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.