![\"\"](\"https:\/\/www.pcbassemblyexpress.com\/blog\/wp-content\/uploads\/2021\/09\/Soldering.png\")
<\/figure><\/div>\n\n\n\n\n\n\n\n
What is Soldering?<\/strong><\/h3>\nSoldering is a process in which electronic components are joined to a printed circuit board using a metal alloy known as solder. Solder has a relative low melting point (e.g. lower than the adjoining metals). When solder is heated up beyond its melting temperature it melts. When it cools down it create an electrical bond known as solder joint.<\/p>\n\n\n\n
\n\n\n\n
![\"\"](\"https:\/\/www.pcbassemblyexpress.com\/blog\/wp-content\/uploads\/2021\/09\/Soldering-Tools.png\")
<\/figure><\/div>\n\n\n\nSoldering tools<\/strong><\/h3>\n\n\n\nThe basic tools require for soldering are: <\/p>\n\n\n\n
1. Wire Solder and\/or Solder Paste
\n2. Solder Flux
\n3. A soldering Iron if you are using wire solder. A SMT stencil and a heat source like a hotplate or a reflow oven if you are using solder paste.<\/p>\n\n\n\n
\n\n\n\n
Solder\nFlux is a chemical cleaning agent used during the soldering process. It removes\nthe oxides present on the metal surface and prevents re-oxidation during the\nsoldering process. By preventing the formation of metal oxides, flux enables\nthe solder to adhere to the clean metal surface.<\/p>\n\n\n\n
There\nare many kinds of solder but there are only three categories, lead base solder,\nlead free solder and flux core solder. The most common type of packaging are\nwire solder, solder paste, solder bar and solder balls.<\/p>\n\n\n\n![\"\"](\"https:\/\/www.pcbassemblyexpress.com\/blog\/wp-content\/uploads\/2021\/09\/solder-kind.png\")
<\/figure>\n\n\n\n
\n\n\n\n![\"\"](\"https:\/\/www.pcbassemblyexpress.com\/blog\/wp-content\/uploads\/2021\/09\/Solder.png\")
<\/figure><\/div>\n\n\n\nA\nsoldering iron is a hand tool that supplies heat to melt the solder so it can\nflow between the pieces needed to be soldered. It consists of a metal tip and\nan insulated handle. The tip is applied to the wire solder while holding the\niron by the insulated handle. <\/p>\n\n\n\n
\n\n\n\n
SMT versus Through-hole Soldering<\/strong><\/h3>\n\n\n\nThrough-hole Soldering <\/strong>\u2013 the component leads are inserted into the drilled plated holes on a printed circuit board and soldered to pads on the opposite side either by manual assembly (using a soldering iron) or by the use of an automated machine (e.g. a wave or selective soldering machine). Through-hole components are used for high-reliability products that require stronger connections between layers.<\/p>\n\n\n\n![\"\"](\"https:\/\/www.pcbassemblyexpress.com\/blog\/wp-content\/uploads\/2021\/09\/Through-Hole.png\")
<\/figure>\n\n\n\n SMT Soldering<\/strong> \u2013 the components are mounted directly onto the surface of a printed circuit board. Some SMT components can be soldered manually with a soldering iron, but most of them are too small to solder manually and require hot-air solder reflow equipment.<\/p>\n\n\n\n
\n\n\n\nPCB Assembly using automated equipment<\/strong><\/h3>\n\n\n\nIn this day and age, most original equipment manufacturers (OEM) and electronic contract manufacturers have to use automated equipment to solder electronic components to printed circuit boards. Furthermore, the equipment used to deal with SMT components is completely different than that used for through-hole components. Depending on the production volume, companies have one or more SMT lines. A typical SMT line has the following configuration: an automated stencil printer, an automated pick and place machine and a reflow oven with multiple zones. Our SMT lines include an automated optical inspection machine (AOI).<\/p>\n\n\n\n
\n\n\n\n
The SMT process<\/strong><\/h3>\n\n\n\nPrinting\nis the first step of the SMT process, an automated stencil printer is used to\napply the solder paste on the bare PCBs. Mechanical fixtures inside the printer\nhold the PCB and the SMT stencil together, the pads on the PCB and the\napertures on the stencils are perfectly aligned using the printer\u2019s vision\nsystem. The thickness of the stencil, the size of the apertures, the pressure\nand velocity of the squeegee blade control the amount of paste deposited on the\nSMT pads on the PCBs. <\/p>\n\n\n\n
