BGA Warpage Control via Pre-Reflow Adhesive Curing
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Solution Overview
Problem
Conventional surface mounting technologies for BGA modules on PCBs suffer from warpage during the re-flow process, leading to insufficient solder contact at the edges, resulting in open circuits due to increased spacing between BGA balls and PCBs.
Innovation Solution
Applying an adhesive with a curing temperature lower than the start-melting temperature of BGA balls between the BGA module and the PCB, ensuring the adhesive is cured before the re-flow process to prevent warpage by fixing the BGA module's shape.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional surface mounting technology is used without adhesive, then the re-flow process can be performed directly, but warpage occurs causing BGA balls at edges to fail contact with PCB
Solution Approach 1:
The adhesive is applied and cured before the re-flow process to pre-establish a stable mechanical bond between the BGA module and PCB. This preliminary bonding action prevents warpage-induced separation during subsequent heating, ensuring all BGA balls maintain proper contact throughout the re-flow process.
Solution Approach 2:
The adhesive serves as an intermediary material between the BGA module and PCB that absorbs and compensates for thermal expansion differences. This mediator layer maintains consistent contact pressure and positioning during temperature changes, preventing edge ball failures while allowing the re-flow process to proceed.
2Reliability
If adhesive is applied and cured before re-flow, then warpage is reduced and BGA ball contact is maintained, but an additional process step is added
Solution Approach 1:
The adhesive application and curing process is merged with the existing re-flow process sequence. The adhesive curing is performed as a preliminary step that integrates seamlessly into the standard manufacturing workflow, followed by the conventional re-flow process, thereby achieving improved reliability without requiring fundamentally new equipment or processes.
3Shape
If adhesive curing temperature is lower than BGA ball melting temperature, then adhesive cures before re-flow preventing warpage, but temperature control must be precisely managed
Solution Approach 1:
The adhesive is specifically selected with a curing temperature parameter that is lower than the BGA ball melting temperature. This parameter selection creates a clear thermal window where adhesive curing can be completed before re-flow heating begins, enabling shape stabilization through controlled temperature progression without requiring complex real-time temperature adjustment mechanisms.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This method significantly reduces warpage, ensuring BGA balls at the edges maintain contact with the PCB, enhancing production yield without altering the existing re-flow process.
Implementation Method 1
An adhesive is applied between and contacting the BGA module and the base substrate. The adhesive is then cured.
Implementation Method 2
The BGA balls are re-flowed after the step of curing the adhesive
Implementation Method 3
During the re-flow process, the temperatures of BGA module 10 and PCB 14 are elevated. As a result, warpage occurs to BGA module 10.
Data Source
AI summary
A method of manufacturing an integrated circuit package includes providing a ball grid array (BGA) module including BGA balls on a side of the BGA module; providing a base substrate; and placing the BGA module on the base substrate. The BGA balls are placed between the BGA module and the base substrate. An adhesive is applied between and contacting the BGA module and the base substrate. The adhesive is then cured. The BGA balls are re-flowed after the step of curing the adhesive.