Thursday, March 28, 2024
 - 
Afrikaans
 - 
af
Albanian
 - 
sq
Amharic
 - 
am
Arabic
 - 
ar
Armenian
 - 
hy
Azerbaijani
 - 
az
Basque
 - 
eu
Belarusian
 - 
be
Bengali
 - 
bn
Bosnian
 - 
bs
Bulgarian
 - 
bg
Catalan
 - 
ca
Cebuano
 - 
ceb
Chichewa
 - 
ny
Chinese (Simplified)
 - 
zh-CN
Chinese (Traditional)
 - 
zh-TW
Corsican
 - 
co
Croatian
 - 
hr
Czech
 - 
cs
Danish
 - 
da
Dutch
 - 
nl
English
 - 
en
Esperanto
 - 
eo
Estonian
 - 
et
Filipino
 - 
tl
Finnish
 - 
fi
French
 - 
fr
Frisian
 - 
fy
Galician
 - 
gl
Georgian
 - 
ka
German
 - 
de
Greek
 - 
el
Gujarati
 - 
gu
Haitian Creole
 - 
ht
Hausa
 - 
ha
Hawaiian
 - 
haw
Hebrew
 - 
iw
Hindi
 - 
hi
Hmong
 - 
hmn
Hungarian
 - 
hu
Icelandic
 - 
is
Igbo
 - 
ig
Indonesian
 - 
id
Irish
 - 
ga
Italian
 - 
it
Japanese
 - 
ja
Javanese
 - 
jw
Kannada
 - 
kn
Kazakh
 - 
kk
Khmer
 - 
km
Korean
 - 
ko
Kurdish (Kurmanji)
 - 
ku
Kyrgyz
 - 
ky
Lao
 - 
lo
Latin
 - 
la
Latvian
 - 
lv
Lithuanian
 - 
lt
Luxembourgish
 - 
lb
Macedonian
 - 
mk
Malagasy
 - 
mg
Malay
 - 
ms
Malayalam
 - 
ml
Maltese
 - 
mt
Maori
 - 
mi
Marathi
 - 
mr
Mongolian
 - 
mn
Myanmar (Burmese)
 - 
my
Nepali
 - 
ne
Norwegian
 - 
no
Pashto
 - 
ps
Persian
 - 
fa
Polish
 - 
pl
Portuguese
 - 
pt
Punjabi
 - 
pa
Romanian
 - 
ro
Russian
 - 
ru
Samoan
 - 
sm
Scots Gaelic
 - 
gd
Serbian
 - 
sr
Sesotho
 - 
st
Shona
 - 
sn
Sindhi
 - 
sd
Sinhala
 - 
si
Slovak
 - 
sk
Slovenian
 - 
sl
Somali
 - 
so
Spanish
 - 
es
Sundanese
 - 
su
Swahili
 - 
sw
Swedish
 - 
sv
Tajik
 - 
tg
Tamil
 - 
ta
Telugu
 - 
te
Thai
 - 
th
Turkish
 - 
tr
Ukrainian
 - 
uk
Urdu
 - 
ur
Uzbek
 - 
uz
Vietnamese
 - 
vi
Welsh
 - 
cy
Xhosa
 - 
xh
Yiddish
 - 
yi
Yoruba
 - 
yo
Zulu
 - 
zu
Subscriber Login

Cleaning technologies in electronics industry

by Admin
0 comment

Analytical methods for cleaning

Fourier Transform Infrared Spectroscopy (FTIR) is the most widely used analytical method for efficiently determining the precise identity of the contamination. High Performance Liquid Chromatography (HPLC) and UV-Vis Spectroscopy can be used to identify residual rosin. Scanning Electron Microscopy (SEM), Energy Dispersive X-ray (EDX) analysis and Auger analysis are also suitable for determination of residues and contaminants on a PCB and each has its own specific advantage. The equipment required to set up these types of experiments are costly and require a lot of maintenance and are therefore rarely used in production environments.

A common method of determining the degree of ionic contamination is to measure Resistivity of Solvent Extract (ROSE), also known as Solvent Extract Conductivity (SEC). The theory of ROSE is that as the concentration of ions in a solution increases, the resistivity decreases. Simple automated versions of ROSE testing, the Omega Meter, Ionograph or ZeroIon, are used by a number of electronic assembly houses for quality control testing.

Maintaining Standards

The industry standard, IPC-TM-650, employs a solution of isopropanol and deionised water to extract the contaminants whilst the meter measures the change in conductivity. This type of testing is widely accepted and offers rapid results but can be restrictive. Originally designed to test residues from traditional rosin based fluxes and utilise a cheap, readily available solvent (IPA), the scope of this method is now somewhat outdated and may not alert users to possible changes resulting in non-soluble residues.

