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.