Efficient solder paste printing machines ensure error-free manufacturing (July 2015)

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Printed circuit boardClean and perfectly designed printed circuit boards (PCBs) are now a reality; thanks to solder paste printing machines that make the very first step of PCB manufacturing an accurate process. Read about some of these efficient machines here before making a choice

By Gunjan Piplani

Solder paste printing is a highly critical process in PCB manufacturing and needs to be planned for when the PCB is being designed. According to a report by IPC — Association Connecting Electronics Industries (formerly known as the Institute for Printed Circuits), 70 per cent of the defects in surface mount technology (SMT) set-ups occur in the printing stage itself.
In order to run an error-free manufacturing plant, the solder paste printing process needs to be perfect. “A solder paste printing system is fundamental to setting up a PCB assembly line based on SMT. One cannot wish away with this process. Moreover, perfecting this process is both an art and science,” says Amit Madan, country manager – India, TransTechnology India Pvt Ltd.

Moving from manual to automated systems
The demand for PCBs may be on the rise, but their size is getting smaller. PCB manufacturing machines need to be aligned with these changing needs of the industry. The printing process, which was completely manual earlier, has now become semi-automated and fully automated, depending on the budget of the buyer.
Shailendra Mathur, general manager, India, ASYS Group, says, “The solder paste printing system has its own important role in the assembly of surface mount technology devices, using the reflow oven soldering technique. As packages shrink in size and increase in lead count, it is essential to have accuracy and speed to address the diverse market demands. The main reasons for solder paste defects are stencils, the environment, solder paste and stencil printing parameters. These defects can be avoided by a solder paste printing system which can deliver the best accuracy with repeatability and high speed.”

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Types of Solder Paste printing Processes

Fully automatic screen printing machines: This machine system is connected with other process machines, in line, and can communicate with them through the Surface Mount Equipment Manufacturers Association (SMEMA) interface. It requires no operator involvement, which helps to maintain the quality of the printing system. These machines use various cameras to read fiducials and the alignment of the PCB and screen. The cleaning of stencils is automated. All the important process parameters like squeegee angle, pressure, snap-off distance, cleaning process, etc, can be adjusted and fixed as per the product and industry standards.
Semi-automatic screen printing machines: This machine system allows manual handling of the PCB during the manufacturing process. It is an offline machine system, in which the loading and unloading of bare PCBs are done manually, whereas the printing process is automatic. This system requires an operator for setting up the process.
Manual screen printing: This is the most economical way of printing solder paste but has the highest error probability. This process is 100 per cent operator dependent and hence huge deviations in the results can be seen. PCB alignment, squeegee pressure, snap-off distance, etc, cannot be fixed at all.

Key elements of a solder paste printing machine
• Printed wiring boards (PWB)
• Stencil
• Solder paste
• Squeegee (angle)
• Mechanical set-up: support, alignment, contact and gasketing
• Separation

Accuracy ensures the desired results

Solder paste printing machines are of three types: fully automated, semi-automated and manual. These machines are upgraded from time to time to make the solder paste printing process more efficient, scalable, accurate and clean. “Being the first machine in the production process, it should be capable of providing accurate results with the least possible errors. Screen printers have a long list of variables, which increases the probability of deviation in the desired results,” says Soni Saran Singh, executive director, NMTronics India Pvt Limited.

After working on these variables, manufacturers like ASYS are now able to offer accuracy levels as high as 12.5 micron at 6 Sigma. Apart from this accuracy, ASYS also focuses on flexibility and scalability of manufacturing. The company has introduced a dual lane solution based on the Serio print platform. This machine features scalable printing, along with the flexibility possible with the dual lane.
NMTronics has introduced the BTB 125 Speedline by Momentum in India. This also offers an accuracy of 12.5 micron, which ensures high throughput and yield, low cost of ownership and a printing platform that will withstand even the toughest manufacturing environments. “This machine is made on the Can Open architecture which makes it easy to maintain. Moreover, due to its complete metal structure, the repeatability and accuracy are the same throughout,” adds Singh.
An important development in these machines is with respect to the cycle time which, even when faster, makes sure that the required solder paste is dispensed. This ensures no wastage nor the use of excess solder paste, which results in smooth and error-free manufacturing of the PCB.
Yamaha has also unveiled a new machine called the YCP10–an inline SMT solder paste printer–with 10 micron accuracy at 6 Sigma. It offers a fast cycle time of eight seconds with repeatability pegged at 10 micron, and the ability to handle a board size ranging from 50mmx50mm to 510mm x 460mm. Moreover, this machine has a 3S head instead of the traditional W type double squeegee. The 3S head allows the user to dynamically change the attack angle from 45 degrees to 65 degrees in steps of 1 degree each. These features help in offering optimum cycle time, and solder paste is dispensed in such a way that unused paste does not need to be collected after the batch has been finished.

