Laminate, ceramic substrate and method for making the ceramic substrate

A method for making a ceramic substrate, comprising:

• a step of preparing a first green sheet which includes a first glass comprising:
• 10 to 30 percent by mass of Si in terms of SiO2;
• a total of 5 to 30 percent by mass of at least one of Mg and Zn in terms of MgO and ZnO, respectively;
• 10 to 30 percent by mass of B in terms of B2O3;
• and
• Al and M which is at least one of Sr and Ba, a relationship between Al content and M content being so defined that a position represented by percent by mass of Al in terms of Al2O3 and percent by mass of M in terms of MO on a coordinate system is on or in a range defined by straight lines connecting point A (Al=1, M=21), point B (Al=1, M=35), point C (Al=9, M=45), point D (Al=20, M=45), point E (Al=20, M=35), and point F (Al=9, M=21) on the coordinate system;
• a step of preparing a second green sheet which includes a second glass comprising:
• Si whose percent by mass in terms of SiO2 is larger than the percent by mass of Si in terms of SiO2 in the first glass by 1 to 40 percent by mass;
• and
• B whose content in terms of B2O3 is 3 percent by mass or more and at least 5 percent by mass less than the B content in terms of B2O3 in the first glass;
• a step of laminating the first green sheet and the second green sheet to prepare a laminate;
• and
• a step of firing the laminate by shrinking the first green sheet and then shrinking the second green sheet so that a shrinkage ratio in an X-Y direction parallel to a main surface of each green sheet is 5% or less.
• wherein the second glass contains 20 to 60 percent by mass of Si in terms of SiO2, 10 to 25 percent by mass of Al in terms of Al2O3, 8 to 35 percent by mass of Mg in terms of MgO, and 10 to 20 percent by mass of M which is at least one of Sr and Ba in terms of MO, and
• wherein a ratio MgO/SiO2 of MgO to SiO2 is in a range of 0.20 to 0.87.