Fabricación de circuitos con tecnología de montaje superficial (SMT). De la teoría a la práctica.

Seminario)práctico Miguel)Ángel)Pedraza)Torres DEPARTAMENTO)DE)TECNOLOGÍA)ELECTRÓNICA Málaga,)Enero)2017 Iniciación'a'la'soldadura'de' componentes'electrónicos 1.)INTRODUCCIÓN)A)LA)SOLDADURA •¿Qué)es)una)soldadura? •¿Qué)es)soldar? 1.)INTRODUCCIÓN)A)LA)SOLDADURA Uno de los procesos mas importante en el proceso de elaboración de circuitoselectrónicos •Proporciona una sujeción mecánica de los componentes, para asegurar la integridad del circuito. •Permite conectar los componentes entre si por medio de las pistas ocables. En el caso de las placas de circuito impreso el tipo de soldadura es soldadura blanda,puesto que se realiza auna temperaturainferior de 450ºC. 2.)SOLDADURA)COMPONENTES)PASANTES 1. Preparador)del)soldador Permite)al)soldador)alcanzar)la)temperatura)a)la)que)funde)el)material)(estaño) •Punta)a)temperatura)deseada •Limpieza)con)esponja) •Aplicación)fina)capa)de)estaño Punta)sin)limpiar)(izquierda))y)punta)limpia)reestañada (derecha) 2.)SOLDADURA)COMPONENTES)PASANTES 2. Limpieza)de)la)superficie)y)fijación)del)componente La)limpieza)depende)del)estado)de)la)placa Apply the solder Touch the end of the solder to the joint so that it contacts both the solder pad and the component lead or pin. It should melt and flow smoothly onto both the pin and the pad. If the solder does not flow, heat the joint for another second or two and try again. Let It Flow Keep heating the solder and allow it to flow into the joint. It should fill the hole and flow smoothly onto both the solder pad and the pin or component lead. Let It Cool Once enough solder has been added to the joint and it has flowed well onto both the component lead and the solder pad, remove the iron from the joint and allow it to cool undisturbed. Trim the Lead Use your diagonal cutters to trim the lead close to the board. Note: This step applies only to components with wire leads. It is not necessary to trim the pins on Integrated circuit chips or sockets. © Adafruit Industries https://learn.adafruit.com/adafruit-guide-excellent-soldering Page 14 of 35 Fijación)de)un)componente)a)la)placa 2.)SOLDADURA)COMPONENTES)PASANTES 3. Realizar)la)soldadura d •Calentar)unión •Añadir)estaño)a)la)unión Calentamiento)del)pad y)terminal Making a good solder joint Once you have prepared the your tools and the joint to be soldered, making a good solder joint requires just a few simple steps. Heat the joint Heat the joint with the tip of the iron. Be sure to heat both the solder pad and the component lead or pin. A small drop of solder on the tip will help to transfer the heat to the joint quickly. © Adafruit Industries https://learn.adafruit.com/adafruit-guide-excellent-soldering Page 13 of 35 Apply the solder Touch the end of the solder to the joint so that it contacts both the solder pad and the component lead or pin. It should melt and flow smoothly onto both the pin and the pad. If the solder does not flow, heat the joint for another second or two and try again. Let It Flow Keep heating the solder and allow it to flow into the joint. It should fill the hole and flow smoothly onto both the solder pad and the pin or component lead. Let It Cool Once enough solder has been added to the joint and it has flowed well onto both the component lead and the solder pad, remove the iron from the joint and allow it to cool undisturbed. Trim the Lead Use your diagonal cutters to trim the lead close to the board. Note: This step applies only to components with wire leads. It is not necessary to trim the pins on Integrated circuit chips or sockets. © Adafruit Industries https://learn.adafruit.com/adafruit-guide-excellent-soldering Page 14 of 35 Apply the solder Touch the end of the solder to the joint so that it