Issues Realting to How to Derate Transistors and Resulting Failures

There are two main pages in this section of the web site; How to derate Transistors by Temperature [Power x Temperature], and Diode Derating [Current x Temperature]. An interrelated page details how to read and Interpret Temperature Derating Curves, which works for diodes or transistors.

 One of the new pages covers component mounting consideration, as Lead Length vs Thermal Resistance [power dissipation for leaded parts]. This particular topic shows why lead length is an important consideration in component power dissipation [in addition to increased circuit inductance]. A companion page covers Copper Pad Area vs Thermal Resistance, to address surface mount components.

The second new page covers Junction Temperature and Wirebond Life, the bond holding the wire between the semiconductor chip and package lead frame. Wire-Bond failure rate vs junction temperature is another way to cover the same topic as the derating charts already do; However, some derating curves do cover ambient temperature, heat-sink temperature and case temperature, in addition to junction temperature.

Related links include Maximum Safe Operating Area,
Over the last 30 days I have added almost 30 new pages, but they were so inter-related that I didn't think blogging about them would really help. Either each blog posting would read almost the same or they would have had almost no text. So I'll generated a new xml site-map for Google in a few weeks to catch the new pages, or wait until Google reads the pages their linked from. In the mean time I have been adding links to the new pages to the human readable [html] sitemap that covers the site [Engineering Site-Map].

So these are two of the nearly 30 new pages added over the last month. I may add them in a larger posting rather than one posting per new page.

TO-276 Three-Terminal Surface Mount Package

What is a TO-276 device?
A 3-Terminal Surface Mount Component, shown on; TO-276 Transistor Package.
As discussed on that page the package may be used for any number of different semiconductors, but the term transistor is used in general. As with all the other related packages the TO-276 page is linked off the Transistor Packages page.

There's not much left to say, as this posts relates to the last two previous posts, which have already covered every thing.

This is the first surface mount package added to that section of the web site, all the other pages cover some type of through hole package. However I have had pending data on several other surface mount styles but the data has not been added yet because I been working other site issues ~ I'm not sure if I can add yet another package type in the next few days or not. Of course the Site-Map was also up-dated.

Transistor Die Bonding

Component Derating Guidelines

In support of the section on Transistor Derarting, a page was added to explain how to Interpret the derating Curves. Many of the pages already had some text regarding reading the graph, but why keep adding more text to each page if it's the same over and over. The 'How-to' page uses a derating graph from a 2N2904 Transistor, in a TO-39 metal Can.

It was just random chance that I added a picture of a 2N3637 SOA in this posting. I already had a page covering that topic out on Google Sites; Maximum Safe Operating Area.
Normally I don't post new pages added to Google Sites, but I did add two pages today [no text yet]. The internal Construction of a Capacitor, and the internal Construction of a Resistor.

Any other page changes [to either site] today were just small updates.

Graph; Safe Operating Area [SOA] Power Curve, 2N3637 Transistor.

Relay Derating

I just notice that the page covering How to Derate a Relay was never listed in the blog when it was added to the web site. Looks like the page was added back in March, or at least that was the day of the first page view.

The page doesn't get that many hits, just a few a-day. I went ahead and added a new link at the top of the page covering Manufacturers of Relays. Then I did the same thing to the page covering Manufacturers of Mechanical Relays.

I also removed two manufacturers links, one looks like it went bad and the other appeared to be a relay distributor. Also added a picture of a relay.

The three pages covering relay manufacturers have dropped 50% over the last three years. Seems odd, as the relay pages come up as number 1 and 2 on a Google search for relay manufacturers....

When to Dearte a Transistor

Copied another page on how to derate a transistor into two other pages that used the same derating chart.

2N4237 Temperature-Power Derating Curve, duplicated to.

2N4238 Derating Graph.

2N4239 Derating Graph.

A few other related pages in the section were also updated

2N3498 Derating Graph.

2N2906 Derating Graph.

2N3634 Derating Graph.

