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SMT (Surface Mounted Technology) circuit board quality monitoring method

A quality monitoring and circuit board technology, which is applied in the direction of assembling printed circuits with electrical components, can solve the problems of user loss, inability to detect, and inability to obtain reflow temperature curves, etc., and achieve the effect of improving quality

Inactive Publication Date: 2013-04-03
东莞市若迪自动化科技有限公司
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

Therefore, sometimes such a circuit board looks good on the surface of the solder joints, but in fact, due to staying in the high temperature zone for too long or experiencing too high a temperature, the mechanical and electrical properties of the electronic components will deteriorate, and the reliability of the solder joints will deteriorate. This kind of hidden danger cannot be detected in production, but it will be displayed after a period of use, which may cause irreparable losses to users
[0004] However, in the process of reflow soldering, it is impossible to directly set the temperature measuring probe on the solder joint, and there is no way to know the preheating and reflow temperature of the solder joint, and it is also impossible to obtain the reflow temperature curve, so the quality monitoring of the circuit board is a difficult problem

Method used

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Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0019] The SMT circuit board quality monitoring method of the present embodiment, the steps include:

[0020] (a) In the circuit board that has been soldered, at least select the solder point with the largest heat absorption and the solder point with the smallest heat absorption to set the temperature measuring element.

[0021] During the soldering process, when the heat absorption of the solder joint with the largest heat absorption is insufficient, the solder joint is not stable. At the same time, the solder joint with the smallest heat absorption may have absorbed too much heat, resulting in solder oxidation. There are also hidden dangers in welding, so choose heat absorption By measuring the temperature of the solder joint with the largest amount of heat and the least heat absorption, the soldering quality of all solder joints on the entire circuit board can be standardized.

[0022] The heat absorption of each solder joint of the circuit board that has been soldered is d...

Embodiment 2

[0037] The SMT circuit board quality monitoring method of the present embodiment, the steps include:

[0038](a) Select two solder joints with the largest heat absorption, two solder joints with the smallest heat absorption, and a solder joint with heat absorption between the first two in the soldered circuit board to set the temperature measuring element.

[0039] (b) Set the furnace temperature curve of the reflow soldering furnace according to the temperature curve of the solder used; set the preset value range Sw1 to Sw2 of the process factors of the solder joints, and the process factors include the temperature curve of each solder joint The slope, the temperature time of the preheating zone, the temperature time of the holding zone, the temperature time of the reflow zone, the total heating time, the peak temperature and the transportation speed, the slope includes the maximum rising slope and the maximum falling slope.

[0040] (c) Calculate the process quality window i...

Embodiment 3

[0078] As in Embodiment 2, the solder Sn62Pb36Ag2 is still taken as an example.

[0079] (1). The actual measured maximum temperature rise slope Pw1 of a certain solder joint is 2.0°C / s, and the preset value is Sw2=3°C / s, Sw1=1°C / s.

[0080] Maximum rising slope QWI=[Pw1-(Sw2+Sw1) / 2] / [(Sw2+Sw1) / 2]×100%:

[0081] =[2-(3+1) / 2] / [(3+1) / 2]×100%

[0082] =0%

[0083] (2). The actual measured maximum temperature drop slope Pw1 of a certain solder joint is -2°C / s, Sw2=-1°C / s, Sw1=-4.0°C / s.

[0084] Maximum falling slope QWI=[Pw1-(Sw2+Sw1) / 2] / [(Sw2+Sw1) / 2]×100%:

[0085] =[-2-(-1.0+(-4.0)) / 2] / [(-1.0+(-4.0)) / 2]×100%

[0086] =-60%

[0087] (3). The actual measured temperature time Pw1 in the preheating zone of a certain solder joint is 190s, and the preset value is Sw2=90s, Sw1=60s.

[0088] Preheating zone temperature time QWI=[Pw1-(Sw2+Sw1) / 2] / [(Sw2+Sw1) / 2]×100%:

[0089] =[190-(90+60) / 2] / [(90+60) / 2]×100%

[0090] =153%

[0091] (4). The actual measured temper...

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PUM

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Abstract

The invention relates to an SMT (Surface Mounted Technology) circuit board quality monitoring method which comprises the following steps: (a) arranging temperature-measuring elements on at least one welding spot with the maximum heat absorption capacity and one welding spot with the minimum heat absorption capacity on a welded circuit board; (b) setting preset values of process factors of the welding spots; (c) based on the actual measurement values Pw1 of the process factors of the welding spots, calculating process quality window indices (QWI) corresponding to the process factors; (d) if QWIs corresponding to all the process factors of each welding spot are within + / -99%, indicating that the furnace temperature curve setting of a reflow welding furnace of the circuit board is reasonable; and (e) carrying out reflow welding according to the reasonably set furnace temperature curve obtained in the step (d). By using the SMT circuit board quality monitoring method, the quality of the whole circuit board is judged based on the preset values and real-time measurement actual values of the process factors, and the furnace temperature curve of the reflow welding furnace is set as reasonably as possible, thereby improving the quality and reliability of the SMT circuit board product to the greatest extent.

Description

technical field [0001] The invention relates to Surface Mounted Technology (SMT, Surface Mounted Technology), in particular to a method for monitoring the quality of an SMT circuit board. Background technique [0002] SMT is currently the most popular technology and process in the electronics assembly industry. The process steps mainly include: (a) printing solder to the solder joints of the circuit board to prepare for component welding; (b) mounting electronic components on the solder joints of the circuit board; (c) reflow soldering, mounting with The circuit board of the electronic component passes through the reflow soldering furnace driven by the conveying guide rail to melt the solder, so that the electronic component is bonded to the circuit board; (d) cooling the circuit board, so that the electronic component is firmly bonded to the circuit board. [0003] Among them, the reflow soldering step is the core technology of SMT, and the temperature control in its produ...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): H05K3/34
Inventor 唐岳泉
Owner 东莞市若迪自动化科技有限公司