Tuesday, September 15, 2015

Processing High Voltage SMD Diodes...Is it Possible?

VMI LogoSMF and SXF high voltage diodes are constructed using a hermetically-sealed diode over-molded with a rigid epoxy.  

The advantages of using a diode such as this is that they are easy to pick-and-place, and are cost effective.  They pack a lot of high voltage iN a small footprint.

Many diodes can be overmolded.  Some of the more popular devices include - 

SMD Part Number

Base Diode Vr Io Trr
SMF6529 1N6529 2kV 250mA 70ns
SMF6531 1N6531 3kV 100mA 70ns
SMF6533 1N6533 5kV 50mA 70ns
SXF6521 1N6521 2kV 500mA 70ns
SXF6523 1N6523 3kV 250mA 70ns
SXF6525 1N6525 5kV 150mA 70ns

High Temp Diodes

SMF6531HT 1N6531HT 3kV 100mA 70ns
SMF6533HT 1N6533HT 5kV 50mA 70ns
SXF20FF3HT X20FF3HT 2KV 420mA 30ns

High Speed Diodes

SXF20FF3 X20FF3 2kV 420mA 30ns
SMF50FF3 M50FF3 5kV 40mA 30ns
SXF50FF3 X50FF3 5kV 75mA 30ns

SMF and SXF High Voltage Diode Package

Hi-rel processing similar to JANTX type testing can be done, but there are differences.  Due to device construction, environemntal testing such as power burn-in and High Temperature Reverse Bias (HTRB) testing is done prior to encapsulation.  The diode is hermetically sealed at that point, but has not been over molded.  Once the diode is overmolded it can be electrically tested - Final Electrical, for example - but no further environmental processing is done.  

A second difference is that a custom number is assigned to the device to differentiate it from standard products.

Don't hestitate to contact us for your diode processing needs.  VMI offers a range of diode testing services, and we're more than happy to take a look at your requirements.

Monday, August 31, 2015

Mirror Image

As circumstance would have it, two VMI employees are simulaneously experiencing foot/leg issues, and are both required to wear 'booties'.  In the olden days, they would be wearing casts.

And, as it so happens, it's Karen S.'s birthday!  So here's a photo taken in the office of Karen S. and Brooks N., with their respective booties in place.

Speedy recovery to both of them!

Happy Birthday to Karen S., and a speedy and full recovery to her, and Brooks N.

Thursday, August 27, 2015

High Voltage Optocoupler App Note -

Every once in a while Voltage Multipliers Inc. receives an inquiry about parts being sensitive to ambient light.

One question recently was about one of the high voltage optocouplers - the OC150 family.  The OC150 family uses two LED to illuminate light-sensitive silicon junctions in high voltage diode (the photo diode).  

Glass encapsulated diodes can be sensitive to ambient light.  Just how sensitive depends on many factors - the wavelength of the light, temperature, orientation of the diode junctions, distance from the light source, thickness of the glass, and so on.

Normally it's not an issue, but when you're dealing with very low levels of leakage current, light sensitivity can be a problem.

For that reason, many VMI customers take steps to protect their optocouplers from ambient light by over potting them with an optically opaque material.  Another strategy is to coat the optocoupler with a non-conductive coating, making sure that you're not creating a leakage path that might allow the optocoupler to arc.

The OC100 and OC150 Optocouplers - 10kV and 15kV

Tuesday, August 25, 2015

2016 Trade Shows

Looking ahead, Voltage Multipliers Inc. will be attending the following trade shows in 2016.

Several of our engineers and sales people will be there.  VMI representatives, and local sales reps will be available to meet with you, so be sure to look us up!  

2016 Trade Show Schedule 
Trade Show      Date  Booth  Place   
Photonics West     Feb 16-18th  4324 San Francisco, CA USA
Pittcon     March 6-10th  Atlanta, GA  USA
APEC     March 20-24th  1533 Long Beach, CA  USA
IEEE IPMHVC     July 5-10th San Francisco, CA USA 
Electronica 2016    November 2016 Germany 

Check back often.  We update the list as more information and trade shows are added.  

Thursday, July 9, 2015

High Voltage Adaptability

VMI Adaptability

Voltage Multipliers Inc. LogoIt’s not unusual for VMI customers to contact us with new, exciting, applications for existing designs.  The questions are often centered around adapting those designs to new applications, new environments, higher outputs, less noise, or new-but-similar product lines.  

