Thermal simulation - Wave Technology Inc.

Simulation Items	Analysis output
Study of optimum structure for thermal dissipation	Maximum Chip temperature(Tjmax) Thermal Resistance(θｊａ)
Design of thermal dissipation Fin	Maximum Chip temperature(Tjmax) Thermal Resistance(θｊａ)
Temperature distribution of PKG unit caused by IC chip heat generation (Assembled on board)	Maximum Chip temperature(Tjmax) Thermal Resistance(θｊａ)
Temperature distribution of PKG unit caused by IC chip heat generation (suspended in the air)	Maximum Chip temperature(Tjmax) Thermal Resistance(θｊａ)
Temperature distribution assembled on client board	Maximum Chip temperature(Tjmax) Thermal Resistance(θｊａ)

2. Definition of the heat

* In case of single chip type IC

Total thermal resistance θja, Internal thermal resistance θjc, External thermal resistance θca of IC package are defined as shown in the figure below.

θja=θjc+θca = (Tj-Ta)／Pd (℃/W)
θjc= (Tj-Tc)／Pd (℃/W)
Pd=ΔT／θja or θjc (W)

Tj ： Junction(chip) Temperature (℃)
Ta：Ambient Temperature (℃)
Tc：Case Temperature (℃)
Pd：Power Dissipation (W)

3. Simulation model

The IC lead pattern is faithfully reproduced and the 3D model is finally realized.
By running the simulation, Tjmax is obtained as the output and using this value, the thermal resistance θja is calculated.

External lead		Mold

Die pad	IC Chip	Thermal analysis
θｊａ（Thermal resistance） =(TemperatureMax-TemperatureAmb)/Heat generation amount

4. Example（Thermal simulation of 144pin QFP）

As the power consumption of the mounted IC chip is 2.4W, it is estimated that the thermal dissipation by using the unit IC chip is difficult. Accordingly, the possibility of thermal dissipation by attaching the thermal dissipation fin is studied.

~Before counter measure~

Tj,max:95.3℃
θja:29.3℃/W
Pd:1.877W (at ΔT=55℃)

Modeling

Simulation results

Attaching the thermal dissipation fin

~After counter measure~

Tj,max:75.88℃
θja:21.2℃/W
Pd:2.594W (at ΔT=55℃)

Thermal fin:Al plate（1mmt）
Adhesive of fin:Resin

Modeling

Simulation results

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