\n\n\n\n
![\"\"](\"https:\/\/www.pcbassemblyexpress.com\/blog\/wp-content\/uploads\/2021\/09\/SMT-Process.png\")
<\/figure><\/figure><\/div>\n\n\n\nPlacement\nis the second step of the SMT, an automatic \u201cPick and Place\u201d machine is used to\nplace the SMT the components on the PCBs. On this machine, a robotic device\nplaces components on the PCB automatically. Before this can happen, the machine\nneeds to be programmed using the design files (Gerber files, BOM and CAD file\nalso known as XY Data). The CAD file contains the location and rotation information\nof all the components on the BOM. <\/p>\n\n\n\n
\n\n\n\n
Reflow\nsoldering is the third step of the SMT process, the PCBs are sent through a\nreflow oven. The solder paste works as a bonding agent holding the components\nduring heating. The oven is programmed with a thermal profile that corresponds\nto the solder paste in used. Once the paste reaches its reflow temperature it\nmelts. In the case of double-side boards, each side has to be done\nindividually.<\/p>\n\n\n\n
\n\n\n\n![\"\"](\"https:\/\/www.pcbassemblyexpress.com\/blog\/wp-content\/uploads\/2021\/09\/Reflow-Solder.png\")
<\/figure>\n\n\n\n
\n\n\n\nTypical SMT line configuration<\/strong><\/h3>\n\n\n\nLoader: <\/strong>automatically loads the PCBs to the stencil printer.<\/p>\n\n\n\nStencil Printer:<\/strong> applies solder paste to the bare boards.<\/p>\n\n\n\nInspection Conveyor: <\/strong>used to inspect the solder paste on the boards as they come out of the stencil printer. <\/p>\n\n\n\nPick and Place Machine: <\/strong>places the SMT components on the boards.<\/p>\n\n\n\nInspection Conveyor: <\/strong>used to inspect placements of components on the boards. <\/p>\n\n\n\nReflow Oven: <\/strong>used to solder the components on the boards.<\/p>\n\n\n\nUnloader: <\/strong>automatically unloads the <\/p>\n\n\n\n
\n\n\n\n![\"\"](\"https:\/\/www.pcbassemblyexpress.com\/blog\/wp-content\/uploads\/2021\/09\/Machines-Line.png\")
<\/figure>\n\n\n\n
\n\n\n\n![\"\"](\"https:\/\/www.pcbassemblyexpress.com\/blog\/wp-content\/uploads\/2021\/09\/Photos_1.png\")
<\/figure><\/div>\n\n\n\nAfter\nSMT the boards are visually inspected. PCB Assembly Express also performs a\nsecond inspection using an automatic optical inspection (AOI) machine.\n
\nWhen the boards have leadless devices (e.g. BGA and QFN) they need to be inspected using an x-ray machine to conform to IPC standards. \n<\/p>\n\n\n\n
\n\n\n\n
Through-hole process<\/strong><\/h3>\n\n\n\nWhen\nthe PCBs have through-hole components, there are two different type of equipment\ncommonly used for soldering, wave soldering machines and selective soldering\nmachines.<\/p>\n\n\n\n
Wave\nsoldering is the preferred method when soldering a large number of through-hole\ncomponents. During wave soldering, the PCBs are passed over a wave of molten\nsolder. The components become soldered to the boards as the PCBs make contact\nwith the wave,. When working with double-sided boards special fixtures known as\nwave pallets can used to prevent solder from going to areas of the boards with\nSMT components.<\/p>\n\n\n\n
\n\n\n\n![\"\"](\"https:\/\/www.pcbassemblyexpress.com\/blog\/wp-content\/uploads\/2021\/09\/Through-Hole_Process.png\")
<\/figure>\n\n\n\n
\n\n\n\n![\"\"](\"https:\/\/www.pcbassemblyexpress.com\/blog\/wp-content\/uploads\/2021\/09\/Photos-02.png\")
<\/figure><\/div>\n\n\n\nSelective soldering is the preferred method when soldering mixed technology PCBs and the boards do not have a lot of through-hole components. During this process, individual through-hole components are soldered on a PCB using a solder fountain. The components to be selectively soldered are usually surrounded by components that have been previously soldered during the surface-mount reflow process. <\/p>\n\n\n\n
\n\n\n\n
![\"\"](\"https:\/\/www.pcbassemblyexpress.com\/blog\/wp-content\/uploads\/2021\/09\/Photos-03.png\")
<\/figure><\/div>\n\n\n\n\n
After\nthe through-hole process the PCBs are visually inspected again. They can also\nbe inspected with an AOI machine. <\/p>\n\n\n\n
\n\n\n\n
