the entire area underneath the chip carrier 13 this leaves an unbonded area 40 where the expansion layer 18 is not attached to the support layer 20 this provides an expansion area wherein the expansion layer 18 is free to expand and contract with chip carrier 13 irrespective of the remainder of the printed wiring board 20 the chip carrier 13 is mounted onto the top 32 of expansion layer 18 by way of solder fillets or joints 42 the area under the chip carrier 13 and solder joints 42 is defined as the footprint of the chip carrier in accordance with the present invention the adhesive layer 38 provides no bonding at locations beneath the chip carrier footprint the area of non bonding will extend slightly outward from the footprint as best shown at 44 and 46 in fig2 this provides a non bonded portion of the expansion layer 18 which does not lie directly beneath the chip carrier footprint it is essential that this extra non bonded portion be provided the expansion layer 18 is made from a material having low modulus of elasticity such as a polyimide film a preferred polyimide film is marketed by e i dupont under.