The basic process composition and process flow of SMT The basic process composition of SMT includes: silk screen (or dispensing), placement (curing), reflow soldering, cleaning, inspection, rework silk screen: its function is to print solder paste or patch glue on the pad of PCB, which is yuan Prepare the soldering of the device. The equipment used is a screen printing machine (screen printer), located at the forefront of the SMT production line. Dispensing: It is a fixed position where the glue is dri

- Sep 27, 2019-

 

The basic process composition and process flow of SMT

The basic process composition of SMT includes: silk screen (or dispensing), placement (curing), reflow soldering, cleaning, inspection, rework silk screen: its function is to print solder paste or patch glue on the pad of PCB, which is yuan Prepare the soldering of the device. The equipment used is a screen printing machine (screen printer), located at the forefront of the SMT production line.

Dispensing: It is a fixed position where the glue is dripped onto the PCB. Its main function is to fix the components to the PCB. The equipment used is a dispenser located at the forefront of the SMT line or behind the inspection equipment.

Curing: Its function is to melt the patch glue, so that the surface-mount components and the PCB board are firmly bonded together. The equipment used is a curing oven located behind the placement machine in the SMT line.

Mounting: Its function is to accurately mount surface-mounted components to a fixed position on the PCB. The equipment used is a placement machine located behind the screen printing machine in the SMT line. produce

Reflow soldering: The function is to melt the solder paste, so that the surface-mount components and the PCB board are firmly bonded together. The equipment used is a reflow oven located behind the placement machine in the SMT line.

Cleaning: The function is to remove the welding residue (such as flux) which is harmful to the human body on the assembled PCB. The equipment used is a washing machine, the position can be fixed, it can be online or not.

Inspection: Its function is to test the quality and assembly quality of the assembled PCB. The equipment used includes a magnifying glass, a microscope, an on-line tester (ICT), a flying probe tester, an automatic optical inspection (AOI), an X-RAY inspection system, and a function tester. The position can be configured in a suitable place on the production line according to the needs of the inspection.

Rework: Its role is to rework PCB boards that have failed. The tools used are soldering irons, rework stations, and the like. Configure anywhere in the production line.

SMT process inspection:

First, single-sided assembly:

Incoming material inspection => screen printing solder paste (point patch adhesive) => patch => drying (curing) => reflow soldering => cleaning => detection => rework

Second, double-sided assembly:

A: incoming inspection => PCB A-side silk-screen solder paste (point patch adhesive) => patch => drying (curing) => A-side reflow soldering => cleaning => flap => PCB side B Screen printing solder paste (point patch adhesive) => patch => drying => reflow soldering (preferably only for side B => cleaning => detection => repair)

This process is suitable for use when mounting large SMDs such as PLCC on both sides of the PCB.

B: incoming material inspection => PCB A-side silk-screen solder paste (point patch adhesive) => patch => drying (curing) => A-side reflow soldering => cleaning => flap => PCB side B Point patch glue => patch => cure => B surface wave soldering => cleaning => detection => repair)

This process is suitable for reflow soldering on the A side of the PCB and B wave soldering on the B side. This process should be used in SMDs assembled on the B side of the PCB only when the SOT or SOIC (28) pins are below.

Third, single-sided mixing process:

Incoming material inspection => PCB side A screen printing solder paste (point patch adhesive) => patch => drying (curing) => reflow soldering => cleaning => plug-in => wave soldering => cleaning => detection = > Rework

Fourth, double-sided mixing process:

A: incoming inspection => PCB B-side patch adhesive => patch => curing => flap => PCB A-side plug-in => wave soldering => cleaning => detection => repair

First post-inserted, suitable for SMD components more than separate components

B: incoming material detection => PCB A-side plug-in (pin bending) => flap => PCB B-side patch adhesive => patch => cure => flap => wave soldering => cleaning => Detection => Rework

Insert first and then paste, suitable for the case where the separation component is more than the SMD component

C: incoming material inspection => PCB A-side silk screen solder paste => patch => drying => reflow soldering => plug-in, pin bending => flap => PCB B-side patch adhesive => Patch => Cure => Flap => Wave Soldering => Cleaning => Detection => Rework

A side mixed, B side mounted.

D: incoming material detection => PCB B-side point patch adhesive => patch => curing => flap => PCB A-side silk screen solder paste => patch => A-side reflow soldering => plug-in => B-side wave soldering => cleaning => detection => repair

A side mixed, B side mounted. First two-sided SMD, reflow soldering, post-insertion, wave soldering

E: incoming material inspection => PCB B-side silk screen solder paste (point patch adhesive) => patch => drying (curing) => reflow soldering => flip board => PCB A-side silk screen solder paste => Patch => Drying =>

Reflow soldering 1 (local soldering is possible) => plug-in => wave soldering 2 (if there are few plug-in components, manual soldering can be used) => cleaning => detection => rework

A-side mounting and B-side mixing.

Five, SMT process ------ double-sided assembly process

A: incoming material inspection, PCB A-side silk screen solder paste (point patch adhesive), patch, drying (curing), A-side reflow soldering, cleaning, flipping; PCB B-side silk screen solder paste (point patch) Glue), SMD, Drying, Reflow Soldering (preferably only for B-side, cleaning, inspection, rework) This process is suitable for use on large SMDs such as PLCC on both sides of the PCB.

B: incoming material inspection, PCB A-side silk-screen solder paste (point paste), patch, drying (curing), A-side reflow soldering, cleaning, flipping; PCB B-side patch adhesive, patch , curing, B-side wave soldering, cleaning, inspection, rework)

This process is suitable for reflow soldering on the A side of the PCB and B wave soldering on the B side. This process should be used in SMDs assembled on the B side of the PCB only when the SOT or SOIC (28) pins are below.

The above is the industry consultation provided by smt patch processing factory Shenzhen Pengzexiang Technology Co., Ltd., I hope to help you! Please contact us if necessary: http://www.oem-pcb.com pcb@sunsoartech.com

 

 


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