The change in accepted cleanliness levels also highlights the development of the cleaning industry. Traditionally for the CFC-113 type cleaners mentioned earlier an accepted limit of 1.56μg/cm2 (10μg/in2) equivalent NaCI is detailed as per ANSI/J-STD-001. Today, most assemblies are now achieving well below this level, typically in the region of 0-1μg/in2. This method is also only capable of measuring ionic contamination and cannot define exactly where or what that contamination is.

Two further methods provide valuable data are the measurement of Surface Insulation Resistance (SIR) and Ion Chromatography (IC). The former involves measuring the change in electrical current over time via an interleaved comb pattern PCB and is typically performed at elevated temperatures and humidity levels. The presence of contamination lowers the insulation resistance of the material between the conductors. The latter, Ion Chromatography (IC), is a newer method for cleanliness evaluation which can be used for identifying and quantifying specific ionic species that are present on an electronic device.

The test method details a specific list of ionic residues which can be removed by specific media. Subsequent analysis of the fluid can separate, identify and quantify the residue. Substrate handling and preparation are critical for this method making it particularly expensive and time consuming. Therefore, it is not used for general quality control purposes but as a more specific analytical technique.

The type of cleaner chosen depends widely on the manufacturing conditions. Whether solvent based or water based technology is chosen, the correct application method and set up is imperative in order to achieve successful cleaning. Many specifications have been outlined for cleanliness evaluation; IPC TM-650 is the industry standard. It details methods for many of the cleaning tests described above, giving precise guidelines for analysis. It is clear that some methods are costly and rather time consuming, however they can provide extremely accurate data on the type, location and quantity of the residue. Other, less intense methods can be employed for fast, efficient quality control.

Cleaning equipment market

Industrial cleaning tanks available in the market provide ultrasonic cleaning power for large, small and delicate items. The price of these tanks brings ultrasonic cleaning within the budgets of small and medium sized businesses. Made from stainless steel, the tanks range in size from 1.3l to 13l, with the transducers generating between 50W and 400W of ultrasonic power. Heaters built in to the larger models enhance the cleaning performance, while the stainless steel basket and rack protects and permanently suspends the items being cleaned. Each unit features a 30 minute timer and LCD display. The unit heats the liquid inside the tank to a maximum of 70°C.

Using just water or a cleaning solvent, the ultrasonic sound waves agitate the liquid to such a force that contaminants are lifted from the surface of the items within a matter of minutes. Ultrasonic cleaning will attack previously impenetrable agents such as limescale, mould and bacteria from the surfaces of items.

In yet another form of cleaning, Hydroxide solution is used for Tungsten cleaning, which helps in removing graphite from Tungsten wire for units manufacturing Cathode & Heaters for TV Picture Tubes & CRT’s.

Plasma processing

Plasma processing is also gaining popularity due to its environmentally friendly nature and cost effectiveness compared to wet chemistries. Plasma activation is commonly used in electronics, more specifically in electronic connectors and sensors prior to potting and encapsulation as it ensures an excellent hermetic seal, reduces current leakage and provides stronger physical bonding to the device.

Plasma activation effectively raises surface energies and ensures good wettability. This in turn promotes more complete flow of resins onto almost all low energy polymer materials, including PTFE, silicone rubber and Kapton®. Plasma processing makes polymer surfaces bondable by the reactive chemistry present in the plasma. New chemical functional groups are formed with strong chemical bonds to the bulk of the plastic allowing both aqueous based solutions and adhesives to wet into every crevice of the material. This results in improved bonding, with increases of up to 50 times the strength of the traditional bond not uncommon.

Plasma processing enables the cleaning of residual organics at the molecular level on materials such as glass, metals, plastics, polymers or composites prior to bonding, potting, printing, marking, painting or labelling. It can also be used on PCB’s prior to metallization, where plasma de-smear and etch-back of PCB’s allows for the smear left on via walls after drilling to be removed.

Challenges

The Electronics industry today finds a challenge in the usage of electronic grade IPA, which is used for cleaning of fluxes and other residues from the PCBAs. As of today the industry is looking for a cleaning agent which will avoid the white patches on the boards. When IPA reacts with the flux, it leaves a white patch at the solder joints though it’s not bad it’s definitely indicating an ineffective cleaning.

In summary, selection of the most suitable cleaning process, which provides the required level of cleanliness, is the key to ensuring maximum reliability at minimum cost. Experts point out that this can be accomplished through combining the most advanced cleaning technologies in an energy-efficient design.

You may also like

Leave a Comment

Clean India Journal, remains unrivalled as India’s only magazine dedicated to cleaning & hygiene from the last 17 years.
It remains unrivalled as the leading trade publication reaching professionals across sectors who are involved with industrial, commercial, and institutional cleaning.

The magazine covers the latest industry news, insights, opinions and technologies with in-depth feature articles, case studies and relevant issues prevelant in the cleaning and hygiene sector.

Top Stories

Subscribe To Our Newsletter

Copyright © 2005 Clean India Journal All rights reserved.

Subscribe For Download Our Media Kit

Get notified about new articles