Browse Prior Art Database

Thermal path substrate with thermal compression bonding in PoP

IP.com Disclosure Number: IPCOM000248386D
Publication Date: 2016-Nov-23
Document File: 5 page(s) / 459K

Publishing Venue

The IP.com Prior Art Database

This text was extracted from a PDF file.
This is the abbreviated version, containing approximately 32% of the total text.

Page 01 of 5

Thermal path substrate with thermal compression bonding in PoP

Background

Various Package-on-package (PoP) structures have been developed for many applications, such as hand phones and other portable devices in which the circuit board space is limited. The PoP technology faces a major challenge of reducing the interconnect pitch between the top package and the bottom package. The bus width between the top and the bottom packages increases continuously, but the interconnect pitch between the top and the bottom substrates can only accommodate a certain number of signals. To replace the traditional solder reflow process, thermal compression bonding method is developed to overcome the non-wet issue for the PoP pre-stack process and /or the interposer attached process.

But the conventional way of thermal compression bonding process has a major disadvantage of low overall throughput, due to the unsatisfactory thermal conductivities of the substrate and / or the interposer. In addition, solder resist (SR) material of the substrate and interposer is easy to be discoloured and thermally damaged under heat and pressure. Shown in Fig. 1, the conventional interposer is discoloured after the thermal compression bonding process when heat and pressure are applied by a conventional bond head which has a flat bottom surface and thus provides a large contact area to the interposer. Therefore, an effective way of thermal compression bonding process is highly expected.

Fig. 1 The conventional way of thermal compression bonding process

Description

The subject invention discloses a thermal path substrate or interposer for the thermal compression bonding method in a PoP pre-stack process or an interposer attach process. Thermal path is fabricated inside the substrate or the interposer, which connects the heat source to the target solder structures, including ordinary solder ball, solder ball with copper core, copper column, copper post and substrate pad. In addition, the warpage issue can be solved by minimizing the bonding time and the contact area in the thermal compression bonding process when thermal paths are introduced in the subject invention. The possible process flows are also demonstrated in the invention.

In Fig. 2, a thermal path interposer of the subject invention is shown for the thermal compression bonding process. Thermal paths of high heat conductivity are fabricated through


Page 02 of 5

Thermal path substrate with thermal compression bonding in PoP

the interposer on the left and right sides. In the compression bonding process, the top surface of the thermal path is in direct contact with the bond head and the bottom surface is in contact with the solder ball on the bottom of the interposer. In addition, a cavity bond head is also introduced in the subject invention with a cavity in the center of the bottom side. The portion of the bottom surface inside the cavity of the cavity bond head is not in contact with the interposer, which red...