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

Thursday, April 9, 2015

Don't Need Mil-Grade Processing?

Voltage Multipliers Inc. 
Last time, several high voltage QPL diodes, and their data sheets, were presented.  But what if you don't need a mil-grade device?  What if you need just a little testing?  Don't be dismayed.  There are options. 

Mil-grade Processing Too Expensive, or You Don't Need All that Testing?

For QPL-lite testing, visit VMI's Screening Guidelines. The screening guidelines are based on Mil-Prf-19500, but are not as lengthy in duration, and are much less costly.

VMI has developed Screening Guidelines for

  • Discrete High Voltage (HV) Diodes
  • Bridge Rectifiers
  • HV Components
  • HV SM/Hybrid Multipliers
  • Over-molded Diodes 

JANS Level

VMI is not qualified to JANS level, but we have performed equivalent testing in accordance with customer specifications. If you have a need for a JANS device, we may be able to help.
Custom Testing

If you have a special requirement for high voltage testing, contact us. We offer many tests not available from other manufacturers. 

Tuesday, April 7, 2015

QPL High Voltage Diodes

Voltage Multipliers Inc.
VMI maintains two Mil QPL levels on several high voltage, discrete diodes. They are JANTX and JANTXV.


JANTX and JANTXV testing includes extensive Group A, Group B, and Group C testing that ranges from physical, electrical, life testing, to destruct testing, based on Mil-Prf-19500. Test parameters are called out in the device's associated slash sheets (/575, /576, 577). Tests are usually performed at rated voltages and currents. Depending on the device, some undergo Power Burn-in, High Temperature Reverse Bias, Thermal Shock, and more.

QPL Diodes

Available axial-leaded diodes range from -
  • 2kV 2A devices to 10kV 500mA devices.

Surface mount devices range from -

  • 3kV 3.5A devices to 5kV 2A devices. 

For more information on QPL processing, check out Mil-Prf-19500.

For more information on VMI's high voltage QPL diodes, visit our QPL page. 

QPL JANTX and JANTXV Diode Data Sheets


There are axial-leaded, hermetically sealed, high voltage diodes.  They range from 2kV to 10kV, and 10mA to 500mA.  Devices in the same row are found on the same data sheet. 

Surface Mount

The 1N6515US and 1N6517US surface mount diodes are basically the same device as the axial-leaded diode, with the exception of the terminations.  Instead of an axial lead, the SM diodes use a copper tab.  To prevent oxidation and ensure solderability, the tabs are coated with a tin/lead solder.

They range from 3kV to 5kV, up to 3.5A.  

Don't Need Mil-grade Processing?

For QPL-lite testing, visit VMI's Screening Guidelines. The screening guidelines are based on Mil-Prf-19500, but are not as lengthy in duration, and are less costly.

VMI has developed Screening Guidelines for

  • Discrete High Voltage (HV) Diodes
  • Bridge Rectifiers
  • HV Components
  • HV SM/Hybrid Multipliers
  • Over-molded Diodes 

JANS Level

VMI is not qualified to JANS level, but we have performed equivalent testing in accordance with customer specifications. If you have a need for a JANS device, we may be able to help.
Custom Testing

If you have a special requirement for high voltage testing, contact us. We offer many tests not available from other manufacturers.