an implantable pump having a bulkhead , a reservoir structure attached to the bulkhead and upper and lower cases attached to the bulkhead by a single outer seal as well as a method of making such a pump is disclosed . the reservoir structure forms a reservoir that contains fluid drug or other medicaments . the upper and lower cases are attached to the bulkhead by first connecting either the upper or lower case directly to the bulkhead . then , the lower or upper case not attached to the bulkhead is attached to the upper or lower case that had been previously attached to the bulkhead .