Advanced modelling technique achieves near to zero set up time and minimal tuning

Advanced modelling technique achieves near to zero set up time and minimal tuning

Automatic Optical Inspection (AOI) is now an established solution for the reliable inspection of printed circuit boards (PCB’s) in the electronic manufacturing industry. AOI systems have developed considerably since their introduction in the mid 90’s, and now appear on most surface mount technology (SMT) production lines World-Wide. The majority of AOI systems utilize standard vision analysis technology in the form of multiple controlling algorithms and although there are many variations of this approach most are “programmed” and “tuned” in the same way. Modelling technology however is completely different in that it does not use a standard algorithmic approach but calculates process variation in real time on real production data by analysing pixel by pixel the image of the real production PCB. First conceived in the mid 1990’s and extensively developed since

Modelling [1] is based on Principle Component Analysis (PCA) and has many advantages for companies looking for a fast and versatile system that can be deployed to production very quickly and with the minimum of on-going production tuning.





Importance of fast set up & minimal tuning time

One of the key metrics when selecting AOI solutions is the total cost of ownership of the system once deployed to production. Programming time and production tuning time are major contributors to the on-going ownership costs hence should be measured and understood well in advance of production integration. In low volume / high mix applications set up time is even more important as the AOI program has to be ready and capable of reliable inspection before the production run is complete to have any real value. With production batch sizes below 20 x PCB’s this is very difficult to achieve on most algorithm systems.

Limitations of Algorithm technology approach for fast set up

Most algorithm technology systems are set up with the user having to anticipate the possible range of defects that could occur in production. The set up process includes selecting combinations of algorithms and setting their parameters in addition to those controlling image acquisition. This can be very time consuming with careful attention required to ensure everything is set up accurately.

Advantages of modelling technology for controlling process variation

Statistical Appearance Modelling technology is set up very easily and simply from an image of the first production PCB. The system “learns real world variation” based on operator interaction with the reported results of the inspection tasks. This results in a very accurate statistical description of the normal variation in the product. Using this description during inspection allows accurate reporting of what is acceptable and what is not acceptable to the user based on individual process or quality requirements. Clear advantages of this approach are that the user does not have to anticipate potential defects or process issues as the system will “flag” anything that is outside of the “normal production range” and secondly because the system is programmed with real production variation it is very sensitive to small subtle changes enabling very reliable defect detection. Recent developments to this technology include autonomous prediction of process variation which enables the AOI system to be set up from a single PCB with production ready performance. Set up time can


be as low as 15 minutes from data input to first PCB inspection making it extremely attractive for new product introduction (NPI) and first off verification.


Performance comparison of modelling technology versus Algorithm technology

The tables below are results taken from a recent production evaluation in the Automotive Industry. The PCB tested is a 6 up panel 300mm in length and 260mm in width with a total component count of 1380 and 73 individual component types. The inspection set up included tasks to reliably detect all component body, position, text, value, and solder joint related defects and the total individual inspection task count was 8,307

Table 1 below clearly illustrates a significant performance advantage of the modelling approach versus algorithm technology on this application with results of up to 3 x faster set up time for the modelling system. Of course a fast set up is only advantageous if the system can reliably inspect PCB’s afterwards with a very low false failure rate and provide some immediate value to the user





Table 2 below again illustrates a significant advantage from the modelling system when counting false failures after programming from 1, 10, and 30 panels. Again the modelling system was around 3 x lower in false failure rates.


AOI systems have developed considerably over the past twenty years and with the constant advances in computational technology there is no doubt that this pace of development will continue. Modelling technology is a key area of image analysis that is benefiting from these advances and is already a very attractive alternative to traditional algorithm technology when applied in SMT inspection.

With the ever increasing demand for faster set ups and improved inspection performance on a wide range of applications, statistical modelling technology is a very interesting and valuable solution especially where set up times and cost of ownership are critical to success.

What is SMT production line？

SMT is the traditional electronic components compressed into a volume of only a few tenths of the device directly to the surface assembly components paste, printed on the printed circuit board surface location of the assembly technology. Compared with the traditional process, SMT has high density, high reliability, low cost, miniaturization, sound field automation and other five characteristics.