Final quality inspection<\/strong><\/h3>\n\n\n\nAfter\nthe boards are washed (if water soluble flux was used) and depanelized (if the\nboards were panelized) they go through a final visual inspection before they\nare packaged and shipped. The boards are inspected according to their class\ndesignation: Class 1 – General Electronic Products, Class 2 – Dedicated Service\nElectronic Products, and Class 3 – High Reliability Electronic Products. <\/p>\n\n\n\n
\n\n\n\n
PCB testing<\/strong> <\/h3>\n\n\n\nIn-circuit testing (ICT) and\nfunctional testing (FCT) are two of the most popular testing methods. ICT, also\nknown as bed-of-nails, can be used to test individual components and measure\ntheir performance. It can almost provide 100% coverage. FCT helps ensure that\nthe PCBs function properly according to the project\u2019s specifications and that\nthey do not have defects.<\/p>\n
\n\n\n\n
<\/figure><\/div>\n\n\n\nSoldering tools<\/strong><\/h3>\n\n\n\nThe basic tools require for soldering are: <\/p>\n\n\n\n
1. Wire Solder and\/or Solder Paste
\n2. Solder Flux
\n3. A soldering Iron if you are using wire solder. A SMT stencil and a heat source like a hotplate or a reflow oven if you are using solder paste.<\/p>\n\n\n\n
\n\n\n\n
Solder\nFlux is a chemical cleaning agent used during the soldering process. It removes\nthe oxides present on the metal surface and prevents re-oxidation during the\nsoldering process. By preventing the formation of metal oxides, flux enables\nthe solder to adhere to the clean metal surface.<\/p>\n\n\n\n
There\nare many kinds of solder but there are only three categories, lead base solder,\nlead free solder and flux core solder. The most common type of packaging are\nwire solder, solder paste, solder bar and solder balls.<\/p>\n\n\n\n<\/figure>\n\n\n\n
\n\n\n\n<\/figure><\/div>\n\n\n\nA\nsoldering iron is a hand tool that supplies heat to melt the solder so it can\nflow between the pieces needed to be soldered. It consists of a metal tip and\nan insulated handle. The tip is applied to the wire solder while holding the\niron by the insulated handle. <\/p>\n\n\n\n
\n\n\n\n
SMT versus Through-hole Soldering<\/strong><\/h3>\n\n\n\nThrough-hole Soldering <\/strong>\u2013 the component leads are inserted into the drilled plated holes on a printed circuit board and soldered to pads on the opposite side either by manual assembly (using a soldering iron) or by the use of an automated machine (e.g. a wave or selective soldering machine). Through-hole components are used for high-reliability products that require stronger connections between layers.<\/p>\n\n\n\n<\/figure>\n\n\n\n SMT Soldering<\/strong> \u2013 the components are mounted directly onto the surface of a printed circuit board. Some SMT components can be soldered manually with a soldering iron, but most of them are too small to solder manually and require hot-air solder reflow equipment.<\/p>\n\n\n\n
\n\n\n\nPCB Assembly using automated equipment<\/strong><\/h3>\n\n\n\nIn this day and age, most original equipment manufacturers (OEM) and electronic contract manufacturers have to use automated equipment to solder electronic components to printed circuit boards. Furthermore, the equipment used to deal with SMT components is completely different than that used for through-hole components. Depending on the production volume, companies have one or more SMT lines. A typical SMT line has the following configuration: an automated stencil printer, an automated pick and place machine and a reflow oven with multiple zones. Our SMT lines include an automated optical inspection machine (AOI).<\/p>\n\n\n\n
\n\n\n\n
The SMT process<\/strong><\/h3>\n\n\n\nPrinting\nis the first step of the SMT process, an automated stencil printer is used to\napply the solder paste on the bare PCBs. Mechanical fixtures inside the printer\nhold the PCB and the SMT stencil together, the pads on the PCB and the\napertures on the stencils are perfectly aligned using the printer\u2019s vision\nsystem. The thickness of the stencil, the size of the apertures, the pressure\nand velocity of the squeegee blade control the amount of paste deposited on the\nSMT pads on the PCBs. <\/p>\n\n\n\n
\n\n\n\n