contacts both the solder pad and the component lead or pin. It should melt and flow smoothly onto both the pin and the pad. If the solder does not flow, heat the joint for another second or two and try again. Let It Flow Keep heating the solder and allow it to flow into the joint. It should fill the hole and flow smoothly onto both the solder pad and the pin or component lead. Let It Cool Once enough solder has been added to the joint and it has flowed well onto both the component lead and the solder pad, remove the iron from the joint and allow it to cool undisturbed. Trim the Lead Use your diagonal cutters to trim the lead close to the board. Note: This step applies only to components with wire leads. It is not necessary to trim the pins on Integrated circuit chips or sockets. © Adafruit Industries https://learn.adafruit.com/adafruit-guide-excellent-soldering Page 14 of 35 Añadiendo)suficiente)estaño 2.)SOLDADURA)COMPONENTES)PASANTES 4. Corte)de)las)patas)terminales,)limpieza)e)inspección •Eliminar las patillas de los terminales aras de la soldadura para evitar cortocircuitos yproblemas derivados de conexiones flotantes •Limpieza de las zonas soldadas, puesto que el flux contenido en el estaño puede dejar residuos conductores. •Inspección la soldadura para comprobar que la distribución del estaño sea uniforme yel aspecto brillante 3.)SOLDADURA)ELEMENTOS)SUPERFICIALES) (SMD) 1. Preparador)del)soldador Permite)al)soldador)alcanzar)la)temperatura)a)la)que)funde)el)material)(estaño) •Punta)a)temperatura)deseada •Limpieza)con)esponja) •Aplicación)fina)capa)de)estaño Punta)sin)limpiar)(izquierda))y)punta)limpia)reestañada (derecha) 2. Fijación)del)componente •Lo ideal es soldar un terminal del componente una vez esté posicionado correctamente el componente. •Una vez soldado el primer terminal, es posible corregir un poco la posición del componente, especialmente el alineamiento. Fijación)del)primer)terminal)del)componente Surface Mount Components The previous page showed how to make a good through-hole joint. But more and more components are only available in surface mount form these days. Not all surface mount packages are easily worked by hand, but there are plenty that can be managed with the same basic tools used for through-hole soldering. Let's start with a surface-mount part common to several Adafruit kits: The SD Card Holder: Immobilize the Joint Unlike many surface mount components, immobilizing the SD card holder is relatively easy. There are small pegs on the back that fit into positioning holes in the board. Once it is in place, solder the four small corner tabs to make it permanent. Heat the Joint Start by putting the tip of the hot iron on the solder pad adjacent to the pin. The pad will take longer to heat, so we apply most of the heat to the pad to start. © Adafruit Industries https://learn.adafruit.com/adafruit-guide-excellent-soldering Page 17 of 35 3.)SOLDADURA)ELEMENTOS)SUPERFICIALES) (SMD) 6.)PROBLEMAS)COMUNES)DE)LA)SOLDADURA) •Soldadura)insuficiente Solución:Recalentar la superficie yañadir más estaño para reforzar la unión. Solder Starved A solder starved joint simply does not have enough solder. It may make good electrical contact, but it is hard to verify by inspection. In any case, it is not a strong joint and may develop stress cracks and fail over time. Repair: Re-heat the joint and add more solder to make a good strong joint. © Adafruit Industries https://learn.adafruit.com/adafruit-guide-excellent-soldering Page 29 of 35 Solder Starved A solder starved joint simply does not have enough solder. It may make good electrical contact, but it is hard to verify by inspection. In any case, it is not a strong joint and may develop stress cracks and fail over time. Repair: Re-heat the joint and add more solder to make a good