Types of SMT production lines
SMT production line can be divided into two types, according to the degree of automation can be divided into automatic production lines and semi-automatic production lines; in accordance with the size of the production line can be divided into large, medium and small production lines.
Automatic production line refers to the entire production line equipment are fully automatic equipment, through the automatic board machine, buffer cable and unloading machine all the production equipment with a production line;
Semi-automatic production line is the main production equipment is not connected or not fully connected, the press is semi-automatic, the need for manual printing or manual loading and unloading PCB.

SMT production line of the main components are: by the surface assembly components, circuit boards, assembly design, assembly process;
The main production equipment, including printing presses, dispensers, placement machines, reflow soldering furnace and wave soldering machine. Auxiliary equipment, testing equipment, repair equipment, cleaning equipment, drying equipment and materials storage equipment.


The importance of SMT testing
SMT inspection is an important step in improving the quality of SMT products, it can improve product quality, and strive to achieve "zero defect."
The cost of assembling to the instrument and finding the fault is several times the cost of finding the fault when assembling the printed circuit board;
And the cost of finding the product after the product is put into the market will be hundreds of times the cost of finding the fault when assembling the printed circuit board.


In order to ensure the quality of SMT products, it is necessary to carry out effective testing, timely detection of defects and failures and repair, thereby effectively reducing the manufacture of products and failures caused by the cost of repair.

ICT tester
ICT is In Circuit Tester English abbreviation, the Chinese meaning is the online tester, is the modern electronic enterprise essential PCBA (Printed Circuit Board Assembly, printed circuit board assembly) production of test equipment.
ICT use, high accuracy of the measurement, the detection of the problem clear, even if the general level of electronic technology workers to deal with the problem of PCBA is also very easy.

The most basic instrument used for electrical testing is the On-Line Tester (ICT), which uses a component-level test method to test each component on the assembled circuit board.
ICT can be divided into needle bed ICT and flying needle ICT.
Flying needle ICT basically only static test, the advantage is no need to make fixture, the program development time is short.
Needle-type ICT can be simulator function and digital device logic function test, high failure rate.

In the SMT production line, the time on behalf of the efficiency.
The use of ICT can greatly improve production efficiency and reduce production costs, online tester detection failure coverage of up to 95%, its reasonable configuration in the production line can be found as soon as possible manufacturing failure and timely maintenance, or timely adjustment of the production process, Effectively reducing the cost of manufacturing defective products and repairing.

BGA REWORK|SMT Technology

Since the late 1990s ball grid array (BGA) packages have been gaining as a preferred package style for several reasons. Their IO density compared with the previous high density ultra fine pith quad flat packs (QFPs) is such that they have shrunk the necessary footprint on the PCB by a factor of 50%. If we lump the BGA style of package, a high density IO with solder balls for the interconnection in with its stacked version counterpart the POP then this increase in density approaches nearly 100%. The ability to get more done in less space along with shorter trace spacing and length requirements for board layouts using this package style have allowed boards to be clocked at much higher rates

thereby increasing processing speed. In addition the reliability of the placement of BGAs has been high as initially the tin lead solder balls “self centered” on the pads during reflow. Lastly the reliability

of BGA packages has been increased with the use of underfills, the use of specialty flex solder balls and even solder columns with integrated springs.

The increased use of BGAs and the underlying trend of ever-smaller package sizes, finer pitches and their placement on to ever denser printed circuit boards has led to greater and greater challenges in BGA rework. In addition to these challenges there are many others that have made the job of BGA rework technicians more and more difficult. One of the trends in making BGA rework more difficult is their ever-increasing usage in handheld device. Due to the drop test requirements of these products

in many cases the BGAs and other higher density devices need to be underfilled. Underfilled BGAs have the challenge of the tacky material “squirt out” causing solder shorts underneath the BGA. In

addition, the tacky nature of this material tends to lift pads as well as destroying the underlying solder mask underneath he BGA. This makes the BGA rework even more challenging. The ever-thinning device packages of BGAs cause the packages to warp. This too makes BGA rework difficult.

While large packages with large-sized pitches placed on sparsely populated printed circuit boards made BGAs simple to remove and replace, BGA rework today requires a greater level of machine sophistication. With pitches down in to the 0.3mm areas and package sizes routinely under 10 x

10mm placement with a vision system using a highly precise and repeatable XY motion system is required. Placement accuracies for today’s BGA rework need to be in the less than a 1mil tolerance

range. In addition with the lead free packages the rework system now require sophisticated temperature control with programmable multi zone bottom heaters, nitrogen capability and low flow rates at the air nozzle. In addition to the rework equipment set the inspection equipment needs to be of a higher capability. X-ray inspection equipment with very small spot sizes is a requirement for BGA inspection post BGA rework. The ability to measure the sphericity of the solder balls, the solder ball diameter, the ability to shoot through RF shields as well as higher density ground planes is now a necessity for the x-ray equipment requirements for BGA rework. Also the endoscope is a necessity for checking the ball collapse, the surface of the BGA ball post reflow, the wetting action as well as other attributes is important in BGA rework.

