Effects of Ultrasonic Cleaning

April 12, 2016

Effects of Ultrasonic Cleaning

http://www.circuitnet.com/experts/52525.html

Does ultrasonic cleaning have an adverse effect on crystals or other components on a PCBA?
If there is a negative affect are there any ultrasonic cleaning methodologies that would prevent problems?

K.U.

Experts Comments

The answer is no. The answer is yes. Take your pick. There are two schools on this subject. Smart, intelligent, and experienced engineers will tell you that there is significant risk of component damage when exposed to ultrasonic energy. From damaged crystals to wire bond fractures, that fact is that there is the possibility of damage. In fact, several years ago, a major assembler of electronic assemblies published data linking component damage to ultrasonic energy. In reality, while the above statements are true, the chance of component damage on modern ultrasonic cleaning equipment is rare. Modern ultrasonic cleaning equipment utilizes frequencies of 40 kHz. The frequency is "swept" up and down to reduce potential component damage. Also, if the watts to fluid volume is low enough, damage will be further reduced. Here's the real issue. It doesn't really which school of thought you subscribe to. What matters is what your customer, QC manager, reliability engineer, and others think. The fact that there is legitimate belief that ultrasonic energy has the potential to cause component damage normally precludes it from being used to preform a defluxing process. The fact that you are asking this question, illustrates my point that ultrasonic energy is not openly accepted in the defluxing world, despite compelling arguments to the contrary. I would strongly recommend spray-in-air technology for your cleaning / defluxing requirements. It is universally accepted as the conventional wisdom for defluxing applications and is never suspected of contributing to component damage.

Mike Konrad President Aqueous Technologies Mr. Konrad has been in the electronic assembly equipment industry since 1985. He is founder and CEO of Aqueous Technologies Corporation, a manufacturer of automatic de-fluxing equipment, chemicals, and cleanliness testing systems.

We have several published articles available for download on our web site, click on the "Recommended Reading" button. The article by B.P. Richards et al. "Does Ultrasonic Cleaning of PCBs Cause Component Problems: An Appraisal" best addresses your question: "Does Ultrasonic cleaning have an adverse affect on crystals or other components on a PCBA?" My paper, "Reducing the Cost of Misprinted PCBs", addresses the parameters that would help prevent potential problems. I also recommend the IPC-7526, "Stencil and Misprinted Board Cleaning Handbook."

Bill Schreiber President Smart Sonic Corporation Mr. Schreiber developed the original ultrasonic stencil cleaning process in 1989. Obtained the only EPA Verification for specific parameters of Environmental Safety, User Safety and Cleaning Efficiency for a stencil cleaning process.

If the frequency of the crystal matches the frequency of the ultrasound, then there is resonance and the component can fail. Regular cleaners are better than ultrasonic cleaners precisely for this reason.

Karthik Vijay Technical Manager - Europe Indium Corp. Currently with Indium Corporation and responsible for technology programs and technical support for customers in Europe. Over 15 yrs experience in SMT, Power, Thermal & Semiconductor Applications. Masters Degree in Industrial Engg, State University of New York-Binghamton.

In the early days of integrated circuits, say the 1960s and 1970s, ultrasonic cleaning was generally not used for cleaning components. The affect was not on the crystals or components themselves, but on the leads going through the packaging. Repeated, high-powered ultrasonic cleaning simply vibrated the leads too strongly, causing metal fatigue and component failure. This was particularly true for military and aerospace systems, which actually banned ultrasonic cleaning in one of the now-long-forgotten mil specs. Modern ultrasonic cleaners use "sweep" frequency management to avoid this problem. The machines change frequency constantly, so the energy is never on a harmonic frequency of the lead for very long, and never at the same power setting, which has been proven to minimize damage to components. At the same time, I think every expert would urge careful and thorough testing on your boards, your components and your systems before certifying the process to be trouble-free. A better answer might be to look at vapor degreasing. Vapor degreasing is a much gentler form of cleaning that does not need ultrasonics to work well. Check out one source at Micro Care, Why is Cleaning With Vertre Better than Cleaning With Water or Some Other Solvent ? or another option is Does MicroCare Have Any Solvents Suitable for Use in Vapor Degreasers?

Mike Jones Vice President Micro Care Mr. Jones is an electronics cleaning and stencil printing specialist. Averaging over one hundred days a year on the road, Mike visits SMT production sites and circuit board repair facilities in every corner of the globe, helping engineers and technicians work through the complex trade-offs today's demanding electronics require.

Pin-in-Paste Hole Fill

July 7, 2016

Pin-in-Paste Hole Fill

We are about to implement Pin-in-Paste technology.

How can we ensure proper plated hole fill during the screen printing process? Will the process require using a different solder paste than the one we use for pure SMT assemblies?

