Thursday, December 22, 2016

Running Diodes in Oil - New App Note

Voltage Multipliers Inc. LogoRecently concluded testing indicates that running high voltage diodes in oil may allow for operating beyond the forward current ratings (Io).

All cautions apply - we do not recommend exceeding the current rating of any diode without extensive testing in your application, and basically the trick is to keep the diode junctions cool.  In other words, strive to get the heat out.

Here's the App Note -  AN0400 - 1N6519 Power Dissipation in Oil

Give us a call if you have any questions - 559.651.1402, or visit the website for more app notes and FAQs.

1N6519 10kV 500mA 70ns high voltage diode
1N6519 - 10kV, 500mA, 70ns High Voltage Diode

Wednesday, December 21, 2016

How to Test Vf and Polarity in High Voltage Diodes

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High Voltage Diode Vf Testing

Here at VMI, by virtue of working in the niche high voltage area, we get all manner of customer questions about issues that are somewhat more complicated by virtue of our unique devices.  

Recently, a customer asked how they could confirm - 

              1)      The working ability of a high voltage diode 
              2)      Double-check the polarity of the device.


High voltage diodes have a higher VF than the ‘ideal’ model of 0.7V, so that many of the traditional ways of checking to make sure a diode is not failed shorted, or to verify the polarity of the device, will not work with high voltage diodes.  

Using a Fluke handheld multi-meter that has a diode check function, for instance, probably won’t be able to overcome the forward voltage of a diode, even at low currents.  A multi-meter is providing perhaps 2.4V and some of our diodes have a rated VF of over 30V!

VMI Vf and Polarity Test Methods

VMI measures the VF of our diodes using precision, current controlled power supplies capable of providing 50V or more.  Though not necessarily readily available to all users, the easiest way to test the polarity and functionality of a high voltage diode is a similar method.

Current Limiting

Current limiting a power supply to a low level of perhaps 100µA – 1mA and connecting it up to the diode will do the trick without much effort.  You need a power supply that can provide more voltage than the rating of the diode, but make sure the power supply is limited so that it cannot provide more voltage than the breakdown level of the diode. 

See the simplified block diagram below for an idea on how to connect the power supply up to the diode.  Depending on your power supply, you might need to use a current limiting resistor and an external current meter.

How To Tell the High Voltage Diode is Good

Once you have your setup, the diode should conduct your current (100µA – 1mA, depending on how you limited the supply) in the anode-cathode direction.  Reversing the current flow by flipping the diode to cathode-anode should block the current down to the leakage levels of the diode (less than 1µA).  If the diode conducts in both directions, then you have a failed (shorted) diode.  If current does not flow in either direction, you have a failed (open) diode.

Questions?  We would be happy to help, so give us a call - 559.651.1402.

Wednesday, June 15, 2016

Tom Rowan Jr., Former NASA Engineer, Has Retired

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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.