VMI can delivery across a range of volumes and time-to-market – anywhere from a few days to a few years, depending on the complexity, and one or two prototype products to full ramp-up.  

(Okay, a project that takes six months or longer would probably be better defined as ‘custom’).  Regardless of the length of development time, VMI treats each application with thoroughness and accuracy.  

No Short Cuts

Development time is directly proportional to the complexity of the design, and when time runs short, it can be vera, vera tempting to cut testing down, or assume things will be okay.  VMI's reputation rests on quality.  Consequently, VMI DOES.NOT.TAKE.SHORTCUTS.
It may take longer, but it will be right.


Our suppliers go through a vendor-qualification process.  Their performance is tracked and monitored.  VMI has an excellent reputation for fairness, accuracy, professionalism, and cooperation, among our suppliers.  We strive to keep our working relationship open, and mutually beneficial, and we want to keep it that way.

The same applies to our customers.  VMI’s reputation is one of delivering high quality products on time, excellent customer service, and responsive Engineering and Sales teams.

We want to keep our relationships with suppliers and customers healthy and happy as evidenced by open communication and working together as a team.  


High voltage has been VMI’s focus for over three and a half decades, and we’re going strong.

Manufacturing Success

Instrumental to our manufacturing success is our philosophy, and manufacturing techniques.  They include -   
  • A lean, Pull-system Factory
  • IPC Certified In-house Trainers and Manufacturing Operators
  • Precision Controlled Encapsulation and Cure Processes
  • RoHS complaint production lines
  • Automatic Inspection Systems
  • Environmental Stress Test Capability
  • Supplier Quality Programs
  • In-house Quality Programs
  • Instrument Calibration Control Systems

To that end, VMI is - 
  • ISO 9001-2008 certified
  • QPL Lab Suitability Qualified

So the next time you need a high voltage design, custom or adapted from a standard product, give us a call.  

Tuesday, July 7, 2015

Current Ratings in High Voltage Diodes, and the SXF6525 in Particular

The current ratings of a diode (including surge currents) are best though of as guidelines.  The thing that keeps a diode from successfully operating at higher currents in excess of the published rating is the generated heat, and the inability to remove the heat from the junction.  

If the diode heats up too fast, the rapid expansion of the materials inside the diode could lead to mechanical breakage (at times heavy surge testing here can cause diodes to fall apart or even ‘pop’ and have a chunk of glass chip out).  The diode is said to have been thermally shocked.  Think of what happens when you pour rapidly boiling water into a glass pitcher.  You might get away with it once or twice, but eventually the pitched will crack, sometimes quite spectacularly.  

Okay, back to diodes.  As the diode heats up more gradually, the VF rating of the diode drops and the diode slows down (TRR increases) which, depending on the system, will likely cause the diode to generate more heat (either through higher forward current from the VF change or more reverse power losses from the TRR decreasing) which will cause the VF to decrease more and the TRR to increase more, which will cause more heating – eventually leading to a thermal runaway situation.

So, the current ratings of diodes are mostly guidelines to manage the heat generated during the operation of the diode.  And how much the diode is going to heat up is going to depend greatly on the application of the diode, and what the thermal path is for the diode.  Since the SXF6525 is a surface mount part, it is good at getting the heat out of the silicon of the diode, but if there is not sufficient heat sinking on the PCB or substrate where the diode is mounted, it can still go into thermal runaway conditions.

From just a guidelines point of view for the SXF6525, we do not advise power derating in the diode until 100°C (See graphs below). 

So we would then advise a repetitive forward surge current of 2A at 75°C.  It is, however, something that should defiantly be tested in the customers specific application with special attention and observation of the temperature of the diode and whether or not it will stabilize or go into thermal runaway.

Heat management is a complicated issue when it comes to semiconductors and therefore current ratings could vary considerably depending on the diode and application.  If you would like clarification or additional information for your application, please contact us.

Thursday, July 2, 2015

200°C, 2kV, 30ns Diode - SXF20FF3HT

SXF20FF3HT 2kV, 200°C,  Diode

Introducing VMI's latest addition to the 200°C, high temperature, high voltage diode family.
The SXF20FF3HT (HT for "High Temperature) is rated at 200°C.  It will block 2kV in the reverse direction and conduct 420mA in the forward direction.  Reverse Recovery Time (Trr) is 30ns or less.