Some of these preexisting pages may not have ever been listed out here as new pages, so this may be their first posting. In any case it's yet another external link generated.

There are three different possible guidelines a designer can use when implementing a transistor circuit. 

1. The engineer may use a generic guideline using a simple Derating Factor;

     Example: Derate 50% up to a maximum junction temperature [Derating Factors].

2. The engineer may use a Linear equation which is more a design recommendation;

     Example: Derate Linearly at 12.7mW/ degree C, above 25C [Derating Recommendations].

3. The engineer may use a Temperature-Power Curve which should be treated as a design rule;

     Shown on any number of pages, [Derating Rules].

There were two other pages up-dated to hold the links for the page just generated;

Guideline to Derating Transistors, and Guideline to Derating NPN BJTs.

Addtional related pages on the web site:

Manufacturers of Transistors.

Transistor Amplifier  Circuits.

Transistor Circuit Schematics.

Transistor Multivibrator Circuit Schematics.

Definition of Transistor Terms.

Additional related pages on this blog:

Rules for Derating a Transistor.

Transistor Derating Guidelines.

Recommendation on how to Derate a Transistor.

Derate a BJT by Temperature.

FET Derating Guidelines.

NPN Transistor Derating Curve.

Power Derating for Transistors.

Rules for Derating a Transistor

Following yesterdays transistor posting, I've added two more pages relating to how to derate a particular transistor. Like the previous post the new transistor pages are near a copy of a preexisting page, that happened to use the same derating graph.

MIL-PRF-19500/539D:

2N6301 Temperature-Power Derating Curve [NPN BJT].

2N6300 Temperature-Power Derating Curve [NPN BJT].

MIL-PRF-19500/545G:

2N5153 Temperature-Power Derating Curve [PNP BJT].

2N5151 Temperature-Power Derating Curve [PNP BJT].

Three other page up-dates then followed;

How to Derate Transistors.

How to Derate NPN Transistors.

How to Derate PNP Transistors.

Which were updated to hold the links to the new pages. In addition each new page links to it's copy that holds the same MIL Spec and Derating Graph.

Also added a new line item to the Transistor Derating Recommendations page, which only provide Derating Equations with no Derating Curves.

It may of taken over a hour to generate the page up-dates but it was an easy way to generate two new pages and add more page to page links.In addition four other related pages were updated:

MIL-PRF-19500/396K;

2N3764 Temperature Derating Graph.

2N3765 Temperature Derating Graph.

MIL-PRF-19500/396K;

2N3762 Temperature Derating Graph.

2N3762U4 Temperature Derating Graph.

So in this derating sections there were 10 page up-dates and 2 new page additions. There were also another dozen unrelated page updates.

Guidelines to Component Derating.

Transistor Derating Guide Lines

Added a new page to cover power derating of a 2N3765 transistor. The page is almost a copy of the page for the 2N3764 transistor because they both use the same derating graph. Links have been added to their related transistors covered by the same specifications; 2N3762U4 transistor and 2N3762UA transistor, both surface mount devices. A reference was also added to the page covering PNP transistor curves, and derating transistors.

A few other unrelated pages were also up-dated, including;

Derating a 2N930.

Derating a surface mount 2N930UB.

2N718 derating graph.

2N1613 derating curves.

2N3055 transistor derating curves.

All the pages provide a Temperature-Power Derating Curve, and some also provide a derating equation. Use one or the other as a guideline for derating the device.

Related pages;

Recommendation on how to Derate a Transistor.

Derate a BJT by Temperature.

FET Derating Guidelines.

NPN Transistor Derating Curve.

Power Derating for Transistors.

Recommendation on how to Derate a Transistor

Starting with the long list of Transistor Derating Curves, I added in several transistor links to Transistor Derating Guidelines [which is the new page]. Or, recommendations on how to derate a transistor based on a linear equation, with no graphic [Derating Curve].

The new transistor links pick up missing devices in the list, but because I didn't have a derating chart they all point to the new page which provides the derating recommendation for each of the devices. The recommendation for each transistor is how much to decrease power dissipation over increasing temperature, mW/C [and that's all].

