Analysis and Summary of Common Defects in SMT Assembly

During the process of processing and manufacturing products, we always encounter some problems in circuit board patching. We consulted the technicians of Shenzhen JJY Industrial Technology Co., Ltd. and sorted out and summarized the problems to facilitate everyone's learning and understanding.

inSMTDuring the surface mount technology (SMT) production process, soldering defects occur from time to time. The common defects mainly include solder beads (solder balls), short circuits, misalignment, stele standing, and empty soldering, etc. The causes of these adverse phenomena are due to multiple factors. To avoid the occurrence of these adverse phenomena, it is necessary to have a clear idea and analyze the adverse problems step by step in order to solve the fundamental problems. Next up is Shenzhen JJYSolder paste manufacturerAnalyze for everyoneSMTAnalysis and Summary of Common Defects in Surface Mount Technology (SMT), hoping to be of some help to you!

one.Tin ball

Summary of years of operation experience of Xiyi Electronics: Circuit boardsSMTCommon undesirable phenomena and causes of surface mount technology (SMT)

1Before printing, the solder paste was not fully thawed and stirred evenly.

2If the ink is not refluxed for too long after printing, the solvent will evaporate and the paste will turn into dry powder and fall onto the ink.

3The printing is too thick, and the excess solder paste overflows after the components are pressed down.

4,REFLOWThe temperature rises too fast.SLOPE>3It causes a boiling over.

5The pressure of the surface mount is too high, and the downward pressure causes the solder paste to collapse onto the ink.

6Environmental impact: Excessive humidity, normal temperature25+/-5Humidity40-60%It is accessible when it rains95%Dehumidification is needed.

7The shape of the pad opening is not good and no anti-solder bead treatment has been done.

8The solder paste has poor activity, dries too quickly, or there are too many small tin powder particles.

9The solder paste was exposed to an oxidizing environment for too long and absorbed moisture from the air.

10The preheating is insufficient and the heating is too slow and uneven.

11The printing offset caused some solder paste to stickPCBUp.

12The scraper speed was too fast, causing poor edge collapse. After reflux, it led to the formation of tin balls.

P.S:The diameter requirement of the tin ball is less than0.13MM,or600Square millimeters less than5a.

Ii. Erection of a Monument:

Summary of years of operation experience of Xiyi Electronics: Circuit boardsSMTCommon undesirable phenomena and causes of surface mount technology (SMT)

1Uneven printing or excessive offset, with thick tin on one side and greater tensile force, and thin tin on the other side with less tensile force, causes one end of the component to be pulled to one side, resulting in an empty solder joint, and the other end to be lifted up, forming a monument.

2The patch is offset, causing uneven force distribution on both sides.

3One end of the electrode is oxidized, or the size difference of the electrodes is too large, resulting in poor tinning property and uneven force distribution at both ends.

4The different widths of the pads at both ends result in different affabilities.

5The solder paste was left for too long after printing.FLUXExcessive evaporation leads to a decline in activity.

6,REFLOWInsufficient or uneven preheating results in higher temperatures where there are fewer components and lower temperatures where there are more components. The areas with higher temperatures melt first. The tensile force formed by the solder is greater than the adhesive force of the solder paste on the components, and uneven force application causes monument erection.

Iii. Short Circuit

1.STENCILToo thick, severely deformed, orSTENCILThere is a deviation in the opening, andPCBThe position of the solder pads is not correct.

2.The steel plates were not cleaned in time.

3.Improper setting of the scraper pressure or deformation of the scraper.

4.Excessive printing pressure causes the printed graphics to be blurry.

5.Reflux183The duration is too long. (The standard is.40-90S), or the peak temperature is too high.

6.Poor incoming materials, such asICPoor coplanarity of the pins.

7.The solder paste is too thin, including a low content of metals or solids in the solder paste, low shake solubility, and the solder paste is prone to cracking when pressed.

8.The solder paste particles are too large and the surface tension of the flux is too small.

As a 16-year-old veteran solder paste manufacturer, JJY has always been committed to the research and development, production and sales of solder paste. The quality of the solder paste is stable, without solder bonding, false soldering or establishing a reputation. Residual Wuxi beads, bright and full solder joints, firm welding, and excellent electrical conductivity. If you have any needs, please feel free to contact us.