It is the fastest recovery time, and highest current in the high temperature diode line.  If you don't need 30ns, or need a higher reverse voltage and lower forward current, two excellent choices include the SMF6531HT (3kV), and the SMF6533HT (5kV).  Both are rated for operation at 200°C.

Physical Dimensions

The SXF20FF3HT is the same size as both the SMF6531HT, and SMF6533HT.  All are less than 1/4" (6.10mm) in length.  That means you can pack a lot of voltage in a very small package.  For precise dimensions and recommended pad layout, see below.
Physical Dimenions of the SMF6533HT High Temp, High Voltage Diode

Recommended Pay Layout

The dimensions are given in inches, with mm in parentheses. 
Pad layout recommendations for SMF6531HT High Temp Diode
SMF6533HT Pad Layout

Data Sheet

For more information on the 200°C, 5kV, 50mA, 70ns, SMF6533HT diode, download the data sheet.  or contact VMI.

Tuesday, June 30, 2015

200°C High Temperature, High Voltage, 5kV Diode - SMF6533HT

SMF6533HT 5kV, 200°C,  Diode

Introducing VMI's latest addition to the 200°C, high temperature, high voltage diode family.
The SMF6533HT (HT for "High Temperature) is rated at 200°C.  It will block 5kV in the reverse direction and conduct 50mA in the forward direction.  Reverse Recovery Time (Trr) is 70ns or less.

Physical Dimensions

The SMF6533HT is the same size as the SMF6531HT, and less than 1/4" in length.  That means you can pack a lot of voltage in a very small package.  For precise dimensions and recommended pad layout, see below.
Physical Dimenions of the SMF6533HT High Temp, High Voltage Diode

Recommended Pay Layout

The dimensions are given in inches, with mm in parentheses. 
Pad layout recommendations for SMF6531HT High Temp Diode
SMF6533HT Pad Layout

Data Sheet

For more information on the 200°C, 5kV, 50mA, 70ns, SMF6533HT diode, download the data sheet.  or contact VMI.

Thursday, June 25, 2015

New 200°C High Temp, High Voltage Diode - SMF6531HT

SMF6531HT 3kV, 200°C,  Diode

Introducing VMI's latest addition to the 200°C, high temperature, high voltage diode family.
The SMF6531HT (HT for "High Temperature) is rated at 200°C.  It will block 3kV in the reverse direction and conduct 100mA in the forward direction.  Reverse Recovery Time (Trr) is 70ns or less.

Physical Dimensions

The SMF6531HT is less than 1/4" in length, which means you conserve board space.  For precise dimensions and recommended pad layout, see below.

SMF6531HT Physical Dimensions
Physical Dimenions of the SMF6531HT High Temp, High Voltage Diode

Recommended Pay Layout

The dimensions are given in inches, with mm in parentheses. 
Pad layout recommendations for SMF6531HT High Temp Diode
SMF6531HT Pad Layout

Data Sheet
For more information on the 200°C, 3kV, 100mA, 70ns, SMF6531HT diode, download the data sheet.  or contact VMI.

Tuesday, June 23, 2015

High Voltage, Voltage Multipliers

High voltage multipliers are used in many applications including image enhancement, instrumentation, CRT displays (remember them?), high voltage power supplies, and more.

High Voltage

"High Voltage" for a VMI voltage multiplier is anything with a voltage output between 1kV and 120kV.  Output currents range from nA to ten's of Amps, and depends largely on size constraints and output voltage.   

Custom Multiplier Designs

Most of VMI's multipliers are custom designs.  When a customer first contacts us with their requirements, we review the information, and usually give them a call back with questions.  VMI understands that not all parameters are known up-front, and not all of them are important.  For instance, some applications run multipliers in large oil tanks with ample space.  Size limitations are less critical than, say, a multiplier going on a satellite or space probe.

We ask questions because we want to meet the customer's needs, with the understanding that the information may change, or it may be unknown, or to-be-determined.    

Conflicting Design Parameters

Sometimes it isn't possible to meet all the requirements.  The customer may have to prioritize which characteristic is more important. 

