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标题: Hobbybotics Reflow Controller V8.03 [打印本页]

作者: liyf 时间: 2012-10-6 20:46
标题: Hobbybotics Reflow Controller V8.03
IntroductionA while ago I decided to start designing my circuits using Surface Mount Devices (SMD).  There are many advantages to using SMD components over through-hole components.  Some of the major advantages are size and cost.  The smaller size means I can make the circuit boards smaller.  In addition, smaller components and smaller circuit boards means lower costs.  One of the disadvantages to SMD components is they are more difficult to solder than through-hole components.  The solution is to use what is called a reflow oven.  Within the scope of this project, we will cover a little bit of theory behind reflow soldering.  Next, we will discuss the basics of Proportional, Integral and Derivative (PID) control necessary (IMHO) for the repeatable success of a reflow system.  Then, we will provide the meat and potatoes of the project so that others may construct their own.  Finally, we will comb through key parts of the firmware and round out this project with a summary of the windows interface application.  For those of you that are already familiar with reflow and PID concepts, you may elect to skip the theory and jump to the build section.  For others that are looking for a brief explanation,  we will begin with a closer look at the reflow soldering process.
The Reflow ProcessA reflow oven is used to reflow solder surface mount components onto a Printed Circuit Board (PCB).  The basic process entails applying either a leaded or unleaded solder paste to the pads on the PCB.  Next, the SMD components are placed on the board and the board put into the reflow oven.  The reflow oven applies/adjusts the amount of heat in stages in order to bond (solder) the components to the board.  Each stage must be performed using a strict procedure.  There are 5 stages for a typical reflow system (Preheat, Soak, Reflow, Dwell and Cooling).
Stage 1 – PreheatThe temperature inside the reflow oven is raised to approximately 125°C at a rate of approximately 2°C per second.  This heating rate must be gradual in order to not cause the solder to bubble and splatter.  The flux becomes liquid at this temperature and the excess flux will flow away from the pads leaving behind grains of solder.
Stage 2 – SoakThe temperature is slowly raised to approximately 170°C – 175°C and maintained for approximately .  At this stage, the temperature of the circuit board and components are nearly the same.  Equalizing the temperature prevents cracking or warping of the PCB and/or components during soldering.  In addition, the solder flux liquefies and coats the pads.
Stage 3 – ReflowThe temperature inside the oven is ramped up to the soldering temperature of approximately approximately 220°C - 240°C as quickly as possible.  At this stage, the grains of solder begin to melt and bond the metal contacts of the components to the associated solder pad.
Stage 4 – DwellThe soldering temperature is maintained for approximately 10-30secs.  The solder is now melted and drawn together by surface tension.  The flux is also force outward by the surface tension leaving behind a bond between the component and PCB pad.
Stage 5 – Cool DownThe temperature inside the oven is slowly decreased to room temperature.  The cool down must take place slowly to prevent potential warping or cracking of the components and/or PCB because of thermal shock.

温度曲线

pcb

原理图

控制板连线

制作资料，固件源代码，上位机软件源代码（c#），文件比较大，分包了

brooksware2000-Hobbybotics-Reflow-Controller-1cb7351.part1.rar (3.81 MB, 下载次数: 2)

brooksware2000-Hobbybotics-Reflow-Controller-1cb7351.part2.rar (3.81 MB, 下载次数: 1)

brooksware2000-Hobbybotics-Reflow-Controller-1cb7351.part3.rar (3.38 MB, 下载次数: 9)

作者: zyh555 时间: 2012-10-13 14:51
翻译一下:介绍前一段时间，我决定开始我的电路设计，采用表面贴装器件（SMD）。使用SMD元件的通孔元件有许多优点。的一些主要优点是尺寸和成本。更小的尺寸意味着我可以做小的电路板。此外，更小的组件，更小的电路板意味着更低的成本。到SMD元件的缺点之一是，他们是比较困难比通孔元件焊接。解决的办法是使用所谓的回流焊炉。在这个项目的范围内，我们将介绍一点点背后的理论回流焊接。接下来，我们将讨论必要的（恕我直言）的回流系统的可重复的成功比例，积分和微分（PID）控制的基本知识。然后，我们将提供该项目的香饽饽，让别人也可以构建自己的。最后，我们将关键部件的固件梳理和完善了该项目的摘要的Windows界面应用程序。对于那些你已经熟悉的回流和PID的概念，你可以选择跳过理论和跳构建部分。对于其他人都在寻找一个简短的解释，我们将开始仔细一看，在回流焊接工艺。
回流焊过程中一个回流炉使用的印刷电路板（PCB）上的回流焊接表面贴装元件。其基本过程需要采用含铅或无铅焊膏的PCB的焊盘上。接下来，SMD组件被放置在董事会和董事会投入的回流炉。回流炉适用于以债券（焊接）的组件板/调整阶段中的热量。必须执行的每个阶段，使用严格的程序。这是一个典型的回流系统（预热，浸泡，回流焊，停留时间和冷却）5个阶段。
第1阶段-预热回流炉的内部温度升高到约125℃下约2℃每秒的速率。该加热速率必须是渐进的焊料，以不引起气泡和飞溅。的磁通在此温度下变成液体，多余的磁通将流远离留下的焊料颗粒的焊盘。
第2阶段-浸泡温度慢慢升高到约170℃ - 175℃，并保持约。在此阶段中，所述电路板和元件的温度几乎相同。均衡温度，钎焊过程中，防止开裂或翘曲的印刷电路板和/或组件。此外，焊剂液化和大衣焊盘。
第3阶段-回流焊烘箱内的温度上升到焊接温度约220℃ - 240℃下尽可能快地。在这个阶段中，晶粒的焊料开始熔化并粘结的组件相关联的焊料焊盘金属触点。
第4阶段-停顿的焊接温度保持为约10 - 30秒。现在熔化的焊料，并通过表面张力拉到一起。磁通也迫使留下的组件和印刷电路板的焊盘之间的键通过表面张力的外侧。
阶段5 -烘箱内的温度冷却至室温，缓慢地减少。降温必须慢慢地发生，以防止潜在的翘曲或开裂的组件和/或印刷电路板，因为热冲击。

作者: robter 时间: 2015-10-25 22:34
感谢楼主提供这么好的交流平台

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