Module substrate and production method
View Patent ↗A module substrate includes a multilayer substrate that includes a plurality of layers, a bottommost of the layers being a ceramic layer. Solderable contacts, which include fired pads composed of a conductive paste, are applied to the bottommost ceramic layer. A covering layer overlies the pads. The covering layer covers all outer edges of the pads. A window is cut out of the covering layer. A metallic coating is applied to each pad exclusively within the window.
1. A method for producing solderable contacts, the method comprising:
applying pads composed of an electrically conductive paste to a multilayer substrate that comprises a bottommost ceramic layer;
after applying the pads, applying a covering layer over the pads, wherein the covering includes a plurality of windows, each window overlying one of the pads such that the covering layer completely covers all edges of the pads; and
depositing a solderable metallization as a metallic coating in the windows and electrically connected to the pads;
wherein an electrically conductive paste containing silver particles is printed on and fired for the pad; and
wherein a second paste comprising glass particles is printed on and fired as the covering layer such that the pad and the covering layer are fired in a common step.
2. The method according to claim 1 , wherein depositing the solderable metallization comprises electrolytically depositing from a solution.
3. The method according to claim 1 , wherein depositing the solderable metallization comprises depositing in an electroless fashion.
4. The method according to claim 1 , wherein applying the covering layer comprises applying and patterning a photopatternable resist.
5. The method according to claim 1 , wherein a footprint that predefines the size and position of the solderable contacts is predefined for the substrate,
wherein the pads are produced with a maximum geometrically and electrically permissible size,
wherein the windows are provided in the covering layer with an arrangement and size corresponding to the footprint in such a way that each window is arranged over the pad and the covering layer covers all outer edges of the pad and also a marginal strip of the pad, the marginal strip following the outer edges.
6. The method according to claim 1 , wherein depositing the solderable metallization comprises using metal-containing deposition baths set in an acidic or alkaline fashion and wherein the covering layer is resistant to the deposition baths.
7. The method according to claim 6 , wherein the covering layer covers all outer edges of the pads such that a transition between the pad and ceramic layer is protected against undercutting when depositing the solderable metallization comprises using the metal-containing deposition baths.
8. The method according to claim 1 , depositing a solderable metallization comprises first depositing at least one electrically loadable metal layer and then applying a gold layer.
9. The method according to claim 1 , wherein the covering layer comprises a glass.
10. A method for producing solderable contacts, the method comprising:
applying pads composed of an electrically conductive paste to a multilayer substrate that comprises a bottommost ceramic layer;
after applying the pads, applying a covering layer over the pads, wherein the covering includes a plurality of windows, each window overlying one of the pads such that the covering layer completely covers all edges of the pads, wherein an electrically conductive paste containing silver particles is printed on and fired as the covering layer; and
depositing a solderable metallization as a metallic coating in the windows and electrically connected to the pads.
11. A method for producing solderable contacts, the method comprising:
applying pads composed of an electrically conductive paste to a multilayer substrate that comprises a bottommost ceramic layer;
after applying the pads, applying a covering layer over the pads, wherein the covering includes a plurality of windows, each window overlying one of the pads such that the covering layer completely covers all edges of the pads; and
depositing a solderable metallization as a metallic coating in the windows and electrically connected to the pads, wherein depositing a solderable metallization comprises first depositing at least one electrically loadable metal layer and then applying a gold layer and wherein depositing the at least one electrically loadable metal layer comprises depositing an Ni layer and then a Pd layer.
12. The method according to claim 11 , wherein depositing the solderable metallization comprises electrolytically depositing from a solution.
13. The method according to claim 11 , wherein depositing the solderable metallization comprises depositing in an electroless fashion.
14. The method according to claim 11 , wherein an electrically conductive paste containing silver particles is printed on and fired for the pad.
15. The method according to claim 14 , wherein a second paste comprising glass particles is printed on and fired as the covering layer such that the pad and the covering layer are fired in a common step.
16. The method according to claim 11 , wherein an electrically conductive paste containing silver particles is printed on and fired as the covering layer.
17. The method according to claim 11 , wherein applying the covering layer comprises applying and patterning a photopatternable resist.
18. The method according to claim 11 , wherein a footprint that predefines the size and position of the solderable contacts is predefined for the substrate,
wherein the pads are produced with a maximum geometrically and electrically permissible size,
wherein the windows are provided in the covering layer with an arrangement and size corresponding to the footprint in such a way that each window is arranged over the pad and the covering layer covers all outer edges of the pad and also a marginal strip of the pad, the marginal strip following the outer edges.
19. The method according to claim 11 , wherein depositing the solderable metallization comprises using metal-containing deposition baths set in an acidic or alkaline fashion and wherein the covering layer is resistant to the deposition baths.
20. The method according to claim 11 , depositing a solderable metallization comprises first depositing at least one electrically loadable metal layer and then applying a gold layer.