Today, most of electronic parts are developed into smaller size. The small chips are downsized from 1206 to 0805, 0603, 0402, 0201, even to 01005. The size of chip is smaller; the required solder volume is less.
Moreover, the required stencil thickness becomes thinner from 0.18mm to 0.10mm. Some parts, however, cannot be downsized unlimitedly, such as external connectors. For example, a line socket of telephone, a network line socket, a smart card reader, and other devices require a certain amount of solder volume to ensure the soldering strength and quality. In addition, some traditional insertion parts (Dual in line package process, DIP) with paste-in-hole process require extra solder volume as well.
Today, the SMD parts become smaller and smaller. Their sizes can be developed to 0402, 0201, and even 01005 (Note 1). Moreover, the pitch between the pins of a common IC (integrated circuit) is shorten to fine pitch of 0.5mm, even 0.3 mm. The improvement becomes a challenge for the SMT process.
A great challenge for each SMT engineer is how to weld these thin electronic parts on circuit boards without any non-wetting or short-circuit. In addition, it is more difficult to solder few larger parts and a lot of thin ones on a circuit board than to solder thin parts without any larger ones.
Since the electronic product design moves from desktop to portable devices, the manufacturer also make electronic component as small as possible to meet this popular trend. Besides, the PCB thickness also become thinner and the associated soldering pads on the PCB are tiny size. This make the SMT manufacturing process more difficult and challenge.
You may know that portable device always has BGA malfunction risk during impact drop test. Most of company dispense the underfill glue to fix this kind of BGA crack issue. My company did the same thing too. WorkingBear think there shall be another way to enhance the soldering pad strength to eliminate the underfill glue since underfill process spend money and waste labor hours.
As the career of Manufacturing Process Engineering(MPE), WorkingBear always find there is rope wall between R&D, Marketing and Manufacturer. The R&D and Marketing always like the design be thin, sleek, and modern looking. The manufacturer always like the assembly be robust, solid, rigid, and not easily scratch on the surface. But both of them same ask low cost.
So, here comes two common questions from R&D and marketing people.
- Why thinner PCB will ask special carrier or template for the reflow process?
- Aren’t all PCBs reflowed as a panel, which requires a support fixture for de-panelization?
Since WorkingBear is MPE, so I will answer these two questions as manufacturing point.
Last time WorkingBear mentioned the potential root causes to bring the screw boss crack after mold-in screw nut insert. Actually we received the complaint from the field then asked EMS and plastic supplier to double check their inventory and found about 1% of the screw boss cracked after mold-in screw nut insert before box build assembly. That means no extra force and screw driver give to these screw bosses and the crack happen just from its inner stress. The defect rate increase to 30% after screw in the plastic case together.
So, what make this happened? Workingbear had pointed out 4 potential root causes to bring the screw boss crack for the mold-in nut screw insert process.
- Using too much of the re-grind resin
- No pre-heat on the screw Insert parts
- The improper molding parameter
- Design risk
Since we had proved the boss crack really happened from plastic parts itself. We held these poor quality plastic parts and question the plastic supplier why crack happen? The interesting is that plastic supplier challenged me back that they didn’t change any parameter for this plastic parts and they really don’t know what happen and how come the screw boss crack now?