Technical Library | 2022-07-11 09:24:48.0
The change of squeegee pressure has a significant impact on printing. Too small pressure will make the solder paste unable to effectively reach the bottom of the stencil opening and not be well deposited on the pad. Too much pressure will cause tin The paste is printed too thin and can even damage the stencil.
Technical Library | 2018-03-21 22:44:30.0
Solder paste printing is the first step in the surface mount manufacturing process for PCBA assembly. When the solder paste printing process is uncontrolled, defects can be produced, which may not become apparent until the PCBA is downstream. (...)This paper will discuss how Lean Six Sigma techniques were used to optimize the solder paste printing process. It will highlight how a cross-functional team used the structured Define, Measure, Analyze, Improve and Control (DMAIC) methodology to identify and control the critical inputs. The advantage of the Lean Six Sigma methodology is that it guides the team through the rigorous structured process so that all possible inputs are considered and the critical ones can be identified.
Technical Library | 2020-11-24 23:12:27.0
In a lead-free reflow process, temperatures are higher, and materials use outgasses more than in a leaded reflow process. The trends toward higher density populated boards and more pin-in-paste technology also increase solder paste use. More components and more solder paste result in more outgassing of chemistry during the reflow process. Some assemblies report condensation of vapors when the cold printed circuit board enters the oven. Little is known about the interaction between these condensed materials in terms of the interaction between these condensed materials and the reliability of the assembly. Apart from the question of reliability, a printed circuit board contaminated with a small film of residues after reflow soldering is not desirable.
Technical Library | 2019-08-07 22:56:45.0
The requirement to reconsider traditional soldering methods is becoming more relevant as the demand for bottom terminated components (QFN/BTC) increases. Thermal pads under said components are designed to enhance the thermal and electrical performance of the component and ultimately allow the component to run more efficiently. Additionally, low voiding is important in decreasing the current path of the circuit to maximize high speed and RF performances. The demand to develop smaller, more reliable, packages has seen voiding requirements decrease below 15 percent and in some instances, below 10 percent.Earlier work has demonstrated the use of micro-fluxed solder preforms as a mechanism to reduce voiding. The current work builds upon these results to focus on developing an engineered approach to void reduction in leadless components (QFN) through increasing understanding of how processing parameters and a use of custom designed micro-fluxed preforms interact. Leveraging the use of a micro-fluxed solder preform in conjunction with low voiding solder paste, stencil design, and application knowhow are critical factors in determining voiding in QFN packages. The study presented seeks to understand the vectors that can contribute to voiding such as PCB pad finish, reflow profile, reflow atmosphere, via configuration, and ultimately solder design.A collaboration between three companies consisting of solder materials supplier, a power semiconductor supplier, and an electronic assembly manufacturer worked together for an in-depth study into the effectiveness of solder preforms at reducing voiding under some of the most prevalent bottom terminated components packages. The effects of factors such as thermal pad size, finish on PCB, preform types, stencil design, reflow profile and atmosphere, have been evaluated using lead-free SAC305 low voiding solder paste and micro-fluxed preforms. Design and manufacturing rules developed from this work will be discussed.
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