Surfaces

 
We distinguish between chemical deposition processes and the Hot Air Leveling - Hot Air Leveling (HAL) - for making a solderable PCB surface. The chemical processes basically have the advantage that a very good surface planarity is achieved, which is increasingly important for the soldering of ever smaller SMD components. However, the surfaces have a significant disadvantage. In particular chem. Sn (also chem. Ag) surfaces have the property of being difficult or impossible to solder when not properly stored.
The HAL with a SnPb alloy (Lead content ~ 37%) had established itself over the past decades as the standard interface. Unfortunately, the use of lead with the enactment of RoHS was prohibited as of 1 July 2006. Nevertheless, EPN uses the HAL method with the proven SnPb solder. A variety of clients (10-15% of jobs) use this, as the RoHS permits some - as we now know - but not alot of exceptions.

Already in 2005, we introduced an alternative RoHS compliant HAL method. The proportion of the surfaces which is assigned to the new soldering (SnCu 0.7 / Ni 0.1) is 80%.

For several days we also have qualified the chem. Sn surface as a coating in our house. The proportion chem. Sn is currently about 5% and rising. The chem. Sn surface is very controversial, but the opinions about the pros and cons very far apart. Advantages are the low price compared to chem. Ni / Au surface. An advantage is the absolute planarity of SMD landing areas. Disadvantage is the relatively short storage period of 6-9 months, when conditions are favorable, for a few weeks longer.

Highly susceptible to environmental influences is the chem. Ag surface. The storage time is shorter than for chem. Sn. Due to the low demand EPN does not offer this surface.
In the coming years, we expect a decrease in HAL surfaces of about 50%. The chem. Sn surface will rise to at least 30%. OSP is difficult to assess. Worldwide, the proportion is probably over 30%. The demand is rather low for us. The proportion chem. Ni / Ag together with OSP have 10-20%.

The table shows a comparison of the major surface coatings.


Characteristics of the PCB surfaces
 
  Thickness
(µm)
Solderability Wettability Monthly Storage Time Bonding
Al-Wire    Bonding
Bonding
Au-Wire
0,5-10 +++ +++ 12-24 - -
0,5-10 +++ +++ 12-24 - -
0,3-0,5 + + 6 - -
0,7-1,1 ++ ++ 6-9 - -
0,3-0,5 + + < 6 + -
4-6
0,07- 0,1
++ + 12-24 +++ -
4-6
0,4-0,8
- - 12-24 + ++
 

* Leaflet chem. Tin

+++ =
++ =
+ =
- =

   

This project is part-financed by the European Union and the Free State of Thuringia.

   

Suche  

   
© 2019 EPN - ELECTROPRINT GmbH

epn homelink