<\/figure><\/figure><\/div>\n\n\n\nPlacement\nis the second step of the SMT, an automatic \u201cPick and Place\u201d machine is used to\nplace the SMT the components on the PCBs. On this machine, a robotic device\nplaces components on the PCB automatically. Before this can happen, the machine\nneeds to be programmed using the design files (Gerber files, BOM and CAD file\nalso known as XY Data). The CAD file contains the location and rotation information\nof all the components on the BOM. <\/p>\n\n\n\n
\n\n\n\n
Reflow\nsoldering is the third step of the SMT process, the PCBs are sent through a\nreflow oven. The solder paste works as a bonding agent holding the components\nduring heating. The oven is programmed with a thermal profile that corresponds\nto the solder paste in used. Once the paste reaches its reflow temperature it\nmelts. In the case of double-side boards, each side has to be done\nindividually.<\/p>\n\n\n\n
\n\n\n\n<\/figure>\n\n\n\n
\n\n\n\nTypical SMT line configuration<\/strong><\/h3>\n\n\n\nLoader: <\/strong>automatically loads the PCBs to the stencil printer.<\/p>\n\n\n\nStencil Printer:<\/strong> applies solder paste to the bare boards.<\/p>\n\n\n\nInspection Conveyor: <\/strong>used to inspect the solder paste on the boards as they come out of the stencil printer. <\/p>\n\n\n\nPick and Place Machine: <\/strong>places the SMT components on the boards.<\/p>\n\n\n\nInspection Conveyor: <\/strong>used to inspect placements of components on the boards. <\/p>\n\n\n\nReflow Oven: <\/strong>used to solder the components on the boards.<\/p>\n\n\n\nUnloader: <\/strong>automatically unloads the <\/p>\n\n\n\n
\n\n\n\n<\/figure>\n\n\n\n
\n\n\n\n<\/figure><\/div>\n\n\n\nAfter\nSMT the boards are visually inspected. PCB Assembly Express also performs a\nsecond inspection using an automatic optical inspection (AOI) machine.\n
\nWhen the boards have leadless devices (e.g. BGA and QFN) they need to be inspected using an x-ray machine to conform to IPC standards. \n<\/p>\n\n\n\n
\n\n\n\n
Through-hole process<\/strong><\/h3>\n\n\n\nWhen\nthe PCBs have through-hole components, there are two different type of equipment\ncommonly used for soldering, wave soldering machines and selective soldering\nmachines.<\/p>\n\n\n\n
Wave\nsoldering is the preferred method when soldering a large number of through-hole\ncomponents. During wave soldering, the PCBs are passed over a wave of molten\nsolder. The components become soldered to the boards as the PCBs make contact\nwith the wave,. When working with double-sided boards special fixtures known as\nwave pallets can used to prevent solder from going to areas of the boards with\nSMT components.<\/p>\n\n\n\n
\n\n\n\n<\/figure>\n\n\n\n
\n\n\n\n<\/figure><\/div>\n\n\n\nSelective soldering is the preferred method when soldering mixed technology PCBs and the boards do not have a lot of through-hole components. During this process, individual through-hole components are soldered on a PCB using a solder fountain. The components to be selectively soldered are usually surrounded by components that have been previously soldered during the surface-mount reflow process. <\/p>\n\n\n\n
\n\n\n\n
<\/figure><\/div>\n\n\n\n\n
After\nthe through-hole process the PCBs are visually inspected again. They can also\nbe inspected with an AOI machine. <\/p>\n\n\n\n
\n\n\n\n
Final quality inspection<\/strong><\/h3>\n\n\n\nAfter\nthe boards are washed (if water soluble flux was used) and depanelized (if the\nboards were panelized) they go through a final visual inspection before they\nare packaged and shipped. The boards are inspected according to their class\ndesignation: Class 1 – General Electronic Products, Class 2 – Dedicated Service\nElectronic Products, and Class 3 – High Reliability Electronic Products. <\/p>\n\n\n\n
\n\n\n\n
PCB testing<\/strong> <\/h3>\n\n\n\nIn-circuit testing (ICT) and\nfunctional testing (FCT) are two of the most popular testing methods. ICT, also\nknown as bed-of-nails, can be used to test individual components and measure\ntheir performance. It can almost provide 100% coverage. FCT helps ensure that\nthe PCBs function properly according to the project\u2019s specifications and that\nthey do not have defects.<\/p>\n