In addition to the equipment requirements for modern day BGA rework, the skill level, dexterity and process knowledge of the rework technicians working on BGA rework is even more demanding today. The BGA rework technician needs to understand reflow profiles in order to deal with printed circuit boards with a high density of ground planes. The BGA rework technician must also understand flux chemistries and how this impacts the kind of cleaning which can be done underneath the device. The BGA rework technician must also be able to understand how a variety of conformal coatings can be removed from the PCB as well as underneath the BGA. BGA rework technicians must also understand how device which neighbor the BGA to be reworked can or could be impacted by the BGA rework process profile.

As BGA packages have become more widely-accepted the BGA rework process has become more difficult. This has meant that both the equipment used in BGA rework as well as the technicians doing the rework have had to become more sophisticated.

Solder wire and paste feature| SMT Technology

Solder wire and paste feature| SMT Technology

Solder voiding is present in the majority solder joints and is generally accepted when the voids are small and the total void content is minimal. X-ray methods are the predominate method for solder void analysis but this method can be quite subjective for non grid array components due to the two dimensional aspects of X-ray images and software limitations. A novel method of making a copper “sandwich” to simulate under lead and under component environs during reflow has been developed and is discussed in detail. This method has enabled quantitative solder paste void analysis for lead free and specialty paste development and process refinement. Profile and paste storage effects on voiding are discussed. Additionally an optimal design and material selection from a solder void standpoint for a heat spreader on a BCC (Bumpered Chip Carrier) has been developed and is discussed.

Solder voids in solder joints are a common occurrence in SMT assemblies. Their origins are not well understood but are typically faulted as a failure of the solder fillet to thoroughly expel flux remnants during the reflow process. The amount of solder voiding can vary significantly within an assembly, between different flux formulations, solder alloys, board and component metalizations. Reflow profiles as well as stencil aperture designs can often affect the overall level of voiding.

Adding to the mystery of solder voiding is a lack of quantitative measurement tools in the industry with few exceptions. BGA void analysis software is one of these exceptions. This software uses gray level pixel analysis to determine the perimeter of the solder sphere and the internal perimeters of the voids. Once the perimeters are established the areas within these structures can be measured and an overall percent voiding can be calculated. This type of measurement works well if the voids are large or found on the outer edges of the sphere but if the void is small and centrally located where the sphere density is the greatest then the void may be invisible due to its relatively similar gray level to the surrounding material. Increasing the X-ray power will reveal the small void but also shrink the measured area of the sphere and yield an inaccurate and inflated percent voiding. This problem is even more complicated in a chip or a leaded component solder joint. When X-raying a completed assembly, internal traces, vias and even components on the backside of the board that intersect the image of the solder joint confound the software algorithms ability to accurately determine the perimeter of the solder joint. In simple terms the X-ray image is two-dimensional and the ideal structure must be symmetrical about the Z-axis such as a box or a cylinder.

Novel Approach

Based on the assumption that the ideal quantitative void measurement method will utilize BGA analysis software and a symmetrical Z-axis reflow structure, the “sandwich” concept was developed.

This a novel approach simulates the worst conditions of a solder joint for voiding, under the component where flux evacuation is the most difficult while maintaining the same reflow thermal environment and metallurgies if desired. This idea was born out of a quest for a quantitative method of determining the percent voiding on a Ceramic Column Grid Array (CCGA)1. In the CCGA the columns are 10/90 Sn/Pb and cover about 45% of the solder fillet. If enough power is used to see through these dense columns, the perimeter of the solder joint is washed out and 55% of the total fillet is invisible. If adequate power is used to see the perimeter of the circular fillet, the area under the columns is invisible. The effort is complicated by column parallax, internal traces and vias as can be seen in Figure 1. With the thought of a column the same diameter as the solder pad that is thin enough to be X-rayed without excessive power, a solder preform was selected. In this application the preform alloy was selected to be the same as the 10/90 columns to minimize the variables that could contribute to solder voiding. Several thicknesses were tested with a 30 mil diameter by 5 mil thick as the final solution.