For example, you need a low ripple of 100mV, but you also need it to be very, very, small.  In fact, maybe your desired dimensions are not large enough to accommodate the capacitors needed to meet the 100mV ripple.  In that situation, you get to choose between low ripple voltage or small size.  There are options available , and VMI will present them to you.  For instance, if size is the number one priority, then perhaps an external filter could be used.  Or, if the part will be operating at room temperature, then maybe a capacitor with a high dielectric at room temperature could be used.  

Multiple Iterations Are The Norm

Often the first go-round generates more questions, and more options, and because VMI engineers are easily accessible, it makes the design and development process smooth. 

Cut-Away View of a Typical 6-stage Voltage Multiplier

Contact Us

Feel free to contact VMI with your voltage multiplier requirements.  If we can't assist you, we'll help you find someone who can.

Thursday, June 18, 2015

High Voltage Multipliers

VMI makes several standard multipliers, namely the Hybrid Multipliers found here.  They typically

Surface Mount Multipliers
have 3kV to 14kV outputs, and low current - 50uA to 200uA.  They are small, reliable, high voltage, low current, surface mount multipliers.  And they're standard products.

Custom Designed High Voltage Multipliers

But what happens if they are not exactly what you need?  Well, it's VMI to the rescue!  VMI is one of the few remaining companies who design custom multipliers.  We'll ask you a few questions and take it from there.

If you don't know the answer to the questions we ask, we'll help you answer them.  It's really that simple.  Of course, the more information you have going in to a new design, the better, but we understand that not parameters are clearly defined in the beginning, or they may change.  That's okay too.  We're flexible.

Design Questions

Below is a sampling of the kinds of questions you might be asked during the design phase to better help us understand your particular needs and application.  

Here goes - 

  •  How many stages do you want in your multiplier?
  • What size/shape is acceptable for your multiplier?
  • What is your input voltage?
  • What is your input frequency?
  • Do you have ripple requirements? Regulation requirements?
  • Do you want the multiplier to be surface mount?
  • Any information you can provide on the application?
  • Environmental factors (temperature, altitude, moisture, etc.)?
  • Target price?
  • Quantity (annual, prototype, etc.)?

Based on the information you provide, we can help you get exactly the multiplier you need for your application.

It's that easy!

JANTX Level Processing

Voltage Multipliers Inc. continues to manufacture several military-grade, JANTX, and JANTXV high voltage diodes in accordance with Mil-Prf-19500.

JANTXV Processing Capability

What you may not know is that VMI has the capability to process non-QPL diodes to the JANTX or JANTXV levels.  We can't certify them as JANTX/JANTXV, but they have been processed as if they were JANTX/JANTXV diodes.  The same tests, conditions, sampling plans, and read-and-record data, still apply.  

1N6525U and 1N6517US High Voltage Diodes

QPL Surface Mount Diodes
For example, the 1N6525U is a 5kV, 150mA, 70ns, surface-mount diode, and is basically a commercial device.  It can be processed to the JANTX or JANTXV level, but cannot be labeled as such.

QPL and Non-QPL Part Number Designations

In comparision, VMI is qualified to manufacture (QPL'ed) the 1N6517US (note the "S" on the end of the part number).  The part number is specified in the governing slash sheet (Mil-Prf-19500), and includes an "S" on the end.  The 1N6517US is a 5kV, 2.0A, 70ns surface-mount diode.  It can be processed to the JANTX or JANTXV level.  It's full part number would be JANTX1N6517US or JANTXV1N6517US, depending on the level of processing needed.    

Coming Soon!

VMI is pursuing qualification of the formed leaded devices and the SXF/SMF devices, so check our list of QPL devices often.  

Tuesday, June 16, 2015

To Be, or Not to Be Digital! THAT is the Question! Part 3

The ViPS-40 has several advantages over standard analog control power suppliers.  

In our previous post, we outlined several challenges to integrating the tube power supply into an X-ray system. 

During the design and development stages, tube characteristics are often in flux, which means the power supply outputs are subject to change.  

When power supply outputs change, so can physical or electrical characteristics - either of which can send a designer back to the drawing board.  The ViPS40 can prevent having to start from scratch with it's adjustable outputs, for just such an occasion.  

You're not locked into tube characteristics because you have room to move.  Sweet!    

ViPS40 Features

ViPS40 PC User InterfaceTube Tracking

A unique feature of the ViPS40 not available in analog controlled power supplies is the ability to record the life-time of the x-ray tube, and to track and display the tube ‘on’ time.