R. L.

Experts Comments

 

Paste-in-hole processes are somewhat more complex than traditional SMT from a process control standpoint, but with good engineering practices and the properly optimized stencil, it can be a very controllable process for many users. The key is doing some math on the front end and determining how much paste will be needed to fill the space between the barrel of the through-hole and the lead of the component. Since paste is generally about 50-55% metal by volume, you will generally find that you need to overprint the pad area to ultimately deliver enough solder to the solder joint. Various stencil design techniques will work; contact your solder paste and/or stencil supplier for more detailed pointers. As for picking the right paste for paste-in-hole applications, many standard solder pastes may drop into this type of process without any issues. However, there are two additional solder paste performance requirements for paste selection in paste-in-hole versus traditional SMT. These include coalescence behavior and anti-dripping behavior. The coalescence behavior becomes more of an issue than usual due to the likelihood of overprinting onto the solder mask on the top side of the board. The anti-dripping requirements stem from the fact that some pastes can drip off the bottom of the component lead upon heating, resulting in less solder than expected for the solder joint. This can be avoided by selecting a solder paste that was designed not to drip in a paste-in-hole application.

 

Brian Smith General Manager - Electronic Assembly Americas DEK International Mr. Smith has been supporting customers in the electronics assembly industry since 1994. His expertise is focused on solder paste printing and reducing soldering defects. He holds a BS in Chemical Engineering and an MBA in Marketing. He has authored several papers in trade magazines and at industry conferences. He is an SMTA Certified Process Engineer.

To ensure proper plated hole fill during the screen printing process you must have the proper volume of solder paste. Here's an example of the formula you can use: H=Hole diameter D=Lead diameter T=Board thickness L=Width of lead in the X direction (For square lead) W=Width of lead in the Y direction (For square lead) Pi =3.14 Hole Volume (HV)=(3.14)(H/2)(H/2)(T) Lead Volume (LV)=(3.14)(D/2)(D/2)(T) (For round leads) Lead Volume (LV)=(L)(W)(T) (For square or rectangular leads) Annular Ring Area(RA)=(3.14)(L/2)(L/2)-(3.14)(H/2)(H/2) Solder volume (SV)=HV-LV Print Volume (PV)=(2)(SV) (50%) Print Area (PA)=(F)(PV)/stencil thickness F=Inspection Factor .7=no fillet .9=fillet on both sider 0.8=fillet on primary side 1.0=large fillet on both sides

 

Joe Karcewski Product Manager APS-Novastar, LLC Joe Karcewski has been a Process Engineer for 16 years in the industry. He is a certified IPC-A-610 trainer and is presently working at APS-Novastar as a Product Manager for Soldering Systems including Selective Soldering systems.

The best solution for the Pin-in-Paste process is the ProFlowR enclosed head system. The main reason for this is that ProFlow allows independent control of paste pressure and, therefore, the ability to control the amount of paste fill for the through-hole apertures. If you are unable to use ProFlow, then a 45 degree squeegee can increase the paste pressure. But, if the board is thicker than 1mm, several print stokes will be required, which could degrade the SMT deposits. Standard solder paste should be used for this application.

 

Clive Ashmore Global Process Manager Dek Printing Machine Mr. Ashmore is responsible for the Global Applied Process Engineering group for DEK. Clive specializes in all aspects of manufacturing engineering, with special emphasis on mass imaging technologies.

Same paste should work. You can calculate amount of paste required knowing 4 items: pin dimension, board thickness, hole size, and annular ring size. Paste to solder shrinkage is usually about 50%. Paste volume can be achieved in 3 ways: Overprint, Step-up Stencil, through-hole paste fill. Good reference paper is in SMT Magazine Nov and Dec 2006 "Intrusive Reflow for Lead Free paste."

 

Bill Coleman Vice President Technology Photo Stencil For over 18 years, Dr. Coleman has been the vice president of technology for Photo Stencil, working closely with customers to understand their printing requirements. His efforts have resulted in several new stencil products.

The use of an off-line x-ray inspection system post paste that offers oblique angle views without tilting of the actual board to inspect a representative sample of boards will allow you to see the amount of paste that is located down the holes prior to reflow, non-destructively. The same test can also be used post reflow to quickly confirm that the resultant pin-in-paste hole fill meets the IPC 610D recommendations of a minimum of 75% fill.

 

Dr. David Bernard Product Manager Dage Precision Industries Mr. Bernard has been the X-ray Systems Product Manager at Dage for over 5 years and have been involved in all aspects of x-ray inspection and test for printed circuit board assembly applications. Prior to this, Dr. Bernard was working with radiation measurement instrumentation.

There are numerous tradeoffs to consider when pin in paste hole fill is the goal. First, overprinting can be problematic due to the possibility of mid chip solder balls. Step stencils are more expensive than standard stencils, and will likely result in reduced throughput and material expense due to the need to increase underwipe frequency. One technology which is becoming very popular is the use of solder preforms in tape and reel packaging. The preforms come in standard sizes, such as 0402, 0603 and 0805 to name a few. They are packaged exactly like chip capacitors and resistors. Placement is done after paste printing. Only 20-25% of the preform needs to contact the solder paste. Since the preform is solid metal, a preform as large as four times the volume of the paste volume can be added and still achieve perfect reflow results.

