Circuit board, process for producing the same and a power module employing the same
AssigneeDowa Mining Co., Ltd.
InventorsMasahiro Hara, Hideyo Osanai
Life of this patent
Estimating the term…
Abstract
Composite member 2 consisting of ceramic insulator substrate 3 and two metal layers 4A and 4B such as aluminum sheets is subjected to milling in order to remove the unwanted areas of metal layer 4A (where inter-element spacings are to be formed). In order to suppress cracking due to substrate warpage, a small bottom portion of 4A is left intact as residual metal layer 4Aa which is preferably removed by etching. Milling is performed after thin-film layer of etching resist 5 is applied to the surface of metal layer 4A. By milling in two stages, a step is formed at the bottom of lateral sides of a pattern element to make a skirt which contributes to reducing external stresses.
Claims16
A process for producing a circuit board comprising the steps of:
- (a) forming a metal layer on at least one surface of an insulator to prepare a metal-insulator composite member,
- (b) forming an etching resist on the surface of said metal layer,
- (c) milling an unwanted area of the metal layer with the etching resist in order to form a pattern so that a portion of the thickness of the metal layer of the unwanted area remains,
- (d) performing etching to remove a remaining metal layer of the unwanted area, and
- (e) removing said etching resist to form a pattern.
A process for producing a circuit board comprising the steps of:
- (a) forming a metal layer on at least one surface of an insulator to prepare a metal-insulator composite member,
- (b) milling an unwanted area of the metal layer in order to form a pattern so that a portion of the thickness of the metal layer of the unwanted area remains,
- (c) forming an etching resist on the surface of said metal layer except for a milled portion,
- (d) performing etching to remove a remaining metal layer of the unwanted area, and
- removing said etching resist to form a pattern.
A process for producing a circuit board comprising the steps of:
- (a) forming a metal layer on at least one surface of an insulator to prepare a metal-insulator composite member,
- (b) milling an unwanted area of the metal layer in a first milling in order to form a pattern so that a portion of the thickness of the metal layer of the unwanted area remains,
- (c) milling an unwanted area of the metal layer in a second milling with an end mill having a diameter which is different from a diameter of an end mill employed in the first milling of step (b) in order to form a pattern so that a portion of the thickness of the metal layer of the unwanted area remains, and
- (d) performing etching to form a pattern.
A process for producing a circuit board comprising the steps of:
- (a) forming a metal layer on at least one surface of an insulator to prepare a metal-insulator composite member,
- (b) milling an unwanted area of the said metal layer in a first milling in order to form a pattern so that a portion of said metal layer of the unwanted area remains,
- (c) performing etching to remove a remaining metal layer of the unwanted area, and
- (d) milling at least a portion of said metal layer in a second milling with an end mill having a different diameter from a diameter of an end mill employed in the first milling of step (b) so as to form a pattern.
Dependencies are inferred from the claim text.