har-bus HM+ connector was designed for Pin in
Hole Intrusive Reflow with features like an inspection friendly black
colour, tape and reel packaging for automated handling and it is self
retaining on pcb. The design – moulded from high temperature resistant
material – ensures good heat distribution, so that current solder temperature
profiles can be used. The special material of the insulation body withstands
also the higher temperatures of lead free soldering.
Advantages for using har-bus® HM 6-row connectors are:
Partial dip soldering or press fitting is no longer required
High mechanical stability
Complete compatibility with Surface Mount Technology
Savings through integration into the automated assembly process
Reduced floor space in the production plant
Application of solder paste
Before the components are assembled, solder paste is applied to all the solder pads and the plated through holes. Usually a screen printing process is used for this purpose. A squeegee moves across the pcb, which is masked with screens and presses the solder paste into all unmasked areas. A good solder joint is basically determined by the amount of the applied solder paste. Only a few parameters (illustrated on the right) will lead to the right quantity.
An an alternative to screen printing, the solder paste can be applied by means of a dispenser. A highprecision robot moves the dispenser to all required positions on the pcb. The dispensing method is particularly suitable for small pcb´s or applications which demand high precision and flexibility in dispensing volumes.
Dispenser in operation:
Solder paste volume
There are numerous scientific studies dealing with calculation of the required quantity of solder paste. These studies use various parameters, e.g. the shrinking factor of the paste during soldering or the thickness of the screens used for masking the pcb. Since such calculation methods are complicated to apply, the following rule of thumb has proved valuable in practive:
VPaste = 2 (VH-VP)
in which:
VPaste=
Required volume of solder paste
VH= Volume of
the plated through hole
VP= Volume of
the connector termination in the hole
Comment: the multiplier "2" compensates for solder paste shrinkage during soldering. For this purpose, it was assumed that 50 % of the paste consists of the actual solder, the other 50 % being soldering aids.
Requirements for the solder connection
At the beginning of a new production batch, the process parameters, such as quantity of solder paste and soldering temperature, can be set by interpreting simple cross-sections of the soldered connection. A reliable measure for achieving optimum parameters is the quantity of solder required to fill the hole. In soldered connections of high quality, the holes are filled to between 75 % and 100 %.
Plated through hole with connector termination:
