From: Victor Roberts
Organization: Roberts Research & Consulting, Inc.
X-Mailer: Mozilla 4.78 [en] (Win98; U)
Subject: Re: luxeon star leds
References: <3DDD9A57.58900EFB@RobertsResearchInc.com> <email@example.com> <3DDDB646.96D0D9D2@RobertsResearchInc.com> <3DDE7264.CD48F4F8@RobertsResearchInc.com> <firstname.lastname@example.org> <3DDEB081.884EC92A@RobertsResearchInc.com> <3DE03D65.932BF9BF@RobertsResearchInc.com> <3DE15871.EF8FF9EA@RobertsResearchInc.com>
Date: Mon, 25 Nov 2002 13:24:23 GMT
NNTP-Posting-Date: Mon, 25 Nov 2002 05:24:23 PST
Bob Wilson wrote:
> In article <3DE15871.EF8FF9EA@RobertsResearchInc.com>,
> Vic@RobertsResearchInc.com says...
> >Watson 'Atto Parsec' Name wrote:
> >> In article <3DE03D65.932BF9BF@RobertsResearchInc.com>,
> >> Vic@RobertsResearchInc.com talked about...
> >> > Watson 'Atto Parsec' Name wrote:
> >> > >
> >> > > I don't buy this convection from the top because I'm using the Luxeon
> >> > > Star/O which has the whole top of the LED covered by the lens
> >> >
> >> > You are certainly entitled to your opinion, but don't you
> >> > think that the lens assembly will have convective losses
> >> > when it gets hot? The lens assembly will, of course, get hot
> >> > under steady state conditions if the metal base is not
> >> > conected to a heat sink. Considering that the lens assembly,
> >> > including its cylindrical holder, has a much greater surface
> >> > area than the top of the "bare" Luxeon Star, the "convective
> >> > effect" should be more pronounced for a Luxeon with the lens
> >> > assembly than for one without.
> >> The heat from the aluminum base will conduct up thru the barel of the
> >> assy and be 'convected' away, as much if not moreso than the internal
> >That's a good point.
> Interesting that it is expected that any significant amount of heat will be
> conducted up through an insulating plastic barrel, that is only 1mm thick.
> Even more interesting how this can be expected to be significant, in view of
> the Luxeon LED itself, being mounted on a metal core PCB, and that being
> mounted to to a heatsink. Quite obviously any small amount of heat
> that manages to be conducted up the small cross section of insulating
> plastic barrel, will be totally insignificant when compared to that which
> flows through the large area of 0.1mm thick FR4 laminated to the aluminum
> backing directly behind the metal base of the LED, and directly into a
You are correct, if the Luxeon were mounted on a heatsink.
However, this whole discussion started because of some
unexpected results that were published about a Luxeon that
was NOT mounted on a heatsink.