\n2. Solder Flux
\n3. A soldering Iron if you are using wire solder. A SMT stencil and a heat source like a hotplate or a reflow oven if you are using solder paste.<\/p>\n\n\n\n
\n\n\n\n
<\/figure>\n\n\n\n\n\n\n\n
<\/figure><\/div>\n\n\n\nA\nsoldering iron is a hand tool that supplies heat to melt the solder so it can\nflow between the pieces needed to be soldered. It consists of a metal tip and\nan insulated handle. The tip is applied to the wire solder while holding the\niron by the insulated handle. <\/p>\n\n\n\n
\n\n\n\n
SMT versus Through-hole Soldering<\/strong><\/h3>\n\n\n\nThrough-hole Soldering <\/strong>\u2013 the component leads are inserted into the drilled plated holes on a printed circuit board and soldered to pads on the opposite side either by manual assembly (using a soldering iron) or by the use of an automated machine (e.g. a wave or selective soldering machine). Through-hole components are used for high-reliability products that require stronger connections between layers.<\/p>\n\n\n\n<\/figure>\n\n\n\n SMT Soldering<\/strong> \u2013 the components are mounted directly onto the surface of a printed circuit board. Some SMT components can be soldered manually with a soldering iron, but most of them are too small to solder manually and require hot-air solder reflow equipment.<\/p>\n\n\n\n
\n\n\n\nPCB Assembly using automated equipment<\/strong><\/h3>\n\n\n\nIn this day and age, most original equipment manufacturers (OEM) and electronic contract manufacturers have to use automated equipment to solder electronic components to printed circuit boards. Furthermore, the equipment used to deal with SMT components is completely different than that used for through-hole components. Depending on the production volume, companies have one or more SMT lines. A typical SMT line has the following configuration: an automated stencil printer, an automated pick and place machine and a reflow oven with multiple zones. Our SMT lines include an automated optical inspection machine (AOI).<\/p>\n\n\n\n
\n\n\n\n
The SMT process<\/strong><\/h3>\n\n\n\nPrinting\nis the first step of the SMT process, an automated stencil printer is used to\napply the solder paste on the bare PCBs. Mechanical fixtures inside the printer\nhold the PCB and the SMT stencil together, the pads on the PCB and the\napertures on the stencils are perfectly aligned using the printer\u2019s vision\nsystem. The thickness of the stencil, the size of the apertures, the pressure\nand velocity of the squeegee blade control the amount of paste deposited on the\nSMT pads on the PCBs. <\/p>\n\n\n\n
\n\n\n\n
<\/figure><\/figure><\/div>\n\n\n\nPlacement\nis the second step of the SMT, an automatic \u201cPick and Place\u201d machine is used to\nplace the SMT the components on the PCBs. On this machine, a robotic device\nplaces components on the PCB automatically. Before this can happen, the machine\nneeds to be programmed using the design files (Gerber files, BOM and CAD file\nalso known as XY Data). The CAD file contains the location and rotation information\nof all the components on the BOM. <\/p>\n\n\n\n
\n\n\n\n
Reflow\nsoldering is the third step of the SMT process, the PCBs are sent through a\nreflow oven. The solder paste works as a bonding agent holding the components\nduring heating. The oven is programmed with a thermal profile that corresponds\nto the solder paste in used. Once the paste reaches its reflow temperature it\nmelts. In the case of double-side boards, each side has to be done\nindividually.<\/p>\n\n\n\n
\n\n\n\n<\/figure>\n\n\n\n
\n\n\n\nTypical SMT line configuration<\/strong><\/h3>\n\n\n\nLoader: <\/strong>automatically loads the PCBs to the stencil printer.<\/p>\n\n\n\nStencil Printer:<\/strong> applies solder paste to the bare boards.<\/p>\n\n\n\nInspection Conveyor: <\/strong>used to inspect the solder paste on the boards as they come out of the stencil printer. <\/p>\n\n\n\nPick and Place Machine: <\/strong>places the SMT components on the boards.<\/p>\n\n\n\nInspection Conveyor: <\/strong>used to inspect placements of components on the boards. <\/p>\n\n\n\nReflow Oven: <\/strong>used to solder the components on the boards.<\/p>\n\n\n\nUnloader: <\/strong>automatically unloads the <\/p>\n\n\n\n
