Wednesday, June 15, 2016

Tom Rowan Jr., Former NASA Engineer, Has Retired

Voltage Multipliers Inc. Logo
Congratulations to Tom Rowan, former NASA Engineer, and VMI Sales Representative for many years.

Tom was recently honored by NASA.  His name will be inscribed on the "Wall of Honor" at the NASM monument in Washington D.C.

In Tom's own words, "In January of this year, I turned 75 years old, so I decided to finally retire, after 55 years of working as an engineer and marketing consultant to this Aerospace and Energy Components industry.

A week ago, I received an "Award" from the National Air and Space Museum. That certificate announced that my name would be added to the monument walls at this DC museum, in about a month or so. This documentation is in recognition of all the amazing motion control devices I invented for the aerospace controls and motion devices which were used on NASA space vehicles between 1960 -  1973.

I really appreciate this special recognition, and want to share this announcement with some of my friends and family."

Tom Rowan Jr. - NASA Mars - Viking Soil Sampler

Tom Rowan Jr., Apollo 11 Moon Landing

Wall of Honor - Tom Rowan Jr.

Congratulations to Tom Rowan, Jr. upon retiring.  Best wishes in the years to come.    

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.