Surface mount stress relief interface system and method

An interface device useful in relieving solder joint stress in leadless surface mount packages affixed to printed circuit boards, the interface device comprising:

• an interface printed circuit board having a first surface and a second surface, the interface board having a characteristic coefficient of thermal expansion substantially equal to a printed circuit board to which it is electrically affixed, the interface board having a center section and a plurality of arm-like peninsular sections extending from the center section, the arm-like sections having their proximal ends integrally affixed to the center section and their distal ends formed for receiving a pad, the arm-like sections configured so as to provide a compliant movement between the proximal end distal ends from a force on the distal end within the plane of the interface board and radially from the board center section;
• first electrical contact pads affixed to the board first surface at the arm-like sections distal ends;
• second electrical contact pads affixed to the board second surface at the proximal ends of the arm-like sections, the first and second pad of each arm-like section forming a pad set;
• and
• conduction means within each pad set affixed between the first and second pad of the pad set, the connection means providing electrical contact between each pad of the set, the connection means integrally affixed to each corresponding arm-like section.

A surface mount package system useful in affixing a leadless component to a printed circuit board, the device comprising:

• a surface mount package having a central section comprising a plurality of ground pads, an input section comprising a plurality of input pads, an output section comprising a plurality of output pads, the input and output sections being separated by the ground section;
• an interface printed circuit board having a first surface and a second surface, the interface board having a characteristic coefficient of thermal expansion substantially equal to a printed circuit board to which it is electrically affixed, the interface board having a center section and a plurality of arm-like peninsular sections extending from the center section, the arm-like sections having their proximal ends integrally affixed to the center section and their distal ends positioned for receiving the surface mount package pads, the arm-like sections configured so as to provide a compliant movement between the proximal and distal ends, the movement resulting from a force on the distal end within the plane of the interface board and radially from the board center section, the force caused by thermal effects;
• first interface pads structurally affixed to the arm-like distal ends, each first interface pads electrically affixed to a corresponding input, output and ground surface mount package pad;
• second interface pads structurally affixed to the interface board second surface at the arm-like proximal end, the second interface pads positioned so as to be connected to corresponding input, output and ground pads of the printed circuit board to which the interface board is affixed, each of the plurality of first and second interface pads forming a plurality of interface pad sets;
• and
• electrical connection means affixed between each of the first and second pads, the connection means providing electrical contact between each pad cooperating with a surface mount package pad and a corresponding pad on the printed circuit board, the connection means integrally affixed to a corresponding arm-like section comprising the first and second pad set.

A method for providing stress relief to solder joints used for affixing leadless surface mount packages to printed circuit boards, the method comprising the steps of:

• providing an interface printed circuit board having a first surface and an opposing second surface;
• providing a plurality of first electrical contact pads;
• aligning the first contact pads for receiving the contact pads of a surface mount package with which it is communicating;
• affixing the first contact pads to the first surface;
• providing second contact pads;
• aligning the second contact pads for electrical contact with corresponding pads of a printed circuit board with which it is communicating;
• affixing the second pads onto the second surface;
• displacing the first contact pad from each corresponding second contact pad by a length of interface board sufficient for flexing during movement between the first and second pads, the movement being caused by environmental temperature changes and by differing thermal expansion between the surface mount package and the interface board;
• electrically connecting the first and second pads;
• and
• forming arm-like sections extending from a center portion of the interface board by removing board material on both sides of a path between the first contact pad and the second contact pad, the displacement between the first and second pads in combination with the removing of board materials providing stress relief to the solder joints.

A method for reducing leadless component failure due to stress and creep within solder joints of the component, the method comprising the steps of:

• providing a surface mount package for receiving the leadless electrical component, the package having a plurality of contact pads;
• providing an interface printed circuit board having a first surface and an opposing second surface;
• providing a plurality of first electrical contact pads;
• aligning the first contact pads for receiving the contact pads of the surface mount package;
• affixing the first contact pads to the first surface;
• providing second contact pads;
• aligning the second contact pads for electrical contact with corresponding pads of a printed circuit board with which it is communicating;
• affixing the second pads onto the second surface;
• displacing the first contact pad from each corresponding second contact pad by a length of interface board sufficient for flexing during movement between the first and second pads, the movement being caused by environmental temperature changes and by differing thermal expansion between the surface mount package and the interface board;
• electrically connecting the first and second pads;
• and
• forming arm-like sections extending from a center area of the board by removing board material on both sides of a path between the first contact pad and the second contact pad, the displacement between the first and second pads in combination with the removing of board material providing stress relief to the solder joints.