Technical Library | 2023-01-17 17:19:44.0
A test program was developed to evaluate the effectiveness of vacuum reflow processing on solder joint voiding and subsequent thermal cycling performance. Area array package test vehicles were assembled using conventional reflow processing and a solder paste that generated substantial void content in the solder joints. Half of the population of test vehicles then were re-processed (reflowed) using vacuum reflow. Transmission x-ray inspection showed a significant reduction in solder voiding after vacuum processing. The solder attachment reliability of the conventional and vacuum reflowed test vehicles was characterized and compared using two different accelerated thermal cycling profiles. The thermal cycling results are discussed in terms of the general impact of voiding on solder thermal fatigue reliability, results from the open literature, and the evolving industry standards for solder voiding. Recommendations are made for further work based on other void reduction methods and additional reliability studies.
Technical Library | 2019-05-24 09:22:59.0
There is a smaller process window and a much narrower margin of error when creating and using lead-free reflow profiles for surface mount parts on printed circuit boards (PCBs). Solder balls, dewetting, tombstones, voids, and head-on-pillow problems will occur much more frequently because lead-free alloys behave differently than eutectic pastes. Problems are compounded due to the extra heat necessary for some lead-free pastes to reach their melting points.
Technical Library | 2021-04-21 19:28:30.0
Voids affect the thermal characteristics and mechanical properties of a solder joint, thereby affecting the reliability of the solder interconnect. The automotive sector in particular is requiring the mitigation of solder voids in various electronic control modules to the minimum possible level. Earlier research efforts performed to decrease voids involved varying the reflow profile, paste deposit, paste alloy composition, stencil aperture, and thickness.
Technical Library | 2019-07-24 23:55:32.0
Voiding is a key concern for components with thermal planes because interruptions in Z-axis continuity of the solder joint will hinder thermal transfer. When assembling components with solder paste, there is a high propensity for voiding due to the confined nature of the solder paste deposits under the component. Once reflowed, many factors contribute to the amount of voiding in a solder joint such as the reflow profile, designs of the component, board and stencil, and material factors. This study will focus on the solder paste alloy and flux combination as well as profile and board surface finishes.
Technical Library | 2013-02-08 22:56:47.0
Solder voiding is present in the majority solder joints and is generally accepted when the voids are small and the total void content is minimal. X-ray methods are the predominate method for solder void analysis but this method can be quite subjective for non grid array components due to the two dimensional aspects of X-ray images and software limitations. A novel method of making a copper "sandwich" to simulate under lead and under component environs during reflow has been developed and is discussed in detail. This method has enabled quantitative solder paste void analysis for lead free and specialty paste development and process refinement. Profile and paste storage effects on voiding are discussed. Additionally an optimal design and material selection from a solder void standpoint for a heat spreader on a BCC (Bumpered Chip Carrier) has been developed and is discussed.
Technical Library | 2021-04-21 15:10:16.0
Voids affect the thermal characteristics and mechanical properties of a solder joint, thereby affecting the reliability of the solder interconnect. The automotive sector in particular is requiring the mitigation of solder voids in various electronic control modules to the minimum possible level. Earlier research efforts performed to decrease voids involved varying the reflow profile, paste deposit, paste alloy composition, stencil aperture, and thickness. Due to the various advantages they offer, the use of Ball Grid Array packages is common across all industry sectors. They are also prone to process voiding issues. This study was performed to determine if vacuum assisted reflow process can help alleviate the voids in area array solder joints. Test parameters in this study largely focused on vacuum pressure level and vacuum dwell time.
Technical Library | 2022-10-31 18:35:40.0
Voids affect the thermal characteristics and mechanical properties of a solder joint, thereby affecting the reliability of the solder interconnect. The automotive sector in particular is requiring the mitigation of solder voids in various electronic control modules to the minimum possible level. Earlier research efforts performed to decrease voids involved varying the reflow profile, paste deposit, paste alloy composition, stencil aperture, and thickness. Due to the various advantages they offer, the use of Ball Grid Array packages is common across all industry sectors. They are also prone to process voiding issues. This study was performed to determine if vacuum assisted reflow process can help alleviate the voids in area array solder joints. Test parameters in this study largely focused on vacuum pressure level and vacuum dwell time.
Technical Library | 2017-11-15 22:49:14.0
While a significant level of voiding can be tolerated in solder joints where electrical conductivity is the main requirement, voiding at any level severely compromises thermal conductivity. For example, in LED lighting modules effective conduction of heat through the 1st level die attach to the substrate and then through the 2nd level attach to the heat sink is critical to performance so that voiding in the solder joints at both levels must be minimized. (...) In this paper, the authors will review the factors that influence the incidence of voids in small and large area solder joints that simulate, respectively, the 1st and 2nd level joints in LED modules and discuss mitigation strategies appropriate to each level. They will also report the results of a study on the effect on the incidence of voids of flux medium formulation and the optimization of the thermal profile to ensure that most of the volatiles are released early in the reflow process.
Technical Library | 2018-10-03 20:41:44.0
Voids in solder joints plague many electronics manufacturers. Do you have voids in your life? We have good news for you, there are many excellent ways to "Fill the Void." This paper is a continuation of previous work on voiding in which the following variables were studied: water soluble lead-free solder pastes, a variety of stencil designs, and reflow profiles. Quad Flat No-Lead (QFN) component thermal pads were used as the test vehicle. The voiding results were summarized and recommendations were made for reduction of voiding.
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.