Programmable Outputs

The ViPS40 power supply can be easily reprogrammed to support different outputs, putting you in charge.  Move with ease from application to application with no software changes.  Just enter the desired voltage outputs, current outputs, control inputs, and operating limits through a user-friendly PC-interface.  The ViPS40 puts you in control.

Real-time Monitoring

Operating conditions like temperature, output voltage, and output current levels can be constantly monitored.  You can also adjust the voltage and current levels of power supply through the interface.  The ability to monitor real-time conditions gives the design engineer information and the ability to maximize system run-time, to determine likely failure, minimize down-time, and provide valuable data to a Repair Technician. 

Advantages of the ViPS40

Lower Component Count

The lower component count keeps costs down without compromising on regulation and output control.  

Integrated Protection and Auxiliary Functions

Protection functions such as over-voltage, over-current, and over-temperature, are easily integrated.  Auxiliary functions like fan control and data logging are available.  The ViPS40 is capable of storing power supply voltage and current levels, and filament voltage levels.

Firmware Changes Not Required

No changes to firmware means faster system integration time, and lower integration costs.

Yes, high voltage design can be exciting and fun! 

Contact VMI for more information!

Thursday, June 11, 2015

To Be, or Not to Be Digital! THAT is the Question! Part 2

In the first post we discussed high voltage x-ray tubes and system, and interesting things about high voltage designs.

In this post we'll discuss the challenges to integrating high voltage power supplies into x-ray systems and introduce the ViPS40, 40kV high voltage power supply.

Challenges to Integrating High Voltage Power Supplies

Power supply integration is more difficult when tube characteristics are in flux, as is often the case during the design and development stages.  Further, some power supplies have fixed inputs or outputs making them less adaptable to different tube parameters, and requiring hard ware changes, which slows down the development process. 
From a manufacturing perspective, the more applications one power supply can be used in, the better for inventory levels and component counts.  One power supply used in several applications may increase the volume, triggering volume discounts.  This makes it even more attractive.  

To Go Digital, or Not to Go Digital.  THAT is the question!  Or is it?

Good news!  You CAN have it all.  Or at least, the best parts of the digital and analog worlds because digital and analog are no longer mutually exclusive.       
Now there is a high voltage power supply that will help you monitor, power, and control, your x-ray tube - digitally.  

ViPS40 Solution 

The ViPS-40 is one of the first of its kind – a digitally controlled, PC-based, fully programmable 40kV power supply designed specifically for high voltage x-ray applications.
Standard features such as fully programmable output voltage and current set points, and a soft-start function to limit in-rush current, are controlled via the digital control loop.    

In our next post we'll delve deeper into the ViPS49 features, and why it's your high voltage solution.

Tuesday, June 9, 2015

To Be, or Not to Be Digital! THAT is the Question! Part 1

In the first of three posts, we'll look at the advantages and drawbacks of analog and digitally-controlled high
voltage power supplies.

To Go Digital, or Not to Go Digital.  THAT is the question!

 X-ray system designers and power supply engineers have enough headaches deciding between analog or digital controls in low voltage designs. 

Did You Know?

For starters, low voltage designs differ from high voltage designs in that low voltage designs are not usually concerned with corona (that fun thing that happens when trapped gas is repeatedly polarized over time, resulting in insulation degradation and shorts), or unintentional solder peaks that serve as lightning rods for arcs, or board spacing through air or other mediums.    
The use of high voltage increases the complexity of the design and the decision making process because of these special circumstances, making the “analog or digital” decision even more difficult.    

High Voltage X-ray Tubes and Systems

If you’re working with x-ray systems and tubes, you understand how challenging it can be to accurately control the power supply that controls the tube.  Direct output measurements are not always available and sometimes feedback signals are not easily verified.     
Specialized applications coupled with the growing X-ray analysis market mean high voltage power supplies are not just an afterthought, like in the good old days.  X-ray tube power supplies can, and should, play a central role in X-ray system design.  The sooner the power supply can be integrated into the system, the better. 

In our next post, we'll look at the challenges of integrating high voltage power supplies, and what that means to design engineers.

Tuesday, May 26, 2015

Soldering High Voltage Diodes

Occasionally VMI receives a customer inquiry regarding recommended soldering practices for our axial-leaded diodes.

