|Trouble||Suggested Remedies (Solutions)|
|Shot-to-shot dimensional variations||
First of all, with the rapid growth of mobile phone technology, the Electronic Manufacturing Service (EMS) in mainland China sometimes meet serious labor shortage. Second, the Industry 4.0 promotes the requirement of factory automation for each EMS. Therefore, many parts which cannot adopt SMT reflow process are requested to fulfill Paste-In-Hole process (PIH process), such as the type-A USB connectors, Ethernet connector, power supply sockets, transformers, and so on. Originally, most of these kind of devices were touch-up soldered after SMT process.
Because of labor shortage, also for the purpose of saving process cost, and under the consideration of quality, many SI and EMS have requested that the parts which cannot adopt SMD process should fulfill at least PIH process, so that the soldering of all the electronic parts on circuit board can be completed after SMT process.
Today, one question from my boss, “Is there any difference or influence on the process and design if we like to convert the SMD parts to DIP type and go through the PIH(Paste-In-Hole) process?”
Later, I realized that the question aimed to avoid the damage of connector caused by customers’ misuse.
Sometimes, Paste-In-Hole (PIH) is also called Pin-In-Paste (PIP).
First, since the traditional insertion parts through PIH process is necessary to be manufactured with high-temperature reflow process, the part design should fulfill the considerations listed as follows:
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.