US 6,191,022 B1 · Fine pitch solder sphere placement

Abstract

In forming an interconnection between a component and an electronic circuit, a base with precise component pockets is loaded with components. The components are patterned with a thin layer of solder paste. Next, a frame including a stencil, vertical walls and locating or keying features is placed onto the base. The stencil rests a controlled distance above the components. A multitude of solder spheres are dispensed into the frame. Solder balls retained within the frame are passed through the stencil and into contact with solder paste. Most preferably, due to controlled spacing between the stencil and components, only one solder ball is able to pass through each stencil hole. The remaining solder spheres in the frame are collected through various alternative techniques, including a disclosed emptying gate. Then the frame with stencil is removed from the base. The solder paste and solder spheres are heated, resulting in a reflow of the solder paste and a bonding of the solder spheres to the component. Subsequent processing may also include further reflowing of the solder spheres, cleaning of any residue from the components, and device testing, as appropriate.

Claims21

Dependent claims

A method for fine pitch placement of solder spheres onto components of an assembly, comprising the steps of:

a) providing a base with pockets therein;
b) providing a stencil with holes therethrough that is attached to a frame having elevated walls, said frame and said base being mechanically keyed to orient and physically engage together in a single, precise position;
c) inserting said components into said pockets;
d) aligning said stencil with said base by engaging said frame firmly in contact with said base to thereby rigidly position said stencil relative to said frame so that said stencil is vertically above said base by a precise, repeatable distance and said elevated walls extend vertically from said stencil;
e) introducing solder spheres into said frame and onto said stencil;
f) moving said solder spheres relative to said stencil to pass a subset of said solder spheres through said stencil into position adjacent said components;
g) pouring a remainder of said solder spheres that are not a part of said subset of said solder spheres off of said stencil through a gate in said frame;
h) removing said stencil and frame from said base;
and
i) heating said components to adhere said subset of said solder spheres thereto.

7 more elements

An apparatus for precisely and repeatably dispensing solder spheres onto components, comprising:

a) abase having a surface, an array of receptacles adapted for receiving and holding components therein, each component having a surface with electrical connection points thereon;
b) a lower frame circumscribing said base and configured for mechanical engagement with said base in a single unique relationship and wherein said lower frame is removable from said base and may be removed and reattached repeatedly in alignment with said base, wherein said alignment is ensured by said mechanical engagement;
c) a stencil rigidly attached to an upper surface of said lower frame, said lower frame spacing said stencil a precise distance from said component surfaces;
and
d) an upper frame rigidly attached to an upper surface of said stencil and circumscribing said stencil to guide and control said solder spheres to said stencil.

2 more elements

Dependencies are inferred from the claim text.

Fine pitch solder sphere placement

Life of this patent

Fine pitch solder sphere placement

Life of this patent

Abstract

Claims21