Magnetically permeable adhesives and adhesive-joined shield structures

The formulation of magnetically permeable adhesives (MPA´s) and their use to join multisection magnetic shields are examined with application to shielding for magnetic bubble memory packages. MPA´s offer a joining technique which reduces package size and avoids the degradation of shielding which occurs in assembling annealed shield cans by welding. It is shown that MPA´s with permeability μ up to 10 with more than adequate mechanical strength can be formulated, and that μ can be increased by as much as 60% by magnetically orienting the MPA during setting. Design principles and shield designs compatible with MPA´s are described, and data are provided to show that these new designs provide a marked improvement in shielding (by as much as a factor of four) along with size and weight reductions when compared with an earlier welded shield design.