How to Prevent Solder Bridging in 3528 PLCC6 RGB LEDs?

The 3528 PLCC RGB LED*, such as theLG LEMCS32F00AZ01, has ultra high brightness in a compact size. Heat dissipation should be considered during layout design. The traces that connect each LED pad should be designed as wide as possible. Pad sizes need to follow the manufacturer’s recommended land pattern. However, we still found there was very big amount of the solder bridging defect (0.1%) occurring in the prototype stage.

Solder bridging occurs randomly between LED pads. It is pretty hard to detect because it could be happening underneath the components. Only a functional test can tell you what’s wrong with the light color emitting LED.

When we checked the LED pads on a bare PCB with a microscope, we observed there there was no solder mask in the gap between the pads. Furthermore, after we reviewed the pads’ design in EDA software and found that the size of the pad’s solder mask override was 0.106mm (4 mil) as the default value. But the gap between the pads was only 0.2mm as per the manufacturer’s recommendation. It was less than twice the solder mask override (2 x 0.106 = 0.212mm). This confirmed that there was no solder mask between the pads. When we placed the LED onto the board, the solder paste on the pads was squeezed to the edge of the pads. It was possible for them to be in contact with one another because the gap was small. We think this was root cause of the defect.

The next step was to redesign the pads’ solder mask size. We set up manually the solder mask override value to 0.

We also redesigned a new stencil for paste printing with a shrinking aperture size width from 0.65mm to 0.55mm and an extending aperture size length from 0.85 to 0.95 mm.

The production results were very positive. The solder bridging defects dropped down to zero in the following 10,000 pcs assembly.

* 3528 (body size 3.5 x 2.8 mm) PLCC (6-pin package) RGB LED

Keywords:

SMT Reflow Oven, Lead free Reflow Oven, Reflow Oven Manufacturer, LED reflow oven, PCB Reflow Oven, Nitrogen Reflow Oven, Dual Rail Reflow Oven, China Reflow Oven, wave soldering machine, Dual Rail Wave Soldering Machine, Nitrogen Wave Soldering Machine, Wave Soldering Machine Manufacturer.

Flason Electronic Co.,ltd provide a full SMT assembly line solutions, including SMT Reflow Oven,  Wave Soldering Machine,  Pick and Place Machine,  SMT Stencil Printer,  SMT AOI SPI Machine,  SMT Reflow Oven,  SMT Peripheral Equipment,  SMT Assembly line,  SMT Spare Parts  etc any kind SMT machines you may need, please contact us for more information: wechat whatsapp:+8613691605420, Skype: flasonsmt, Email: sales@flason-smt.com
FAQ
1) This is the first time I use this kind of machine, is it easy to operate?
There is English manual or guide video that show you how to use machine.
If you still have any question, please contact us by e-mail / skype/ phone /trademanager online service.
2) If machine have any problem after I receive it, how can I do ?
Free parts send to you in machine warranty period.
If the part is less than 0.5KG, we pay the postage.
If it exceeds 0.5KG, you need to pay the postage.
3) MOQ ?
1 set machine, mixed order is also welcomed.
4) How can I buy this machine from you? ( Very easy and flexible !)
A. Consult us about this product on line or by e-mail.
B. Negotiate and confirm the final price , shipping , payment methods and other terms.
C. Send you the proforma invoice and confirm your order.
D. Make the payment according to the method put on proforma invoice.
E. We prepare for your order in terms of the proforma invoice after confirming your full payment.
And 100% quality check before shipping.
F.Send your order by air or by sea.
5)Why choose us ?
A. Gold supplier on Alibaba !
B. Trade assurance to US$54,000 !
C. Best price & Best shipping & Best service !