PD243X, PD353X, PD443X

2006-01-23

14

Post Solder Cleaning Procedures

The least offensive cleaning solution is hot D.l. water (60°C) for

less than 15 minutes. Addition of mild saponifiers is acceptable.

Do not use commercial dishwasher detergents.

For faster cleaning, solvents may be used. Carefully choose the

solvents as some may chemically attack the package. Maximum

exposure should not exceed two minutes at elevated tempera-

tures. Acceptable solvents are: TF (trichlorotrifluoroethane), TA,

111 Trichloroethane, and unheated acetone.

(1)

Note:

1)

Acceptable commercial solvents are: Basic TF Arklone P.

Genesolv D, Genesolv DA, BlacoTron TF and Blaco-Tron TA.

Do not use solvents containing alcohol, methanol, methylene chlo-

ride, ethanol, TP35, TCM, TMC, TMS+, TE, and TES. Since many

commercial mixtures exist, you should contact your preferred sol-

vent vendor for chemical composition information. Some major sol-

vent manufacturers are: Allied Chemical Corporation, Specialty

Chemical Division, Morristown, NJ; Baron-Blakeslee, Chicago, IL;

Dow Chemical, Midland, Ml; E.l. DuPont de Nemours & Co., Wilm-

ington, DE.

For further information refer to Appnotes 18 and 19.

An alternative to soldering and cleaning the display modules is to

use sockets. Naturally, 20 pin DIP sockets 15.24 mm (0.600")

wide with 2.54 mm (0.100") centers work well for single displays.

Multiple display assemblies are best handled by longer SIP sock-

ets or DIP sockets when available for uniform package alignment.

Socket manufacturers include: Aries Electronics, Inc., French-

town, NJ; Garry Manufacturing, New Brunswick, NJ; Robin-

son-Nugent, New Albany, IN; and Samtec Electronic Hardware,

New Albany, IN.

For further information refer to Appnote 22.

Optical Considerations

The character heights of these displays allows readability up to

eight feet. Proper filter selection allows the user to build a display

that can be used over this distance.

Filters allow the user to enhance the contrast ratio between a lit

LED and the character background. This will maximize discrimina-

tion of different characters as perceived by the display user. The

only limitation is cost. So first consider the ambient lighting envi-

ronment to maximize the cost benefit ratio for using filters.

Incandescent (with almost no green) or fluorescent (with almost no

red) lights do not have the flat spectral response of sunlight. Plas-

tic band-pass filters are inexpensive and effective in optimizing

contrast ratios. The PD2435/3535/4435 is high efficiency red dis-

play and should be matched with a long wavelength pass filter in

the 570 nm to 590 nm range. The PD2436/3536/4436 is a stan-

dard red display and should be matched with a long wavelength

pass filter in the 600 nm to 620 nm range. The PD2437/3537/4437

should be matched with a yellow-green band-pass filter that peaks

at 565 nm. For displays of multiple colors, neutral density grey fil-

ters offer the best compromise.

Additional contrast enhancement can be gained through shading

the displays. Plastic band-pass filters with built-in louvers offer the

“next step up” in contrast improvement. Plastic filters can be fur-

ther improved with anti-reflective coatings to reduce glare. The

trade-off is “fuzzy” characters. Mounting the filters close to the dis-

play reduces this effect. Care should be taken not to overheat the

plastic filters by allowing for proper air flow.

Optimal filter enhancements for any condition can be gained

through the use of circular polarized, anti-reflective, band-pass fil-

ters. The circular polarizing further enhances contrast by reducing

the light that travels through the filter and reflects back off the dis-

play to less than 1%. Proper intensity selection of the displays will

allow 10,000 foot candle sunlight viewability.

Several filter manufacturers supply quality filter materials. Some of

them are: Panelgraphic Corporation, W. Caldwell, NJ; SGL Homa-

lite, Wilmington, DE; 3M Company, Visual Products Division, St.

Paul, MN; Polaroid Corporation, Polarizer Division, Cambridge,

MA; Marks Polarized Corporation, Deer Park, NY; Hoya Optics,

Inc., Fremont, CA.

One last note on mounting filters: recessing display and bezel

assemblies is an inexpensive way to provide a shading effect in

overhead lighting situations. Several Bezel manufacturers are:

R.M.F. Products, Batavia, IL; Nobex Components, Griffith Plastic

Corp., Burlingame, CA; Photo Chemical Products of California,

Santa Monica, CA; I.E.E.Atlas, Van Nuys, CA.

See Appnote 23.

Published by

OSRAM Opto Semiconductors GmbH

Wernerwerkstrasse 2, D-93049 Regensburg

www.osram-os.com

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