds for the ionic contamination were easily met and bondable surfaces ensured.

HL PlanartechnikHE System Electronic
MediumVigon A 200 (30%) Vigon A 200 (20%) + 1% Vigon CI 20
Time10 min10 min
Rinse 1+2
MediumSoftened waterSoftened water (+ Defoamer 30)
Time3 min in each case1 min in each case
Rinse 3+4
MediumDemineralised water Demineralised water
Temp40oC + 50oC50oC
Time3 min + 2min2 min in each case
MediumCirculating air
Time30 min35 min
Overall process time50 min50 min

Table 1: Comparative process parameters

A Miele IR 6001/Vigon A 200 cleaning process suits a wide spectrum of cleaning applications including cleaning misprinted PCBs. Using a corresponding cleaning medium, stencils or solder frames and condensation traps can also be cleaned.

This process meets diverse requirements while only needing a minimal base. The compact, automated process can be used for cleaning applications across SMT production. A high degree of flexibility holds attractive potential savings for companies with a range of different cleaning requirements.

Regarding application, users found close collaboration between the equipment and cleaner manufacturers particularly helpful.