7030 cool/cold white SMD LEDs and paper circuitry (using copper tape + 3M 9703 anisotropically conductive tape)

I was looking for some large-ish SMD LEDs to incorporate in a paper circuit, using copper tape for the traces, on a note card, to try out 3M 9703 tape (3M Electrically Conductive Adhesive Transfer Tape 9703), sometimes referred to as z-axis conductive tape because it doesn’t conduct laterally (from side to side, i.e. along the x-axis or y-axis) but only vertically, between the upper and lower surfaces of the tape material.

A cut-down segment of the longer tape of these LEDs that I found in the 'LARGE SMD LEDS' drawer in one of my components cases. — A cut-down segment of the longer tape of these LEDs that I found in the LARGE SMD LEDS drawer in one of my components cases.

These 7030 SMD LEDs, in a coiled tape of a hundred inside an unlabeled ziplock baggie, were the most suitable-looking occupants of a little drawer labeled Large SMD LEDs in one of my components boxes. I’d bought them years earlier and the bag was unlabeled, but I found by searching through my Taobao order history that they were cool or cold white 6V, 1W LEDs, but no model number or manufacturer was listed. The entry in my purchase history gives the forward voltage and power consumption and says it’s a dual LED (two LEDs in one package).

The original product listing is gone when I click through but the seller is still in business and selling different, but similar large SMD LEDs. I gather that the intended use may be for screen back-lighting.

One of the LEDs on a note card. Beneath the yellow phosphor material, you can see the outlines of two square LED chips (this is a dual-chip LED) connected by fine bond wires.

Underside of one of these LEDs. The oblong thermal pad is also part of the cathode (negative terminal). The other LEDs I've removed from the same bit of tape don't have a dark spot in the middle of the thermal pad. I'd guess it's corrosion. — Underside of one of these LEDs. The oblong thermal pad is part of the cathode (negative terminal). The other LEDs I’ve removed from the same bit of tape don’t have a dark spot in the middle of the thermal pad. I’d guess it’s corrosion.

Each of these LEDs has four legs (making them what seems to be termed a 4-SMD part) and a thermal pad on the bottom. The legs at the end with one curved corner in the white plastic case material on top and a bellybutton-like feature on the underside are the positive leads. The two legs at the opposite end are the negative leads. The thermal pad on the bottom is connected to the latter as well.

Closeup of the anode (positive) end of the underside of one of these LEDs. The bellybutton-like feature is probably an 'anode mark' and the text seems to be a serial number as it varies from one LED to the next. — Closeup of the anode (positive) end of the underside of one of these LEDs. The bellybutton-like feature is probably an ‘anode mark’ and the text seems to be a serial number as it varies from one LED to the next.

A closeup of the negative end of the underside of the same LED shown in the preceding image. Text reads 'AaE3'. — A closeup of the negative end of the underside of the same LED shown in the preceding image. Text reads ‘AaE3’.

The same features from a different LED from a different location on the same cut piece of tape. The serial number is different and the four-character string is 'KeCa'. — The same features from a different LED from a different location on the same cut piece of tape. The serial number is different and the four-character string this time is ‘KeCa’.

On its underside, each LED has an eight-character alphanumeric string identifier printed or etched into its white plastic case next to the bellybutton mark at the anode end and a four-character string inside an oval shape at the cathode end. These both differ from LED to LED, as you can see in the preceding images.

I used a Chinese SMD LED tester to run one of these LEDs. Apologies for the poor placement, LED catywompus between the tester's pogo pins, but it lights up). The number one on the screen is the power level of the tester. It can be bumped up, in increments of one, to a maximum of four and decreased stepwise to zero using the left and right double-arrow buttons. — I used a Chinese SMD LED tester to run one of these LEDs. Apologies for the poor placement, LED catywompus between the tester’s pogo pins, but it lights up).

I established continuity between the legs on each side and between the pad on the underside and the two legs on the other side (which would turn out to be the cathode) using my multimeter, working under a tabletop-arm-mounted magnifier with one of these LEDs embedded, belly-up in a finger-rolled blob of white Blu Tack, but I didn’t know which pair of leads were positive and which were negative.

SMD LEDs of this size (7030, i.e. 7mm x 3mm) seem to be rare. I couldn’t find anything very similar at Mouser or Digikey. Unlike these, the most similar-seeming LEDs for which I could find datasheets online had a mark at the cathode (negative) end and two of four leads, one on each side, marked nc (not connected or no connection).

On the first try after cramming one into a Chinese SMD LED tester, I lucked out and it turned on. The number 1 on the screen is the power level of the tester. It can be bumped up, in increments of one, to a maximum of four and decreased stepwise to zero using the left and right double-arrow buttons.

Zoomed-in view of the negative pins of the LED in the tester. Each cathode pin makes contact with a pogo pin.

Zoomed-in view of the positive pins of the LED in the tester. Each anode pin also makes contact with a pogo pin.

Below is a snapshot of part of a paper circuit I made using some of these LEDs and copper tape. The transparent material between the copper tape and the bottom of the LED is a small piece of 3M 9703 (3M Electrically Conductive Adhesive Transfer Tape 9703, often referred to as Z-Axis Conductive Tape). The things that look like air bubbles are particles of electrically conductive material that from the top of the tape to the bottom of the tape but not from side to side.