Methods for Soldering High Voltage Diodes


Normally an axial-leaded diode would be hand soldered, but there are instances where it could be wave-soldered.  Wave-soldering does not typically require a thermal shunt or heat sink.

Hand Soldering

When hand soldering, VMI recommends using a soldering iron with a 600 degree F tip for most tin/lead solders, and a 700 degree F tip for lead-free solders such as Sn96.

Soldering Station - Image Credit
Although other factors can impact the soldering process such as the size of the connection, lead thickness & material, the type of parts being joined, the typical dwell sime should be completed within three seconds.

This same soldering practices can apply to VMI's high voltage rectifiers such as the SPJ high voltage stacks, SP high voltage stacks, and the high current, high voltage FP rectifier stacks.

Friday, May 15, 2015

When Changes to Standard Products Adversely Effect Customers

According to the Pew Research Center, as of October 2014, 90% of American adults have cell-phones, and of that 90%, 64% have smart phones.  If you're reading this post, you are most likely also a cell phone user, and odds are better than 50/50 that you use a smart phone to boot.

Those Annoying Automatic Software Updates

So where am I going with this?  Well, if you have a smart phone, you also have been, or will be, subjected to those pesky little automatic soft-ware updates that happen in the middle of the night while you're sound asleep.  You wake up the next morning to find your phone icons rearranged, or annoying notifications from apps you never use, never downloaded, and don't want.  If it's a really bad one, you might lose contact information.  Now, I know they say that never happens, but it does.

Well, the same kind of thing can happen with just about any standard product, be it a smart phone, a high voltage diode, or a sprinkler valve.

Data Credit

Fighter Jets and Standard Parts

What happens when the manufacturer makes necessary changes to a standard product, and the product has already been designed into a sub-assembly that goes on a fighter jet, for example?  (This would never happen because fighter jets don't typically use standard products, they use custom ones, or highly tested 'commerical' ones, or something like that).

It becomes a bit of a conflict because, by definition, most manufacturers of standard products reserve the right to make changes to the product.  It says so on their data sheets - "Specifications Are Subject to Change".  That phrase allows the company to respond to market pressures, react to material shortages, improve reliability, make process changes, or deal with a myriad of problems that may arise, quickly and efficiently.

On the Other Hand

On the other hand, what happens when a customer designs in a part, and the changes made by the manufacturer start to effect the customer's yield, or performance?  That's where it gets tricky.  The automobile industry deals with that situation a lot.  The questions become complex very quickly.  Of course, it's an easy decision to make if the changes or defects impact reliability or safety, but the waters get a little murkier when quality or reliability are not impacted.

While every situation is different, VMI's position is that we will support our customers through changes made to standard products, and we won't make changes to custom devices without our customer's approval.

That's just one of the things that makes VMI's customer service second to none.


Thursday, May 7, 2015

R.I.P. Mercury Messenger Space Probe

NASA's Messenger probe crashed into the surface of Mercury at 3:26 p.m. EDT on April 30th.

Planet Mercury
Launched more than ten years ago, Messenger far exceeded it's design specifications.  Originally designed to expire after orbiting planet Mercury for a year starting in 2011, it continued to operate and respond to commands for another three years.  The probe finally just ran out of fuel.

During it's operating lifetime, Messenger confirmed layers of frozen water on Mercury's poles, and provided an opportunity for NASA to test out heat-resistant shade cloth and ceramics by exposing it to temperatures in excess of 700F.

Messenger's Landing Place

R.I.P. Messenger....


"Messenger:  Highlighted Team Member - Carl Jack Ercol",   http://messenger.jhuapl.edu/who_we_are/member_focus_06252009.html, retrieved 5/5/2015.

"In its final act of defiance, NASA’s Messenger probe prepares to crash into Mercury’s surface and die", http://www.electronicproducts.com/Aerospace/Spacecraft/In_its_final_act_of_defiance_NASA_s_Messenger_probe_prepares_to_crash_into_Mercury_s_surface_and_die.aspx

Tuesday, May 5, 2015

Customer Driven Testing on High Voltage Surface Mount Multipliers

Recently a customer needed additional information about one of VMI's surface mount, high voltage, voltage multipliers.  They were seeing something unusual in their system, and were wondering whether it could have something to do with the multiplier.

