As we all know, the continuous progress of electronic equipment and circuit technology, the peak of engineering art in the design, development and manufacture of printplaat (PCB) is getuig deur mense regoor die wêreld. Our planet is full of highly intelligent machines, automated robots and scientific marvels, and of course, there are plenty of PCBS in every corner of the planet, no matter what country or city it is. Hierdie PCBS verskil egter in funksionaliteit, kompleksiteit, vervaardigingskoste, kwaliteit en betroubaarheid. Hierdie artikel fokus op die laaste twee punte, die kwaliteit en betroubaarheid van PCBS.

Ja, potensiële kliënte wil altyd elektronika van hoë gehalte hê, maar dit is baie duur en kan komplekse vervaardigingsprosesse behels. In die ingewikkelde proses van die vervaardiging, montering en toetsing van PCB, is daar ‘n baie belangrike proses wat ‘conformal coating’ van PCB genoem word. Hierdie konformale laag is baie belangrik in PCBS wat kwaliteit en betroubaarheid betref.

Wat is konforme laag en die belangrikheid daarvan:

Conforming coating, an ultra-thin protective coating of polymer film, can be used in conjunction with assemblies mounted on assembly surfaces to protect assembly leads, solder joints, exposed wiring, and other metal points on the PCB surface from corrosion, dust, or chemicals due to various operating or environmental conditions.

Die konformale laag kan so dun as 25 mikron wees en ‘pas’ by die vorm en komponentuitleg van die printplaat. Soos hierbo genoem, is die rede vir die aanbring van ‘n gelykvormige laag op die oppervlak (bo en onder) van ‘n PCB om die PCB te beskerm teen ongunstige eksterne omgewingstoestande, waardeur die lewensduur van die PCB en gepaardgaande elektroniese toerusting verleng word.

Soos hoë temperature wat in industriële, fabriek- en hoëkragelektronika voorkom, kan hierdie PCBS met konforme bedekkings uiterste temperature weerstaan. Net so kan elektroniese toerusting wat in gebiede/gebiede naby die see of die oseaan geïnstalleer word, beïnvloed word deur hoë humiditeit, soos elektroniese navigasietoestelle wat blootgestel kan word aan korrosie/erosie wat kan lei tot metaaloksidasie. Similarly, in microbiology laboratories and the medical industry, sensitive electronic equipment can be exposed to toxic chemicals, acidic and alkaline solvents that can accidentally spill onto a PCB, but the PCB’s “conformation coating” will protect the PCB and components from fatal injury.

Hoe om ‘n konformale laag toe te pas?

In fact, the method of applying “conformal paint” in the right way is so important that careful consideration must be given to how conformal paint is applied. It is as important to choose suitable conformal coating materials.

Die belangrikste faktore wat die korrekte toediening van conformal coatings bepaal, is:

1- Dikte van verf

2- The level of coverage achieved

3- The degree of adhesion of paint to wood panels and their components.

There are five methods for applying conformal coatings:

1- Verf met die hand met ‘n kwas

2- Aërosolbedekking

3- Atomizing spray gun coating

4- Automatic dip coating

5- Automatic selection of coating

Konformale verhardings-/droogmetode:

Conformal coatings themselves can be classified according to the drying and curing methods used after conformal coatings are completed. These methods are:

1- Heat/heat curing: Conformal coating is dried at high temperature. Drying rate is much faster than normal room temperature drying/curing.

2- Kondensasie-uitharding: Die konforme laag van PCB word gedroog by kamertemperatuur, vog in die atmosfeer vertraag die uithardings- of droogproses.

3- ULTRAVIOLET (UV) curing: Here PCB with conformal coating is exposed to UV radiation. The uv energy determines the curing speed of PCB conformal coating

4- Oksidasie-uitharding: In hierdie metode word PCB-gelykvormers blootgestel aan ‘n opelugomgewing met groot hoeveelhede atmosferiese suurstof, wat sal help met die droog/uitharding van oplosmiddels gebaseerde gelykvormers

5- Catalytic curing: This is the process of curing conformal coating in which two materials are fused together, one of which is conformal coating. Nadat die laag met ander katalisatormateriaal gesmelt is, kan die verhardingsproses nie gestop word voordat dit voltooi is nie.

