ee:soldering
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ee:soldering [2025/03/06 15:32] FKR@staff.hsrw |
ee:soldering [2025/03/06 15:50] (current) FKR@staff.hsrw |
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| ==== Flux ==== | ==== Flux ==== | ||
| - | The purpose of flux is to remove the oxidised layer on the PCB and the component directly before the soldering process. Usually there is a sufficient amount of flux in the solder wire (or paste). In some occasions it is needed to add extra flux to improve soldering. For example hen repairing or when the soldering process is taking too long. The flux pens you will find in the lab are of the "No-Clean"-type, which means it can stay on the PCB after soldering and does not need to be cleaned. | + | The purpose of flux is to remove the oxidised layer on the PCB and the component directly before the soldering process. Usually there is a sufficient amount of flux in the solder wire (or paste). In some occasions it is needed to add extra flux to improve soldering. For example when repairing or when the soldering process is taking too long. If there is a "nose" in the soldering there was not enough flux. The flux pens you will find in the lab are of the "No-Clean"-type, which means it can stay on the PCB after soldering and does not need to be cleaned. |
| Using flux gel is sometimes help as it will stay in place after dispensing it. Most soldering fluxes come in liquid form. | Using flux gel is sometimes help as it will stay in place after dispensing it. Most soldering fluxes come in liquid form. | ||
| * Use only as much flux as needed. | * Use only as much flux as needed. | ||
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| The soldering tin wire be the same as in THT soldering, however there are smaller sizes available. In the lab we stock 0.35mm solder wire. The soldering temperature will often be smaller than in THT soldering, however there are SMD components with big ground connectors and pads with big connections to the ground plane(s) which require more heat and/or time. | The soldering tin wire be the same as in THT soldering, however there are smaller sizes available. In the lab we stock 0.35mm solder wire. The soldering temperature will often be smaller than in THT soldering, however there are SMD components with big ground connectors and pads with big connections to the ground plane(s) which require more heat and/or time. | ||
| - | In the best case the solder tin fills the pad completely and it forms a cone shape on the side of the component of 25% of the height of the component. Solder should not touch the component. | + | In the best case the solder tin fills the pad completely and it forms a cone shape on the side of the component of more than 25% of the height of the component. Solder may not touch the component (exeption SOT packages). A component offset is acceptable (up to 25% in class 3). |
| ==== Microscope soldering ==== | ==== Microscope soldering ==== | ||
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| * Stencil printing (only possible if you have a stencil for your PCB) | * Stencil printing (only possible if you have a stencil for your PCB) | ||
| * Solder paste is applied all at once using a squeegee held at an angle of 45-60°. | * Solder paste is applied all at once using a squeegee held at an angle of 45-60°. | ||
| + | * high viscosity paste | ||
| * Individual dispensing using a hand dispenser which employs compressed air | * Individual dispensing using a hand dispenser which employs compressed air | ||
| + | * very low viscosity paste | ||
| Please note that there are different pastes for each of the two options due to the different viscosities needed. | Please note that there are different pastes for each of the two options due to the different viscosities needed. | ||
| + | |||
| + | Solder paste consists of powder which comes in different particle sizes. In general the the inner diameter of the dispensing needle shall be 7 times the biggest particle size. For class 4 solder paste (20-38 μm) use an orange needle. Metal needles are for dispensing sodler paste, plastic needles can also be used for flux. | ||
| + | Solder paste needs to be stored refrigerated. Take it out of the fridge before you use it and give it some time to heat to room temperature (approx. 1 hour). | ||
| ===== ESD protection ===== | ===== ESD protection ===== | ||
ee/soldering.txt · Last modified: 2025/03/06 15:50 by FKR@staff.hsrw
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