\n\n\n\n<\/figure>\n\n\n\n
\n\n\n\n<\/figure><\/div>\n\n\n\nAfter\nSMT the boards are visually inspected. PCB Assembly Express also performs a\nsecond inspection using an automatic optical inspection (AOI) machine.\n
\nWhen the boards have leadless devices (e.g. BGA and QFN) they need to be inspected using an x-ray machine to conform to IPC standards. \n<\/p>\n\n\n\n
\n\n\n\n
Through-hole process<\/strong><\/h3>\n\n\n\nWhen\nthe PCBs have through-hole components, there are two different type of equipment\ncommonly used for soldering, wave soldering machines and selective soldering\nmachines.<\/p>\n\n\n\n
Wave\nsoldering is the preferred method when soldering a large number of through-hole\ncomponents. During wave soldering, the PCBs are passed over a wave of molten\nsolder. The components become soldered to the boards as the PCBs make contact\nwith the wave,. When working with double-sided boards special fixtures known as\nwave pallets can used to prevent solder from going to areas of the boards with\nSMT components.<\/p>\n\n\n\n
\n\n\n\n<\/figure>\n\n\n\n
\n\n\n\n<\/figure><\/div>\n\n\n\nSelective soldering is the preferred method when soldering mixed technology PCBs and the boards do not have a lot of through-hole components. During this process, individual through-hole components are soldered on a PCB using a solder fountain. The components to be selectively soldered are usually surrounded by components that have been previously soldered during the surface-mount reflow process. <\/p>\n\n\n\n
\n\n\n\n
<\/figure><\/div>\n\n\n\n\n
After\nthe through-hole process the PCBs are visually inspected again. They can also\nbe inspected with an AOI machine. <\/p>\n\n\n\n
\n\n\n\n
Final quality inspection<\/strong><\/h3>\n\n\n\nAfter\nthe boards are washed (if water soluble flux was used) and depanelized (if the\nboards were panelized) they go through a final visual inspection before they\nare packaged and shipped. The boards are inspected according to their class\ndesignation: Class 1 – General Electronic Products, Class 2 – Dedicated Service\nElectronic Products, and Class 3 – High Reliability Electronic Products. <\/p>\n\n\n\n
\n\n\n\n
PCB testing<\/strong> <\/h3>\n\n\n\nIn-circuit testing (ICT) and\nfunctional testing (FCT) are two of the most popular testing methods. ICT, also\nknown as bed-of-nails, can be used to test individual components and measure\ntheir performance. It can almost provide 100% coverage. FCT helps ensure that\nthe PCBs function properly according to the project\u2019s specifications and that\nthey do not have defects.<\/p>\n
<\/figure>\n\n\n\n SMT Soldering<\/strong> \u2013 the components are mounted directly onto the surface of a printed circuit board. Some SMT components can be soldered manually with a soldering iron, but most of them are too small to solder manually and require hot-air solder reflow equipment.<\/p>\n\n\n\n In this day and age, most original equipment manufacturers (OEM) and electronic contract manufacturers have to use automated equipment to solder electronic components to printed circuit boards. Furthermore, the equipment used to deal with SMT components is completely different than that used for through-hole components. Depending on the production volume, companies have one or more SMT lines. A typical SMT line has the following configuration: an automated stencil printer, an automated pick and place machine and a reflow oven with multiple zones. Our SMT lines include an automated optical inspection machine (AOI).