Xa ubushushu bebhodi eprintiweyo yeTg ephakamileyo iphakama kwindawo ethile, i-substrate iya kutshintsha ukusuka "kwi-glass state" ukuya kwi "rubber state", kwaye iqondo lokushisa ngeli xesha libizwa ngokuba yi-glass transition temperature (Tg) yebhodi.

Ngamanye amazwi, i-Tg lelona qondo lobushushu liphezulu (°C) apho i-substrate igcina ukuqina. Oko kukuthi, izinto eziqhelekileyo ze-substrate ze-PCB azivelisi kuphela ukuthambisa, ukuguqulwa, ukunyibilika kunye nezinye iziganeko kumaqondo aphezulu, kodwa zibonisa ukwehla okubukhali kwiimpawu zoomatshini kunye nombane (ndicinga ukuba awufuni ukubona oku kwiimveliso zakho) .

Ngokubanzi, iipleyiti ze-Tg zingaphezulu kwe-130 degrees, i-Tg ephakamileyo ngokuqhelekileyo inkulu kune-170 degrees, kwaye i-Tg ephakathi imalunga ne-150 degrees. Ngokuqhelekileyo ibhodi eprintiweyo yePCB eneTg≥:170℃ ibizwa ngokuba yibhodi eprintiweyo yeTg ephezulu. I-Tg ye-substrate iyanda, kwaye ukuchasana nokushisa, ukunyanzeliswa komswakama, ukuchasana kweekhemikhali, ukuzinza kunye nezinye iimpawu zebhodi eprintiweyo ziya kuphuculwa kwaye ziphuculwe. Ukuphakama kwexabiso le-TG, bhetele ukumelana nokushisa kwebhodi, ngokukodwa kwinkqubo yokukhokela, apho izicelo eziphezulu ze-Tg zixhaphake kakhulu. I-Tg ephakamileyo ibhekisela ekuxhathiseni ukushisa okuphezulu.

Ngophuhliso olukhawulezayo lweshishini lombane, ngakumbi iimveliso ze-elektroniki ezimelwe ziikhompyuter, uphuhliso lwentsebenzo ephezulu kunye ne-multilayers ephezulu ifuna ukuxhathisa ubushushu obuphezulu bezinto ezincinci ze-PCB njengesiqinisekiso esibalulekileyo.

Ukuvela kunye nophuhliso lobuchwepheshe obuphezulu obuphezulu obumelelwe yi-SMT.CMT yenze ii-PCBs zikwazi ukwahlula ngakumbi kwinkxaso yokumelana nobushushu obuphezulu be-substrates ngokubhekiselele kwi-aperture encinci, isiphaluka esihle kunye nokunciphisa. Ngoko ke, umahluko phakathi kwe-FR-4 jikelele kunye ne-Tg FR-4 ephezulu: ngamandla omatshini, ukuzinza kobukhulu, ukunamathela, ukuxutywa kwamanzi, kunye nokuchithwa kwe-thermal yezinto eziphantsi kwemeko eshushu, ngakumbi xa kushushu emva kokufunxa ukufuma. Kukho iiyantlukwano kwiimeko ezahlukeneyo ezifana nokwandiswa kwe-thermal, iimveliso ze-Tg eziphezulu ngokucacileyo zingcono kunezixhobo eziqhelekileyo ze-PCB substrate. Kwiminyaka yakutshanje, inani labathengi abafuna iibhodi eziprintiweyo eziphezulu zeTg liye landa unyaka nonyaka.