Soldering is a cornerstone technique in electronics assembly, it’s used to connect electrical pieces and mechanically attach them to a PCB (Leiterplatte). A key step to this process is such a concept as “solder wetting.” In this article, we’ll go over the basics of solder wetting, why it’s essential, what causes poor wetting, and how to prevent wetting issues so as to ensure reliable, long lived solder joints.
Solder wetting refers to a process in which solder is molten and spreading to the surface of PCB components. The liquid solder tends to move freely over the surface containing the solder and it forms a uniform shiny surface covering metallurgically bonded to the surface on cooling. If the wetting is good, we can see the solder is smooth and shiny. jedoch, the poor wetting is easy to spot with its rough, dull, granular appearance.
Achieving proper solder wetting is crucial for several reasons:
Elektrische Leitfähigkeit: Good wetting would help improve electrical conductivity as it can help lower signal loss risk and resistance.
Mechanische Festigkeit: Strong and durable bonds formed by good wetting are able to withstand thermal cycling as well as mechanical stress.
Zuverlässigkeit: Properly wetted joints will fail less than cracks, cold joints or intermittent connections.
Visuelle Inspektion: If the solder joint is well wetted, the solder joint is going to look smooth and shiny, and the quality control operator will be able to find defects easily.
Thermisches Management: Good wetting additionally offers superior heat dissipation, which is essential for temperature sensitive components.
While ideal solder wetting is the goal, various issues can occur during the soldering process:
If the solder doesn’t spread as well as it should, the process is called poor wetting. The consequence is higher contact angles, more uneven solder distribution and a potential void or gap in the joint. A poorly wetted joint may function at the beginning, but it’s more likely to fail over time.
Non-wetting is a type of soldering issue where the solder cannot make a bond with a PCB metal alloy. jedoch, if the terminals of electrical components, as well as the pads for the PCB cannot bond, attach and give a secure connection. The board material is left exposed on the surface. The solder also looks like lusterless or giant at the same time. Zusätzlich, direct voiding is also caused by non-wetting. This is a process of creating holes within joints of solder that may lack materials of solder.
Dewetting process is a process where the solder pastes coat the terminals of the components and PCB-Pads, but they leave some of the parts. This leaves thin surfaced solder on metal alloys and thick and irregular clumps. The surface material of PCB is generally not exposed all the time. But when dewetting occurs, it usually affects the joint of solder and filet quality first.
Soldering is all about detail and control, it has to be dealt with in a good wetting manner. Here are some key strategies to prevent wetting issues:
Zuerst, cleaning the PCB surface and components. And we can use a general solvent wipe to remove dirt, oils and any other contamination.
Soldering to a hot tip will prevent oxidation. Keep your tips tin it for iron to turn off and to keep your iron ready primed for proper wetting. You’ll save time and money on the extremely clunky process of constantly buying new tips.
In such case, high activity solder pastes can provide better wetting and is beneficial also in case of complicated surface finish. Zusätzlich, high activity solder pastes will be helpful to avoid poor wetting during reflow.
The soldering iron has to be preheated with the optimal temperature. The solder doesn’t melt completely at the wrong temperature and this leads to cold joints. Therefore its adhesion will not be reliable.
We do have a lot of strategies for soldering, but poor wetting of the solder is inevitable. Don’t worry—when the problem happens we can fix it despite that. Start over, just wait for the solder joints to cool, remove the flux, reheat the joint.
Proper solder wetting techniques determine how well an electronic device will be assembled and works. What’s really important is to know how this fundamental process works if you are working in electronics production. Technicians can see what causes wetting issues, and should use best practices to improve wetting on their soldering skills, and get better and more reliable results. It’s powerful knowledge that is essential to producing high quality electronic assemblies that meet industry standards and performance requirements.
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