<\/p>\n\n\n\n Printing\nis the first step of the SMT process, an automated stencil printer is used to\napply the solder paste on the bare PCBs. Mechanical fixtures inside the printer\nhold the PCB and the SMT stencil together, the pads on the PCB and the\napertures on the stencils are perfectly aligned using the printer\u2019s vision\nsystem. The thickness of the stencil, the size of the apertures, the pressure\nand velocity of the squeegee blade control the amount of paste deposited on the\nSMT pads on the PCBs. <\/p>\n\n\n\n Placement\nis the second step of the SMT, an automatic \u201cPick and Place\u201d machine is used to\nplace the SMT the components on the PCBs. On this machine, a robotic device\nplaces components on the PCB automatically. Before this can happen, the machine\nneeds to be programmed using the design files (Gerber files, BOM and CAD file\nalso known as XY Data). The CAD file contains the location and rotation information\nof all the components on the BOM. <\/p>\n\n\n\n Reflow\nsoldering is the third step of the SMT process, the PCBs are sent through a\nreflow oven. The solder paste works as a bonding agent holding the components\nduring heating. The oven is programmed with a thermal profile that corresponds\nto the solder paste in used. Once the paste reaches its reflow temperature it\nmelts. In the case of double-side boards, each side has to be done\nindividually.<\/p>\n\n\n\n Loader: <\/strong>automatically loads the PCBs to the stencil printer.<\/p>\n\n\n\n Stencil Printer:<\/strong> applies solder paste to the bare boards.<\/p>\n\n\n\n Inspection Conveyor: <\/strong>used to inspect the solder paste on the boards as they come out of the stencil printer. <\/p>\n\n\n\n Pick and Place Machine: <\/strong>places the SMT components on the boards.<\/p>\n\n\n\n Inspection Conveyor: <\/strong>used to inspect placements of components on the boards. <\/p>\n\n\n\n Reflow Oven: <\/strong>used to solder the components on the boards.<\/p>\n\n\n\n Unloader: <\/strong>automatically unloads the <\/p>\n\n\n\n After\nSMT the boards are visually inspected. PCB Assembly Express also performs a\nsecond inspection using an automatic optical inspection (AOI) machine.\n When\nthe PCBs have through-hole components, there are two different type of equipment\ncommonly used for soldering, wave soldering machines and selective soldering\nmachines.<\/p>\n\n\n\n Wave\nsoldering is the preferred method when soldering a large number of through-hole\ncomponents. During wave soldering, the PCBs are passed over a wave of molten\nsolder. The components become soldered to the boards as the PCBs make contact\nwith the wave,. When working with double-sided boards special fixtures known as\nwave pallets can used to prevent solder from going to areas of the boards with\nSMT components.<\/p>\n\n\n\n Selective soldering is the preferred method when soldering mixed technology PCBs and the boards do not have a lot of through-hole components. During this process, individual through-hole components are soldered on a PCB using a solder fountain. The components to be selectively soldered are usually surrounded by components that have been previously soldered during the surface-mount reflow process. <\/p>\n\n\n\n \n After\nthe boards are washed (if water soluble flux was used) and depanelized (if the\nboards were panelized) they go through a final visual inspection before they\nare packaged and shipped. The boards are inspected according to their class\ndesignation: Class 1 – General Electronic Products, Class 2 – Dedicated Service\nElectronic Products, and Class 3 – High Reliability Electronic Products. <\/p>\n\n\n\n In-circuit testing (ICT) and\nfunctional testing (FCT) are two of the most popular testing methods. ICT, also\nknown as bed-of-nails, can be used to test individual components and measure\ntheir performance. It can almost provide 100% coverage. FCT helps ensure that\nthe PCBs function properly according to the project\u2019s specifications and that\nthey do not have defects.<\/p>\n
\n\n\n\nPCB Assembly using automated equipment<\/strong><\/h3>\n\n\n\n
\n\n\n\nThe SMT process<\/strong><\/h3>\n\n\n\n
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\n\n\n\nTypical SMT line configuration<\/strong><\/h3>\n\n\n\n
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\nWhen the boards have leadless devices (e.g. BGA and QFN) they need to be inspected using an x-ray machine to conform to IPC standards. \n<\/p>\n\n\n\n
\n\n\n\nThrough-hole process<\/strong><\/h3>\n\n\n\n
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After\nthe through-hole process the PCBs are visually inspected again. They can also\nbe inspected with an AOI machine. <\/p>\n\n\n\n
\n\n\n\nFinal quality inspection<\/strong><\/h3>\n\n\n\n
\n\n\n\nPCB testing<\/strong> <\/h3>\n\n\n\n