FCBGA Package Warpage 2

Warpage is an assembly manufacturing problem resulting in opens, weak joints, Head on Pillow (HOP) and None Wet Open (NWO) defects. With the IC's becoming increasingly thinner, the silicon has less ability to resist deformation of the component package. This deformation combined with short IC leads and a very flexible substrate often exceeds the termination-to-solder paste gap.  The net result is that warpage will become an increasing problem in the future.  Warpage as a result of the thickness of the IC's used,along with defects such as open joints or very weak joints can be caused by short leads on the IC's combined with very flexible carriers. This combination will most likely cause interconnections that will be poorly made or never made  In phase 2 of this project, we will characterize the newly defined process from FCBGA Package Warpage 1 and develop a consistent methodology to use in normal production.

Project stage: 
Project type: 
Lead company: 
Plexus

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Idea Information

Background: 

 

 

Basic Concept of Hot Air Rework Equipment and Process

 

In today's High Density Packaging, board warpage trends are increasing. This is primarily driven by thinner package substrates and thinner die. Simultaneously to the packages becoming thinner, the Package/Board contacts are getting smaller and occurring in finer grids thereby reducing the ability to overcome the increased warpage. In addition to all this, the advent of lead free soldering, the assembly temperatures have increased and the warpage impact has been exacerbated.  All these conflicting attributes have increased the concern for the solder joint quality.

 

Most of the electronic industry is experiencing assembly problems with the decreasing thickness of IC packages. With denser packages (QFN's, Area Array's and Stacked Packages), the flatness of the packages and PWB (warpage) becomes critical. Warpage is an assembly manufacturing problem resulting in open,weak joints, Head on Pillow (HOP) and None Wet Opens (NWO) defects. With the IC's becoming increasingly thinner, the silicon has less ability to resist deformation of the component package. This deformation combined with short IC leads and a very flexible substrate often exceeds the termination- to -solder paste gap.

 

Using the commercially viable solution identified in Phase 1, as shown in the above picture of this project to address the warpage/defect issue, this phase of the project will establish a limit for dynamic package warpage that can be mitigated during board assembly without impacting solder joint quality.

 

The second phase of this project will characterize the amount of warp that can be accommodated and adjusted for to improve the effect on of the package warpage problem.

Problem: 

         

During the component assembly process in the formation of a PCBA, there are several causes of solder joint failure. The major unaddressed area is that of the mismatch between the PCB and the component.  This mismatch or misalignment can be caused by substrate warping and the package not wetting properly allowing the solder joint to be a dry joint and therefore poor or even not a joint at all.  In addition to the non wetting of the joint, the poor joint can also be caused by the lifting of the ball from the pad during the liquidious portion of the normal heating/cooling cycle in the attach process, when the substrate is warped due to the mismatch of the multiple materials and the Tg of each material and causes the ball to shift and raise at a different rate from the other balls on the same component.

Definition Information

Goals / Benefits: 

Project Goal:

  Establish a limit for dynamic package warpage that can be mitigated during board assembly without impacting solder joint quality

 

Benefits:

  The main benefit of this project is to improve the process yield and reduce the cost of assembly. 

Some additional benefits might be:

1- Quicker turnaround tie of assembly because of the reduction of rework.

2- Reduction of stocked parts.

3- A reduction of hazardous waste disposal.


 

 

High level objectives: 

 

This phase will leverage phase 1’s output to:

  • Establish the maximum warp an optimized process can accommodate 
  • Characterize the contribution of the mitigation techniques on the process yield.

 

Approach: 

The project will be a designed experiment that compae the video made during the attach process, using the rework machine, and the data collected during the pry and dye analysis of the components that wre attached durng that process.  

Key Participants: 
Celestica
Curtiss-Wright
Elite Material Co. EMC
Flex
Fujitsu
H3C Technologies
Hitachi Chemical
Indium
Isola Group
Juniper
Keysight Technologies
Kyzen
Nihon Superior
Nokia
NVIDIA
Oracle
Panasonic
Plexus
Sanmina
Shengyi
TTM Technologies
Public