On Thu, Mar 25, 2021 at 05:25 PM, Dave Peterson wrote:
I found it likely _not_ merely coincidence that this transistor has failed
_and_ has some form of manufacturing defect. An engineering axiom brought to
my attention some time ago is that engineers/designers/manufacturers rarely do
or add anything without good reason. I doubt the "goo" is there only to secure
the leads. Mind too that these particular components were manufactured by
Tektronix in the late 60's or early 70's. I don't think the industry had quite
settled down at that time. Wink. My use of passivation seemed an apt term.
Perhaps I should have stuck with goo. Wink.
I really don't see a manufacturing defect. Your image shows the underside (base) of the package, with its glass(-like) lead feed-throughs. Packages are purchased by the transistor manufacturer complete with leads and feed-throughs. There is a plateau on top, where the semiconductor chip (die) is affixed by the transistor manufacturer. The chip itself is passivated/glassivated during chip production. A cap is placed on top of the base during manufacturing, completely enclosing the die hermetically.
TO-5 cases' bottoms often look similar. With TO-39's, the glass is usually just visible as a thin "ring" around each lead (usually base and emitter), flush with the package bottom.
Raymond
Raymond Domp Frank