Method of assembling a packaged high frequency circuit module
Projecting elongate stub walls are provided on the planar surfaces of a substrate at positions where bonding of the substrate to a clamping lid or base is to be carried out. On firing of the substrate, the surfaces thereof are mechanically processed but since the stub walls protrude from the substrate, the grinding and polishing tools make contact with the surfaces of these stub walls, rather than with the entire substrate surface. As a result, the area of the substrate to be processed is minimised and problems with dishing and erosion are alleviated. This allows the clamping lid, or frame to be bonded, using conventional conductive adhesive processes, avoiding the cracking and stress problems associated with non-uniformity of the surface of the ceramic substrates.
1. A method of assembling a packaged high frequency circuit module including the steps of:
providing a ceramic substrate;
firing the ceramic substrate; to form one or more elongate stub walls projecting from a planar surface of the substrate
processing the fired substrate until the planar surface of the one or more elongate stub walls is uniform and parallel;
applying a conductive adhesive to the processed surfaces of the one or more stub walls; and
placing a housing lid over the substrate, the lid having one or more members projecting from a planar surface thereof so that the one or more members align with the one or more stub walls of the substrate to form a composite structure.
2. The method according to claim 1 , wherein the one or more stub walls extends, at least partially, around the periphery of the planar surface of the substrate.
3. The method according to claim 2 , wherein one or more elongate stub walls project from an inner wall track of the substrate.
4. The method according to claim 2 , wherein the projection of the one or more stub walls from the planar surface of the substrate is proportional to predetermined surface distortion values for the substrate.
5. The method according to claim 2 , wherein processing a surface of the substrate comprises one or more of grinding, lapping or polishing the surface.
6. The method according to claim 1 , wherein the one or more stub walls project from an inner wall track of the substrate.
7. The method according to claim 6 , wherein processing a surface of the substrate comprises one or more of grinding, lapping or polishing the surface.
8. The method according to claim 6 , wherein the projection of the one or more stub walls from the planar surface of the substrate is proportional to predetermined surface distortion values for the substrate.
9. The method according to claim 1 , wherein the projection of the one or more stub walls from the planar surface of the substrate is proportional to predetermined surface distortion values for the substrate.
10. The method according to claim 9 , wherein processing a surface of the substrate comprises one or more of grinding, lapping or polishing the surface.
11. The method according to claim 1 , wherein processing a surface of the substrate comprises one or more of grinding, lapping or polishing the surface.
12. The method according to claim 1 , further comprising the steps of
applying pressure to the composite structure and curing the conductive adhesive.
13. The method according to claim 1 , wherein the one or more elongate stub walls project from an upper planar surface of the substrate.
14. The method according to claim 1 , wherein the one or more elongate stub walls project from a lower planar surface of the substrate.
15. The method according to claim 1 , wherein the one or more elongate stub walls are integrally formed on the ceramic substrate.
16. The method according to claim 1 , wherein the one or more elongate stub walls are formed on the ceramic substrate such that during the processing step, processing tools make contact with the surfaces of the one or more stub walls and not with the planar surface of the substrate in order to minimize the area of the substrate that is processed.