Two of the main links off the transistor derating page are NPN Derating Curves, and PNP Derating Curves, but I don't have any plans to add the new links to either of those pages.

Individual transistor pages not yet listed in the blog;
2N3250 Derating Curve.
2N3467 Derating Curve.
2N3485 Derating Curve.
2N3634 Derating Curve.
2N3740 Derating Curve.

A related list; How to derate FETs.
2N6764 Derating Curve.
2N6766 Derating Curve.
2N6768 Derating Curve.

How to Derate a Component.
Site Home page; Computer Bus pin Outs.

Derate a BJT by Temperature

I've posted about adding some pages covering transistor derating, but I never really linked any of the new pages here. I don't have any new pages to blog about, so I'll list a few of the pages covering transistor derating.

These are just a random sampling of a few pages;
2N2484 PNP Transistor.
2N2906 NPN Transistor.
2N3743 PNP Transistor.
2N4029 PNP Transistor.
2N6676 NPN Transistor.

There's nothing special about these pages, in fact a few seemed to be some of the smaller pages in the group. But they each point to other pages with the same or similar device in a different package style. So I'm really pointing to a dozen pages while only listing 5 here.

These pages were added around the first of December, and up-dated once to add more data. Looks like a few could still use some more data, but I'll be up-dating the pages that haven't changed yet.

FET Derating Guidelines

Derating guidelines for a 2N7000 Field Effect Transistor [FET] was added; 2N2700 Derating.
Unlike the other pages within the FET Derating section, this page only offers recommendations.
All the other pages, or many of them, provide derating curves that should be considered as absolute rules rather than recommendations.
Of course a FET is a style of Transistor, which are covered on the Transistor Derating Guidelines.

The over-all section is Component Derating, if you see a table than it's a guideline, while a curve will imply a rule. The goal is to not exceed the devices junction temperature.

The 2N27002 FET is also covered on the page link.
The 2N7000 device is a plastic TO-92 package, while the 2N7002 is a SOT23 plastic package.

Of course Connector derating guidelines and Cable derating guidelines are also provided within this section, neither of which have a semiconductor junction. Their package or molding is being derated. A Thermal Couple is used to monitor the body of the package for temperature increases. There's a limit to the number of wires in a cable or pins on a connector that can carry some amount of current. Sure one pin may handle an amp of current, but if the connector or cable has 50 leads, does it imply that the component can deal with 50 amps of heat dissipation [no].

For reference;
2N6770 Maximum Case Temperature.
2N6768 Maximum Case Temperature.
2N6766 Maximum Case Temperature.
2N6764 Maximum Case Temperature.

How to Derate Diodes at high temperatures

A few of the last posts were related to Transistor Derating Curves. Although that was a new page addition, none of the new pages listed or linked from that page were ever listed here ~ because there were more than a few new pages. Here are a few examples:
2N3762 Transistor Derating Curve.
2N4029 Transistor Derating Curve.
2N6249 Transistor Derating Curve.

Diode Derating Curves have also been added over the last month, with no sub-pages listed here. So here are a few examples of those as well.
1N4954 Zener Diode Derating Curve.
1N5968 Zener Diode Derating Curve.
1N6036 Diode Derating Curve, TVS.

These links are just a sample, the pages have been on the web for a month now and there is no longer a need to re-list them here. However I did want to point out that new pages have been added, but not listed in this blog.

I also started a page on Diode Package Styles, or discrete component packages. The component package styles page is still small with only five sub-pages, but it's a start.

NPN Transistor Derating Curve

In addition to adding more pages covering Transistor Derating Guidelines, two new pages were added to subdivide the listing.

One page covers NPN Transistor Derating Guidelines, while another page covers PNP Transistor Derating Guidelines. The new pages show each transistor link shown in a derating chart, even if the link points to a simular page already listed. One Temperature-Power Derating Curve may cover more than one transistor.