Raws li peb txhua tus paub, kev nce qib txuas ntxiv ntawm cov cuab yeej hluav taws xob thiab thev naus laus zis thev naus laus zis, qhov siab tshaj ntawm kev kos duab engineering hauv kev tsim qauv, txhim kho thiab tsim khoom ntawm luam tawm hauv Circuit Court board (PCB) tau pom los ntawm tib neeg thoob ntiaj teb. 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. Txawm li cas los xij, cov PCBS no txawv hauv kev ua haujlwm, nyuaj, tus nqi tsim khoom, zoo thiab ntseeg tau. Kab lus no tsom mus rau ob lub ntsiab lus kawg, qhov zoo thiab ntseeg tau ntawm PCBS.

Yog, cov neeg siv khoom muaj peev xwm ib txwm xav tau cov khoom siv hluav taws xob zoo, tab sis qhov no kim heev thiab tuaj yeem koom nrog cov txheej txheem tsim khoom. Hauv cov txheej txheem nyuaj ntawm PCB kev tsim khoom, sib dhos thiab ntsuas, muaj txheej txheem tseem ceeb heev hu ua “txheej txheej” ntawm PCB. Cov txheej txheej txheej txheem no tseem ceeb heev hauv PCBS hais txog qhov zoo thiab ntseeg tau.

Dab tsi yog txheej txheej thiab nws qhov tseem ceeb:

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.

Cov txheej txheem txheej txheem tuaj yeem ua kom nyias li 25 microns thiab “ua raws” rau cov duab thiab cov qauv txheej txheem ntawm pawg thawj coj saib xyuas vaj huam sib luag. Raws li tau hais los saum no, qhov laj thawj rau kev thov txheej txheej txheej rau saum npoo (saum toj thiab hauv qab) ntawm PCB yog txhawm rau tiv thaiv PCB los ntawm qhov tsis zoo ib puag ncig ib puag ncig, yog li ua rau kev pab lub neej ntawm PCB thiab cov khoom siv hluav taws xob cuam tshuam.

Zoo li qhov kub tau pom hauv kev lag luam, lub Hoobkas, thiab cov khoom siv hluav taws xob muaj zog, cov PCBS no nrog cov txheej txheej zoo tuaj yeem tiv taus qhov kub. Ib yam li ntawd, cov khoom siv hluav taws xob teeb tsa hauv thaj chaw/thaj chaw ze rau hiav txwv lossis dej hiav txwv tuaj yeem cuam tshuam los ntawm cov av noo siab, xws li kev siv cov khoom siv hluav taws xob hauv nkoj tuaj yeem raug xeb/yaig uas tuaj yeem ua rau hlau oxidation. 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.

Yuav ua li cas thov txheej txheej txheej?

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.

Lub hauv paus tseem ceeb txiav txim siab qhov kev thov tsim nyog ntawm cov txheej txheej yog:

1- Thickness ntawm cov xim

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- Xim ntawm tes nrog txhuam

2- Aerosol txheej

3- Atomizing spray gun coating

4- Automatic dip coating

5- Automatic selection of coating

Cov txheej txheem txheej txheej kom qhuav/kom qhuav:

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- Kev ua kom qhuav hws: Cov txheej txheej txheej ntawm PCB tau qhuav ntawm qhov kub ib puag ncig, noo noo hauv huab cua ua rau qeeb lossis ua kom qhuav.

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- Kev kho cov tshuaj tua kab mob: Hauv txoj kev no, PCB cov neeg ua haujlwm tau nthuav tawm rau huab cua qhib ib puag ncig nrog cov pa ntau hauv huab cua, uas yuav pab ua kom qhuav/kho ntawm cov kuab tshuaj raws cov neeg ua haujlwm.

5- Catalytic curing: This is the process of curing conformal coating in which two materials are fused together, one of which is conformal coating. Thaum txheej tau fused nrog lwm cov khoom siv catalyst, cov txheej txheem tua tsis tuaj yeem nres kom txog thaum nws ua tiav.

Classification of conformal coatings:

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

L Acrylic cob (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.

kev pab cuam:

1 – tus nqi qis

2- Yooj yim rau daim ntawv thov lossis tsis siv neeg hlau

3- Easy to rework

4- Kev tiv thaiv ya raws zoo heev

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

tsis zoo:

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

2- Tsawg viscosity txij nkawm

3- Tsawg hnav tsis kam thiab tiv taus tshuaj

L Epoxy conformal coating (ER) :

Cov txheej txheej zoo sib xws raws li cov tshuaj epoxy tuaj yeem ua tiav los ntawm txhais tes txhuam, tshuaj tsuag lossis txau txheej. Tshuaj tsuag tau pom zoo rau qhov ntau dua thiab rau qhov ntim me me lossis cov qauv PCBS.

kev pab cuam:

1- High moisture resistance and good dielectric resistance

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

tsis zoo:

1-epoxy conformal paint is very hard and rigid and can damage PCB and its components if attempted peeling or removal. Tshem tawm txheej txheej los ntawm kev siv cov kuab tshuaj lom

2- Kev ua haujlwm kub tsis zoo

3- Kev kho kom siab ntsws

4- Lawv nyuaj rau rov ua dua

L Silicone cob (OSR) txheej txheej:

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

kev pab cuam:

1- Tshuaj tiv thaiv zoo, tiv taus ya raws, tshuaj tsuag ntsev thiab kub ntau txog 200 OC

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

3- Haum rau PCB daim ntawv thov sab nraum zoov nrog cov av noo siab

Qhov phem:

1- Tsis hnav tiv taus vim cov khoom siv roj hmab

2- tuaj yeem rov ua dua, tab sis tsis yooj yim, xav tau cov kuab tshuaj tshwj xeeb, ntev so so thiab nplawm zoo li txhuam lossis ultrasonic da dej

3- Low mechanical strength, weak adhesion to PCB substrate

L Polyurethane (PU) txheej txheej:

Haum rau PCB daim ntawv thov hauv tsheb, kev lag luam, kev ntsuas thiab kev sib txuas lus. Hauv aerospace, tshwj xeeb, cov pa roj tas li sib tsoo nrog lub cev tseem ceeb ntawm cov cuab yeej siv hluav taws xob thiab yog li nkag mus rau sab hauv thiab cuam tshuam rau PCB pawg thawj coj saib.

kev pab cuam:

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

tsis zoo:

1- Tom qab lub sijhawm ntev ntawm cov txheej txheem ua kom tiav, nws zoo li tig daj thaum kub vim nws cov ntsiab lus VOC siab

2- Zoo li silicon, nws tsis yooj yim tshem tawm tag nrho

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.

kev pab cuam:

1- Excellent dielectric strength

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

3- Can be applied evenly with very thin paint.

tsis zoo:

1- Kev sib cais/rov ua haujlwm yog qhov nyuaj heev

2- Tus nqi siab yog qhov teeb meem loj tshaj plaws.