Measuring the Height of Pressed-in Pins (Through Hole Technology)

In order to inspect the height of pressed-in contact pins on PCBs immediately after the assembly process, scanCONTROL laser scanners from Micro-Epsilon are used. These create a 3D profile of each PCB. Faced with miniature targets, the sensors must fulfill high requirements in terms of precision and speed.

In addition to high precision with miniature dimensions, the production of electronic components also requires high speed processes that provide the highest quality. Therefore, many production steps in this area are highly automated such as the assembly or quality control of circuit boards. For example, PCBs are assembled based on the so-called Through Hole Technology (THT). The respective component is pressed into the hole with the contact pins which are finally soldered to the PCB. The company Automationpro has developed a machine that automatically inspects the height of pressed-in contact pins immediately after the assembly process during production. The inspection of the height is of vital importance, since pins that are incompletely pressed will impair the function of the PCB.

In order to avoid failure of single components, scanCONTROL laser scanners are used to create a 3D profile of each PCB. During this pressing process, the PCBs are fixed onto a rotary table which moves the assembled module from the press-in position to the scanning position. The scanCONTROL laser scanner is moved over the entire PCB by an actuator connected to an encoder which is used for triggering the line scanner to ensure regular profile distances.

Depending on the cycle time of the process, the component undergoes a complete scan within 7 seconds, generating 1,280 points per profile. The recorded measurement values are transmitted to the customer’s image processing software as raw data via the Gigabit Ethernet interface for Machine Vision (GigE Vision). For evaluation and processing purposes of the raw data, Automationpro developed specific image processing algorithms. The entire system structure enables this profile data to be transmitted and evaluated at high speeds. Consequently, the entire evaluation per PCB is carried out in less than one second.

The customer software calculates the pin height relative to the surrounding surface area on the PCB. The result is transmitted to the control system where it is evaluated immediately. This means any faulty PCB can immediately be rejected automatically.