After sending application specific info, VMI engineers were able to devise a relatively simple test that ultimately gave them the information they needed.  As it turns out, the question was answered by testing a few samples under specific loads, at a constant frequency and input voltage.  The data was then graphed.  It is presented below for your convenience.

Basically what the graph shows is a tendency for the output of the multiplier to drop as the load current increases.  There's no surprise there, since the per-stage capacitors are small - less than 1000pf, and typical load currents for a device of this type is in the 50uA range.

Data was collected at an operating frequency of 40kHz.  Vin was kept steady at 600Vp-p input.  The device under test, VM1548, is a standard, 4kV, six stage multiplier.  The graph shows that at 50uA load current, the output voltage will be just under 1700Vd.c.  At a load current of 212uA, the output voltage will be just over 1200Vd.c.  Your results may vary since operating frequency and input voltage impact the output voltage.      

Vo vs. Io - VM1548 Surface Mount Multiplier
Providing data to help customers answer questions or solve problems is something Voltage Multipliers Inc, is good at.  If you have a question about one of our products, please contact us.  It may be that there are tests we can do to help out.  High voltage is a niche, and VMI has a lot of high voltage test equipment.  We test our own devices.

And we've found that when a customer has a question, we can learn something too.

Tuesday, April 28, 2015

Prevent Board Failures with Hermetically Sealed High Voltage Diodes

VMI manufactures glass body, hermetically sealed, high voltage diodes, along with epoxy, non-hermetically sealed, high voltage diodes (among other things).

"Hermetically sealed" implies "air tight", and is usually taken to mean "liquid proof" as well.

What's the difference between an epoxy diode and a glass diode?  

The terms "epoxy" and "glass" refer to how a diode p-n junction is passivated.  Without passivation, and because the distances involved are so short, any applied voltage across a p-n junction would cause it to arc in an unpassivated device.

Passivation is required to prevent internal arcing.  In a glass passivated diode, commonly referred to as 'glass diode', or 'glass-body diode', a glass slurry is applied to the diode junctions.  The device is then fired at a high temperature to solidify the glass.  During the firing process, the glass shrinks and bonds to the surface of the silicon wafers.  Once the glass is fired, the diode is hermetically sealed and passivated.  It can survive a high reverse voltage without arcing.

An epoxy diode uses a specially adapted varnish capable of withstanding high temperatures and high voltage to passivate the diode p-n junctions.  The varnish is applied to the p-n junctions.  Once the varnish has dried and cured, the assembly is encapsulated in a rigid epoxy.  At that point, the diode can be tested, and a high reverse voltage applied.

Hermetically Sealed Advantages

The primary advantage of using a hermetically sealed diode is that it is impervious to liquids and gases.  If it wasn't, chances are a penetrating liquid or gas would short out the diode junctions and the diode would not be able to block reverse voltages.  

When installed on a printed circuit board (PCB) that is immersed in cleaning solvents, a hermetically sealed diode offers a significant advantage over a non-hermetic device.  Unsealed components often require a bake-out after the cleaning process.  Sometimes even a bake-out, where the PCB is subjected to dry heat at temperatures high enough to drive off all liquid solvents, is not enough to salvage an assembly.  Solvents are used to clean excess solder or flux residue from printed circuit boards.  A hermetically sealed device will not absorb the solvent.

Why is a Hermetic Seal important?  

In the case of a diode, the glass passivation also serves to protect the junctions.  If the diode absorbed liquid, and it penetrated deep enough into the device, the liquid could short out the junction so that when a reverse voltage was applied, the diode would not block it.  The diode would appear to be shorted.

K-Body High Voltage Diode


The main disadvantage of a hermetic device is they generally have lower voltage and current ratings than a comparable epoxy encapsulated diode.  The K50UF, 5kV diode is rated at 2.2A compared to the 1N6517 5kV diode rated at 1.0A.  Several factors are at work, but K-body diodes can get the heat out faster than an equivalent glass-body diode, which means they can handle higher reverse voltages and forward currents.

A second disadvantage of epoxy type diodes such the K-body type, is cost.  Epoxy diodes with a varnish passivation are typically more expensive.  That does not apply to epoxy over-molded glass-passivated diodes such as the SMF6533, or SXF6525.  The SMF6533 and SXF6535 take a hermetically sealed diode and over-encapsulate it.  The advantage of these devices is they are surface mount, easily pick-and-placed, and the diode is hermetically sealed.

