国产高潮国产高潮久久久,,,

Welcome to the official website of Legret Metal Company
Focus on electronic welding for 20 yearsDONGGUAN LEGRET METAL.,LTD
National consultation hotline:135-2799-2739
Contact US
mobile phone: 135-2799-2739
Service hotline: 0769-38893080
Email: lzd@dglzd.com
Address: Dongguan lvzhidao Metal Co., Ltd
Contact person: Manager Zeng
Industry information

What are the main factors that affect the properties of SMT solder paste?

作者:Lvzhidao solder factory 2021-04-28 0

What are the main parameters that affect the properties of SMT solder paste?


The main parameters that affect the properties of SMT solder paste are: the composition of alloy solder, the composition of flux and the ratio of alloy solder to flux; Particle size, shape and distribution uniformity of alloy solder powder; Oxygen content on the surface of alloy powder; Viscosity; Thixotropic index and slump; Working life and storage life.


1. The composition, proportion and flux content of alloy solder are generally 75% to 90% by weight of alloy solder powder, but the appropriate weight percentage of alloy solder powder should be selected according to different flux systems.


2. Viscosity


The viscosity is related to the particle size and diameter of solder paste, and mainly depends on the composition of flux system in solder paste and the proportion of other additives.


If the viscosity is too high, it is easy to cause the solder paste not to print to the bottom of the template opening, but also to stick to the scraper. If the viscosity is too low, it is not easy to control the deposition shape of solder paste. After printing, it will collapse, which is easy to produce bridging. At the same time, if the viscosity is too low, the solder paste will be scraped away from the template opening when using a soft scraper or when the pressure of the scraper is high, thus forming concave solder paste deposition, resulting in insufficient solder and false soldering. The viscosity of solder paste is usually due to the formula. If the viscosity is too low, it can be adjusted by changing the printing temperature and scraper speed. The decrease of temperature and scraper speed will increase the size of solder paste. Generally, the best viscosity range of fine pitch solder paste is 800 PA · s ~ 1300 PA · s, and that of common pitch solder paste is 500 PA · s ~ 900 PA · s


3. Melting point


The melting point of SMT solder paste mainly depends on the composition and proportion of alloy solder powder. With the different composition and melting point of SMT solder paste, different reflow soldering temperature is needed, and the welding effect and performance are also different


4. Shape, particle size and distribution of solder alloy powder


Generally, the diameter of solder particles is about 1 / 5 of the opening size of the template. For the pad with narrow spacing of 0.5mm, the opening size of the template is 0.25mm, and the maximum diameter of solder particles is not more than 0.5mm, otherwise it is easy to cause blocking during printing


5. Working life and storage period


Because the properties of SMT solder paste, especially the viscosity, change with time and room temperature, after a certain time, SMT solder paste will lose its original characteristics and cannot be used. The working life is generally required to be 12-24 hours, at least 4 hours of effective working time. If the solvent contained in SMT solder paste is too volatile, it is easy to make SMT solder paste dry and difficult to work, It is easy to lose the adhesion to the components. The storage life is generally stipulated as one year at 2-10 ℃, at least 3-6 months


6. Thixotropic index and slump


The slump of SMT solder paste is mainly related to the viscosity and thixotropy of SMT solder paste



精品人伦一区二区三区蜜桃免费 | 免费播放男人添女人下边| 成人免费视频在线观看| 未满十八岁可以激光脱毛吗女生| 中字幕视频在线永久在线观看免费 | 亚洲电影在线观看| 一尘网中国投资资讯网| 无码人妻少妇伦在线电影| 国产我和子的乱视频| 老旺的大肉蟒进进出出视频| 精品久久久久成人码免费动漫| 十八禁久久成人一区二区| 啊灬啊灬啊灬快灬高潮了女| 亚洲熟妇无码av在线播放| 校草被老师肉到失禁h| 女人高潮的24种图片| 杨敏思版1-5完整无删减版| 肉伦娇喘连连蜜汁横流| 久久亚洲精品中文字幕无男同 | 狠狠人妻久久久久久综合蜜桃| 日本激情公妇厨房嗯嗯| 双腿张开被9个男人调教| 蜜臀AV精品一区二区三区| 又白又嫩毛又多12p| 国产+成+人| 中国熟妇色xxxxx中国学生| 久久精品国产亚洲av无码麻豆| g0g0全球高清大胆人休艺术网| 玩弄人妻少妇500系列视频| 国产又猛又黄又爽| 夫妇当面交换作爱| 高h猛烈失禁潮喷a片在线观看| 国产三级片在线观看| 久久精品夜色噜噜亚洲a∨| 男男互攻互受h啪肉np文| 国产97在线 | 亚洲| 2023国产麻豆剧传媒鱿鱼游戏| 午夜精品一区二区三区在线观看| 全肉变态重口调教高辣小说| 狠狠夜色午夜久久综合热 | 性一交一乱一乱一视频|