Classification of conformal coatings:

There are five main conformal coatings used: acrylic resin, epoxy resin, silicone, polyurethane (PU) and polyparaxylene coating.

L Akrielhars (AAR):

Acrylics are ideal for (low-cost and high-volume) common electronics because AAR is inexpensive and can be easily applied to PCB surfaces by brush, dip, and manual or automatic spraying, reducing turnaround time and producing cost-effective products.

Voordele:

1 – lae koste

2- Easy for manual or automatic robot applications

3- Easy to rework

4- Excellent moisture protection

5- Good surface elasticity, can withstand static voltage discharge, and does not react with the atmosphere, therefore helps cure through solvent evaporation

Nadele:

1- Due to the use of atmospheric curing/drying methods for this material, proper ventilation systems need to be ensured

2- Onderhoud met lae viskositeit

3- Lae slytasieweerstand en chemiese weerstand

L Epoxy conformal coating (ER) :

Konformale bedekkings gebaseer op epoxyhars kan met ‘n handborsel, spuit- of diplaag voltooi word. Spuit word aanbeveel vir groter volumes en vir kleiner volume of prototipe PCBS.

Voordele:

1- High moisture resistance and good dielectric resistance

2- Excellent chemical resistance, abrasion resistance, moisture resistance and high temperatures up to 150 O C

Nadele:

1-epoxy conformal paint is very hard and rigid and can damage PCB and its components if attempted peeling or removal. Verwyder die laag met ‘n gevaarlike oplosmiddel

2- Swak prestasie by lae temperature

3- Hoë krimping

4- Dit is moeilik om te herhaal

L Silikonhars (OSR) -vormige laag:

The softest of the above two types of conformal coatings is silicone resin (OSR) conformal coatings. They are widely used in LED lamp PCBS without reducing light intensity or color change. Ideal for PCB installation at high humidity and exposure to air. Suitable for PCB with high operating temperature and high power

Voordele:

1- Goeie chemiese weerstand, vogbestandheid, soutbespuiting en hoë temperature tot 200 ° C

2- Good flexibility makes it resistant to vibration stress on PCB from external environment.

3- Geskik vir buitentoepassings met PCB met hoë humiditeit

Die slegte:

1- Nie bestand teen slytasie nie weens rubber eienskappe

2- Kan herwerk word, maar nie maklik nie, en vereis spesiale oplosmiddels, lang weektye en roer soos ‘n kwas of ultraklankbad

3- Low mechanical strength, weak adhesion to PCB substrate

L Poliuretaan (PU) konformale laag:

Geskik vir PCB -toepassings in motor-, nywerheids-, instrumentasie- en telekommunikasie. Veral in die lugvaart bots brandstofdampe voortdurend met die hoof van elektroniese toerusting en dring dus in die binnekant en beïnvloed die printplaat

Voordele:

1- High resistance to moisture, chemicals (acid and alkali) and wear

Nadele:

1- Na ‘n lang tyd van ‘n volledige genesingsproses, is dit geneig om geel te word by hoë temperature vanweë die hoë VOC-inhoud

2- Net soos silikon, is dit nie maklik om heeltemal te verwyder nie

L polyparaxylene conformal coating:

This type of coating is suitable for avionics, microelectronics, sensors, high-frequency circuits, and densely populated PCB-based components. It is applied by means of vapor deposition.

Voordele:

1- Excellent dielectric strength

2- High resistance to moisture, solvents, extreme temperatures and acid corrosion

3- Can be applied evenly with very thin paint.

Nadele:

1- Disassembly/rework is very difficult

2- Hoë koste is die grootste nadeel.