If I used a via of 8 mils diameter with 20 um thickness. As per sierra tool calculator it can carry current of 1 A at 10 degree rise in temperature. What happens if the current is more than 1 A? When will the via fail? How the failure will be in PCB?
10 °C rise isn’t much for a PCB trace. Even 20 °C or 30 °C is usually fine. In some cases, voltage drop across the trace, or power dissipated in the trace, are too high for system design reasons when the rise gets high, say 30 °C or 50 °C.
From a strictly thermal standpoint, there are maximum temperatures for the dielectric being used. For common FR4, this is often 110 °C to 130 °C and is determined by the rated Tg (glass transition temperature). Above this temperature, the board becomes soft, and mechanical and electrical properties are degraded.
In the absence of detailed information, I’d keep thermal rise to 10 °C to 30 °C absolute worst case, and if pushing 30 °C, check that voltage drops aren’t an issue.
Higher temperatures are also undesirable due to thermal stress and cycling. The laminate expands much more than the copper plated onto it, causing the copper to stretch, fatigue, and eventually crack.
Reduce heat by using less current in the first place, using more vias in parallel, wider traces, more layers, etc.
Kwa mfano, kama una njia ya mviringo ya mviringo wa 8mm na unene wa mviringo wa 20mm. Kwa mfano, kwa mfano, sierra calculator inaweza kubeba umeme wa 1A kwa kuongezeka kwa joto la digrii 10. Nini kinatokea wakati umeme wa umeme ni zaidi ya 1A? Njia hiyo itashindwa lini? Jinsi ya kufanikiwa katika PCB Kuongezeka kwa joto la 10 ° C sio mengi kwa alama ya PCB. Hata 20 ° C au 30 ° C ni kawaida nzuri. Katika baadhi ya kesi, voltage kushuka katika trace, au nguvu dissipated katika trace, ni juu sana kwa sababu ya kubuni mfumo wakati kupanda inakuwa juu, kusema 30 ° C au 50 ° C. Kutoka kwa mtazamo wa joto kabisa, kuna joto la juu kwa dielectric inayotumiwa. Kwa FR4 ya kawaida, hii ni mara nyingi 110 ° C hadi 130 ° C na huamuliwa na Tg ya kiwango (joto la mabadiliko ya kioo). Juu ya joto hili, bodi inakuwa laini, na mali ya mitambo na umeme huharibika. Kwa kukosekana kwa habari ya kina, ningeendelea kuongezeka kwa joto kwa 10 ° C hadi 30 ° C hali mbaya kabisa, na ikiwa kushinikiza 30 ° C, angalia kwamba kushuka kwa voltage sio suala. Viwango vya juu vya joto pia havipendwi kwa sababu ya mkazo wa joto na baiskeli. Laminati hiyo huenea zaidi kuliko shaba iliyofunikwa juu yake, na kusababisha shaba hiyo kunyooka, kuchoka, na hatimaye kuvunjika. Kupunguza joto kwa kutumia chini ya sasa katika nafasi ya kwanza, kutumia vias zaidi kwa sambamba, nyayo pana, tabaka zaidi, nk.