Radiation shielding of plastic integrated circuits

A formulation for a shield material to protect an integrated circuit device having a plastic body with internal elements from damage caused by natural radiation in outer space, consisting essentially of:

• a high atomic weight substance for radiation shielding selected from the group consisting of tungsten, tantalum and lead;
• a low atomic weight substance for radiation shielding to act as an extender to decrease the overall density of the shield material and selected from the group consisting of copper, aluminum and silicon;
• and
• wherein the shield material includes an overall mixture of about 90% high atomic weight substance and about 10% low atomic weight substance.

A method of making a radiation shield composition for an integrated circuit device having a plastic body with internal elements to protect against damage caused by natural radiation in outer space, the method comprising:

• visualizing the location of the internal elements;
• cutting away selectively certain portions of the plastic body while avoiding contacting the internal elements to create a plurality of cutout portions;
• providing complementary shaped shielding members dimensioned suitably to fit within said cutout portions;
• affixing the complementary shaped shielding members within said cutout portions to shield the integrated circuit from radiation;
• modeling the integrated circuit application environment based upon orbit or trajectory data to calculate the total dose exposure that the integrated circuit must survive over its useful life;
• formulating a radiation shielding material with radiation shielding characteristics sufficient to protect the integrated circuit in its proposed application environment;
• fabricating a custom radiation shield component composed of the radiation shield material formulated to protect the integrated circuit in the application environment;
• said step of formulating a radiation shielding material including:
• determining the stopping power for a group of high Z materials for a first bin for a first radiation producing particle;
• determining the stopping power for a group of low Z materials for said first bin for said first radiation producing particle;
• determining the stopping power for a group of high Z materials for a first bin for a second radiation producing particle;
• determining the stopping power for a group of low Z materials for said first bin for said second radiation producing particle;
• determining the stopping power for a group of high Z materials for a first bin for a third radiation producing particle;
• determining the stopping power for a group of low Z materials for said first bin for said third radiation producing particle;
• determining the stopping power for a group of high Z materials for a first bin for a fourth radiation producing particle;
• determining the stopping power for a group of low Z materials for said first bin for said fourth radiation producing particle;
• determining the stopping power for a group of high Z materials for a second bin for a first radiation producing particle;
• determining the stopping power for a group of low Z materials for said second bin for said first radiation producing particle;
• determining the stopping power for a group of high Z materials for a second bin for a second radiation producing particle;
• determining the stopping power for a group of low Z materials for said second bin for said second radiation producing particle;
• determining the stopping power for a group of high Z materials for a second bin for a third radiation producing particle;
• determining the stopping power for a group of low Z materials for said second bin for said third radiation producing particle;
• determining the stopping power for a group of high Z materials for a second bin for a fourth radiation producing particle;
• determining the stopping power for a group of low Z materials for said second bin for said fourth radiation producing particle;
• determining the stopping power for a group of high Z materials for an nth bin for a first radiation producing particle;
• determining the stopping power for a group of low Z materials for said nth bin for said first radiation producing particle;
• determining the stopping power for a group of high Z materials for an nth bin for a second radiation producing particle;
• determining the stopping power for a group of low Z materials for said nth bin for said second radiation producing particle;
• determining the stopping power for a group of high Z materials for an nth bin for a third radiation producing particle;
• determining the stopping power for a group of low Z materials for said nth bin for said third radiation producing particle;
• determining the stopping power for a group of high Z materials for an nth bin for a fourth radiation producing particle;
• determining the stopping power for a group of low Z materials for said nth bin for said fourth radiation producing particle;
• summing all of said determined stopping powers for all of said bins to ascertain the percentage by weight of each material to be admixed in the shield composition, said steps of determining and summing being accomplished according to the following formula:
• each one of said steps of determining being accomplished by using:
• SP.sub.qm =(radiation in)-(radiation shielded)
• where,
• q=radiation type and energy bin
• m=material type, high and/or low Z;
• wherein said step of summing to ascertain the percentage by weight of each material to be admixed in the shield composition is performed by:
• initially calculating the total weighted amount of radiation permitted through each material based on material type and radiation type for an initial combination of high atomic material and low atomic material, using:
• .SIGMA.SP(e.sub.i, X)=a.sub.1 *SP.sub.e1X +a.sub.2 *SP.sub.e2X +. . . +a.sub.i *SP.sub.eiX
• .SIGMA.SP(e.sub.i, Y)=a.sub.1 *SP.sub.e1Y +a.sub.2 *SP.sub.e2Y +. . . +a.sub.i *SP.sub.eiY
• where,
• X=low Z material, transported as m above;
• Y=high Z material, transported as m above;
• and
• subsequently calculating total summations, using:
• .SIGMA..sub.TOT =.SIGMA.SP(e.sub.i,X)+.SIGMA.SP(e.sub.i,Y)+.SIGMA.SP(P.sub.i,X)+.SIGMA.SP( p.sub.i,Y)+.SIGMA.SP(t.sub.i,X)+.SIGMA.SP(t.sub.i, Y)+.SIGMA.SP(r.sub.i,X)+.SIGMA.SP(r.sub.i, Y).
• repeating said step of formulating for other combinations of said high atomic weight material and said low atomic weight material to determine total summations therefor;
• said step of fabricating said custom radiation shield component including finally determining the preferred radiation shield material as including preferred percentages of high atomic weight substances and low atomic weight substances to reduce greatly the weighted sum of each energy level stopping power by determining the smallest one of said total summations.