Browse Prior Art Database

Design of Substrate Material for increased mechanical Performance and improved Quality

IP.com Disclosure Number: IPCOM000126651D
Published in the IP.com Journal: Volume 5 Issue 8A (2005-08-25)
Included in the Prior Art Database: 2005-Aug-25
Document File: 2 page(s) / 38K

Publishing Venue

Siemens

Related People

Juergen Carstens: CONTACT

Abstract

For the assembly of substrate based packages of ICs, normally polymeric materials (e.g. FR4 or BT) are used, mechanically reinforced with a mesh of glass fiber. These meshes are usually woven over cross. The arrangement of the packages on the substrates is parallel to the glass fibers. In consequence, also the slotted holes, substrate edges and the package edges are parallel to the glass fiber mesh. During the stamping as well as during the milling of the slotted holes or the substrate stripes, glass fibers can get off from the mesh and protrude over the edge of the slotted hole (or substrate edge) or even get loose and contaminate in this way the substrate or the substrate surrounding. Especially, contaminations within the slotted holes are critical, because the wire bonding is performed through these bond channels, and this process will be affected. A secure electrical connection of the wire to the bond pad or to the wedge area cannot be guaranteed anymore. In addition, the alignment of the glass fiber is affecting the stability of the substrate in the wrong way. The substrate bending in the length or the width (crossbow or coil set) can cause problems, especially with very thin substrates or substrates with partial or complete removed solder mask. Here the mechanical stability of the substrates can get weak and additional measures, like handling frames or other external reinforcements, might be necessary.

This text was extracted from a PDF file.
At least one non-text object (such as an image or picture) has been suppressed.
This is the abbreviated version, containing approximately 53% of the total text.

Page 1 of 2

S

Design of Substrate Material for increased mechanical Performance and improved Quality

Idea: Dr. Martin Reiss, DE-Dresden; Anton Legen, DE-Munich; Steffen Kroehnert, DE-Dresden; Dr.

Carsten Bender, DE-Dresden

For the assembly of substrate based packages of ICs, normally polymeric materials (e.g. FR4 or BT) are used, mechanically reinforced with a mesh of glass fiber. These meshes are usually woven over cross. The arrangement of the packages on the substrates is parallel to the glass fibers. In consequence, also the slotted holes, substrate edges and the package edges are parallel to the glass fiber mesh.

During the stamping as well as during the milling of the slotted holes or the substrate stripes, glass fibers can get off from the mesh and protrude over the edge of the slotted hole (or substrate edge) or even get loose and contaminate in this way the substrate or the substrate surrounding. Especially, contaminations within the slotted holes are critical, because the wire bonding is performed through these bond channels, and this process will be affected. A secure electrical connection of the wire to the bond pad or to the wedge area cannot be guaranteed anymore. In addition, the alignment of the glass fiber is affecting the stability of the substrate in the wrong way. The substrate bending in the length or the width (crossbow or coil set) can cause problems, especially with very thin substrates or substrates with partial or complete removed solder mask. Here the mechanical stability of the substrates can get weak and additional measures, like handling frames or other external reinforcements, might be necessary.

The problems mentioned above can be solved by changing the alignment of the glass fiber layers within the substrate already during the substrate manufacturing. The basic material, i.e. the prepreg or the Copper Clad Laminate (CCL), should be aligned in about 45 degrees to the substrate edges, which will also provide an angle of about 45 degrees to the glass fibers at all other milled or stamped edges (bond channel, package edges).

The benefits of this solution are:

- All the edges of the substrate and package will never run parallel to the glass fiber mesh. The single glass fibers at the edges will stay fixed within the polymeric matrix. This leads to a better processing at the milling or stamping, and no protruding glass fibers (burr) will be generated anymore.

- The w...