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The phenomenology of the iron pnictide superconductor can be described by the three-band <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mi>s</mi><mo>±</mo></mrow></semantics></math></inline-formula> Eliashberg theory in which the mechanism of superconducting coupling is mediated by antiferromagnetic spin fluctuations and whose characteristic energy <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><msub><mi mathvariant="sans-serif">Ω</mi><mn>0</mn></msub></semantics></math></inline-formula> scales with <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><msub><mi>T</mi><mi>c</mi></msub></semantics></math></inline-formula> according to the empirical law <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msub><mi mathvariant="sans-serif">Ω</mi><mn>0</mn></msub><mo>=</mo><mn>4.65</mn><msub><mi>k</mi><mi>B</mi></msub><msub><mi>T</mi><mi>c</mi></msub></mrow></semantics></math></inline-formula>. This model presents the universal characteristics that are independent of the critical temperature, such as the link between the two free parameters <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><msub><mi>λ</mi><mn>13</mn></msub></semantics></math></inline-formula> and <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><msub><mi>λ</mi><mn>23</mn></msub></semantics></math></inline-formula> and the ratio <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msub><mo>Δ</mo><mi>i</mi></msub><mo>/</mo><msub><mi>k</mi><mi>B</mi></msub><msub><mi>T</mi><mi>c</mi></msub></mrow></semantics></math></inline-formula>.