strong joint. © Adafruit Industries https://learn.adafruit.com/adafruit-guide-excellent-soldering Page 29 of 35 Ejemplos)de)soldadura)insuficiente 6.)PROBLEMAS)COMUNES)DE)LA)SOLDADURA) •Exceso)de)soldadura Solución:Es posible eliminar el exceso de estaño con la punta del soldador, con una bomba de desoldar, empleando la malla de desoldar odando un leve golpe mientras el estaño esta caliente. Ejemplos)de)soldadura)en)exceso Too Much Solder This might be a perfectly good joint, but we can't tell for sure. It is entirely possible that this blob of solder wets neither the pin nor the pad and is not a reliable electrical connection. The best evidence of proper wetting (and good electrical contact) is a nice concave surface as on the joint on the far left. Repair: It is usually possible to draw off some of the excess solder with the tip of a hot iron. In extreme cases, a solder-sucker or some solder wick can be helpful as well. © Adafruit Industries https://learn.adafruit.com/adafruit-guide-excellent-soldering Page 30 of 35 6.)PROBLEMAS)COMUNES)DE)LA)SOLDADURA) •Terminales)sin)cortar Solución:'Simplemente) cortar)los)terminales)a)la)altura)de)la)soldadura. Ejemplos)de)terminales)sin)cortar Untrimmed Leads Leads that are too long are potential short circuits. The two joints on the left are an obvious danger of touching. But the one on the right is long enough to be dangerous as well. It would not take much force to bend that lead over to touch an adjacent trace. Repair: Trim all leads just at the top of the solder joint. © Adafruit Industries https://learn.adafruit.com/adafruit-guide-excellent-soldering Page 31 of 35 6.)PROBLEMAS)COMUNES)DE)LA)SOLDADURA) •Puente)de)estaño Solución:Amenudo se puede eliminar arrastrando la punta del soldador caliente para eliminar el exceso de estaño.Si esto no funciona, se puede recurrir amétodos como la mecha de desoldar, la bomba de succión oun leve golpe, tal ycomo ocurría con el caso del exceso de soldadura. Ejemplos)de)puente)de)estaño Solder Bridge The left two solder joints have melted together, forming an unintended connection between the two. Repair: Sometimes the excess solder can be drawn off by dragging the tip of a hot iron between the two solder joints. If there is too much solder, a solder sucker or solder wick can help get rid of the excess. Prevention: Solder bridges most often happen between joints with too much solder to begin with. Use only enough solder to make a good joint. © Adafruit Industries https://learn.adafruit.com/adafruit-guide-excellent-soldering Page 32 of 35 6.)PROBLEMAS)COMUNES)DE)LA)SOLDADURA) •Pista)levantada)o)dañada Solución:La primera de ellas es doblar el terminal si se encuentra cerca de la pista intacta.En caso de que la placa disponga de máscara de soldadura, será necesario rascar con mucho cuidado para no dañar la pista ydejar al aire la capa de de cobre.Es conveniente limpiar la superficie yaplicar flux. Lifted Pad This photo shows a solder pad that has become detached from the surface of the circuit board. This most often occurs when trying to de-solder components from the board. But it can result simply from overworking the joint to the point where the adhesive bond between copper and the board is destroyed. Lifted pads are especially common on boards with thin copper layers and/or no throughplating on the holes. © Adafruit Industries https://learn.adafruit.com/adafruit-guide-excellent-soldering Page 33 of 35 Repairing a Lifted Pad It may not be pretty, but a lifted pad can usually be repaired. The simplest repair is to fold the lead over to a still-attached copper trace and solder it as shown to the left. If your board has a solder-mask, you will need to carefully scrape off enough to expose the bare copper. Other alternatives are to follow the trace to the next via