There were numerous challenges placing these discs. The first problem was a reliable source cup shaped and stacked discs were the first problems to solve. The second problem was the mechanics of actually placing the discs in that the vision systems in the pick and place were never programmed to recognize round components, only components with corners like typical chips. This relegated a “ballistic” pick and place strategy. For this problem a precision matrix tray with cylindrical pockets, each holding one preform, was developed as in Figure 2. Next came improvements to the pick and place nozzle. The stock smallest nozzle OD was the same as the preform. This presented numerous pick problems if the preform was not perfectly centered, occasionally the preform would flip on its edge after pick and crash on placement deforming the preform. Several improvements were made ultimately reducing the nozzle tip down to what would be typical for a 0201 chip as in Figure 3. Reducing the nozzle tip surface area helped eject the preform better in the placement operation.

Assembly of the CCGA test coupons is simple SMT assembly beginning with a “pads only” ceramic coupon to maintain the geometries and pad metalization of the application. This coupon is free of internal traces as in Figure 4. The solder paste is printed through a circular aperture that is 1 mil smaller in diameter than the pad, the preform is placed over the solder paste and then reflowed as in Figure 5. It was established that if the preform was off pad less than 4 mils that it would self-center. Careful attention to Z-axis placement is required to prevent shorting with adjacent preforms.

After assembly the coupon area was X-rayed and quantitative void analysis was performed on the image using off- the-shelf BGA analysis software as in Figure 6. This software provides both total percent voiding and a pass/fail status if any individual void within a structure is larger than a preset number (ie 5%). This technique worked very well for the custom formulated 63/37 Sn/Pb based solder paste or any other alloy with a similar melt point but when tested with lead free (Sn/Ag/Cu, Mp 219°C) it was noticed that the preforms had appeared to melt and partially join the underlying solder paste under test. This was remedied by switching to OFHC copper preforms of identical geometries. For generic paste void benchmarking2 a dedicated pad test area (Figure 7) was included in the Benchmarker II test board. This allows the testing of solder pastes on standard PCB surfaces such as Entek OSP (Organic Solder Protectant) and ENIG (Electroless Nickel Immersion Gold). Quite simply we are making copper sandwiches (Figure 8) that result in cylindrical structures, which permit highly quantitative void analysis with standard BGA analysis software.

rom this data there are clearly different trends for the two materials as well as a significant difference in void behavior between them. The effect of time on Material A is accelerated in cold storage and just the opposite with Material B. Both materials have the exact same source and specifications of the inorganics (powder + additives).

Profile Effects
The effect of the reflow profile can be significant but the magnitude varies greatly from one formulation to another. The following example involves two 63/37 Sn/Pb no clean materials3,4, tested over Entek passivated copper using the copper preforms with the 4 profiles as illustrated in Figure 10. This profile matrix is designed to expose profile sensitivity of a given formulation, in this case relating to voiding. There are two profiles with a ramp style preheat and two with a soak preheat. There are 2 profiles with a peak of 225°C with 60 seconds over liquidous and two hotter profiles with a peak of 240°C with an extended liquidous of 90 seconds. The X-ray data has been compressed into a single “point scale” to facilitate comparisons. These points (100 is best) are calculated .

Advanced modelling technique achieves near to zero set up time and minimal tuning

Advanced modelling technique achieves near to zero set up time and minimal tuning

Automatic Optical Inspection (AOI) is now an established solution for the reliable inspection of printed circuit boards (PCB’s) in the electronic manufacturing industry. AOI systems have developed considerably since their introduction in the mid 90’s, and now appear on most surface mount technology (SMT) production lines World-Wide. The majority of AOI systems utilize standard vision analysis technology in the form of multiple controlling algorithms and although there are many variations of this approach most are “programmed” and “tuned” in the same way. Modelling technology however is completely different in that it does not use a standard algorithmic approach but calculates process variation in real time on real production data by analysing pixel by pixel the image of the real production PCB. First conceived in the mid 1990’s and extensively developed since

Modelling is based on Principle Component Analysis (PCA) and has many advantages for companies looking for a fast and versatile system that can be deployed to production very quickly and with the minimum of on-going production tuning.

