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 phriontáilte chuaird Chonaic daoine ar fud an domhain (PCB). 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. Mar sin féin, tá difríochtaí idir feidhmiúlacht, castacht, costas monaraithe, cáilíocht agus iontaofacht na PCBS seo. This article focuses on the last two points, the quality and reliability of PCBS.

Sea, bíonn leictreonaic ardchaighdeáin ag teastáil ó chustaiméirí ionchasacha i gcónaí, ach tá sé seo an-chostasach agus d’fhéadfadh próisis casta déantúsaíochta a bheith i gceist leis. Sa phróiseas casta de mhonarú, cóimeáil agus tástáil PCB, tá próiseas an-tábhachtach ar a dtugtar “sciath comhréireach” de PCB. Tá an sciath chomhréireach seo an-tábhachtach i PCBS i dtéarmaí cáilíochta agus iontaofachta.

What is conformal coating and its importance:

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.

The conformal coating can be as thin as 25 microns and “conforms” to the shape and component layout of the circuit board. Mar a luadh thuas, is é an chúis atá le sciath comhréireach a chur i bhfeidhm ar dhromchla (barr agus bun) PCB ná an PCB a chosaint ar dhálaí comhshaoil ​​seachtracha dochracha, agus ar an gcaoi sin saol seirbhíse an PCB agus an trealamh leictreonach gaolmhar a mhéadú.

Cosúil le teochtaí arda atá le fáil i leictreonaic thionsclaíoch, monarchan agus ardchumhachta, is féidir leis na PCBS seo le bratuithe comhréireacha teocht an-mhór a sheasamh. Ar an gcaoi chéanna, d’fhéadfadh go mbeadh tionchar ag taise ard ar threalamh leictreonach atá suiteáilte i gceantair / ceantair atá gar don fharraige nó don aigéan, mar shampla trealamh cabhlaigh leictreonach nascleanúna a bheith faoi réir creimeadh / creimeadh a bhféadfadh ocsaídiú miotail a bheith mar thoradh air. 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.

Conas sciath comhréireach a chur i bhfeidhm?

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.

Is iad na príomhfhachtóirí lena gcinntear cur i bhfeidhm ceart bratuithe comhréire:

1- Tiús péint

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- Paint by hand with a brush

2- Cumhdach aerasóil

3- Atomizing spray gun coating

4- Automatic dip coating

5- Automatic selection of coating

Modh leigheas / triomú sciath neamhfhoirmiúil:

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- leigheas comhdhlúthaithe: Déantar sciath comhréireach PCB a thriomú ag teocht chomhthimpeallach, déanann taise san atmaisféar moilliú ar an bpróiseas leigheas nó triomú.

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- Curadú ocsaídiúcháin: Sa mhodh seo, tá conraitheoirí PCB nochtaithe do thimpeallacht faoin aer ina bhfuil go leor ocsaigine atmaisféaraigh, rud a chuideoidh le triomaithe / leigheas na gcumadóirí tuaslagóir-bhunaithe

5- Catalytic curing: This is the process of curing conformal coating in which two materials are fused together, one of which is conformal coating. Nuair a dhéantar an sciath a chomhleá le hábhair chatalaíoch eile, ní féidir an próiseas leigheas a stopadh go dtí go mbeidh sé críochnaithe.

Classification of conformal coatings:

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

L Roisín aicrileach (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.

Sochair:

1 – low cost

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

Míbhuntáistí:

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

2- Cothabháil slaodachta íseal

3- Friotaíocht caitheamh íseal agus friotaíocht ceimiceach

L Epoxy conformal coating (ER) :

Conformal coatings based on epoxy resins can be completed by hand brush, spray or dip coating. Moltar spraeáil le haghaidh méideanna níos mó agus le haghaidh PCBS toirt nó fréamhshamhla níos lú.

Sochair:

1- High moisture resistance and good dielectric resistance

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

Míbhuntáistí:

1-epoxy conformal paint is very hard and rigid and can damage PCB and its components if attempted peeling or removal. Bain an sciath trí thuaslagóir guaiseach a úsáid

2- Feidhmíocht ísealteocht íseal

Laghdú ard-leigheas

4- Is deacair iad a athdhéanamh

L sciath sciath comhréireach roisín silicone (OSR):

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

Sochair:

1- Friotaíocht mhaith cheimiceach, friotaíocht taise, spraeála salann agus teocht ard suas le 200 OC

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

3- Oiriúnach d’iarratais lasmuigh PCB le taise ard

An droch:

1- Gan caitheamh resistant mar gheall ar airíonna rubair

2- Can be reworked, but not easily, requiring special solvents, long soaking times and stirring like a brush or ultrasonic bath

3- Low mechanical strength, weak adhesion to PCB substrate

Cumhdach comhréireach L Polúireatán (PU):

Oiriúnach d’iarratais PCB i ngluaisteáin, tionscail, ionstraimíocht agus teileachumarsáid. San aeraspás, go háirithe, imbhuaileann gaile breosla i gcónaí le príomhchorp an trealaimh leictreonaigh agus dá bhrí sin téann siad isteach sa taobh istigh agus bíonn tionchar acu ar bhord an PCB

Sochair:

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

Míbhuntáistí:

1- Tar éis tréimhse fhada de phróiseas cneasaithe iomlán, bíonn claonadh aige dul buí ag teochtaí arda mar gheall ar a cion ard VOC

2- Like silicon, it is not easy to remove completely

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.

Sochair:

1- Excellent dielectric strength

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

3- Can be applied evenly with very thin paint.

Míbhuntáistí:

1- Disassembly/rework is very difficult

2- High cost is the biggest drawback.