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Interposer attach jig for mass reflow

IP.com Disclosure Number: IPCOM000249382D
Publication Date: 2017-Feb-23
Document File: 4 page(s) / 636K

Publishing Venue

The IP.com Prior Art Database

This text was extracted from a PDF file.
This is the abbreviated version, containing approximately 54% of the total text.

Interposer attach jig for mass reflow

Background

In a package-on-package (PoP) structure, an interposer is adopted and mounted to the bottom

substrate in a thermal compression bonding method. Shown in Fig. 1, in the process the

interposer is attached to the bottoms of a ceramic collect and a bond head, while the bottom

substrate is placed on a heating block. The thermal compression bonding method renders a

high process yield because the reflow process is not needed after the interposer attaching (IA)

process. However, this method needs a high process cost and a heavy machine investment.

Fig. 1 A package-on-package (PoP) structure in the thermal compression bonding method

The mass reflow method without jig is developed as a low cost solution. Shown in Fig. 2, the

interposer is attached to the bottom of a bond head, while the bottom substrate is placed on a

vacuum plate. After the IA process, a convection reflow has to be conducted for solder joint

formation between the interposer and the bottom substrate to form stable interconnections.

However, a misaligning defect and/or a flying chip (or interposer) issue may be observed

after the mass reflow by the convection air in the process.

Fig. 2 A package-on-package (PoP) structure in the Mass reflow method without jig

Description

The subject invention discloses a structure to prevent the misaligning defect and the flying

chip (or interposer) issue in the mass flow method by placing a flat top cover on the top of the

strip after the IA process.

Shown in Fig. 3, all of the failure modes in the conventional mass reflow relate to the severe

warpage problems of the thin interposer, at either room temperature (RT), high temperature

(HT) or room temperature (RT) for a final product, because the pressure applied is not

sufficient to the package. In the case of a low gap, the top cover touches the top package at

both RT and HT; as a result, a short fail is caused by excessive pressing solder paste bridging

Interposer attach jig for mass reflow

for the final product at RT. In the case of a high gap, the top cover does not touch the top

package at both RT and HT; as a result, an open fail is caused by the non-wetting or non-

contacting in the interconnection.

In addition, if the clearance is too low, the top cover touches the top surface of the interposer

and presses one or two of its corners upon the top cover placement, either right after the IA

process or at the beginning of the reflow process, or at the point of the highest temperature

during reflowing, which causes a misalignment defect and would further lower down the

process yield.

Fig. 3 The failure modes in the conventional mass reflow method in the cases of a low gap and a high gap at room temperature (RT), high temperature (HT) and room temperature (RT...