Importance of fast set up & minimal tuning time

One of the key metrics when selecting AOI solutions is the total cost of ownership of the system once deployed to production. Programming time and production tuning time are major contributors to the on-going ownership costs hence should be measured and understood well in advance of production integration. In low volume / high mix applications set up time is even more important as the AOI program has to be ready and capable of reliable inspection before the production run is complete to have any real value. With production batch sizes below 20 x PCB’s this is very difficult to achieve on most algorithm systems.

Limitations of Algorithm technology approach for fast set up

Most algorithm technology systems are set up with the user having to anticipate the possible range of defects that could occur in production. The set up process includes selecting combinations of algorithms and setting their parameters in addition to those controlling image acquisition. This can be very time consuming with careful attention required to ensure everything is set up accurately.

Advantages of modelling technology for controlling process variation

Statistical Appearance Modelling technology is set up very easily and simply from an image of the first production PCB. The system “learns real world variation” based on operator interaction with the reported results of the inspection tasks. This results in a very accurate statistical description of the normal variation in the product. Using this description during inspection allows accurate reporting of what is acceptable and what is not acceptable to the user based on individual process or quality requirements. Clear advantages of this approach are that the user does not have to anticipate potential defects or process issues as the system will “flag” anything that is outside of the “normal production range” and secondly because the system is programmed with real production variation it is very sensitive to small subtle changes enabling very reliable defect detection. Recent developments to this technology include autonomous prediction of process variation which enables the AOI system to be set up from a single PCB with production ready performance. Set up time can


be as low as 15 minutes from data input to first PCB inspection making it extremely attractive for new product introduction (NPI) and first off verification.


Performance comparison of modelling technology versus Algorithm technology

The tables below are results taken from a recent production evaluation in the Automotive Industry. The PCB tested is a 6 up panel 300mm in length and 260mm in width with a total component count of 1380 and 73 individual component types. The inspection set up included tasks to reliably detect all component body, position, text, value, and solder joint related defects and the total individual inspection task count was 8,307

Table 1 below clearly illustrates a significant performance advantage of the modelling approach versus algorithm technology on this application with results of up to 3 x faster set up time for the modelling system. Of course a fast set up is only advantageous if the system can reliably inspect PCB’s afterwards with a very low false failure rate and provide some immediate value to the user

Table 2 below again illustrates a significant advantage from the modelling system when counting false failures after programming from 1, 10, and 30 panels. Again the modelling system was around 3 x lower in false failure rates.


AOI systems have developed considerably over the past twenty years and with the constant advances in computational technology there is no doubt that this pace of development will continue. Modelling technology is a key area of image analysis that is benefiting from these advances and is already a very attractive alternative to traditional algorithm technology when applied in SMT inspection.

With the ever increasing demand for faster set ups and improved inspection performance on a wide range of applications, statistical modelling technology is a very interesting and valuable solution especially where set up times and cost of ownership are critical to success.

How to calibrate smt feeder | technology

How to calibrate smt feeder

SMT feeder is used for a long time, there will be accuracy error, it needs to be calibrated to ensure that smt feeder work more smoothly and more efficient, the following describes the process of smt feeder calibration.

1.Choose a feeder with best chip-placement ratio, install the Calibration Ruler on this feeder, then place feeder to calibration equipment’s position table.

2.Adjusting the focus-distance H-Axis makes display position centeral on FEEDER component, display show cross cursors in the middle of intersection, make it clear then lock tight, readjust X, Y -Axis makes display position centeral on FEEDER component -eyelet centeral in the middle of intersection, and lock tightly. Then prepare work have complete, please never adjust X, Y, H- Axis again.

3. Remove the FEEDER with Calibration Ruler from calibration equipment, Place the calibration ruler into the feeder need adjust and set up to the Jig position, press Auto/Manual key observe cross cursor centeral whether component cross place to superposition together, if not, please adjust FEEDER bolt-pin to make with display superposition together.Check once wheel gear, and lock screw tightly.

4. How to adjust bolt-pin of the feeder?

a） Adjust Y-Axis: loose screw in Picture A & B, then turn pin in Picture C to adjust Y-Axis, after adjustment completed, pls lock the screw in Picture A & B tightly:

b） Adjust X-Axis:: loose screw in Picture D & E, then turn pin in Picture F to adjust X-Axis, after adjustment completed, pls lock the screw in Picture D & E tightly.

More details refer to : Joy Technology Co.,Limited