Electronic control device
In an electronic control device, an electrically-conductive adhesive is arranged on an outer edge portion of a first surface of a circuit board as a stress reducing portion for reducing stress of the circuit board received by a molding resin. An elastic modulus of the electrically-conductive adhesive is lower than that of the circuit board. The electrically-conductive adhesive is covered by an adhesion improving member. When peeling stress is applied to the circuit board from the molding resin, the electrically-conductive adhesive and the adhesion improving member receive the peeling stress to be deformed. Therefore, the peeling stress to the circuit board is reduced.
1. An electronic control device comprising:
a circuit board having a first surface and a second surface that is an opposite surface of the first surface;
a base member that forms a heat sink, wherein the base member has a circuit board side surface, to which the second surface of the circuit board is bonded;
an electronic component mounted on the first surface;
a molding resin that entirely seals the circuit board and the circuit board side surface of the base member; and
a stress reducing portion arranged at least on an outer edge portion of the first surface of the circuit board, wherein:
the stress reducing portion is held between the circuit board and the molding resin to reduce stress of a joint portion between the circuit board and the molding resin via the stress reducing portion at the outer edge portion in comparison to stress of a joint portion between the circuit board and the molding resin which are bonded together without holding the stress reducing portion there between;
an elastic modulus of the stress reducing portion is lower than an elastic modulus of the circuit board;
the stress reducing portion is made of an electrically-conductive adhesive;
the electronic component is bonded to the first surface of the circuit board by an electrically-conductive adhesive, which is the same as the electrically-conductive adhesive of the stress reducing portion; and
an adhesion improving member, which has an elastic modulus lower than an elastic modulus of the electrically-conductive adhesive of the stress reducing portion and an elastic modulus of the molding resin, is interposed between the electrically-conductive adhesive of the stress reducing portion and the molding resin and contacts the electrically-conductive adhesive of the stress reducing portion and the molding resin.
2. The electronic control device according to claim 1 , wherein
the stress reducing portion is arranged at a region farthest from a center of the first surface in the outer edge portion of the first surface.
3. The electronic control device according to claim 1 , wherein
the circuit board has a stepped portion configured by a plane portion and a side portion at the outer edge portion of the first surface, and
the stress reducing portion is arranged to cover the stepped portion.
4. The electronic control device according to claim 1 , wherein
the stress reducing portion is arranged to cover a corner portion configured by the first surface and a lateral surface adjacent to the first surface.
5. The electronic control device according to claim 1 , wherein
the stress reducing portion is coated with the adhesion improving member, which firmly attaches the molding resin to the circuit board.
6. The electronic control device according to claim 1 , wherein
the stress reducing portion is arranged in the form of L-shape on the outer edge portion of the first surface.
7. The electronic control device according to claim 1 , wherein
the stress reducing portion is arranged entirely on the outer edge portion to surround the first surface.
8. The electronic control device according to claim 1 , wherein
the stress reducing portion is arranged intermittently on the outer edge portion of the first surface.
9. The electronic control device according, to claim 1 , wherein
the stress reducing portion is arranged on the outer edge portion of the first surface in a dot shape.
10. The electronic control device according to claim 1 , wherein an opposite surface of the base member, which is opposite from the circuit board side surface of the base member in a direction perpendicular to a plane of the circuit board side surface of the base member, is exposed from the molding resin.
11. The electronic control device according to claim 1 , wherein:
the electrically-conductive adhesive is silver paste; and
the adhesion improving member is made of polyamide-imide.
12. The electronic control device according to claim 1 , wherein
the elastic modulus of the stress reducing portion is lower than the elastic modulus of the molding resin.