Making a long-term decision
Selecting a solder paste printing machine can be a critical decision, and should depend on various parameters. First of all, a buyer should keep in mind the longevity of the technology being offered since these machines are a long term investment. Buyers should also keep in mind the requirements they have, such as the accuracy of the machine, the cycle time, process requirements, the technology including the camera system, the machine’s power and air pressure, feedback control and user interface.
Says Mathur, “Keeping in mind the critical nature of the machine and its application, we should consider certain parameters like the printing process support available in India, accuracy of the screen printer, closed loop printing capability, upgradability of features post installation, scalability, high accuracy vision system, easy programming to address operator attrition, local availability of service and spares and original equipment manufacturers (OEM) support.”
“Purchase decisions should be governed by the end application in mind. If the end application is replete with fine pitch devices, micro to mini surface mounting devices (SMDs), etc, it is important to consider a machine that matches these manufacturing requirements,” says Madan.
Additionally, Kumud Tyagi, vice president, Bergen Associates Pvt Ltd says, “When making a choice, one should look look at certain basic parameters including machine foot print, multi-functionality of the printer, i.e., one with inbuilt automated optical inspection (AOI) which ensures 100 per cent inspection of prints; an inbuilt dispenser for correction application and cleaning functions at a best price performance ratio.”
So if you are planning to upgrade your PCB manufacturing set-up, you will need to invest in one of these efficient machines which ensure that the manufacturing process is error-free and the final product is perfect.

CHECKLIST
 Longevity of the technology
 Accuracy of the machine
 Cycle time
 Application it will be used for
 Upgrading capability of the machine
 Availability of Indian after-sales support
 Availability of spare parts


Newly Launched Machines in the Market


ASYS

Model: ASYS’ dual lane solution on the Serio print platform

  • Alignment repeatability ± 12.5 micron at 6 Sigma
  • EVA – EKRA vision alignment system
  • Cycle time: 11/9s + print
  • Print format up to 610mm x 510mm
  • Suitable for stencils up to .78m
  • Program changeover < 2 minutes
  • Simple operation driven by SIMPLEX user interface

USP: Printing capability with true scalable platform available in the market today with multi-touch SIMPLEX operations.
Contact details:+011 41070801, [email protected], www.asys-group.com
Indian distributor: Accurex Solutions Pvt Ltd, DVS India Pvt Ltd and Innotronics Technologies Pvt Ltd


Ersa-VERSAPRINT-S1-01
Model: Ersa’s VersaPrint

  • Alignment capability : ±12.5 micron at 6 Sigma
  • Printing accuracy: 25 micron at 6 Sigma
  • Cycle time: Less than 12 seconds
  • Print format up to 700mm x 500mm
  • Flexible stencil mount up to 740mm

USP: True parallel processing for high quality and speed; line scan technology camera for 100 per cent inspection at line speed and closed loop process control for print and post print inspection
Contact details: +91 11 25920283/4/5/6, [email protected], www.ersa.com
Indian distributor: Bergen Associates Pvt Ltd


Speedline
Model: Momentum Speedline BTB 125

  • Alignment capability : ±12.5 micron at 6 Sigma
  • Imaging/printing accuracy: ±20.0 micron at 6 Sigma
  • Service life: 10 years+
  • Maximum board weight: 4.5kg
  • Speed: 305mm/s
  • PCB handling capacity: 60.96cm x 50.8cm
  • Cycle time : 11 seconds standard (for MPM 125)
  • Camera system : Single digital camera-patented look up/down vision

USPs: The machine is made on Can Open architecture and hence is easy to maintain. It is also 100 per cent metal, ensuring the same levels of repeatability and accuracy throughout.
Contact details: Sam Song, +65 6488 9137, [email protected], www.speedlinetesch.com
Indian distributor: NMTronics India Pvt Ltd


yamaha

Model: Yamaha YCP10

  • Alignment capability +/-10 micron at 6 Sigma
  • Volume control: Optional function of detecting remaining solder paste quantity
  • Service life: Approximately 15 years
  • Speed: 8 seconds/cycle
  • Handling capacity: 50mmx50mm to 510mmx460mm PCB
  • Air supply source: 0.45MPa or more, in clean, dry state

USPs: 3S head instead of traditional W-type double squeegee, stencil vacuum feature, graphical layer base alignment function for inconsistent PCBs, bad mark transfer function to prevent loss of cycle time in pick-and-place machines
Contact details: +91-9810449898, [email protected], www.trans-tec.com
Indian distributor: TransTechnology India Pvt Ltd

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