and run a jumper to there. Or, in the worst case, follow the trace to the nearest component and solder your jumper to the leg of that. Not exactly pretty, but functional. Stray Solder Spatters These bits of solder are held to the board only by sticky flux residue. If they work loose, they can easily cause a short circuit on the board. Repair: These are easy to remove with the tip of a knife or tweezers. © Adafruit Industries https://learn.adafruit.com/adafruit-guide-excellent-soldering Page 34 of 35 Ejemplos)de)pista)levantada)y)arreglada 6.)PROBLEMAS)COMUNES)DE)LA)SOLDADURA) •Salpicadura)de)estaño Solución:'Son)sencillas) de)eliminar)con)la)punta)del)soldador,)un)cúter)o)con)las) pinzas. Ejemplos)de)salpicaduras)de)estaño Repairing a Lifted Pad It may not be pretty, but a lifted pad can usually be repaired. The simplest repair is to fold the lead over to a still-attached copper trace and solder it as shown to the left. If your board has a solder-mask, you will need to carefully scrape off enough to expose the bare copper. Other alternatives are to follow the trace to the next via and run a jumper to there. Or, in the worst case, follow the trace to the nearest component and solder your jumper to the leg of that. Not exactly pretty, but functional. Stray Solder Spatters These bits of solder are held to the board only by sticky flux residue. If they work loose, they can easily cause a short circuit on the board. Repair: These are easy to remove with the tip of a knife or tweezers. © Adafruit Industries https://learn.adafruit.com/adafruit-guide-excellent-soldering Page 34 of 35 7.)TIPOS)DE)INTEGRADOS Encapsulado'Through-Hole •Fueron los primeros que se emplearon. •Sólo suelen emplearse en elementos de potencia. •Necesitan agujeros en las placas de circuito impreso para cada pin del encapsulado por el que pasan los pines oterminales de los circuitos impresos. Encapsulado'Surface'Mount •Son los más empleados en la actualidad. •Permiten aumentar la densidad, eliminando los agujeros en el circuito impreso ymejorando las prestaciones eléctricas. TH SMT 7.)TIPOS)DE)INTEGRADOS Encapsulado' Through-Hole DIP SIP TO-92 TO-220 PGA 7.)TIPOS)DE)INTEGRADOS Encapsulado' Surface'Mount SOIC LCC QFP BGA 8.)HERRAMIENTAS)Y)MATERIALES •Estaño Sirve como material adicional para garantizar la correcta unión de los componentes Estaño)en)hilo Estaño)en)pasta 9.)FABRICACIÓN)PCBs A)ESCALA)INDUSTRIAL •Stencil Ejemplo)de)plantilla)de)Stencil Utilización) de)una)plantilla) para)aplicar)pasta)de)soldar 9.)FABRICACIÓN)PCBs A)ESCALA)INDUSTRIAL •Pick and place Varios subsistemas trabajan juntos para recoger ycolocar correctamente los componentes en la PCB. Máquina)de)Pick)and)Place Soldadura)de)Pick)and)Place 9.)FABRICACIÓN)PCBs A)ESCALA)INDUSTRIAL •Soldadura por ola 9.)FABRICACIÓN)PCBs A)ESCALA)INDUSTRIAL •Horno de soldadura La soldadura por horno es un proceso en el que se usa una pasta de soldadura para unir temporalmente uno ovarios componentes electrónicos asus almohadillas de contacto, después de lo cual todo el conjunto es sometido aun aporte de calor controlado, que funde la soldadura yse realiza la soldadura. Horno)de)soldadura 10.)FABRICACIÓN)DE)PROTOTIPOS •Componentespasantes Wire-wrapping Protoboard 10.)FABRICACIÓN)DE)PROTOTIPOS •Componentespasantes Pretaladrada Stripboard 10.)FABRICACIÓN)DE)PROTOTIPOS •ComponentesSMD Socket Con soldador lápiz 10.)FABRICACIÓN)DE)PROTOTIPOS •Componentespasantes Con soldador de pinza Con soldador de aire 11.)NORMATIVA ROHS •Restricción de Sustancias peligrosas en aparatos eléctricos yelectrónicos. –Restricción de plomo yotras sustancias dañinas. ESD •Prevención de descargas electroestáticas. –Pueden provocar fallos de forma aleatoria en los componentes electrónicos que son difíciles de controlar yperseguir. Ejemplo)pulsera)anti)ESD