Multi-layer sheet for mold underfill encapsulation, method for mold underfill encapsulation, electronic component mounting substrate, and production method for electronic component

A method for mold underfill encapsulation of an electronic component mounting substrate, the method comprising:

• a step of preparing a substrate on which an electronic component provided with electrodes having an electrode height (h) of 5 to 250 μm and a width (w) between electrodes of 5 to 500 μm is flip-chip mounted;
• a step of preparing a multi-layer sheet having the following (A)-layer as an outermost layer;
• a step of placing the multi-layer sheet such that the (A)-layer comes into direct contact with the electronic component and the substrate;
• a step of heating and compressing the placed multi-layer sheet:
• (A)-layer:
• a layer formed from a resin composition having a local maximum value of tan δ (loss tangent) of 3 or more at a measurement temperature of 125° C. for a measurement time of 0 to 100 seconds;
• and
• a step of laminating the (A)-layer and the following (B)-layer so as to be in contact with each other,
• (B)-layer:
• a layer formed from a resin composition satisfying the following Formula (1),
• in the following Formula (1), “α” represents the coefficient of thermal expansion α [ppm/K] at 80° C. or lower of a thermoset product obtained after subjecting the resin composition to a thermosetting treatment at 175° C. for one hour;
• and “E” represents the storage modulus E′ [GPa] at 25° C. of the thermoset product:
• 40000≤α×E′≤250000[Pa/K] (1).

An electronic component mounting substrate being mold underfill encapsulated, wherein the mold underfill encapsulation is encapsulated by a multi-layer sheet having:

• the following (A)-layer as an outermost layer:
• (A)-layer:
• a layer formed from a resin composition having a local maximum value of tan δ (loss tangent) of 3 or more at a measurement temperature of 125° C. for a measurement time of 0 to 100 seconds,
• wherein the (A)-layer is configured so as to come into direct contact with an electronic component and a substrate in the mold underfill encapsulation;
• and
• (B)-layer:
• a layer formed from a resin composition satisfying the following Formula (1),
• in the following Formula (1), “α” represents the coefficient of thermal expansion α [ppm/K] at 80° C. or lower of a thermoset product obtained after subjecting the resin composition to a thermosetting treatment at 175° C. for one hour;
• and “E” represents the storage modulus E′ [GPa] at 25° C. of the thermoset product:
• 40000≤α×E′≤250000[Pa/K] (1).

A method for producing a mold underfill encapsulated electronic component mounting substrate, the method comprising:

• a step of preparing a substrate having an electronic component flip-chip mounted thereon;
• a step of preparing a multi-layer sheet having the following (A)-layer as an outermost layer;
• a step of placing the multi-layer sheet such that the (A)-layer comes into direct contact with the electronic component and the substrate;
• and
• a step of heating and compressing the placed multi-layer sheet:
• (A)-layer:
• a layer formed from a resin composition having a local maximum value of tan δ (loss tangent) of 3 or more at a measurement temperature of 125° C. for a measurement time of 0 to 100 seconds;
• and
• a step of laminating the (A)-layer and the following (B)-layer so as to be in contact with each other,
• (B)-layer:
• a layer formed from a resin composition satisfying the following Formula (1),
• in the following Formula (1), “α” represents the coefficient of thermal expansion α [ppm/K] at 80° C. or lower of a thermoset product obtained after subjecting the resin composition to a thermosetting treatment at 175° C. for one hour;
• and “E”′ represents the storage modulus E′ [GPa] at 25° C. of the thermoset product:
• 40000≤α×E′≤250000[Pa/K] (1).