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Alternative Method for Creating the Second Level Interconnects on a BGA Package

IP.com Disclosure Number: IPCOM000010182D
Publication Date: 2002-Oct-30
Document File: 2 page(s) / 85K

Publishing Venue

The IP.com Prior Art Database

Abstract

Disclosed is a method that uses a pre-formed sheet of solder spheres embedded in a phase change flux. The pre-formed sheet contains the specific interconnect pattern for a given device, controlling the pitch and true position of the spheres. Benefits include improved process yields and higher UPH.

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Alternative Method for Creating the Second Level Interconnects on a BGA Package

Disclosed is a method that uses a pre-formed sheet of solder spheres embedded in a phase change flux. The pre-formed sheet contains the specific interconnect pattern for a given device, controlling the pitch and true position of the spheres. Benefits include improved process yields and higher UPH.

Background

Current fluxes are heat activated. The flux materials can very from a thick paste to almost liquid, depending on solvent concentrations.  Solder pre-forms used in the electronics industry use external flux coatings. Currently, fluxing material is applied either by a stencil/screening process or by dispense. The ball placement is conducted either by ball bin with patterned screen or PnP. Fluxing materials and spheres are applied independently to the package body.

The current state of the art increases capital equipment expense for ball placement and flux application. Also, this process is subject to yield loss associated with missing balls.

General Description

The disclosed method uses a “sphere” plate with precisely drilled holes (with specified pitch, diameter, and depth). The spheres are poured onto the plate, then, agitated to fill the holes. The remaining spheres are poured off with additional agitation. After the spheres are in place and all holes are filled, the phase change flux is dispensed, completely covering the plate in a pre-determined thickness. The plate is then submitted f...