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how to choose the right electronic heatsink

How to choose electronic Heatsink and Radiator
Radiator classification:
  Manufacturing process is divided into sections, Insert radiator, radiator and heat pipe heat sink combination; one of the great amount of heat sink according to their shape profiles into a single rib, double rib, shaped and left out in the pages; for users to quickly check
How to choose the radiator
  First determine the electronic components to heat, clear parameters of their work, working conditions, size, installation method, choose the size of the Heatsink bottom mounting surface slightly larger than the components can be, because the installation space constraints, mainly depend on the radiator and air convection to heat, beyond the contact surface with the components of the radiator, the cooling effect with increasing distance and decreasing components. For single rib radiator, radiator if the width of the required vacancy in the table can choose two or three times the width of the radiator can be cut off.
The calculation of choices on the radiator
Parameter definition:
Rt ─ ─ ─ The total resistance, ℃ / W;
Rtj ─ ─ ─ semiconductor device thermal resistance, ℃ / W;
Rtc ─ ─ ─ semiconductor devices and heat sink interface, the interface between the thermal resistance, ℃ / W;
Rtf ─ ─ ─ thermal resistance, ℃ / W;
Tj ─ ─ ─ semiconductor device junction temperature, ℃;
Tc ─ ─ ─ semiconductor shell temperature, ℃;
Tf ─ ─ ─ radiator temperature, ℃;
Ta ─ ─ ─ ambient temperature, ℃;
Pc ─ ─ ─ semiconductor devices using the power, W;
ΔTfa ─ ─ ─ radiator temperature, ℃;
Thermal calculation formula:
Rtf = (Tj-Ta) / Pc - Rtj-Rtc
  Heat sink thermal resistance Rff is the main basis for selection. Tj and Rtj is to provide the parameters of semiconductor devices, Pc is the design parameters, Rtc thermal design expertise from the book look-up table.
(1) Calculate the total resistance Rt:
Rt = (Tjmax-Ta) / Pc
(2) Calculate the thermal resistance Rtf or temperature ΔTfa:
Rtf = Rt-Rtj-Rtc
ΔTfa = Rtf × Pc
(3) determine the radiator
  Working conditions in accordance with the radiator (natural cooling or forced air cooling), according to Rtf or ΔTfa and Pc options radiator, radiator cooling curve of the selected search (Rtf curve or ΔTfa line), the curve less than the calculated detected value, to find the right radiator.
  For profiles radiator, when the thermal resistance curve can not be found or when the temperature curve can be determined as follows:
Radiator temperature rise calculated by the formula ΔTfa, and then calculate the radiator integrated heat transfer coefficient α:
α = 7.2ψ1ψ2ψ3 (√ √ [(Tf-Ta) / 20])
Type in: ψ1 ─ ─ ─ description Radiator L / b of the α effect, (L is the length of the radiator, b for the Lianglei film pitch);
ψ2 ─ ─ ─ description radiator h / b on the impact of α, (h is the height of the radiator fins);
ψ3 ─ ─ ─ description of the radiator to increase the width dimension W when the impact of α;
√ √ [(Tf-Ta) / 20] ─ ─ ─ description of the maximum temperature of the radiator surface temperature of the surrounding environment, the impact on α;
These parameters can be look-up table.
Liang Lei film surface calculated by the dispersion between the power q0
q0 = α × ΔTfa × (2h + b) × L
According to single or double-sided ribbed ribbed radiator fins number n, calculation of cooling power Pc '
Single Fin: Pc '= nq0
Double rib: Pc '= 2nq0



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