PCB Journey 10 :
The solder mask has two interests. The first is to avoid the oxidation of copper and the second is to have perfect insulation between two traces of copper during the assembly process. There are different types of PCB soldermask, such as Epoxy Liquid, Liquid Photoimageable (LPI), or Dry Film. Let’s dive into it!
1 - COATING
There are different ways to apply the solder mask to a PCB: curtain, screen printing or electrospray deposition coating according to IPC standards. Before any solder mask application, the boards must be cleaned with a mechanical or chemical preparation in an over-pressurized cleanroom to prevent dust from entering from the outside.
2 - PRE-CURING
Once the panel is totally covered, it must be pre-cured. This step is essential and removes all the solvent from the ink. Without this step, registration will not be done properly.
For the soldermask, the insolation can be done with the registration with 8 CCD cameras and the artwork. The boards receive a blast of LED light for a few seconds to harden the soldermask where the artwork is clear. The insolation can also be done by LDI, Laser Direct Imaging. This time, no artwork is necessary because the machine directly insoles the selected locations with light beams and hardens the targeted location.
4 - DEVELOPING
The portions not protected and not hardened by the insolation are washed away. Here, in our example, the soldermask around the mechanical through-hole is removed.
5 - CONTROL AND CURING
After the developing phase, all the boards are controlled. Indeed, inspection is needed to check if there are any defective images, traces of ink on the pads or through the holes. Finally, the boards are exposed to a high temperature for one hour to cure the soldermask.
"Kama ilivyoelezwa hapo juu, ""mask ya solder"" ni moja ya njia za kuvutia zaidi za PCB." Kwanza ni kuepuka oxidation ya shaba na pili ni kuwa na kutengwa kamili kati ya alama mbili za shaba wakati wa mchakato wa mkutano. Kuna aina mbalimbali za solder masks PCB, kama vile Epoxy Liquid, Liquid Photoimagable (LPI), au Dry Film. Hebu tupige mbizi ndani yake! Kuna njia tofauti za kutumia solder mask kwenye PCB: curtain, screen printing au electrospray deposition coating kulingana na viwango vya IPC. Kabla ya matumizi yoyote solder mask, bodi lazima kusafishwa na maandalizi ya mitambo au kemikali katika chumba safi overpressurized kuzuia vumbi kutoka kuingia kutoka nje. 2 - PRE-CURING Mara baada ya jopo ni kabisa kufunikwa, ni lazima pre-cured. Hatua hii ni muhimu na huondoa kioevu chote kwenye wino. Bila hatua hii, usajili hautafanywa vizuri. Kwa upande wa solder, unaweza kutumia kamera za CCD 8 na picha za picha. Bodi hupokea mlipuko wa mwanga wa LED kwa sekunde chache ili kuimarisha soldermask ambapo kazi ya sanaa ni wazi. Insulation pia inaweza kufanywa na LDI, Laser Direct Imaging. Wakati huu, hakuna kazi ya sanaa ni muhimu kwa sababu mashine moja kwa moja insoles maeneo waliochaguliwa na beams mwanga na hardens eneo lengo. 4 - KUKUZA Sehemu zisizohifadhiwa na zisizo ngumu na insolation huoshwa mbali. Hapa, katika mfano wetu, soldermask karibu mechanical kupitia-shimo ni kuondolewa. 5 - KUDhibiti na CURING Baada ya awamu ya kuendeleza, bodi zote ni kudhibitiwa. Kwa kweli, ukaguzi unahitajika ili kuangalia kama kuna picha yoyote mbaya, alama za wino kwenye pads au kupitia mashimo. Hatimaye, bodi ni wazi kwa joto la juu kwa saa moja kwa ajili ya kuponya soldermask.