Displacement Theory for Fixturing Design of Thin Flexible Circuit Board Assembly

2000 ◽  
Vol 123 (4) ◽  
pp. 388-393
Author(s):  
Ruijun Chen ◽  
Daniel F. Baldwin
Keyword(s):  
Theoretical Foundation ◽  
Circuit Board ◽  
Flexible Substrates ◽  
Transverse Displacement ◽  
Assembly Process ◽  
Circuit Board Assembly ◽  
Displacement Theory ◽  
Bond Pads ◽  
The Impact ◽  
Displacement Model

The compliant nature of flexible substrates subject to assembly forces can result in severe misregistration of the component leads and substrate bond pads, leading to assembly process defects. Specially dedicated tooling for fixturing thin flexible substrates in standard surface mount assembly equipment is gaining importance. This paper focuses on developing a theoretical foundation for implementing Smart Tooling of fixturing thin flexible substrates. The primary goals are to determine the impact of fixturing tooling on assembly process quality, to develop a displacement theory to predict transverse displacements, and to analyze the optimum perimeter fixturing configuration. The predictive capabilities of the transverse displacement model are verified.

Fundamental Analyses of Smart Tooling for Assembly of Thin Flexible Circuit and Board Systems

1999 ◽  
Author(s):  
Ruijun Chen ◽  
Daniel F. Baldwin
Keyword(s):  
Form Solution ◽  
Circuit Board ◽  
Flexible Substrates ◽  
Solder Paste ◽  
Assembly Process ◽  
Design Data ◽  
Solder Paste Printing ◽  
Bond Pads ◽  
Close Form ◽  
The Impact

Abstract Flexible nature of flexible circuits/boards poses new fixture tooling challenges for standard surface mount assembly equipment. The flexible substrates experience significant transverse displacements under perpendicular assembly forces during solder paste printing and component placement processes. The displacements result in misregistration of the component leads and substrate bond pads, leading to assembly process defects. Solder reflow process further complicates the issue due to the thermo-mechanical warpage induced. Reengineered and specialized dedicated tooling for fixturing flexible substrates in standard assembly equipment is becoming extremely important. This paper focuses on developing analysis methodologies and theories for implementing Smart Tooling. The primary goals being to determine the impact of fixturing on assembly process quality and to determine optimum fixturing configurations for thin flexible circuit board assemblies based on circuit board design data. A mathematical model to describe both transverse and perpendicular displacements of flex substrates is developed, and its close-form solution for transverse displacements is obtained. Using a “near” optimum fixturing configuration to minimize transverse displacements is verified.

The Benefits of Flux-Coated Solder Preforms in a QFN Assembly Process

2015 ◽  
Vol 2015 (1) ◽  
pp. 000827-000832
Author(s):  
Brandon Judd ◽  
Maria Durham
Keyword(s):  
Mechanical Properties ◽  
Form Factor ◽  
Solder Joint ◽  
Circuit Board ◽  
Electrical Performance ◽  
Solder Paste ◽  
Assembly Process ◽  
Circuit Board Assembly ◽  
Difficult Challenge ◽  
Small Form Factor

The use of bottom terminated components (BTCs) such as quad-flat no-leads (QFNs) has become commonplace in the circuit board assembly world. This package offers several benefits including its small form factor, its excellent thermal and electrical performance, easy PCB trace routing, and reduced lead inductance. These components are generally attached to PWBs PCBs via solder paste. The design of these components with the large thermal pad, along with the tendency of solder paste to outgas during reflow from the volatiles in the flux, creates a difficult challenge in terms of voiding control within the solder joint. Voiding can have a serious effect on the performance of these components, including the mechanical properties of the joint as well as spot overheating. Solder preforms with a flux coating can be added to the solder paste to help reduce voiding. This study will focus on the benefits of utilizing solder preforms with modern flux coatings in conjunction with solder paste to help reduce voiding under QFNs, as well as the design and process parameters which provide optimal results.

Failure Analysis of Halogen-Free Printed Circuit Board Assembly Under Board-Level Drop Test

2012 ◽  
Vol 134 (1) ◽  
Author(s):  
Hung-Jen Chang ◽  
Chau-Jie Zhan ◽  
Tao-Chih Chang ◽  
Jung-Hua Chou
Keyword(s):  
Printed Circuit Board ◽  
Drop Test ◽  
Circuit Board ◽  
Printed Circuit Board Assembly ◽  
Printed Circuit ◽  
Plastic Ball ◽  
Circuit Board Assembly ◽  
Halogen Free ◽  
Board Level ◽  
The Impact

In this study, a lead-free dummy plastic ball grid array component with daisy-chains and Sn4.0Ag0.5Cu Pb-free solder balls was assembled on an halogen-free high density interconnection printed circuit board (PCB) by using Sn1.0Ag0.5Cu solder paste on the Cu pad surfaces of either organic solderable preservative (OSP) or electroless nickel immersion gold (ENIG). The assembly was tested for the effect of the formation extent of Ag3Sn intermetallic compound. Afterward a board-level pulse-controlled drop test was conducted on the as-reflowed assemblies according to the JESD22-B110 and JESD22-B111 standards, the impact performance of various surface finished halogen-free printed circuit board assembly was evaluated. The test results showed that most of the fractures occurred around the pad on the test board first. Then cracks propagated across the outer build-up layer. Finally, the inner copper trace was fractured due to the propagated cracks, resulting in the failure of the PCB side. Interfacial stresses numerically obtained by the transient stress responses supported the test observation as the simulated initial crack position was the same as that observed.

scholarly journals An intelligent approach for improving printed circuit board assembly process performance in smart manufacturing

2020 ◽  
Vol 12 ◽  
pp. 184797902094618
Author(s):  
Vincent WC Fung ◽  
Kam Chuen Yung
Keyword(s):  
Printed Circuit Board ◽  
Circuit Board ◽  
Smart Manufacturing ◽  
Process Performance ◽  
Solder Paste ◽  
Assembly Process ◽  
Printed Circuit Board Assembly ◽  
Printed Circuit ◽  
Circuit Board Assembly ◽  
Solder Paste Printing

The process of printed circuit board assembly (PCBA) involves several machines, such as a stencil printer, placement machine and reflow oven, to solder and assemble electronic components onto printed circuit boards (PCBs). In the production flow, some failure prevention mechanisms are deployed to ensure the designated quality of PCBA, including solder paste inspection (SPI), automated optical inspection (AOI) and in-circuit testing (ICT). However, such methods to locate the failures are reactive in nature, which may create waste and require additional effort to be spent re-manufacturing and inspecting the PCBs. Worse still, the process performance of the assembly process cannot be guaranteed at a high level. Therefore, there is a need to improve the performance of the PCBA process. To address the aforementioned challenges in the PCBA process, an intelligent assembly process improvement system (IAPIS) is proposed, which integrates the k-means clustering method and multi-response Taguchi method to formulate a pro-active approach to investigate and manage the process performance. The critical process parameters are first identified by means of k-means clustering and the selected parameters are then used to formulate a set of experimental studies by using the multi-response Taguchi method to optimize the performance of the assembly process. To validate the proposed system, a case study of an electronics manufacturer in the solder paste printing process was conducted. The contributions of this study are two-fold: (i) pressure, blade angle and speed are identified as the critical factors in the solder paste printing process; and (ii) a significant improvement in the yield performance of PCBA can be achieved as a component in the smart manufacturing.

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