Choosing the right diode for your application is critical to the success of your project.  Different diodes offer different advantages.  If you're not sure which diode is right for you, give us a call.  

Wednesday, April 22, 2015

Slashing Water Usage in High Voltage Diode and Assembly Manufacturing

Folsom Lake - Just North of Sacramento 
California continues to suffer from a severe drought, going on four years now.  

Water Wars

For many years, water has been a controversial issue, often pitting regions of the state against one other in legal battles.  One only has to look to Mono Lake and the Owens Valley, as a prime example of water wars fought on paper and in the courts.

San Joaquin Valley 

Voltage Multipliers Inc., is centrally located in the great San Joaquin valley - also known as the breadbasket of the world.  The San Joaquin valley boasts an incredible amount of food grown and exported all over the world.  At least it used to.  The lack of rain fall, almost non-existent snow packs, and lower water tables are threatening that way of life.

Californians are hunkering down and really working hard to reduce water usage and waste.

Sample of an Industrial Sized PH-Treatment System 


This blogger has worked at VMI for almost 25 years and can personally vouch for VMI's environmental policy.  VMI's policy can best be summed up as "do the right thing".  To that end, throughout the years, VMI has continuously worked to improve water efficiency, reduce water use in ALL manufacturing processes, and to re-introduce the water VMI does use, back into the water supply even cleaner than when it came in.  VMI's company culture has always encouraged employees to be innovative when it comes to using natural resources - above and beyond any legal requirements.

Team Effort

Filtration and water chemistry are extremely complex, as are cleaning processes involving solder and solvents. The question of what to do with any left-over residue from the filtration/purification system requires continual assessment.  We live in a state with complicated environmental laws that sometimes conflict with local and state laws and makes navigating them difficult.  Fortunately, VMI has a great team of Chemical Engineers and Process Engineers who work closely with environmental agencies and suppliers to keep VMI up-to-date in the latest clean-manufacturing technology.

Regardless of the cause, it's hard to argue that climate change isn't real.  The results of a four-year long drought are being felt.  There is no end in sight to the drought.  If we are to survive, changes need to be made.  The people at VMI continue to work towards minimizing our environmental footprint, and in this case, it means using less water, and making the most of the water we do use.

Benefits to VMI's Customers

Constant innovation works to benefit customers too.  When fewer resources are used, or used wisely, the result is improved efficiency that translates to lower costs and faster delivery.

We plan to be around for many, many years to come.  We're doing our part to conserve resources while delivering products to our customers that meet, or exceed, their specifications.

Thursday, April 16, 2015

Peek Behind the Scenes at VMI - Our People, Products, and Processes

Voltage Multipliers Inc., recently released three videos outlining who we are, what we do, and how we do it.

We're pleased to provide links to the videos below.

VMI's People, Products, and Processes provided is approximately 8 mins. in length.  In it, Dennis Kemp, VMI President, explains our goals and guidelines to get there.  You'll see Daniel Deschenes, Technical Sales Engineer, give a plant tour as he explains the high voltage diode manufacturing process.

Also included is information on how a 10kV optocoupler operates, as explained by Daniel.  Later on, Dr. Alex Jiang introduces the ViPS40 40kV high voltage, digitally controlled power supply, and demonstrates how the PCB interface is used to control it.  He discusses the advantages of an embedded control system.

Two shorter, break-out videos are available.

One is the ViPS40 High Voltage Power Supply demo by Dr. Jiang, the other is the Optocoupler Demo by Daniel Deschenes.

Both are included in the longer "People, Products, and Processes" video.

Wednesday, April 15, 2015

VMI Sales Representatives in Texas - Meet Delta Components

New Sales Representation in Arkansas, Louisiana, Oklahoma, and Texas 

VMI is happy to announce our association with Delta Components, our sales representatives for Arkansas, Louisiana, Oklahoma, and Texas.

Mike and Natasha West are second generation Delta Component representatives. VMI originally worked with Jim and Betty West, Mike's parents, until their retirement. Now, Mike and Natasha are at the helm. We're excited to have them back.

Delta Components

Area Coverage

Delta Components represents the area of Texas in the lighter shade. (For all other areas in Texas, contact Proper Source). Delta Components represents all of Arkansas, Louisiana, and Oklahoma.

Mailing Address

P.O. Box 700
Crandall, TX

(P) 972.375.5809