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Alternative to MIS using Pre-etched Cu and Photoimageable Dielectric or Premold

IP.com Disclosure Number: IPCOM000248045D
Publication Date: 2016-Oct-21
Document File: 4 page(s) / 436K

Publishing Venue

The IP.com Prior Art Database

This text was extracted from a PDF file.
This is the abbreviated version, containing approximately 48% of the total text.

Page 01 of 4

Alternative to MIS using Pre-etched Cu and Photoimageable Dielectric or Premold

Background

The Conventional substrate is produced by using expensive materials, especially its core material is made of BT and prepreg. Employing these materials also involved the complex and expensive process steps in fabrication, such as repetitive iterations of masking and plating. This invention provides a substrate option to reduce the substrate cost and process time, which is attributed to a method of forming a single metal layer low-cost coreless substrate using the pre-etched and pre-plated Cu base material that is pre-molded, or laminated with photoimageable dielectric. It is distinguishable for its subtractive process compared to the MIS (molded interconnect Substrate), thereof the pre-etched copper forms the solder ball pads through subtractive or etching process rather than plating process. The subtractive process has the potential to shorten cycle time, thus should be cheaper and less cumbersome than plating build up process adopted by the MIS. Moreover, new process method provides the advantage of having unibody solder pad, which is relatively thicker and stronger to promote a more superior reliability performance. The MIS prior arts are shown in Figure 1A for substrate, and Figure 1B for the assembled package using the typical MIS.

Prior Art 1: MIS

Figure 1A: MIS (Molded Interconnect Substrate) Substrate

The Cu metal layer 1 & layer 2 are formed through the additive Cu plating process on Cu carrier. The defined window area of Cu carrier is removed after premolded with resin.

Figure 1B: MIS (Molded Interconnect Substrate) Package

The assembled MIS package is having the Cu base wire bond pad and solder ball pad.


Page 02 of 4

Alternative to MIS using Pre-etched Cu and Photoimageable Dielectric or Premold

The pre-etched Cu structure at the preliminary stage in this invention is different from the finished leadframe structure of QFNs-st-mr, though purportedly similar. The QFNs-st-mr leadframe structure is basically a strip of half etched and un-etched area on the top surface, whereas entirely flat on the bottom surface. The pre-plated Ag or Ni/Pd/Au (PPF) is spotted on top of un-etched Cu surface or standoff lead, while at its corresponding location on the flat bottom side of the strip is pre-plated PPF as solder ball pad as shown in Figure 2A. The isolated Cu stud consisted of the stand-off lead and solder ball pad as a whole is then formed after the etching process in package assembly as observed in Figure 2B. However, the Cu strip used in new invention is having the PPF plating performed on the same surface side, where the pre-plated PPF (NiPd, NiPdAu or NiCuNiPd) on half-etched surface area is to form the bondable trace, and the pre-plated PPF on un-etched base as solder ball pad. The prior art, Figure 2A is showing the respective top view, cross-sectional view, and bottom view of the QFNs-st-mr strip. The related QFNs-st-mr package is s...