共查询到19条相似文献,搜索用时 78 毫秒
1.
第十一章热风整平工艺
11.1概述 热风焊料整平(HASL,又称热风整平HAL,俗称喷锡)工艺,就是将涂有阻焊层(膜)的印制板浸入熔融的低共熔点Sn/Pb比例的焊料锅中,再通过热风将板的表面与孔内多余的焊料吹掉,从而获得一个平滑、均匀又光亮的焊料涂覆层。热风整平又分为垂直式和水平式两种热风整平系统(见图例)。 相似文献
2.
热风整平工艺一直是印刷线路板制作中重要的后处理工艺,但是,随着印刷线路板的精细化和环境保护的需要,热风整平工艺的应用已经受到限制,由此,产生了一些替代工艺,包括化学防氧化、化学镀镍金、化学镀锡及锡合金等,其中化学镀锡及锡合金最有可能成为取代热风整平的主流工艺。 相似文献
3.
在PCB组件中,现在仍有超过60%的组件大量采用热风整平(HAL)工艺技术,但人们大多数的研究工作还是针对ENIG、OSP、浸银和浸锡等。无铅化热风整平PCB组件往往会被忽视。那么热风整平技术能否胜任无铅化应用的要求呢?丈章试图予以简单介绍。 相似文献
4.
5.
6.
7.
热风整平焊料涂覆技术是七十年代才发展起来的新技术。随着印制板工业发展的需要,热风整平焊料涂覆技术近年来发展很快。1980年9月美国GYREX公司来华技术座谈时介绍:当时全世界大约有热风整平装置200台,而在1982年4月加拿大Eietrovert公司来华技术讲座时透露:全世界大约有400台,不到两年热风整平装置的数量就增加了一倍。从机器的功能看,现在的热风整平机有手工操作的,半自动的,全自动的以及微处理机控制的流水线系统。从加工状态看,已经由垂直方向加工发展到水平方向加工。从生产速度看,已由120块/小时提高到500块/小时。由此可见,热风整平技术的发展是相当快的。 相似文献
8.
9.
10.
随着SMOBC工艺的飞速发展,热风整平技术得到了广泛的应用,使用热风整平机的厂家越来越多。要使热风整平机长期可靠的工作,其中必须重视对气动系统的维护保养,并且掌握常见故障的排除方法。只有这样,才能做到防患于未然,将可能发生的故障消灭在萌芽状态;而且即使设备在工作一段时间后,运动部分发生了 相似文献
11.
12.
新型的化学镀锡在无铅焊接之运用 总被引:1,自引:1,他引:0
阐述线路板的绿色表面涂覆的化学镀锡工艺的有关理论和技术,化学镀锡应用是实现取代热风整平表面涂覆绿色化的最重要的手段之一。我司第三代化学镀锡应用是突破目前化学沉锡的供应商共拥硫脲作为电位改变剂配方此环节,是一种新型独特的科技。 相似文献
13.
14.
研究埋入电容多层板的制作工艺。通过试验验证电容容值与电容设计方法的关系,多层板生产流程中层压、热风整平工序对电容容值的影响;通过热冲击试验、老化试验等试验验证了埋入电容的容值在环境试验中的稳定性。通过一系列试验验证了埋入电容具有高温稳定性,可以在多层板内实现多个埋置电容层。可靠性试验证明埋置电容具有很好的稳定性和很高的可靠性。 相似文献
15.
提出一种应用于NAND FLASH上实现FAT文件系统磨损均衡的方法,通过保留已删除文件在FAT表中的表项和重写文件时将内容写入新簇的方式,实现对NAND FLASH的均衡使用.在牺牲一定读写速度的前提下,有效地实现了对NAND FLASH的均衡磨损,延长了NAND FLASH的使用寿命.在文件系统层研究磨损均衡,实现难度小,且对标准FAT文件系统兼容,具有一定的可行性和实用性. 相似文献
16.
A Sn/Bi bilayer was deposited on a hot air solder leveling (HASL)-treated metal-core printed circuit board (MCPCB) using electroplating as a low-temperature die-bonding material for light-emitting diode (LED). The eutectic feature of the Sn/Bi contact enabled the die-bonding process to accomplish through a liquid/solid reaction at 185 °C with a proper compression force. A high-temperature die-bonding structure composed of a Bi layer sandwiched by two intermetallic compounds (IMCs) formed after thermocompression. Employment of the Sn/Bi bilayer for low-temperature die-bonding prevented the LEDs from thermal stress problems, and the resulting high-temperature IMC/Bi/IMC die-bonding structure was capable of withstanding multiple bonding reactions and high temperature/current operation environment. Durability tests including mechanical, thermal, and optical performance were systematically performed and compared with other commercially available die-bonding materials (Ag paste and solder alloys). 相似文献
17.
In high-speed circuits, skin effects and dielectric properties are important factors for signal degradation considerations, especially in the microwave frequency region. When surface finishes are applied to prevent traces from oxidation, the electrical properties of traces are affected. In this work, experimental study and finite element method (FEM) based full wave simulation are used to investigate the effects of hot air solder leveling (HASL) and its alternatives on signal integrity. Classical interconnect structures, microstrip line, and differential mode coupled microstrip lines subjected to different finishes are investigated. Our work reveals that the net conductor loss that results from surface finishes is the dominant factor in signal degradation when the clock frequency is within the microwave frequency region. For microstrip line, the influence of surface finishes on signal distortion is negligible; for differential mode coupled microstrip lines, however, the surface finish effects, especially those with high resistivity, can lead to significant signal distortions. These findings are expected to have strong implications when designing high-speed circuits that meet strict timing requirements. 相似文献
18.
Aging and accelerated thermal cycling (ATC) have been performed on 2512 chip resistors assembled with Sn3.8Ag0.7Cu (wt.%) solder. The boards were finished with immersion Ag (IAg), electroless nickel/immersion gold (ENIG), and hot air solder leveling Sn–Pb eutectic solder (HASL), and the components’ terminations were finished with 100% Sn and Sn8.0Pb (wt.%). The boards were reflowed with an average cooling rate of 1.6 °C/s. It was found that the microstructure and reliability of the solder joints depended on the board surface finish. The boards containing small amounts of Pb (from board/component terminations) were the most reliable. Solder joints to copper showed a significantly higher number of cycles to first failure than the joints on nickel. Better reliability of the Sn3.8Ag0.7Cu/Cu joints was attributed to an increased copper content in the bulk due to substrate dissolution. 相似文献
19.
机电设备装调其实是综合性、实践性比较强的内容,但是在实际的机电设备装调实训中学生的实训效果不理想,很难提高学生的实际操作能力。因此需要积极转变教学理念以及模式,加强机电设备装调的实训,通过使用机电设备装调实训装置进行教学,全面提高学生的机电设备装调水平。 相似文献