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Solder Caps at the Micro-Via Cavity of a Printed Circuit Board

IP.com Disclosure Number: IPCOM000019521D
Publication Date: 2003-Sep-17
Document File: 4 page(s) / 94K

Publishing Venue

The IP.com Prior Art Database

Abstract

Disclosed is a method that deposits solder paste on top of the micro-via cavities of a printed circuit board (PCB). The solder reflow allows the molten solder to fill the cavities, and upon reflow, form a solid barrel. Benefits include the elimination of solder ball voids and improved drill hole size flexibility.

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Solder Caps at the Micro-Via Cavity of a Printed Circuit Board

Disclosed is a method that deposits solder paste on top of the micro-via cavities of a printed circuit board (PCB). The solder reflow allows the molten solder to fill the cavities, and upon reflow, form a solid barrel. Benefits include the elimination of solder ball voids and improved drill hole size flexibility.

Background

The following are attributes of the current state of the art:

 

  • It optimizes reflow processes to minimize the void size to < 20% of the BGA pad area at the solder ball to PCB pad interface.
  • It controls the micro-via cavity diameter at 4.5mils or smaller, because smaller via cavities cause less trapped air.
  • It controls inner layer dielectric ILD thickness at 2mils to reduce micro-via cavity depth. (This allows easier air release.)
  • It uses a flat pad micro-via with dielectric material and plate with a layer of Cu on top of the micro-via. (However, this raises additional PCB costs as high as 20%.)

However, these optimizations or improvements are not robust, and may not totally eliminate void formation, except for the flat pad with micro-via filled solution. The current state of the art only helps to minimize the void size to <20% of the pad area base. Also, the current PCB supplier may not be able to guarantee 100% plating coverage within the micro-via due to plating process limitations.

General Description

To resolve this solder void issue, the disclosed method deposits solder paste directly onto...