Signal transmission device and insulated module

A signal transmission device, comprising:

• a first chip including a primary-side circuit;
• a primary-side die pad on which the first chip is mounted;
• an insulation chip;
• a second chip including a secondary-side circuit configured to perform at least one of transmission of a signal to the primary-side circuit through the insulation chip and reception of a signal from the primary-side circuit through the insulation chip;
• a secondary-side die pad on which the second chip is mounted;
• and
• an insulation plate located between the primary-side die pad and the insulation chip or between the secondary-side die pad and the insulation chip, wherein:
• the insulation chip includes an element insulation layer including a head surface on which a first pad and a second pad are formed, and a back surface at a side opposite the head surface, and
• a first insulation element and a second insulation element arranged in the element insulation layer, wherein:
• the first insulation element includes a first head surface conductive portion located in the element insulation layer closer to the head surface than to the back surface and electrically connected to the first pad, and
• a first back surface conductive portion located in the element insulation layer closer to the back surface than to the head surface, the first back surface conductive portion facing the first head surface conductive portion in a thickness direction of the element insulation layer;
• the second insulation element includes
• a second head surface conductive portion located in the element insulation layer closer to the head surface than to the back surface and electrically connected to the second pad, and
• a second back surface conductive portion located in the element insulation layer closer to the back surface than to the head surface and facing the second head surface conductive portion in the thickness direction of the element insulation layer;
• the first back surface conductive portion is electrically connected to the second back surface conductive portion;
• the first head surface conductive portion and the primary-side circuit are electrically connected by the first pad;
• the second head surface conductive portion and the secondary-side circuit are electrically connected by the second pad;
• wherein the signal transmission device is configured to transmit a signal from the primary-side circuit to the secondary-side circuit through a transformer including the first insulation element and the second insulation element connected in series;
• and
• wherein the insulation plate has a thickness that is greater than both a distance between the first head surface conductive portion and the first back surface conductive portion in the thickness direction of the element insulation layer and a distance between the second head surface conductive portion and the second back surface conductive portion in the thickness direction of the element insulation layer.