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A Printed Circuit Manufacturing Method for Placing MLP Devices

IP.com Disclosure Number: IPCOM000008484D
Publication Date: 2002-Jun-17
Document File: 3 page(s) / 35K

Publishing Venue

The IP.com Prior Art Database

Abstract

Disclosed is a method that introduces a fiducal and a gas channel to the process of attaching an MLP , Micro Leadframe Package to a PCBA. Benefits include a reduction in placement and shorting issues associated with placing MLP devices.

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A Printed Circuit Manufacturing Method for Placing MLP Devices

Disclosed is a method that introduces a fiducal and a gas channel to the process of attaching an MLP , Micro Leadframe Package to a PCBA. Benefits include a reduction in placement and shorting issues associated with placing MLP devices.

Background

In the current MLP placing process, the quantity of solder placed at the center/ground of the device causes random shorting to the contact pads (usually leads or pins on a normal device).  Accurate placement of the device is also greatly compromised because there is no close locator (fiducal) available; this also causes skews and shorting. Figure 1 shows the current art for an MLP device.

General Description

The disclosed method adds a fiducal and a gas channel to the PCB and solder paste stencil artwork.

Figure 2 shows the proposed fiducal placement, plus PCB layout and solder paste artwork. The area around the fiducal is void of top layer metalization, as are the channels running diagonally to the corners of the component outline.

Figure 3 shows the reflow and wetting patterns of the solder. As the solder reaches reflow temperatures, surface tension of the molten solder wets/closes the channels from the center out, driving any out-gassing ahead of it. This reduction in solder paste along the channels also reduces the amount of solder paste applied to the ground pad, removing the majority of solder shorts to the contact pads.

Advantages

The following are advantages of t...