 

Paul J. Koep Global Product Manager Alpha Mr. Koep is responsible for product planning and technical marketing for the Preform Products at Alpha. He is the co-author of several patents in the areas of soldering applications focusing on reflow and alternative methods.

Reader Comment Readers may be interested in the free ebook on "Pin In Hole Intrusive Reflow Design and Assembly" at http://www.pihrtechnology.com The most common problem with the process is the hole to lead ratio, at the design stage its easy to change and it gives design engineers more tracking space. Changing the hole to lead ratio on existing design is easy too as its not going to impact reliability either. Bob Willis, Bobwillisonline.com, UK

Reader Comment Going into the reality of pin-in paste requires a little more than applying paste into the hole. There are usually unforeseen issues which occur after the pin in paste operation. The stencil can be designed to prevent inadequate hole fill by forming a cross pattern with the paste around the top side of the hole. The flux will stay mostly on the top of the pcb under the part instead of flushing out to the bottom pad. The flowed solder will only take what is required to do the job. Making the use of expensive preforms is not necessary. People are asking for advice or suggestions as to which way to perform their particular task at hand. They may not be aware of the pitfalls of following this advice. I know I would prefer to also know what I shouldn't do as well as what I should. Mark A. Maheux Sr., Sr. Manufacturing Engineer, Honeywell Life Safety, USA

 

 

http://www.circuitnet.com/experts/58115.html

Packaging - Shock-n-vibration sensitivity assessment

Packaging - Shock-n-vibration sensitivity assessment from Marcelo Chirai

Cushion testing for shock absorption and vibration attenuation

Cushion testing for shock absorption and vibration attenuation from Marcelo Chirai

Product Reliability - Combined Environmental Conditions Testing

Product Reliability - Combined Environmental Conditions Testing from Marcelo Chirai

Package Integrity Testing

Package Integrity Testing from Marcelo Chirai

Robotiq - Ebook - Getting started with cobots - Part 2-v1

Robotiq - Ebook - Getting started with cobots - Part 2-v1 from Marcelo Chirai

Robotiq - Ebook - 5 steps - Getting started

Robotiq - Ebook - 5 steps - Getting started from Marcelo Chirai

Análise de solda em placas de circuito impresso

Análise de solda em placas de circuito impresso from Marcelo Chirai

Collaborative Robots

From: Karine Simard [mailto:k.simard@robotiq.com]
Sent: sexta-feira, 20 de novembro de 2015 09:09
To: Marcelo Chirai
Subject: What can collaborative robots do? 5-step practical guide to getting started with collaborative robots

Let's explore the possibilities of collaborative robots. This will be useful when we start looking for cells with automation potential.

Not rendering correctly? View this email as a web page here.

Step 1: What can collaborative robots do? In this chapter, we’ll explore the possibilities provided by collaborative robots. This will be useful when we start looking around the factory floor for places with automation potential. Although collaborative robots are a new technology, this does not mean that they are necessarily complex. In fact, it’s the complete opposite. While traditional robots have evolved to satisfy the need for high volume industries, collaborative robots have been designed for the challenges of high mix manufacturing found in all SMEs. Just like traditional robots, collaborative robots can: Move parts around Follow a path to perform a process Work autonomously for extended periods of time, increasing productivity and quality But unlike traditional industrial robots, collaborative robots: Are simple and fast to program by non-experts. Think - half a day of onsite training, compared to 2-days of offsite classes for industrial robots. Have a small footprint. Most applications don't require fencing. Are simple to integrate for the simple tasks. These are the tasks you should start with. Can be repurposed easily for new tasks. The bottom line is that with collaborative robots it is possible to do the same tasks that you would do with industrial robots, but with a smaller, less risky investment and a greater flexibility.   Typical Applications Here are a couple of examples of what can be done using collaborative robots: Machine Tending: Placing a part in a machine for processing. The robot can load and unload the part, hence freeing the operator from this redundant task. Pick-and-place: Moving a part from the output of one process to the input of the next. For example, grabbing parts from a bin and ordering them on a tray. Here again, this is a non-value added task that frees the operator. Lightweight applications: Most applications that can be done by a human without requiring dexterity can be done by a collaborative robot. A great application for full human-robot collaboration is where the robot is moving the part and the operator is using his/her dexterity to assemble the part.   However, before going hog wild and buying just any robot, you need to know which applications are best suited for automation. Get the PDF version for this step here.   What's next: Here are the upcoming chapters in our 5-step practical guide: Week 2: Identify potential processes or tasks for automation. Week 3: Get the team on board with robots. Week 4: Assess your potential applications. Week 5: Get management on board with robots.  We hope you find this series useful in getting your first robotics cell in your factory. Want to discuss your challenge? Request a consultation with our robotics applications experts.

Robotiq   966, chemin Olivier, Suite 325    St-Nicolas,  QC      Canada You received this email because you are subscribed to Getting Started with Collaborative Robots: a 5-Part Practical Guide from Robotiq.